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  • Animals  (743)
  • Chemistry  (230)
  • United States  (119)
  • Geochemistry, Geophysics  (96)
  • American Association for the Advancement of Science (AAAS)  (1,162)
  • 2015-2019  (1,162)
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  • 1
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-07-08
    Description: Separation and purification are critical industrial processes for separating components of chemical mixtures, and these processes account for about half of industrial energy usage (1). Gas mixtures of compounds with very similar physical properties are particularly difficult to separate. On pages 137 and 141 of this issue, Cadiau et al. (2) and Cui et al. (3), respectively, show that microporous materials can be designed to have high adsorption capacity and selectivity for particular hydrocarbons, enabling energy-efficient separation. Author: Jerry Y. S. Lin
    Keywords: Chemistry
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  • 2
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-05-27
    Description: Biomass-degrading microorganisms use lytic polysaccharide monooxygenase (LPMO) enzymes to help digest cellulose, chitin, and starch. By cleaving otherwise inaccessible crystalline cellulose chains, these enzymes provide access to hydrolytic enzymes. LPMOs are of interest to biotechnology because efficient depolymerization of cellulose is a major bottleneck for the production of biologically based chemicals and fuels. On page 1098 of this issue, Kracher et al. (1) compare LPMO-reducing substrates in fungi from different taxonomic groups and lifestyles, based on both biochemical and genomic evidence. The results provide insights into reductive activation of LPMO that are important for developing more efficient industrial enzymes for lignocellulose biorefineries. Author: Angel T. Martínez
    Keywords: Chemistry
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  • 3
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-25
    Description: Author: Marc S. Lavine
    Keywords: Chemistry
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  • 4
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-16
    Keywords: Chemistry
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  • 5
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-16
    Description: The comment and response concerning the report of oxidation of methane to methanol by water (Reports, 5 May 2017, p. 523) do not fully capture the implications of thermodynamic limitations. A nonisothermal process in which each cycle requires a large temperature swing and permits only substoichiometric methane conversion surely could not be carried out on any practical scale.
    Keywords: Chemistry
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  • 6
    Publication Date: 2018-02-16
    Description: Labinger argues that stepwise reaction of methane with water to produce methanol and hydrogen will never be commercially feasible because of its substoichiometric basis with respect to the active site and the requirement of a large temperature swing. This comment is not touching any new ground, beyond describing the thermodynamic feasibility, thermal cycling, and the role of water as discussed previously. Most important, it does not have a solid numerical basis.
    Keywords: Chemistry
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  • 7
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-27
    Keywords: Chemistry
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  • 8
    Publication Date: 2018-07-27
    Description: Vinyl carbocations have been the subject of extensive experimental and theoretical studies over the past five decades. Despite this long history in chemistry, the utility of vinyl cations in chemical synthesis has been limited, with most reactivity studies focusing on solvolysis reactions or intramolecular processes. Here we report synthetic and mechanistic studies of vinyl cations generated through silylium–weakly coordinating anion catalysis. We find that these reactive intermediates undergo mild intermolecular carbon-carbon bond–forming reactions, including carbon-hydrogen (C–H) insertion into unactivated sp 3 C–H bonds and reductive Friedel-Crafts reactions with arenes. Moreover, we conducted computational studies of these alkane C–H functionalization reactions and discovered that they proceed through nonclassical, ambimodal transition structures. This reaction manifold provides a framework for the catalytic functionalization of hydrocarbons using simple ketone derivatives.
    Keywords: Chemistry
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  • 9
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-03
    Keywords: Geochemistry, Geophysics
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  • 10
    Publication Date: 2018-06-22
    Description: It is commonly assumed that recognition and discrimination of chirality, both in nature and in artificial systems, depend solely on spatial effects. However, recent studies have suggested that charge redistribution in chiral molecules manifests an enantiospecific preference in electron spin orientation. We therefore reasoned that the induced spin polarization may affect enantiorecognition through exchange interactions. Here we show experimentally that the interaction of chiral molecules with a perpendicularly magnetized substrate is enantiospecific. Thus, one enantiomer adsorbs preferentially when the magnetic dipole is pointing up, whereas the other adsorbs faster for the opposite alignment of the magnetization. The interaction is not controlled by the magnetic field per se, but rather by the electron spin orientations, and opens prospects for a distinct approach to enantiomeric separations.
    Keywords: Chemistry
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  • 11
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-29
    Keywords: Chemistry
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  • 12
    Publication Date: 2018-12-14
    Description: Theory has established the importance of geometric phase (GP) effects in the adiabatic dynamics of molecular systems with a conical intersection connecting the ground- and excited-state potential energy surfaces, but direct observation of their manifestation in chemical reactions remains a major challenge. Here, we report a high-resolution crossed molecular beams study of the H + HD -〉 H 2 + D reaction at a collision energy slightly above the conical intersection. Velocity map ion imaging revealed fast angular oscillations in product quantum state–resolved differential cross sections in the forward scattering direction for H 2 products at specific rovibrational levels. The experimental results agree with adiabatic quantum dynamical calculations only when the GP effect is included.
    Keywords: Chemistry
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  • 13
    Publication Date: 2018-08-03
    Description: The demise of Lowland Classic Maya civilization during the Terminal Classic Period (~800 to 1000 CE) is a well-cited example of how past climate may have affected ancient societies. Attempts to estimate the magnitude of hydrologic change, however, have met with equivocal success because of the qualitative and indirect nature of available climate proxy data. We reconstructed the past isotopic composition ( 18 O, D, 17 O-excess, and d-excess) of water in Lake Chichancanab, Mexico, using a technique that involves isotopic analysis of the structurally bound water in sedimentary gypsum, which was deposited under drought conditions. The triple oxygen and hydrogen isotope data provide a direct measure of past changes in lake hydrology. We modeled the data and conclude that annual precipitation decreased between 41 and 54% (with intervals of up to 70% rainfall reduction during peak drought conditions) and that relative humidity declined by 2 to 7% compared to present-day conditions.
    Keywords: Geochemistry, Geophysics
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  • 14
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-10
    Keywords: Geochemistry, Geophysics
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  • 15
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Keywords: Chemistry
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  • 16
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Keywords: Geochemistry, Geophysics
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  • 17
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Keywords: Chemistry
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  • 18
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Description: The chemistry of the carbonyl group is essential to modern organic synthesis. The preparation of substituted, enantioenriched 1,3- or 1,5-dicarbonyls is well developed, as their disconnection naturally follows from the intrinsic polarity of the carbonyl group. By contrast, a general enantioselective access to quaternary stereocenters in acyclic 1,4-dicarbonyl systems remains an unresolved problem, despite the tremendous importance of 2,3-substituted 1,4-dicarbonyl motifs in natural products and drug scaffolds. Here we present a broad enantioselective and stereodivergent strategy to access acyclic, polysubstituted 1,4-dicarbonyls via acid-catalyzed [3,3]-sulfonium rearrangement starting from vinyl sulfoxides and ynamides. The stereochemistry at sulfur governs the absolute sense of chiral induction, whereas the double bond geometry dictates the relative configuration of the final products.
    Keywords: Chemistry
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  • 19
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Keywords: Chemistry
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  • 20
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Description: With the recent soaring production of natural gas, the use of methane and other light hydrocarbon feedstocks as starting materials in synthetic transformations is becoming increasingly economically attractive, although it remains chemically challenging. We report the development of photocatalytic C–H amination, alkylation, and arylation of methane, ethane, and higher alkanes under visible light irradiation at ambient temperature. High catalytic efficiency (turnover numbers up to 2900 for methane and 9700 for ethane) and selectivity were achieved using abundant, inexpensive cerium salts as photocatalysts. Ligand-to-metal charge transfer excitation generated alkoxy radicals from simple alcohols that in turn acted as hydrogen atom transfer catalysts. The mixed-phase gas/liquid reaction was adapted to continuous flow, enabling the efficient use of gaseous feedstocks in scalable photocatalytic transformations.
    Keywords: Chemistry
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  • 21
    Publication Date: 2018-08-17
    Description: We document rapid and abrupt clearings of large portions of the subtropical marine low cloud deck that have implications for the global radiation balance and climate sensitivity. Over the southeast Atlantic, large areas of stratocumulus are quickly eroded, yielding partial or complete clearing along sharp transitions hundreds to thousands of kilometers in length that move westward at 8 to 12 meters per second and travel as far as 1000+ kilometers from the African coast. The westward-moving cloudiness reductions have an annual peak in occurrence in the period from April through June. The cloud erosion boundaries reduce cloud at 10-kilometer scale in less than 15 minutes, move approximately perpendicular to the mean flow, and are often accompanied by small-scale wave features. Observations suggest that the cloud erosion is caused by atmospheric gravity waves.
    Keywords: Geochemistry, Geophysics
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  • 22
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-24
    Keywords: Chemistry
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  • 23
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-24
    Keywords: Geochemistry, Geophysics
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  • 24
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-24
    Keywords: Geochemistry, Geophysics
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  • 25
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-24
    Keywords: Chemistry
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  • 26
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-31
    Keywords: Chemistry
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  • 27
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-31
    Description: Intrigued by the potential of nanoscale machines, scientists have long attempted to control molecular motion. We monitored the individual 0.7-nanometer steps of a single molecular hopper as it moved in an electric field along a track in a nanopore controlled by a chemical ratchet. The hopper demonstrated characteristics desired in a moving molecule: defined start and end points, processivity, no chemical fuel requirement, directional motion, and external control. The hopper was readily functionalized to carry cargos. For example, a DNA molecule could be ratcheted along the track in either direction, a prerequisite for nanopore sequencing.
    Keywords: Chemistry
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  • 28
    Publication Date: 2018-09-21
    Description: Phosphorothioate nucleotides have emerged as powerful pharmacological substitutes of their native phosphodiester analogs with important translational applications in antisense oligonucleotide (ASO) therapeutics and cyclic dinucleotide (CDN) synthesis. Stereocontrolled installation of this chiral motif has long been hampered by the systemic use of phosphorus(III) [P(III)]–based reagent systems as the sole practical means of oligonucleotide assembly. A fundamentally different approach is described herein: the invention of a P(V)-based reagent platform for programmable, traceless, diastereoselective phosphorus-sulfur incorporation. The power of this reagent system is demonstrated through the robust and stereocontrolled synthesis of various nucleotidic architectures, including ASOs and CDNs, via an efficient, inexpensive, and operationally simple protocol.
    Keywords: Chemistry
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  • 29
    Publication Date: 2018-09-21
    Description: Here we report an anomalous porous molecular crystal built of C–H···N-bonded double-layered roof-floor components and wall components of a segregatively interdigitated architecture. This complicated porous structure consists of only one type of fully aromatic multijoint molecule carrying three identical dipyridylphenyl wedges. Despite its high symmetry, this molecule accomplishes difficult tasks by using two of its three wedges for roof-floor formation and using its other wedge for wall formation. Although a C–H···N bond is extremely labile, the porous crystal maintains its porosity until thermal breakdown of the C–H···N bonds at 202°C occurs, affording a nonporous polymorph. Though this nonporous crystal survives even at 325°C, it can retrieve the parent porosity under acetonitrile vapor. These findings show how one can translate simplicity into ultrahigh complexity.
    Keywords: Chemistry
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  • 30
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-28
    Keywords: Chemistry
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  • 31
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-28
    Keywords: Chemistry
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  • 32
    Publication Date: 2018-09-28
    Description: Some of the simplest and most powerful carbon-carbon bond forming strategies take advantage of readily accessible ubiquitous motifs: carbonyls and olefins. Here we report a fundamentally distinct mode of reactivity between carbonyls and olefins that differs from established acid-catalyzed carbonyl-ene, Prins, and carbonyl-olefin metathesis reaction paths. A range of epsilon, zeta-unsaturated ketones undergo Brønsted acid–catalyzed intramolecular cyclization to provide tetrahydrofluorene products via the formation of two new carbon-carbon bonds. Theoretical calculations and accompanying mechanistic studies suggest that this carbocyclization reaction proceeds through the intermediacy of a transient oxetane formed by oxygen atom transfer. The complex polycyclic frameworks in this product class appear as common substructures in organic materials, bioactive natural products, and recently developed pharmaceuticals.
    Keywords: Chemistry
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  • 33
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-28
    Description: Alkene aminoarylation with a single, bifunctional reagent is a concise synthetic strategy. We report a catalytic protocol for the addition of arylsulfonylacetamides across electron-rich alkenes with complete anti-Markovnikov regioselectivity and excellent diastereoselectivity to provide 2,2-diarylethylamines. In this process, single-electron alkene oxidation enables carbon-nitrogen bond formation to provide a key benzylic radical poised for a Smiles-Truce 1,5-aryl shift. This reaction is redox-neutral, exhibits broad functional group compatibility, and occurs at room temperature with loss of sulfur dioxide. As this process is driven by visible light, uses readily available starting materials, and demonstrates convergent synthesis, it is well suited for use in a variety of synthetic endeavors.
    Keywords: Chemistry
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  • 34
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-05
    Keywords: Geochemistry, Geophysics
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  • 35
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-05
    Keywords: Chemistry
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  • 36
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-05
    Keywords: Geochemistry, Geophysics
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  • 37
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-05
    Keywords: Chemistry
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  • 38
    Publication Date: 2018-10-05
    Description: Himalayan rivers are frequently hit by catastrophic floods that are caused by the failure of glacial lake and landslide dams; however, the dynamics and long-term impacts of such floods remain poorly understood. We present a comprehensive set of observations that capture the July 2016 glacial lake outburst flood (GLOF) in the Bhotekoshi/Sunkoshi River of Nepal. Seismic records of the flood provide new insights into GLOF mechanics and their ability to mobilize large boulders that otherwise prevent channel erosion. Because of this boulder mobilization, GLOF impacts far exceed those of the annual summer monsoon, and GLOFs may dominate fluvial erosion and channel-hillslope coupling many tens of kilometers downstream of glaciated areas. Long-term valley evolution in these regions may therefore be driven by GLOF frequency and magnitude, rather than by precipitation.
    Keywords: Geochemistry, Geophysics
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  • 39
    Publication Date: 2018-10-05
    Description: Photocatalysis based on optically active, "plasmonic" metal nanoparticles has emerged as a promising approach to facilitate light-driven chemical conversions under far milder conditions than thermal catalysis. However, an understanding of the relation between thermal and electronic excitations has been lacking. We report the substantial light-induced reduction of the thermal activation barrier for ammonia decomposition on a plasmonic photocatalyst. We introduce the concept of a light-dependent activation barrier to account for the effect of light illumination on electronic and thermal excitations in a single unified picture. This framework provides insight into the specific role of hot carriers in plasmon-mediated photochemistry, which is critically important for designing energy-efficient plasmonic photocatalysts.
    Keywords: Chemistry
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  • 40
    Publication Date: 2018-10-05
    Description: Subduction zones are home to the most seismically active faults on the planet. The shallow megathrust interfaces of subduction zones host Earth’s largest earthquakes and are likely the only faults capable of magnitude 9+ ruptures. Despite these facts, our knowledge of subduction zone geometry—which likely plays a key role in determining the spatial extent and ultimately the size of subduction zone earthquakes—is incomplete. We calculated the three-dimensional geometries of all seismically active global subduction zones. The resulting model, called Slab2, provides a uniform geometrical analysis of all currently subducting slabs.
    Keywords: Geochemistry, Geophysics
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  • 41
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Keywords: Chemistry
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  • 42
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Keywords: Chemistry
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  • 43
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Description: Single-electron reduction of a carbonyl to a ketyl enables access to a polarity-reversed platform of reactivity for this cornerstone functional group. However, the synthetic utility of the ketyl radical is hindered by the strong reductants necessary for its generation, which also limit its reactivity to net reductive mechanisms. We report a strategy for net redox-neutral generation and reaction of ketyl radicals. The in situ conversion of aldehydes to α-acetoxy iodides lowers their reduction potential by more than 1 volt, allowing for milder access to the corresponding ketyl radicals and an oxidative termination event. Upon subjecting these iodides to a dimanganese decacarbonyl precatalyst and visible light irradiation, an atom transfer radical addition (ATRA) mechanism affords a broad scope of vinyl iodide products with high Z -selectivity.
    Keywords: Chemistry
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  • 44
    Publication Date: 2018-10-12
    Description: Reactions that form a product with the same reactive functionality as that of one of the starting compounds frequently end in oligomerization. As a salient example, selective aldol coupling of the smallest, though arguably most useful, enolizable aldehyde, acetaldehyde, with just one partner substrate has proven to be extremely challenging. Here, we report a highly enantioselective Mukaiyama aldol reaction with the simple triethylsilyl (TES) and tert -butyldimethylsilyl (TBS) enolates of acetaldehyde and various aliphatic and aromatic acceptor aldehydes. The reaction is catalyzed by recently developed, strongly acidic imidodiphosphorimidates (IDPi), which, like enzymes, display a confined active site but, like small-molecule catalysts, have a broad substrate scope. The process is scalable, fast, efficient (0.5 to 1.5 mole % catalyst loading), and greatly simplifies access to highly valuable silylated acetaldehyde aldols.
    Keywords: Chemistry
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  • 45
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-12-21
    Keywords: Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 46
    Publication Date: 2018-12-21
    Description: Single-molecule magnets (SMMs) containing only one metal center may represent the lower size limit for molecule-based magnetic information storage materials. Their current drawback is that all SMMs require liquid-helium cooling to show magnetic memory effects. We now report a chemical strategy to access the dysprosium metallocene cation [(Cp i Pr5 )Dy(Cp*)] + (Cp i Pr5 , penta-iso-propylcyclopentadienyl; Cp *, pentamethylcyclopentadienyl), which displays magnetic hysteresis above liquid-nitrogen temperatures. An effective energy barrier to reversal of the magnetization of U eff = 1541 wave number is also measured. The magnetic blocking temperature of T B = 80 kelvin for this cation overcomes an essential barrier toward the development of nanomagnet devices that function at practical temperatures.
    Keywords: Chemistry
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  • 47
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-04-29
    Description: Author: Jake Yeston
    Keywords: Chemistry
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  • 48
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-18
    Description: Author: Marc S. Lavine
    Keywords: Chemistry
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  • 49
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-18
    Description: Water plays a central role in scientific disciplines ranging from geology to astronomy to biology. Yet it is an extraordinarily dif cult liquid to understand because of its complex, ever-changing patterns of hydrogen bonds. Studies of small water clusters have provided important insights into the concerted hydrogen-bond motions that can occur in water. These studies are also crucial for developing an accurate potential function for simulating the properties of liquid water and ice (1). On page 1310 of this issue, Richardson et al. (2) provide evidence for a concerted type of motion in which two hydrogen bonds in a water cluster are broken simultaneously (see the figure). The results have implications for many areas of scientific study, including the chemistry of polar solvents, the conformations of proteins, and the dissolution of ions in minerals. Author: David C. Clary
    Keywords: Chemistry
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  • 50
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-18
    Description: Author: Jake Yeston
    Keywords: Chemistry
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  • 51
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-04
    Description: Lower olefins, particularly ethylene (C2H4), propylene (C3H6), and butylene (C4H8), are important intermediates in the manufacture of products such as plastics, solvents, paints, and medicines. They are produced worldwide in amounts exceeding 200 million tons per year (see the photo) (1), mostly from crude oil. More recent approaches use methanol or synthesis gas (syngas; a mixture of carbon monoxide and hydrogen) as feedstocks, but capital investments are high and/or selectivities to lower olefins limited. A bifunctional catalyst reported by Jiao et al. on page 1065 of this issue (2) enables the direct conversion of synthesis gas to lower olefins with a surprisingly high selectivity. Author: Krijn P. de Jong
    Keywords: Chemistry
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  • 52
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-19
    Keywords: Chemistry
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  • 53
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-19
    Description: The development of highly reactive and stereoselective catalytic systems is required not only to improve existing synthetic methods but also to invent distinct chemical reactions. Herein, a homogenized combination of nickel-based Lewis acid–surfactant-combined catalysts and single-walled carbon nanotubes is shown to exhibit substantial activity in water. In addition to the enhanced reactivity, stereoselective performance and long-term stability were demonstrated in asymmetric conjugate addition reactions of aldoximes to furnish chiral nitrones in high yields with excellent selectivities. The practical and straightforward application of the designed catalysts in water provides an expedient, environmentally benign, and highly efficient pathway to access optically active compounds.
    Keywords: Chemistry
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  • 54
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-19
    Keywords: Geochemistry, Geophysics
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  • 55
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-02
    Keywords: Chemistry
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  • 56
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-12-14
    Keywords: Chemistry
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  • 57
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-19
    Description: Seismic J waves, shear waves that traverse Earth’s inner core, provide direct constraints on the inner core’s solidity and shear properties. However, these waves have been elusive in the direct seismic wavefield because of their small amplitudes. We devised a new method to detect J waves in the earthquake coda correlation wavefield. They manifest through the similarity with other compressional core-sensitive signals. The inner core is solid, but relatively soft, with shear-wave speeds and shear moduli of 3.42 ± 0.02 kilometers per second and 149.0 ± 1.6 gigapascals (GPa) near the inner core boundary and 3.58 ± 0.02 kilometers per second and 167.4 ± 1.6 GPa in Earth’s center. The values are 2.5% lower than the widely used Preliminary Earth Reference Model. This provides new constraints on the dynamical interpretation of Earth’s inner core.
    Keywords: Geochemistry, Geophysics
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  • 58
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-26
    Keywords: Chemistry
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  • 59
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-02
    Description: Exploration of intermediates that enable chemoselective cycloaddition reactions and expeditious construction of fused- or bridged-ring systems is a continuous challenge for organic synthesis. As an intermediate of interest, the oxyallyl cation has been harnessed to synthesize architectures containing seven-membered rings via (4+3) cycloaddition. However, its potential to access five-membered skeletons is underdeveloped, largely due to the thermally forbidden (3+2) pathway. Here, the combination of a tailored precursor and a Pd(0) catalyst generates a Pd-oxyallyl intermediate that cyclizes with conjugated dienes to produce a diverse array of tetrahydrofuran skeletons. The cycloaddition overrides conventional (4+3) selectivity by proceeding through a stepwise pathway involving a Pd-allyl transfer and ring closure sequence. Subsequent treatment of the (3+2) adducts with a palladium catalyst converts the heterocycles to the carbocyclic cyclopentanones.
    Keywords: Chemistry
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  • 60
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-16
    Keywords: Chemistry
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  • 61
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-10
    Keywords: Chemistry
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  • 62
    Publication Date: 2018-08-10
    Description: Understanding the practical limitations of chemical reactions is critically important for efficiently planning the synthesis of compounds in pharmaceutical, agrochemical, and specialty chemical research and development. However, literature reports of the scope of new reactions are often cursory and biased toward successful results, severely limiting the ability to predict reaction outcomes for untested substrates. We herein illustrate strategies for carrying out large-scale surveys of chemical reactivity by using a material-sparing nanomole-scale automated synthesis platform with greatly expanded synthetic scope combined with ultrahigh-throughput matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry (MALDI-TOF MS).
    Keywords: Chemistry
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  • 63
    Publication Date: 2018-08-24
    Description: Researchers around the world have observed the formation of molecularly ordered structures of unknown origin on the surface of titanium dioxide (TiO 2 ) photocatalysts exposed to air and solution. Using a combination of atomic-scale microscopy and spectroscopy, we show that TiO 2 selectively adsorbs atmospheric carboxylic acids that are typically present in parts-per-billion concentrations while effectively repelling other adsorbates, such as alcohols, that are present in much higher concentrations. The high affinity of the surface for carboxylic acids is attributed to their bidentate binding. These self-assembled monolayers have the unusual property of being both hydrophobic and highly water-soluble, which may contribute to the self-cleaning properties of TiO 2 . This finding is relevant to TiO 2 photocatalysis, because the self-assembled carboxylate monolayers block the undercoordinated surface cation sites typically implicated in photocatalysis.
    Keywords: Chemistry
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  • 64
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-31
    Keywords: Chemistry
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  • 65
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-31
    Keywords: Chemistry
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  • 66
    Publication Date: 2018-08-31
    Description: The alkaline earth metals calcium (Ca), strontium (Sr), and barium (Ba) typically engage in chemical bonding as classical main-group elements through their n s and n p valence orbitals, where n is the principal quantum number. Here we report the isolation and spectroscopic characterization of eight-coordinate carbonyl complexes M(CO) 8 (where M = Ca, Sr, or Ba) in a low-temperature neon matrix. Analysis of the electronic structure of these cubic O h -symmetric complexes reveals that the metal–carbon monoxide (CO) bonds arise mainly from [M(d )] -〉 (CO) 8 backdonation, which explains the strong observed red shift of the C-O stretching frequencies. The corresponding radical cation complexes were also prepared in gas phase and characterized by mass-selected infrared photodissociation spectroscopy, confirming adherence to the 18-electron rule more conventionally associated with transition metal chemistry.
    Keywords: Chemistry
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  • 67
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-07
    Keywords: Chemistry
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  • 68
    Publication Date: 2018-09-07
    Description: Mystery surrounds the transition from gas-phase hydrocarbon precursors to terrestrial soot and interstellar dust, which are carbonaceous particles formed under similar conditions. Although polycyclic aromatic hydrocarbons (PAHs) are known precursors to high-temperature carbonaceous-particle formation, the molecular pathways that initiate particle formation are unknown. We present experimental and theoretical evidence for rapid molecular clustering–reaction pathways involving radicals with extended conjugation. These radicals react with other hydrocarbon species to form covalently bound complexes that promote further growth and clustering by regenerating resonance-stabilized radicals through low-barrier hydrogen-abstraction and hydrogen-ejection reactions. Such radical–chain reaction pathways may lead to covalently bound clusters of PAHs and other hydrocarbons that would otherwise be too small to condense at high temperatures, thus providing the key mechanistic steps for rapid particle formation and surface growth by hydrocarbon chemisorption.
    Keywords: Chemistry
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  • 69
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-14
    Keywords: Chemistry
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  • 70
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-20
    Keywords: Geochemistry, Geophysics
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  • 71
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-27
    Keywords: Chemistry
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  • 72
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-27
    Keywords: Chemistry
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  • 73
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-27
    Description: Basic heteroarenes are a ubiquitous feature of pharmaceuticals and bioactive molecules, and Minisci-type additions of radical nucleophiles are a leading method for their elaboration. Despite many Minisci-type protocols that result in the formation of stereocenters, exerting control over the absolute stereochemistry at these centers remains an unmet challenge. We report a process for addition of prochiral radicals, generated from amino acid derivatives, to pyridines and quinolines. Our method offers excellent control of both enantioselectivity and regioselectivity. An enantiopure chiral Brønsted acid catalyst serves both to activate the substrate and induce asymmetry, while an iridium photocatalyst mediates the required electron transfer processes. We anticipate that this method will expedite access to enantioenriched small-molecule building blocks bearing versatile basic heterocycles.
    Keywords: Chemistry
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  • 74
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-05-25
    Keywords: Chemistry
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  • 75
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-05-25
    Keywords: Chemistry
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  • 76
    Publication Date: 2018-10-26
    Description: Primary amines are essential constituents of biologically active molecules and versatile intermediates in the synthesis of drugs and agrochemicals. However, their preparation from easily accessible alkenes remains challenging. Here, we report a general strategy to access primary amines from alkenes through an operationally simple iron-catalyzed aminochlorination reaction. A stable hydroxylamine derivative and benign sodium chloride act as the respective nitrogen and chlorine sources. The reaction proceeds at room temperature under air; tolerates a large scope of aliphatic and conjugated alkenes, including densely functionalized substrates; and provides excellent anti-Markovnikov regioselectivity with respect to the amino group. The reactivity of the 2-chloroalkylamine products, an understudied class of amphoteric molecules, enables facile access to linear or branched aliphatic amines, aziridines, aminonitriles, azido amines, and homoallylic amines.
    Keywords: Chemistry
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  • 77
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-09
    Keywords: Chemistry
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  • 78
    Publication Date: 2018-11-09
    Description: Despite the enormous potential for the use of stereospecific cross-coupling reactions to rationally manipulate the three-dimensional structure of organic molecules, the factors that control the transfer of stereochemistry in these reactions remain poorly understood. Here we report a mechanistic and synthetic investigation into the use of enantioenriched alkylboron nucleophiles in stereospecific Pd-catalyzed Suzuki cross-coupling reactions. By developing a suite of molecular descriptors of phosphine ligands, we could apply predictive statistical models to select or design distinct ligands that respectively promoted stereoinvertive and stereoretentive cross-coupling reactions. Stereodefined branched structures were thereby accessed through the predictable manipulation of absolute stereochemistry, and a general model for the mechanism of alkylboron transmetallation was proposed.
    Keywords: Chemistry
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  • 79
    Publication Date: 2018-11-16
    Description: Heterobiaryls composed of pyridine and diazine rings are key components of pharmaceuticals and are often central to pharmacological function. We present an alternative approach to metal-catalyzed cross-coupling to make heterobiaryls using contractive phosphorus C–C couplings, also termed phosphorus ligand coupling reactions. The process starts by regioselective phosphorus substitution of the C–H bonds para to nitrogen in two successive heterocycles; ligand coupling is then triggered via acidic alcohol solutions to form the heterobiaryl bond. Mechanistic studies imply that ligand coupling is an asynchronous process involving migration of one heterocycle to the ipso position of the other around a central pentacoordinate P(V) atom. The strategy can be applied to complex drug-like molecules containing multiple reactive sites and polar functional groups, and also enables convergent coupling of drug fragments and late-stage heteroarylation of pharmaceuticals.
    Keywords: Chemistry
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  • 80
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-06
    Keywords: Chemistry
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  • 81
    Publication Date: 2018-07-06
    Description: Conical intersections play a critical role in excited-state dynamics of polyatomic molecules because they govern the reaction pathways of many nonadiabatic processes. However, ultrafast probes have lacked sufficient spatial resolution to image wave-packet trajectories through these intersections directly. Here, we present the simultaneous experimental characterization of one-photon and two-photon excitation channels in isolated CF 3 I molecules using ultrafast gas-phase electron diffraction. In the two-photon channel, we have mapped out the real-space trajectories of a coherent nuclear wave packet, which bifurcates onto two potential energy surfaces when passing through a conical intersection. In the one-photon channel, we have resolved excitation of both the umbrella and the breathing vibrational modes in the CF 3 fragment in multiple nuclear dimensions. These findings benchmark and validate ab initio nonadiabatic dynamics calculations.
    Keywords: Chemistry
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  • 82
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-13
    Keywords: Chemistry
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  • 83
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-13
    Keywords: Geochemistry, Geophysics
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  • 84
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-13
    Keywords: Geochemistry, Geophysics
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  • 85
    Publication Date: 2018-07-20
    Description: Atmospheric new particle formation (NPF) is an important global phenomenon that is nevertheless sensitive to ambient conditions. According to both observation and theoretical arguments, NPF usually requires a relatively high sulfuric acid (H 2 SO 4 ) concentration to promote the formation of new particles and a low preexisting aerosol loading to minimize the sink of new particles. We investigated NPF in Shanghai and were able to observe both precursor vapors (H 2 SO 4 ) and initial clusters at a molecular level in a megacity. High NPF rates were observed to coincide with several familiar markers suggestive of H 2 SO 4 –dimethylamine (DMA)–water (H 2 O) nucleation, including sulfuric acid dimers and H 2 SO 4 -DMA clusters. In a cluster kinetics simulation, the observed concentration of sulfuric acid was high enough to explain the particle growth to ~3 nanometers under the very high condensation sink, whereas the subsequent higher growth rate beyond this size is believed to result from the added contribution of condensing organic species. These findings will help in understanding urban NPF and its air quality and climate effects, as well as in formulating policies to mitigate secondary particle formation in China.
    Keywords: Geochemistry, Geophysics
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  • 86
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-22
    Keywords: Chemistry
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  • 87
    Publication Date: 2015-09-01
    Description: Glycerophospholipids, the structural components of cell membranes, have not been considered to be spatial cues for intercellular signaling because of their ubiquitous distribution. We identified lyso-phosphatidyl-beta-D-glucoside (LysoPtdGlc), a hydrophilic glycerophospholipid, and demonstrated its role in modality-specific repulsive guidance of spinal cord sensory axons. LysoPtdGlc is locally synthesized and released by radial glia in a patterned spatial distribution to regulate the targeting of nociceptive but not proprioceptive central axon projections. Library screening identified the G protein-coupled receptor GPR55 as a high-affinity receptor for LysoPtdGlc, and GPR55 deletion or LysoPtdGlc loss of function in vivo caused the misallocation of nociceptive axons into proprioceptive zones. These findings show that LysoPtdGlc/GPR55 is a lipid-based signaling system in glia-neuron communication for neural development.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Guy, Adam T -- Nagatsuka, Yasuko -- Ooashi, Noriko -- Inoue, Mariko -- Nakata, Asuka -- Greimel, Peter -- Inoue, Asuka -- Nabetani, Takuji -- Murayama, Akiho -- Ohta, Kunihiro -- Ito, Yukishige -- Aoki, Junken -- Hirabayashi, Yoshio -- Kamiguchi, Hiroyuki -- New York, N.Y. -- Science. 2015 Aug 28;349(6251):974-7. doi: 10.1126/science.aab3516.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. ; RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. Lipid Biology Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. ; Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Sendai, Miyagi 980-8578, Japan. Japan Science and Technology Agency, Precursory Research for Embryonic Science and Technology (PRESTO), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan. ; Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan. ; Synthetic Cellular Chemistry Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. ; Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Sendai, Miyagi 980-8578, Japan. Japan Agency for Medical Research and Development, Core Research for Evolutional Science and Technology (AMED-CREST), 1-7-1 Otemachi, Chiyoda, Tokyo 100-0004, Japan. ; RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. kamiguchi@brain.riken.jp hirabaya@riken.jp.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26315437" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Axons/*physiology ; Chick Embryo ; Coculture Techniques ; Ganglia, Spinal/*cytology/physiology ; Gene Knockout Techniques ; Glycerophospholipids/analysis/metabolism/*physiology ; Glycolipids/analysis/*physiology ; Mice ; Nerve Growth Factor/pharmacology ; Neuroglia/*physiology ; Nociceptors/*physiology ; Receptor, trkA/metabolism ; Receptor, trkC/metabolism ; Receptors, Cannabinoid/genetics/*physiology ; Spinal Cord/*cytology/*embryology ; Tissue Culture Techniques
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  • 88
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2015-02-14
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kloor, Keith -- New York, N.Y. -- Science. 2015 Feb 13;347(6223):699. doi: 10.1126/science.347.6223.699.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25678635" target="_blank"〉PubMed〈/a〉
    Keywords: *Access to Information ; Agriculture/*legislation & jurisprudence ; Biotechnology/*legislation & jurisprudence ; Commerce ; Food Labeling/*legislation & jurisprudence ; Food, Genetically Modified/*adverse effects ; Humans ; Research Personnel ; United States ; Universities
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  • 89
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2015-12-15
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Reczek, Colleen R -- Chandel, Navdeep S -- New York, N.Y. -- Science. 2015 Dec 11;350(6266):1317-8. doi: 10.1126/science.aad8671.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Medicine and Robert H. Lurie Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA. ; Department of Medicine and Robert H. Lurie Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA. nav@northwestern.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26659042" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Ascorbic Acid/*therapeutic use ; Colorectal Neoplasms/*drug therapy/*genetics ; Female ; Humans ; Proto-Oncogene Proteins/*genetics ; Proto-Oncogene Proteins B-raf/*genetics ; ras Proteins/*genetics
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  • 90
    Publication Date: 2015-02-28
    Description: Double-stranded RNAs (dsRNAs) targeted against essential genes can trigger a lethal RNA interference (RNAi) response in insect pests. The application of this concept in plant protection is hampered by the presence of an endogenous plant RNAi pathway that processes dsRNAs into short interfering RNAs. We found that long dsRNAs can be stably produced in chloroplasts, a cellular compartment that appears to lack an RNAi machinery. When expressed from the chloroplast genome, dsRNAs accumulated to as much as 0.4% of the total cellular RNA. Transplastomic potato plants producing dsRNAs targeted against the beta-actin gene of the Colorado potato beetle, a notorious agricultural pest, were protected from herbivory and were lethal to its larvae. Thus, chloroplast expression of long dsRNAs can provide crop protection without chemical pesticides.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhang, Jiang -- Khan, Sher Afzal -- Hasse, Claudia -- Ruf, Stephanie -- Heckel, David G -- Bock, Ralph -- New York, N.Y. -- Science. 2015 Feb 27;347(6225):991-4. doi: 10.1126/science.1261680.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max-Planck-Institut fur Molekulare Pflanzenphysiologie, D-14476 Potsdam-Golm, Germany. ; Max-Planck-Institut fur Chemische Okologie, D-07745 Jena, Germany. ; Max-Planck-Institut fur Molekulare Pflanzenphysiologie, D-14476 Potsdam-Golm, Germany. rbock@mpimp-golm.mpg.de.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25722411" target="_blank"〉PubMed〈/a〉
    Keywords: Actins/*antagonists & inhibitors/genetics ; Animals ; Beetles/*genetics/pathogenicity ; Crops, Agricultural/genetics/*parasitology ; Genetic Vectors ; Pest Control, Biological/*methods ; Plant Leaves/genetics/parasitology ; Plastids/*genetics ; *RNA Interference ; RNA, Double-Stranded/*genetics ; RNA, Small Interfering/*genetics/metabolism ; Solanum tuberosum/genetics/*parasitology ; Transformation, Genetic
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  • 91
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2015-04-18
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bernstein, Rachel -- New York, N.Y. -- Science. 2015 Apr 17;348(6232):269. doi: 10.1126/science.348.6232.269.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25883332" target="_blank"〉PubMed〈/a〉
    Keywords: Engineering/*education/manpower ; Faculty/*statistics & numerical data ; Female ; Humans ; Male ; Mathematics/*education/manpower ; Science/*education/manpower ; Sex Factors ; Technology/*education/manpower ; United States ; Women, Working/*statistics & numerical data
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  • 92
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2015-03-21
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hackett, Perry -- Carroll, Dana -- P01 HD032652/HD/NICHD NIH HHS/ -- New York, N.Y. -- Science. 2015 Mar 20;347(6228):1324. doi: 10.1126/science.347.6228.1324.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Genetics, Cell Biology, and Development, Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA. hacke004@umn.edu. ; Department of Biochemistry, School of Medicine, University of Utah, Salt Lake City, UT 84112, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25792322" target="_blank"〉PubMed〈/a〉
    Keywords: Agriculture/*legislation & jurisprudence ; Animals ; *Government Regulation ; *Organisms, Genetically Modified ; United States
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  • 93
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2015-11-28
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dajani, Rana -- New York, N.Y. -- Science. 2015 Nov 27;350(6264):1043. doi: 10.1126/science.350.6264.1043-b.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology and Biotechnology, Hashemite University, Zarqa, Jordan. rdajani@hu.edu.jo.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26612944" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Art ; Equipment Reuse ; Fibroblasts ; Gloves, Protective ; Jordan ; Laboratories ; Mice ; Recycling/*methods ; United States
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  • 94
    Publication Date: 2015-11-14
    Description: The RNA-guided CRISPR-associated protein Cas9 is used for genome editing, transcriptional modulation, and live-cell imaging. Cas9-guide RNA complexes recognize and cleave double-stranded DNA sequences on the basis of 20-nucleotide RNA-DNA complementarity, but the mechanism of target searching in mammalian cells is unknown. Here, we use single-particle tracking to visualize diffusion and chromatin binding of Cas9 in living cells. We show that three-dimensional diffusion dominates Cas9 searching in vivo, and off-target binding events are, on average, short-lived (〈1 second). Searching is dependent on the local chromatin environment, with less sampling and slower movement within heterochromatin. These results reveal how the bacterial Cas9 protein interrogates mammalian genomes and navigates eukaryotic chromatin structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Knight, Spencer C -- Xie, Liangqi -- Deng, Wulan -- Guglielmi, Benjamin -- Witkowsky, Lea B -- Bosanac, Lana -- Zhang, Elisa T -- El Beheiry, Mohamed -- Masson, Jean-Baptiste -- Dahan, Maxime -- Liu, Zhe -- Doudna, Jennifer A -- Tjian, Robert -- Howard Hughes Medical Institute/ -- New York, N.Y. -- Science. 2015 Nov 13;350(6262):823-6. doi: 10.1126/science.aac6572.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of California, Berkeley, CA, USA. ; Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA. ; Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA. Transcriptional Imaging Consortium, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA. ; Laboratoire Physico-Chimie Curie, Institut Curie, Centre National de la Recherche Scientifique UMR 168, Paris, France. ; Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA. ; Transcriptional Imaging Consortium, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA. Laboratoire Physico-Chimie Curie, Institut Curie, Centre National de la Recherche Scientifique UMR 168, Paris, France. ; Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA. Transcriptional Imaging Consortium, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA. liuz11@janelia.hhmi.org doudna@berkeley.edu jmlim@berkeley.edu. ; Department of Chemistry, University of California, Berkeley, CA, USA. Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA. Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA. Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. Innovative Genomics Initiative, University of California, Berkeley, CA, USA. liuz11@janelia.hhmi.org doudna@berkeley.edu jmlim@berkeley.edu. ; Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA. Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA. Transcriptional Imaging Consortium, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA. Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA. Li Ka Shing Biomedical and Health Sciences Center, University of California, Berkeley, CA, USA. liuz11@janelia.hhmi.org doudna@berkeley.edu jmlim@berkeley.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26564855" target="_blank"〉PubMed〈/a〉
    Keywords: 3T3 Cells ; Animals ; Bacterial Proteins/chemistry/*metabolism ; *CRISPR-Cas Systems ; Chromatin/chemistry/*metabolism/ultrastructure ; Clustered Regularly Interspaced Short Palindromic Repeats ; *DNA Cleavage ; Endonucleases/chemistry/*metabolism ; *Genetic Engineering ; Genome ; Mice ; Single-Cell Analysis
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  • 95
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2015-02-07
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bernstein, Rachel -- New York, N.Y. -- Science. 2015 Feb 6;347(6222):686. doi: 10.1126/science.347.6222.686. Epub 2015 Feb 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Rachel Bernstein is a staf writer for Science Careers. For more on life and careers, visit www.sciencecareers.org. Send your story to SciCareerEditor@aaas.org.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25657252" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Evolution ; Birds ; *Career Choice ; Cooperative Behavior ; Neurobiology/*manpower
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  • 96
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2015-02-24
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dantzer, Ben -- New York, N.Y. -- Science. 2015 Feb 20;347(6224):822-3. doi: 10.1126/science.aaa6480.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Psychology and Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA. dantzer@umich.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25700499" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Biological Evolution ; *Competitive Behavior ; *Ecosystem ; Female ; Male ; *Maternal Behavior ; Songbirds/*physiology
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  • 97
    Publication Date: 2015-02-14
    Description: A new docodontan mammaliaform from the Middle Jurassic of China has skeletal features for climbing and dental characters indicative of an omnivorous diet that included plant sap. This fossil expands the range of known locomotor adaptations in docodontans to include climbing, in addition to digging and swimming. It further shows that some docodontans had a diet with a substantial herbivorous component, distinctive from the faunivorous diets previously reported in other members of this clade. This reveals a greater ecological diversity in an early mammaliaform clade at a more fundamental taxonomic level not only between major clades as previously thought.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Meng, Qing-Jin -- Ji, Qiang -- Zhang, Yu-Guang -- Liu, Di -- Grossnickle, David M -- Luo, Zhe-Xi -- New York, N.Y. -- Science. 2015 Feb 13;347(6223):764-8. doi: 10.1126/science.1260879.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Beijing Museum of Natural History, Beijing 100050 China. ; Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China. ; Committee on Evolutionary Biology, The University of Chicago, Chicago, IL 60637, USA. ; Committee on Evolutionary Biology, The University of Chicago, Chicago, IL 60637, USA. Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, IL 60637, USA. zxluo@uchicago.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25678661" target="_blank"〉PubMed〈/a〉
    Keywords: Animal Feed ; Animals ; *Biodiversity ; China ; Cuspid/anatomy & histology/immunology ; *Dentition ; Forelimb/anatomy & histology/growth & development ; *Herbivory ; Incisor/anatomy & histology/growth & development ; Mammals/anatomy & histology/*classification/*growth & development ; Mandible/anatomy & histology/growth & development ; Phylogeny
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  • 98
    Publication Date: 2015-05-23
    Description: Sex determination in the mosquito Aedes aegypti is governed by a dominant male-determining factor (M factor) located within a Y chromosome-like region called the M locus. Here, we show that an M-locus gene, Nix, functions as an M factor in A. aegypti. Nix exhibits persistent M linkage and early embryonic expression, two characteristics required of an M factor. Nix knockout with clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 resulted in largely feminized genetic males and the production of female isoforms of two key regulators of sexual differentiation: doublesex and fruitless. Ectopic expression of Nix resulted in genetic females with nearly complete male genitalia. Thus, Nix is both required and sufficient to initiate male development. This study provides a foundation for mosquito control strategies that convert female mosquitoes into harmless males.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hall, Andrew Brantley -- Basu, Sanjay -- Jiang, Xiaofang -- Qi, Yumin -- Timoshevskiy, Vladimir A -- Biedler, James K -- Sharakhova, Maria V -- Elahi, Rubayet -- Anderson, Michelle A E -- Chen, Xiao-Guang -- Sharakhov, Igor V -- Adelman, Zach N -- Tu, Zhijian -- AI113643/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 2015 Jun 12;348(6240):1268-70. doi: 10.1126/science.aaa2850. Epub 2015 May 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA. Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. ; Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. Department of Entomology, Virginia Tech, Blacksburg, VA, USA. ; Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. ; Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA. ; School of Public Health and Tropical Medicine, Southern Medical University, Guangdong, People's Republic of China. ; Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. Department of Entomology, Virginia Tech, Blacksburg, VA, USA. ; Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. Department of Entomology, Virginia Tech, Blacksburg, VA, USA. jaketu@vt.edu zachadel@vt.edu. ; Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA. Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. jaketu@vt.edu zachadel@vt.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25999371" target="_blank"〉PubMed〈/a〉
    Keywords: Aedes/*genetics/*growth & development ; Animals ; Caspase 9 ; Clustered Regularly Interspaced Short Palindromic Repeats ; Female ; Gene Knockout Techniques ; *Genes, Insect ; *Genetic Loci ; Male ; Molecular Sequence Data ; Mosquito Control/methods ; Sex Determination Processes/*genetics
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  • 99
    Publication Date: 2015-03-07
    Description: Human higher cognition is attributed to the evolutionary expansion and elaboration of the human cerebral cortex. However, the genetic mechanisms contributing to these developmental changes are poorly understood. We used comparative epigenetic profiling of human, rhesus macaque, and mouse corticogenesis to identify promoters and enhancers that have gained activity in humans. These gains are significantly enriched in modules of coexpressed genes in the cortex that function in neuronal proliferation, migration, and cortical-map organization. Gain-enriched modules also showed correlated gene expression patterns and similar transcription factor binding site enrichments in promoters and enhancers, suggesting that they are connected by common regulatory mechanisms. Our results reveal coordinated patterns of potential regulatory changes associated with conserved developmental processes during corticogenesis, providing insight into human cortical evolution.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4426903/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4426903/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Reilly, Steven K -- Yin, Jun -- Ayoub, Albert E -- Emera, Deena -- Leng, Jing -- Cotney, Justin -- Sarro, Richard -- Rakic, Pasko -- Noonan, James P -- 099175/Z/12/Z/Wellcome Trust/United Kingdom -- DA023999/DA/NIDA NIH HHS/ -- F32 GM106628/GM/NIGMS NIH HHS/ -- GM094780/GM/NIGMS NIH HHS/ -- NS014841/NS/NINDS NIH HHS/ -- P30 CA016359/CA/NCI NIH HHS/ -- R01 DA023999/DA/NIDA NIH HHS/ -- R01 GM094780/GM/NIGMS NIH HHS/ -- T32 GM007223/GM/NIGMS NIH HHS/ -- Medical Research Council/United Kingdom -- New York, N.Y. -- Science. 2015 Mar 6;347(6226):1155-9. doi: 10.1126/science.1260943.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Genetics, Yale School of Medicine, New Haven, CT 06510, USA. ; Kavli Institute for Neuroscience, Yale School of Medicine, New Haven, CT 06510, USA. Department of Neurobiology, Yale School of Medicine, New Haven, CT 06510, USA. ; Department of Genetics, Yale School of Medicine, New Haven, CT 06510, USA. Program in Computational Biology and Bioinformatics, Yale University, New Haven, CT 06511, USA. ; Department of Genetics, Yale School of Medicine, New Haven, CT 06510, USA. Kavli Institute for Neuroscience, Yale School of Medicine, New Haven, CT 06510, USA. Program in Computational Biology and Bioinformatics, Yale University, New Haven, CT 06511, USA. james.noonan@yale.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25745175" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cerebral Cortex/*growth & development ; Enhancer Elements, Genetic/*genetics ; *Epigenesis, Genetic ; *Evolution, Molecular ; *Gene Expression Regulation, Developmental ; Humans ; Macaca mulatta ; Mice ; Organogenesis/*genetics ; Promoter Regions, Genetic/*genetics ; Rats
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 100
    Publication Date: 2015-08-22
    Description: Paradigms of sustainable exploitation focus on population dynamics of prey and yields to humanity but ignore the behavior of humans as predators. We compared patterns of predation by contemporary hunters and fishers with those of other predators that compete over shared prey (terrestrial mammals and marine fishes). Our global survey (2125 estimates of annual finite exploitation rate) revealed that humans kill adult prey, the reproductive capital of populations, at much higher median rates than other predators (up to 14 times higher), with particularly intense exploitation of terrestrial carnivores and fishes. Given this competitive dominance, impacts on predators, and other unique predatory behavior, we suggest that humans function as an unsustainable "super predator," which-unless additionally constrained by managers-will continue to alter ecological and evolutionary processes globally.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Darimont, Chris T -- Fox, Caroline H -- Bryan, Heather M -- Reimchen, Thomas E -- New York, N.Y. -- Science. 2015 Aug 21;349(6250):858-60. doi: 10.1126/science.aac4249.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geography, University of Victoria, Post Office Box 1700, Station CSC, Victoria, British Columbia V8W 2Y2, Canada. Raincoast Conservation Foundation, Post Office Box 2429, Sidney, British Columbia V8L 3Y3, Canada. Hakai Institute, Post Office Box 309, Heriot Bay, British Columbia V0P 1H0, Canada. darimont@uvic.ca. ; Department of Geography, University of Victoria, Post Office Box 1700, Station CSC, Victoria, British Columbia V8W 2Y2, Canada. Raincoast Conservation Foundation, Post Office Box 2429, Sidney, British Columbia V8L 3Y3, Canada. ; Department of Geography, University of Victoria, Post Office Box 1700, Station CSC, Victoria, British Columbia V8W 2Y2, Canada. Raincoast Conservation Foundation, Post Office Box 2429, Sidney, British Columbia V8L 3Y3, Canada. Hakai Institute, Post Office Box 309, Heriot Bay, British Columbia V0P 1H0, Canada. ; Department of Biology, University of Victoria, Post Office Box 3060, Station CSC, Victoria, British Columbia V8W 2Y2, Canada.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26293961" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Evolution ; *Consumer Behavior ; Ecology ; Fishes ; Humans ; Mammals/psychology ; Population Dynamics ; *Predatory Behavior ; Reproduction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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