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  1. Abstract

    Quantifying how grain size and/or deviatoric stress impact (Mg,Fe)2SiO4phase stability is critical for advancing our understanding of subduction processes and deep-focus earthquakes. Here, we demonstrate that well-resolved X-ray diffraction patterns can be obtained on nano-grained thin films within laser-heated diamond anvil cells (DACs) at hydrostatic pressures up to 24 GPa and temperatures up to 2300 K. Combined with well-established literature processes for tuning thin film grain size, biaxial stress, and substrate identity, these results suggest that DAC-loaded thin films can be useful for determining how grain size, deviatoric stress, and/or the coexistence of other phases influence high-pressure phase stability. As such, this novel DAC-loaded thin film approach may find use in a variety of earth science, planetary science, solid-state physics, and materials science applications.

     
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  2. Eclogite bodies exposed across Tibet record a history of subduction-collision events that preceded growth of the Tibetan Plateau. Deciphering the time-space patterns of eclogite generation improves our knowledge of the preconditions for Cenozoic orogeny in Tibet and broader eclogite formation and/or exhumation processes. Here we report the discovery of Permo-Triassic eclogite in northern Tibet. U-Pb zircon dating and thermobarometry suggest eclogite-facies metamorphism at ca. 262–240 Ma at peak pressures of ∼2.5 GPa. Inherited zircons and geochemistry show the eclogite was derived from an upper-plate continental protolith, which must have experienced subduction erosion to transport the protolith mafic bodies to eclogite-forming conditions. The Dabie eclogites to the east experienced a similar history, and we interpret that these two coeval eclogite exposures formed by subduction erosion of the upper plate and deep trench burial along the same ∼3000-km-long north-dipping Permo-Triassic subduction complex. We interpret the synchroneity of eclogitization along the strike length of the subduction zone to have been driven by accelerated plate convergence due to ca. 260 Ma Emeishan plume impingement. 
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    Free, publicly-accessible full text available June 28, 2024
  3. ABSTRACT

    We report on the case of optical periodic modulation discovered in two Active Galactic Nuclei (AGN) and one candidate AGN. Analysing the archival optical data obtained from large transient surveys, namely the Catalina Real-Transient Survey (CRTS) and the Zwicky Transient Facility (ZTF), we find periodicities of 2169.7, 2103.1, and 1462.6 d in sources J0122 + 1032, J1007 + 1248 (or PG 1004 + 1248), and J2131 − 1127, respectively. The optical spectra of the first two indicate that the first is likely a blazar and the second a type 1 Seyfert galaxy, and while no spectroscopic information is available for the third one, its overall properties suggest that it is likely an AGN. In addition, mid-infrared (MIR) light-curve data of the three sources, taken by the Wide-field Infrared Survey Explorer (WISE), are also analysed. The light curves show significant variations, but not appearing related to the optical periodicities. Based on the widely discussed supermassive black hole binary (SMBHB) scenario, we discuss the origin of the optical modulation. Two possible interesting features, an additional 162-d short optical periodicity in J2131 − 1127 and the consistency of the X-ray flux variations of J1007 + 1248 with its optical periodicity, are also discussed within the SMBHB scenario.

     
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  4. This Energy Focus article summarizes the topics presented at the Nanomaterials and Sustainability Workshop held on May 4th, 2023 as part of the annual Advanced Photon Source/Center for Nanoscale Materials Users Meeting. Nanomaterials with novel properties and phenomena offer tremendous opportunities for sustainable technologies that address critical environmental and energy applications. The large variation that is possible for nanomaterials across composition, dimension, size and geometry aids in the range of properties and applications that can conceivably be addressed. However, in order to have maximum impact, earth abundance of materials must be considered and scalable manufacturing technologies must be developed. The opportunities discussed at the workshop are organized into topical areas of Nanostructured Materials for Sustainable Energy Solutions; Nano-bio Hybrid Materials for Energy and CO2 Reduction; and Sustainable Manufacturing at the Nanoscale. 
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    Free, publicly-accessible full text available August 1, 2024
  5. Abstract We explore terrestrial planet formation with a focus on the supply of solid-state organics as the main source of volatile carbon. For the water-poor Earth, the water ice line, or ice sublimation front, within the planet-forming disk has long been a key focal point. We posit that the soot line, the location where solid-state organics are irreversibly destroyed, is also a key location within the disk. The soot line is closer to the host star than the water snow line and overlaps with the location of the majority of detected exoplanets. In this work, we explore the ultimate atmospheric composition of a body that receives a major portion of its materials from the zone between the soot line and water ice line. We model a silicate-rich world with 0.1% and 1% carbon by mass with variable water content. We show that as a result of geochemical equilibrium, the mantle of these planets would be rich in reduced carbon but have relatively low water (hydrogen) content. Outgassing would naturally yield the ingredients for haze production when exposed to stellar UV photons in the upper atmosphere. Obscuring atmospheric hazes appear common in the exoplanetary inventory based on the presence of often featureless transmission spectra. Such hazes may be powered by the high volatile content of the underlying silicate-dominated mantle. Although this type of planet has no solar system counterpart, it should be common in the galaxy with potential impact on habitability. 
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  6. In this study, the first highly chemoselective amidation of Boc and amide groups of N -R- N -Boc arylamides is advanced. This practical and operationally-simple method enables the preparation of either N -aroylureas or imides in good to excellent yields without addition of transition metals. The choice of base plays a significant role in controlling the reactivity of the inequivalent carbonyl groups. The amidation of the Boc group was observed with arylamides, ArCONH 2 , when subjected to KO t Bu while imides were produced with LiOH. DFT studies are employed to explore the divergent mechanisms. It is anticipated that these chemoselective methods will be of interest to the synthetic and medicinal chemistry communities. 
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    Free, publicly-accessible full text available April 11, 2024