Journal Cover Science
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   ISSN (Print) 0036-8075 - ISSN (Online) 1095-9203
   Published by AAAS Homepage  [6 journals]
  • Cancer epigenetics in the driver's seat
    • Authors: Kiberstis P. A.
      Pages: 265
      Keywords: Medicine, Diseases
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-i
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Epigenetic plasticity and the hallmarks of cancer
    • Authors: Flavahan, W. A; Gaskell, E, Bernstein, B. E.
      Abstract: Chromatin and associated epigenetic mechanisms stabilize gene expression and cellular states while also facilitating appropriate responses to developmental or environmental cues. Genetic, environmental, or metabolic insults can induce overly restrictive or overly permissive epigenetic landscapes that contribute to pathogenesis of cancer and other diseases. Restrictive chromatin states may prevent appropriate induction of tumor suppressor programs or block differentiation. By contrast, permissive or "plastic" states may allow stochastic oncogene activation or nonphysiologic cell fate transitions. Whereas many stochastic events will be inconsequential "passengers," some will confer a fitness advantage to a cell and be selected as "drivers." We review the broad roles played by epigenetic aberrations in tumor initiation and evolution and their potential to give rise to all classic hallmarks of cancer.
      Keywords: Medicine, Diseases, Online Only
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aal2380
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Comment on "The [4Fe4S] cluster of human DNA primase functions as a redox
           switch using DNA charge transport"
    • Authors: Baranovskiy, A. G; Babayeva, N. D, Zhang, Y, Blanco, L, Pavlov, Y. I, Tahirov, T. H.
      Abstract: O’Brien et al. (Research Article, 24 February 2017, eaag1789) proposed a novel mechanism of primase function based on redox activity of the iron-sulfur cluster buried inside the C-terminal domain of the large primase subunit (p58C). Serious problems in the experimental design and data interpretation raise concerns about the validity of the conclusions.
      Keywords: Biochemistry, Online Only
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan2396
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Response to Comments on "The [4Fe4S] cluster of human DNA primase
           functions as a redox switch using DNA charge transport"
    • Authors: OBrien, E; Holt, M. E, Thompson, M. K, Salay, L. E, Ehlinger, A. C, Chazin, W. J, Barton, J. K.
      Abstract: Baranovskiy et al. and Pellegrini argue that, based on structural data, the path for charge transfer through the [4Fe4S] domain of primase is not feasible. Our manuscript presents electrochemical data directly showing charge transport through DNA to the [4Fe4S] cluster of a primase p58C construct and a reversible switch in the DNA-bound signal with oxidation/reduction, which is inhibited by mutation of three tyrosine residues. Although the dispositions of tyrosines differ in different constructs, all are within range for microsecond electron transfer.
      Keywords: Biochemistry, Online Only
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan2762
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Comment on "The [4Fe4S] cluster of human DNA primase functions as a redox
           switch using DNA charge transport"
    • Authors: Pellegrini L.
      Abstract: O’Brien et al. (Research Article, 24 February 2017, eaag1789) report that the iron-sulfur cluster of primase has a redox role in enzyme activity. Their analysis is based on a partially misfolded structure of the iron-sulfur cluster domain of primase. In the correctly folded structure, two of the three tyrosines putatively involved in electron transfer, Y345 and Y347, contact the RNA/DNA helix, providing an alternative explanation for the data of O’Brien et al.
      Keywords: Biochemistry, Online Only
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan2954
      Issue No: Vol. 357, No. 6348 (2017)
       
  • How to govern geoengineering'
    • Authors: Pasztor, J; Scharf, C, Schmidt, K.-U.
      Pages: 231 - 231
      Keywords: Editorials
      PubDate: 2017-07-20T10:23:06-07:00
      DOI: 10.1126/science.aan6794
      Issue No: Vol. 357, No. 6348 (2017)
       
  • News at a glance
    • Pages: 232 - 234
      Keywords: Medicine, Diseases
      PubDate: 2017-07-20T10:23:06-07:00
      DOI: 10.1126/science.357.6348.232
      Issue No: Vol. 357, No. 6348 (2017)
       
  • NIH redefines clinical trials, attracting critics
    • Authors: Kaiser J.
      Pages: 236 - 237
      Keywords: Medicine, Diseases, Scientific Community, Science and Policy
      PubDate: 2017-07-20T10:23:06-07:00
      DOI: 10.1126/science.357.6348.236
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Gender discrimination lawsuit at Salk ignites controversy
    • Authors: Wadman M.
      Pages: 237 - 238
      Keywords: Scientific Community
      PubDate: 2017-07-20T10:23:06-07:00
      DOI: 10.1126/science.357.6348.237
      Issue No: Vol. 357, No. 6348 (2017)
       
  • The first Australians arrived early
    • Authors: Gibbons A.
      Pages: 238 - 239
      Keywords: Anthropology, Genetics, Paleontology
      PubDate: 2017-07-20T10:23:06-07:00
      DOI: 10.1126/science.357.6348.238
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Unlocking a key to maize's amazing success
    • Authors: Pennisi E.
      Pages: 240 - 240
      Keywords: Botany, Evolution, Genetics
      PubDate: 2017-07-20T10:23:06-07:00
      DOI: 10.1126/science.357.6348.240
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Zika rewrites maternal immunization ethics
    • Authors: Cohen J.
      Pages: 241 - 241
      Keywords: Medicine, Diseases, Pharmacology, Toxicology, Science and Policy, Virology
      PubDate: 2017-07-20T10:23:06-07:00
      DOI: 10.1126/science.357.6348.241
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Saving Europe's salamanders
    • Authors: Stokstad E.
      Pages: 242 - 245
      Keywords: Ecology, Epidemiology
      PubDate: 2017-07-20T10:23:06-07:00
      DOI: 10.1126/science.357.6348.242
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Sulfur injections for a cooler planet
    • Authors: Niemeier, U; Tilmes, S.
      Pages: 246 - 248
      Keywords: Engineering
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan3317
      Issue No: Vol. 357, No. 6348 (2017)
       
  • A cirrus cloud climate dial'
    • Authors: Lohmann, U; Gasparini, B.
      Pages: 248 - 249
      Keywords: Engineering
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan3325
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Sliding chains keep particles together
    • Authors: Ryu, J; Park, S.
      Pages: 250 - 251
      Keywords: Chemistry
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan6685
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Tuna fin hydraulics inspire aquatic robotics
    • Authors: Triantafyllou M. S.
      Pages: 251 - 252
      Keywords: Physiology
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan8354
      Issue No: Vol. 357, No. 6348 (2017)
       
  • A twist on the Majorana fermion
    • Authors: Pribiag V. S.
      Pages: 252 - 253
      Keywords: Physics
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aao0793
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Can immunotherapy treat neurodegeneration'
    • Authors: Schwartz M.
      Pages: 254 - 255
      Keywords: Neuroscience
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aai8231
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Promote scientific integrity via journal peer review data
    • Authors: Lee, C. J; Moher, D.
      Pages: 256 - 257
      Keywords: Science and Policy
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan4141
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Acknowledging Africa
    • Authors: Emeagwali G.
      Pages: 258 - 258
      Keywords: Scientific Community
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan2480
      Issue No: Vol. 357, No. 6348 (2017)
       
  • About face
    • Authors: Antonakis J.
      Pages: 259 - 259
      Keywords: Psychology
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan6311
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Flawed environmental justice analyses
    • Authors: Emanuel R. E.
      Pages: 260 - 260
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aao2684
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Mexico's basic science funding falls short
    • Authors: Frixione, E; Laclette, J. P.
      Pages: 260 - 261
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aao2866
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Fringe on the brink: Intertidal reefs at risk
    • Authors: Andrades, R; Joyeux, J.-C, Gasparini, J. L, Reis-Filho, J. A, Macieira, R. M, Giarrizzo, T.
      Pages: 261 - 261
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aao0403
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Ecosystem protection payments pay off
    • Authors: Chin G.
      Pages: 263 - 263
      Keywords: Ecology, Economics
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-a
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Volcanoes find a new carbon platform
    • Authors: Grocholski B.
      Pages: 263 - 263
      Keywords: Geochemistry, Geophysics
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-b
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Pulling on bonds counterintuitively
    • Authors: Yeston J.
      Pages: 263 - 263
      Keywords: Chemistry
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-c
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Hydraulic fins
    • Authors: Vignieri S.
      Pages: 263 - 263
      Keywords: Physiology
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-d
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Getting loaded--make mine a double!
    • Authors: Hurtley S. M.
      Pages: 263 - 264
      Keywords: Biochemistry, Molecular Biology
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-e
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Reaching out as a way to grow
    • Authors: Lavine M. S.
      Pages: 263 - 264
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-f
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Greater gait with gravity
    • Authors: Czajka C.
      Pages: 263 - 264
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-g
      Issue No: Vol. 357, No. 6348 (2017)
       
  • A stretchy binder protects the silicon
    • Authors: Lavine M. S.
      Pages: 263 - 264
      Keywords: Chemistry
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-h
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Untangling aggregates one step at a time
    • Authors: Hurtley S. M.
      Pages: 263 - 265
      Keywords: Biochemistry
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-j
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Lighting the way to carbon borylation
    • Authors: Yeston J.
      Pages: 263 - 265
      Keywords: Chemistry
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-k
      Issue No: Vol. 357, No. 6348 (2017)
       
  • A propagating Majorana mode
    • Authors: Stajic J.
      Pages: 263 - 265
      Keywords: Physics
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-l
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Making a large-gap topological insulator
    • Authors: Stajic J.
      Pages: 263 - 265
      Keywords: Materials Science
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-m
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Hitting the highs in solid state
    • Authors: Osborne I. S.
      Pages: 263 - 265
      Keywords: Physics
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-n
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Finding a more flexible mechanical sensor
    • Authors: Grocholski B.
      Pages: 263 - 265
      Keywords: Physics, Applied
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-o
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Geoengineering for temperature control
    • Authors: Fahrenkamp-Uppenbrink J.
      Pages: 263 - 265
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-p
      Issue No: Vol. 357, No. 6348 (2017)
       
  • The amyloid connection in Parkinson's
    • Authors: Ferrarelli L. K.
      Pages: 263 - 265
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.263-q
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Wasp venom evolution
    • Authors: Griffin C.
      Pages: 264 - 265
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.264-a
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Making a quantum-classical hybrid
    • Authors: Stajic J.
      Pages: 264 - 264
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.264-b
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Get ready, get set, get wet
    • Authors: Smith H. J.
      Pages: 264 - 265
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.264-c
      Issue No: Vol. 357, No. 6348 (2017)
       
  • A setback for immune checkpoint therapy'
    • Authors: Alderton G.
      Pages: 264 - 265
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.264-d
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Evolutionarily, the beat goes on
    • Authors: Zahn L. M.
      Pages: 264 - 265
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.264-e
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Babies favor facelike stimuli before birth
    • Authors: Morris E.
      Pages: 264 - 265
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.264-f
      Issue No: Vol. 357, No. 6348 (2017)
       
  • A rhodium catalyst hogs the spotlight
    • Authors: Yeston J.
      Pages: 264 - 265
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.264-g
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Cash for carbon: A randomized trial of payments for ecosystem services to
           reduce deforestation
    • Authors: Jayachandran, S; de Laat, J, Lambin, E. F, Stanton, C. Y, Audy, R, Thomas, N. E.
      Pages: 267 - 273
      Abstract: We evaluated a program of payments for ecosystem services in Uganda that offered forest-owning households annual payments of 70,000 Ugandan shillings per hectare if they conserved their forest. The program was implemented as a randomized controlled trial in 121 villages, 60 of which received the program for 2 years. The primary outcome was the change in land area covered by trees, measured by classifying high-resolution satellite imagery. We found that tree cover declined by 4.2% during the study period in treatment villages, compared to 9.1% in control villages. We found no evidence that enrollees shifted their deforestation to nearby land. We valued the delayed carbon dioxide emissions and found that this program benefit is 2.4 times as large as the program costs.
      Keywords: Ecology, Economics
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan0568
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Ratchet-like polypeptide translocation mechanism of the AAA+ disaggregase
           Hsp104
    • Authors: Gates, S. N; Yokom, A. L, Lin, J, Jackrel, M. E, Rizo, A. N, Kendsersky, N. M, Buell, C. E, Sweeny, E. A, Mack, K. L, Chuang, E, Torrente, M. P, Su, M, Shorter, J, Southworth, D. R.
      Pages: 273 - 279
      Abstract: Hsp100 polypeptide translocases are conserved members of the AAA+ family (adenosine triphosphatases associated with diverse cellular activities) that maintain proteostasis by unfolding aberrant and toxic proteins for refolding or proteolytic degradation. The Hsp104 disaggregase from Saccharomyces cerevisiae solubilizes stress-induced amorphous aggregates and amyloids. The structural basis for substrate recognition and translocation is unknown. Using a model substrate (casein), we report cryo–electron microscopy structures at near-atomic resolution of Hsp104 in different translocation states. Substrate interactions are mediated by conserved, pore-loop tyrosines that contact an 80-angstrom-long unfolded polypeptide along the axial channel. Two protomers undergo a ratchet-like conformational change that advances pore loop–substrate interactions by two amino acids. These changes are coupled to activation of specific nucleotide hydrolysis sites and, when transmitted around the hexamer, reveal a processive rotary translocation mechanism and substrate-responsive flexibility during Hsp104-catalyzed disaggregation.
      Keywords: Biochemistry
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan1052
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Highly elastic binders integrating polyrotaxanes for silicon microparticle
           anodes in lithium ion batteries
    • Authors: Choi, S; Kwon, T.-w, Coskun, A, Choi, J. W.
      Pages: 279 - 283
      Abstract: Lithium-ion batteries with ever-increasing energy densities are needed for batteries for advanced devices and all-electric vehicles. Silicon has been highlighted as a promising anode material because of its superior specific capacity. During repeated charge-discharge cycles, silicon undergoes huge volume changes. This limits cycle life via particle pulverization and an unstable electrode-electrolyte interface, especially when the particle sizes are in the micrometer range. We show that the incorporation of 5 weight % polyrotaxane to conventional polyacrylic acid binder imparts extraordinary elasticity to the polymer network originating from the ring sliding motion of polyrotaxane. This binder combination keeps even pulverized silicon particles coalesced without disintegration, enabling stable cycle life for silicon microparticle anodes at commercial-level areal capacities.
      Keywords: Chemistry
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aal4373
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Photoinduced decarboxylative borylation of carboxylic acids
    • Authors: Fawcett, A; Pradeilles, J, Wang, Y, Mutsuga, T, Myers, E. L, Aggarwal, V. K.
      Pages: 283 - 286
      Abstract: The conversion of widely available carboxylic acids into versatile boronic esters would be highly enabling for synthesis. We found that this transformation can be effected by illuminating the N-hydroxyphthalimide ester derivative of the carboxylic acid under visible light at room temperature in the presence of the diboron reagent bis(catecholato)diboron. A simple workup allows isolation of the pinacol boronic ester. Experimental evidence suggests that boryl radical intermediates are involved in the process. The methodology is illustrated by the transformation of primary, secondary, and tertiary alkyl carboxylic acids as well as a diverse range of natural-product carboxylic acids, thereby demonstrating its broad utility and functional group tolerance.
      Keywords: Chemistry
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan3679
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Bismuthene on a SiC substrate: A candidate for a high-temperature quantum
           spin Hall material
    • Authors: Reis, F; Li, G, Dudy, L, Bauernfeind, M, Glass, S, Hanke, W, Thomale, R, Schäfer, J, Claessen, R.
      Pages: 287 - 290
      Abstract: Quantum spin Hall materials hold the promise of revolutionary devices with dissipationless spin currents but have required cryogenic temperatures owing to small energy gaps. Here we show theoretically that a room-temperature regime with a large energy gap may be achievable within a paradigm that exploits the atomic spin-orbit coupling. The concept is based on a substrate-supported monolayer of a high–atomic number element and is experimentally realized as a bismuth honeycomb lattice on top of the insulating silicon carbide substrate SiC(0001). Using scanning tunneling spectroscopy, we detect a gap of ~0.8 electron volt and conductive edge states consistent with theory. Our combined theoretical and experimental results demonstrate a concept for a quantum spin Hall wide-gap scenario, where the chemical potential resides in the global system gap, ensuring robust edge conductance.
      Keywords: Materials Science
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aai8142
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Remobilization of crustal carbon may dominate volcanic arc emissions
    • Authors: Mason, E; Edmonds, M, Turchyn, A. V.
      Pages: 290 - 294
      Abstract: The flux of carbon into and out of Earth’s surface environment has implications for Earth’s climate and habitability. We compiled a global data set for carbon and helium isotopes from volcanic arcs and demonstrated that the carbon isotope composition of mean global volcanic gas is considerably heavier, at –3.8 to –4.6 per mil (), than the canonical mid-ocean ridge basalt value of –6.0. The largest volcanic emitters outgas carbon with higher 13C and are located in mature continental arcs that have accreted carbonate platforms, indicating that reworking of crustal limestone is an important source of volcanic carbon. The fractional burial of organic carbon is lower than traditionally determined from a global carbon isotope mass balance and may have varied over geological time, modulated by supercontinent formation and breakup.
      Keywords: Geochemistry, Geophysics
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan5049
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Chiral Majorana fermion modes in a quantum anomalous Hall
           insulator-superconductor structure
    • Authors: He, Q. L; Pan, L, Stern, A. L, Burks, E. C, Che, X, Yin, G, Wang, J, Lian, B, Zhou, Q, Choi, E. S, Murata, K, Kou, X, Chen, Z, Nie, T, Shao, Q, Fan, Y, Zhang, S.-C, Liu, K, Xia, J, Wang, K. L.
      Pages: 294 - 299
      Abstract: Majorana fermion is a hypothetical particle that is its own antiparticle. We report transport measurements that suggest the existence of one-dimensional chiral Majorana fermion modes in the hybrid system of a quantum anomalous Hall insulator thin film coupled with a superconductor. As the external magnetic field is swept, half-integer quantized conductance plateaus are observed at the locations of magnetization reversals, giving a distinct signature of the Majorana fermion modes. This transport signature is reproducible over many magnetic field sweeps and appears at different temperatures. This finding may open up an avenue to control Majorana fermions for implementing robust topological quantum computing.
      Keywords: Physics
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aag2792
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Experimentally realized mechanochemistry distinct from force-accelerated
           scission of loaded bonds
    • Authors: Akbulatov, S; Tian, Y, Huang, Z, Kucharski, T. J, Yang, Q.-Z, Boulatov, R.
      Pages: 299 - 303
      Abstract: Stretching polymer chains accelerates dissociation of a variety of internal covalent bonds, to an extent that correlates well with the force experienced by the scissile bond. Recent theory has also predicted scenarios in which applied force accelerates dissociation of unloaded bonds and kinetically strengthens strained bonds. We report here unambiguous experimental validation of this hypothesis: Detailed kinetic measurements demonstrate that stretching phosphotriesters accelerates dissociation of the unloaded phosphorus-oxygen bond orthogonal to the pulling axis, whereas stretching organosiloxanes inhibits dissociation of the aligned loaded silicon-oxygen bonds. Qualitatively, the outcome is determined by phosphoester elongation and siloxane contraction along the pulling axis in the respective rate-determining transition states. Quantitatively, the results agree with a simple mechanochemical kinetics model.
      Keywords: Chemistry
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan1026
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Tailored semiconductors for high-harmonic optoelectronics
    • Authors: Sivis, M; Taucer, M, Vampa, G, Johnston, K, Staudte, A, Naumov, A. Y, Villeneuve, D. M, Ropers, C, Corkum, P. B.
      Pages: 303 - 306
      Abstract: The advent of high-harmonic generation in gases 30 years ago set the foundation for attosecond science and facilitated ultrafast spectroscopy in atoms, molecules, and solids. We explore high-harmonic generation in the solid state by means of nanostructured and ion-implanted semiconductors. We use wavelength-selective microscopic imaging to map enhanced harmonic emission and show that the generation medium and the driving field can be locally tailored in solids by modifying the chemical composition and morphology. This enables the control of high-harmonic technology within precisely engineered solid targets. We demonstrate customized high-harmonic wave fields with wavelengths down to 225 nanometers (ninth-harmonic order of 2-micrometer laser pulses) and present an integrated Fresnel zone plate target in silicon, which leads to diffraction-limited self-focusing of the generated harmonics down to 1-micrometer spot sizes.
      Keywords: Physics
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan2395
      Issue No: Vol. 357, No. 6348 (2017)
       
  • An organic-inorganic perovskite ferroelectric with large piezoelectric
           response
    • Authors: You, Y.-M; Liao, W.-Q, Zhao, D, Ye, H.-Y, Zhang, Y, Zhou, Q, Niu, X, Wang, J, Li, P.-F, Fu, D.-W, Wang, Z, Gao, S, Yang, K, Liu, J.-M, Li, J, Yan, Y, Xiong, R.-G.
      Pages: 306 - 309
      Abstract: Molecular piezoelectrics are highly desirable for their easy and environment-friendly processing, light weight, low processing temperature, and mechanical flexibility. However, although 136 years have passed since the discovery in 1880 of the piezoelectric effect, molecular piezoelectrics with a piezoelectric coefficient d33 comparable with piezoceramics such as barium titanate (BTO; ~190 picocoulombs per newton) have not been found. We show that trimethylchloromethyl ammonium trichloromanganese(II), an organic-inorganic perovskite ferroelectric crystal processed from aqueous solution, has a large d33 of 185 picocoulombs per newton and a high phase-transition temperature of 406 kelvin (K) (16 K above that of BTO). This makes it a competitive candidate for medical, micromechanical, and biomechanical applications.
      Keywords: Physics, Applied
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aai8535
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Hydraulic control of tuna fins: A role for the lymphatic system in
           vertebrate locomotion
    • Authors: Pavlov, V; Rosental, B, Hansen, N. F, Beers, J. M, Parish, G, Rowbotham, I, Block, B. A.
      Pages: 310 - 314
      Abstract: The lymphatic system in teleost fish has genetic and developmental origins similar to those of the mammalian lymphatic system, which is involved in immune response and fluid homeostasis. Here, we show that the lymphatic system of tunas functions in swimming hydrodynamics. Specifically, a musculo-vascular complex, consisting of fin muscles, bones, and lymphatic vessels, is involved in the hydraulic control of median fins. This specialization of the lymphatic system is associated with fish in the family Scombridae and may have evolved in response to the demand for swimming and maneuvering control in these high-performance species.
      Keywords: Physiology
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aak9607
      Issue No: Vol. 357, No. 6348 (2017)
       
  • Bidirectional eukaryotic DNA replication is established by
           quasi-symmetrical helicase loading
    • Authors: Coster, G; Diffley, J. F. X.
      Pages: 314 - 318
      Abstract: Bidirectional replication from eukaryotic DNA replication origins requires the loading of two ring-shaped minichromosome maintenance (MCM) helicases around DNA in opposite orientations. MCM loading is orchestrated by binding of the origin recognition complex (ORC) to DNA, but how ORC coordinates symmetrical MCM loading is unclear. We used natural budding yeast DNA replication origins and synthetic DNA sequences to show that efficient MCM loading requires binding of two ORC molecules to two ORC binding sites. The relative orientation of these sites, but not the distance between them, was found to be critical for MCM loading in vitro and origin function in vivo. We propose that quasi-symmetrical loading of individual MCM hexamers by ORC and directed MCM translocation into double hexamers acts as a unifying mechanism for the establishment of bidirectional replication in archaea and eukaryotes.
      Keywords: Biochemistry, Molecular Biology
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.aan0063
      Issue No: Vol. 357, No. 6348 (2017)
       
  • New Products
    • Pages: 319 - 319
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.319
      Issue No: Vol. 357, No. 6348 (2017)
       
  • The call of the wild
    • Authors: Mendelson J. R.
      Pages: 326 - 326
      PubDate: 2017-07-20T10:23:07-07:00
      DOI: 10.1126/science.357.6348.326
      Issue No: Vol. 357, No. 6348 (2017)
       
 
 
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