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  • American Association for the Advancement of Science (AAAS)  (13)
  • Geological Society of America (GSA)  (3)
  • 1
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    Viruses mobilize plant immunity to deter nonvector insect herbivores (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉A parasite-infected host may promote performance of associated insect vectors; but possible parasite effects on nonvector insects have been largely unexplored. Here, we show that 〈i〉Begomovirus〈/i〉, the largest genus of plant viruses and transmitted exclusively by whitefly, reprogram plant immunity to promote the fitness of the vector and suppress performance of nonvector insects (i.e., cotton bollworm and aphid). Infected plants accumulated begomoviral βC1 proteins in the phloem where they were bound to the plant transcription factor WRKY20. This viral hijacking of WRKY20 spatiotemporally redeployed plant chemical immunity within the leaf and had the asymmetrical benefiting effects on the begomoviruses and its whitefly vectors while negatively affecting two nonvector competitors. This type of interaction between a parasite and two types of herbivores, i.e., vectors and nonvectors, occurs widely in various natural and agricultural ecosystems; thus, our results have broad implications for the ecological significance of parasite-vector-host tripartite interactions.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Rovibrational quantum state resolution of the C60 fullerene (2019)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2019
    Description: 〈p〉The unique physical properties of buckminsterfullerene, C〈sub〉60〈/sub〉, have attracted intense research activity since its original discovery. Total quantum state–resolved spectroscopy of isolated C〈sub〉60〈/sub〉 molecules has been of particularly long-standing interest. Such observations have, to date, been unsuccessful owing to the difficulty in preparing cold, gas-phase C〈sub〉60〈/sub〉 in sufficiently high densities. Here we report high-resolution infrared absorption spectroscopy of C〈sub〉60〈/sub〉 in the 8.5-micron spectral region (1180 to 1190 wave number). A combination of cryogenic buffer-gas cooling and cavity-enhanced direct frequency comb spectroscopy has enabled the observation of quantum state–resolved rovibrational transitions. Characteristic nuclear spin statistical intensity patterns confirm the indistinguishability of the 60 carbon-12 atoms, while rovibrational fine structure encodes further details of the molecule’s rare icosahedral symmetry.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Towards a clarification of the provenance of Cenozoic sediments in the northern Qaidam Basin (2018)
    Geological Society of America (GSA)
    Details
    Publication Date: 2018
    Description: 〈span〉Determining the provenance of sedimentary basin fill in the northern Qaidam Basin is a key step toward understanding the sedimentary system dynamics and mountain-building processes of the surrounding orogenic belts in Tibet. The exceptionally thick (average of 6–8 km) Cenozoic fluvio-lacustrine deposits in the northern Qaidam Basin were once thought to have been eroded from the nearby northern Qaidam Basin margin and the southern Qilian Shan and to reflect the prolonged thrust-related exhumation of these orogenic belts. However, several recent studies, based mainly on paleocurrent and detrital zircon U-Pb age data, suggested that they were derived from the distant East Kunlun Shan to the south, or the Qimen Tagh to the southwest (at least 200 and 350 km from the northern Qaidam Basin, respectively). That model assumed that the East Kunlun Shan and Qimen Tagh formed significant topographic barriers during the earliest sedimentation of Cenozoic strata (e.g., the Lulehe Formation) in the northern Qaidam Basin. Therefore, the tectonic significance of the provenance of the Lulehe Formation remains a fundamental problem in understanding the postcollisional uplift history of the northern Tibetan Plateau. To address this issue, we conducted sedimentological and paleocurrent analyses of the Lulehe Formation and detrital zircon U-Pb dating of Mesozoic strata in the northern Qaidam Basin. The results, in combination with existing paleocurrent and seismic reflection data, collectively indicate that although the source area cannot be specified by matching zircon U-Pb ages in sedimentary rocks with crystalline basement source rocks, other evidence points consistently to a unified proximal northerly source area (the northern Qaidam Basin margin and the southern Qilian Shan). Our results emphasize that noncrystalline basement rocks (e.g., Mesozoic sedimentary rocks) in fold-and-thrust belts should be taken into consideration when seeking potential source areas by correlating zircon U-Pb ages of siliciclastic detritus with related basement rocks. In addition, this study strongly supports the claim that variations in the proportions of age populations should be used with caution when determining source terrane by comparisons of age distributions.〈/span〉
    Print ISSN: 1941-8264
    Electronic ISSN: 1947-4253
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 4
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    Structural insights into the EGO-TC-mediated membrane tethering of the TORC1-regulatory Rag GTPases (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉The Rag/Gtr GTPases serve as a central module in the nutrient-sensing signaling network upstream of TORC1. In yeast, the anchoring of Gtr1-Gtr2 to membranes depends on the Ego1-Ego2-Ego3 ternary complex (EGO-TC), resulting in an EGO-TC-Gtr1-Gtr2 complex (EGOC). EGO-TC and human Ragulator share no obvious sequence similarities and also differ in their composition with respect to the number of known subunits, which raises the question of how the EGO-TC fulfills its function in recruiting Gtr1-Gtr2. Here, we report the structure of EGOC, in which Ego1 wraps around Ego2, Ego3, and Gtr1-Gtr2. In addition, Ego3 interacts with Gtr1-Gtr2 to stabilize the complex. The functional roles of key residues involved in the assembly are validated by in vivo assays. Our structural and functional data combined demonstrate that EGOC and Ragulator-Rag complex are structurally conserved and that EGO-TC is essential and sufficient to recruit Gtr1-Gtr2 to membranes to ensure appropriate TORC1 signaling.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Towards a clarification of the provenance of Cenozoic sediments in the northern Qaidam Basin (2018)
    Geological Society of America (GSA)
    Details
    Publication Date: 2018
    Description: 〈span〉〈div〉Abstract〈/div〉Determining the provenance of sedimentary basin fill in the northern Qaidam Basin is a key step toward understanding the sedimentary system dynamics and mountain-building processes of the surrounding orogenic belts in Tibet. The exceptionally thick (average of 6–8 km) Cenozoic fluvio-lacustrine deposits in the northern Qaidam Basin were once thought to have been eroded from the nearby northern Qaidam Basin margin and the southern Qilian Shan and to reflect the prolonged thrust-related exhumation of these orogenic belts. However, several recent studies, based mainly on paleocurrent and detrital zircon U-Pb age data, suggested that they were derived from the distant East Kunlun Shan to the south, or the Qimen Tagh to the southwest (at least 200 and 350 km from the northern Qaidam Basin, respectively). That model assumed that the East Kunlun Shan and Qimen Tagh formed significant topographic barriers during the earliest sedimentation of Cenozoic strata (e.g., the Lulehe Formation) in the northern Qaidam Basin. Therefore, the tectonic significance of the provenance of the Lulehe Formation remains a fundamental problem in understanding the postcollisional uplift history of the northern Tibetan Plateau. To address this issue, we conducted sedimentological and paleocurrent analyses of the Lulehe Formation and detrital zircon U-Pb dating of Mesozoic strata in the northern Qaidam Basin. The results, in combination with existing paleocurrent and seismic reflection data, collectively indicate that although the source area cannot be specified by matching zircon U-Pb ages in sedimentary rocks with crystalline basement source rocks, other evidence points consistently to a unified proximal northerly source area (the northern Qaidam Basin margin and the southern Qilian Shan). Our results emphasize that noncrystalline basement rocks (e.g., Mesozoic sedimentary rocks) in fold-and-thrust belts should be taken into consideration when seeking potential source areas by correlating zircon U-Pb ages of siliciclastic detritus with related basement rocks. In addition, this study strongly supports the claim that variations in the proportions of age populations should be used with caution when determining source terrane by comparisons of age distributions.〈/span〉
    Print ISSN: 1941-8264
    Electronic ISSN: 1947-4253
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 6
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    A degenerate Fermi gas of polar molecules (2019)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2019
    Description: 〈p〉Experimental realization of a quantum degenerate gas of molecules would provide access to a wide range of phenomena in molecular and quantum sciences. However, the very complexity that makes ultracold molecules so enticing has made reaching degeneracy an outstanding experimental challenge over the past decade. We now report the production of a degenerate Fermi gas of ultracold polar molecules of potassium-rubidium. Through coherent adiabatic association in a deeply degenerate mixture of a rubidium Bose-Einstein condensate and a potassium Fermi gas, we produce molecules at temperatures below 0.3 times the Fermi temperature. We explore the properties of this reactive gas and demonstrate how degeneracy suppresses chemical reactions, making a long-lived degenerate gas of polar molecules a reality.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    A degenerate Fermi gas of polar molecules (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉Experimental realization of a quantum degenerate gas of molecules would provide access to a wide range of phenomena in molecular and quantum sciences. However, the very complexity that makes ultracold molecules so enticing has made reaching degeneracy an outstanding experimental challenge over the past decade. We now report the production of a degenerate Fermi gas of ultracold polar molecules of potassium–rubidium (KRb). Through coherent adiabatic association in a deeply degenerate mixture of a rubidium Bose-Einstein condensate and a potassium Fermi gas, we produce molecules at temperatures below 0.3 times the Fermi temperature. We explore the properties of this reactive gas and demonstrate how degeneracy suppresses chemical reactions, making a long-lived degenerate gas of polar molecules a reality.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Cold molecules: Progress in quantum engineering of chemistry and quantum matter (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-09-08
    Description: Cooling atoms to ultralow temperatures has produced a wealth of opportunities in fundamental physics, precision metrology, and quantum science. The more recent application of sophisticated cooling techniques to molecules, which has been more challenging to implement owing to the complexity of molecular structures, has now opened the door to the longstanding goal of precisely controlling molecular internal and external degrees of freedom and the resulting interaction processes. This line of research can leverage fundamental insights into how molecules interact and evolve to enable the control of reaction chemistry and the design and realization of a range of advanced quantum materials.
    Keywords: Physics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    A Fermi-degenerate three-dimensional optical lattice clock (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-10-06
    Description: Strontium optical lattice clocks have the potential to simultaneously interrogate millions of atoms with a high spectroscopic quality factor of 4 x 10 17 . Previously, atomic interactions have forced a compromise between clock stability, which benefits from a large number of atoms, and accuracy, which suffers from density-dependent frequency shifts. Here we demonstrate a scalable solution that takes advantage of the high, correlated density of a degenerate Fermi gas in a three-dimensional (3D) optical lattice to guard against on-site interaction shifts. We show that contact interactions are resolved so that their contribution to clock shifts is orders of magnitude lower than in previous experiments. A synchronous clock comparison between two regions of the 3D lattice yields a measurement precision of 5 x 10 –19 in 1 hour of averaging time.
    Keywords: Physics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 10
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    The histone demethylase KDM6B regulates temperature-dependent sex determination in a turtle species (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2018-05-11
    Description: Temperature-dependent sex determination is a notable model of phenotypic plasticity. In many reptiles, including the red-eared slider turtle Trachemys scripta elegans ( T. scripta ), the individual’s sex is determined by the ambient temperature during egg incubation. In this study, we show that the histone H3 lysine 27 (H3K27) demethylase KDM6B exhibits temperature-dependent sexually dimorphic expression in early T. scripta embryos before the gonad is distinct. Knockdown of Kdm6b at 26°C (a temperature at which all offspring develop into males) triggers male-to-female sex reversal in 〉80% of surviving embryos. KDM6B directly promotes the transcription of the male sex-determining gene Dmrt1 by eliminating the trimethylation of H3K27 near its promoter. Additionally, overexpression of Dmrt1 is sufficient to rescue the sex reversal induced by disruption of Kdm6b . This study establishes causality and a direct genetic link between epigenetic mechanisms and temperature-dependent sex determination in a turtle species.
    Keywords: Development, Genetics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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