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  • American Association for the Advancement of Science (AAAS)  (12)
  • Geological Society of America (GSA)
  • 1
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    Self-assembly of highly efficient, broadband plasmonic absorbers for solar steam generation (2016)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2016-04-10
    Description: The study of ideal absorbers, which can efficiently absorb light over a broad range of wavelengths, is of fundamental importance, as well as critical for many applications from solar steam generation and thermophotovoltaics to light/thermal detectors. As a result of recent advances in plasmonics, plasmonic absorbers have attracted a lot of attention. However, the performance and scalability of these absorbers, predominantly fabricated by the top-down approach, need to be further improved to enable widespread applications. We report a plasmonic absorber which can enable an average measured absorbance of ~99% across the wavelengths from 400 nm to 10 μm, the most efficient and broadband plasmonic absorber reported to date. The absorber is fabricated through self-assembly of metallic nanoparticles onto a nanoporous template by a one-step deposition process. Because of its efficient light absorption, strong field enhancement, and porous structures, which together enable not only efficient solar absorption but also significant local heating and continuous stream flow, plasmonic absorber–based solar steam generation has over 90% efficiency under solar irradiation of only 4-sun intensity (4 kW m –2 ). The pronounced light absorption effect coupled with the high-throughput self-assembly process could lead toward large-scale manufacturing of other nanophotonic structures and devices.
    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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    Stabilizing halide perovskite surfaces for solar cell operation with wide-bandgap lead oxysalts (2019)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2019
    Description: 〈p〉We show that converting the surfaces of lead halide perovskite to water-insoluble lead (II) oxysalt through reaction with sulfate or phosphate ions can effectively stabilize the perovskite surface and bulk material. These capping lead oxysalt thin layers enhance the water resistance of the perovskite films by forming strong chemical bonds. The wide-bandgap lead oxysalt layers also reduce the defect density on the perovskite surfaces by passivating undercoordinated surface lead centers, which are defect-nucleating sites. Formation of the lead oxysalt layer increases the carrier recombination lifetime and boosts the efficiency of the solar cells to 21.1%. Encapsulated devices stabilized by the lead oxysalt layers maintain 96.8% of their initial efficiency after operation at maximum power point under simulated air mass (AM) 1.5 G irradiation for 1200 hours at 65°C.〈/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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    Application of hydroxyapatite nanoparticles in tumor-associated bone segmental defect (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉Hydroxyapatite (HA) has been widely applied in bone repair because of its superior biocompatibility. Recently, a proliferation-suppressive effect of HA nanoparticles (n-HA) against various cancer cells was reported. This study was aimed at assessing the translational value of n-HA both as a bone-regenerating material and as an antitumor agent. Inhibition of tumor growth, prevention of metastasis, and enhancement of the survival rate of tumor-bearing rabbits treated with n-HA were demonstrated. Activated mitochondrial-dependent apoptosis in vivo was confirmed, and we observed that a stimulated immune response was involved in the n-HA–induced antitumor effect. A porous titanium scaffold loaded with n-HA was fabricated and implanted into a critical-sized segmental bone defect in a rabbit tumor model. The n-HA–releasing scaffold not only showed a prominent effect in suppressing tumor growth and osteolytic lesion but also promoted bone regeneration. These findings provide a rationale for using n-HA in tumor-associated bone segmental defects.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    T cell stemness and dysfunction in tumors are triggered by a common mechanism (2019)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2019
    Description: 〈p〉A paradox of tumor immunology is that tumor-infiltrating lymphocytes are dysfunctional in situ, yet are capable of stem cell–like behavior including self-renewal, expansion, and multipotency, resulting in the eradication of large metastatic tumors. We find that the overabundance of potassium in the tumor microenvironment underlies this dichotomy, triggering suppression of T cell effector function while preserving stemness. High levels of extracellular potassium constrain T cell effector programs by limiting nutrient uptake, thereby inducing autophagy and reduction of histone acetylation at effector and exhaustion loci, which in turn produces CD8〈sup〉+〈/sup〉 T cells with improved in vivo persistence, multipotency, and tumor clearance. This mechanistic knowledge advances our understanding of T cell dysfunction and may lead to novel approaches that enable the development of enhanced T cell strategies for cancer immunotherapy.〈/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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  • 5
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    Human impact overwhelms long-term climate control of weathering and erosion in southwest China (2015)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2015-04-25
    Description: During the Holocene there has been a gradual increase in the influence of humans on Earth systems. High-resolution sedimentary records can help us to assess how erosion and weathering have evolved in response to recent climatic and anthropogenic disturbances. Here we present data from a high-resolution (~75 cm/k.y.) sedimentary archive from the South China Sea. Provenance data indicate that the sediment was derived from the Red River, and can be used to reconstruct the erosion and/or weathering history in this river basin. Accelerator mass spectrometry 14 C dating provides direct age control and reveals coherent variations in clay mineralogy, geochemistry, and terrigenous flux, indicative of strong chemical weathering and physical erosion during the mid-Holocene warm period (6400–4000 cal [calibrated] yr B.P.), followed by weakening from ca. 4000–1800 cal yr B.P., and renewed intensification since 1800 cal yr B.P.. Comparison with climatic records from China indicates that precipitation and temperature controlled both physical erosion and chemical weathering intensity before 1800 cal yr B.P.. However, weathering proxies in the offshore sediment indicate recent increased soil erosion. We suggest that enhanced human activity (deforestation, cultivation, and mining) since the end of the Chinese Han Dynasty (220 CE) has overwhelmed the natural climatic controls on erosion in the Red River.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 6
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    High-speed black phosphorus field-effect transistors approaching ballistic limit (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉As a strong candidate for future electronics, atomically thin black phosphorus (BP) has attracted great attention in recent years because of its tunable bandgap and high carrier mobility. Here, we show that the transport properties of BP device under high electric field can be improved greatly by the interface engineering of high-quality HfLaO dielectrics and transport orientation. By designing the device channels along the lower effective mass armchair direction, a record-high drive current up to 1.2 mA/μm at 300 K and 1.6 mA/μm at 20 K can be achieved in a 100-nm back-gated BP transistor, surpassing any two-dimensional semiconductor transistors reported to date. The highest hole saturation velocity of 1.5 x 10〈sup〉7〈/sup〉 cm/s is also achieved at room temperature. Ballistic transport shows a record-high 36 and 79% ballistic efficiency at room temperature and 20 K, respectively, which is also further verified by theoretical simulations.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Bioinspired polymeric woods (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018-08-11
    Description: Woods provide bioinspiration for engineering materials due to their superior mechanical performance. We demonstrate a novel strategy for large-scale fabrication of a family of bioinspired polymeric woods with similar polyphenol matrix materials, wood-like cellular microstructures, and outstanding comprehensive performance by a self-assembly and thermocuring process of traditional resins. In contrast to natural woods, polymeric woods demonstrate comparable mechanical properties (a compressive yield strength of up to 45 MPa), preferable corrosion resistance to acid with no decrease in mechanical properties, and much better thermal insulation (as low as ~21 mW m –1 K –1 ) and fire retardancy. These bioinspired polymeric woods even stand out from other engineering materials such as cellular ceramic materials and aerogel-like materials in terms of specific strength and thermal insulation properties. The present strategy provides a new possibility for mass production of a series of high-performance biomimetic engineering materials with hierarchical cellular microstructures and remarkable multifunctionality.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Centennial-scale dynamics of the Southern Hemisphere Westerly Winds across the Drake Passage over the past two millennia (2018)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2018
    Description: 〈span〉〈div〉Abstract〈/div〉The Southern Hemisphere Westerly Winds (SHWW) exert important controls on regional and global climate. Instrumental and reanalysis records indicate strengthening and poleward contraction of the SHWW belt since the late twentieth century. Such changes also have implications for Southern Ocean upwelling and CO〈sub〉2〈/sub〉 degassing. Therefore, a better understanding of the long-term SHWW behaviors and dynamics beyond recent decades is critical for projecting future changes. Here, we applied isotope analysis of 〈span〉Sphagnum〈/span〉 moss cellulose from a peat bog in southernmost Patagonia (∼54°S) to reconstruct changes in oxygen isotope composition of precipitation (δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉) that could elucidate past shifts in moisture sources and trajectories. We interpreted the positive shifts in δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉 to indicate weaker SHWW and, importantly, more frequent easterly flows that enhance moisture supply sourced from the Atlantic Ocean. In contrast, negative shifts in δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉 indicate stronger SHWW and intensification of the Andean rain shadow. Our data, along with other evidence from southernmost Patagonia and the Antarctic Peninsula, suggest a coherent pattern of centennial-scale variability in SHWW strength on either side of the Drake Passage over the past two millennia, probably as a teleconnection response to El Niño–Southern Oscillation–like variability. Our study implies that investigations of past changes in the SHWW and associated teleconnection mechanisms should consider synoptic-scale atmospheric circulation patterns, rather than seeing SHWW as a simplistic west-to-east (zonal) wind-flow pattern, particularly on the time scales over which the SHWW express zonal asymmetry among different sectors of the Southern Ocean.〈/span〉
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 9
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    Single-crystalline germanium nanomembrane photodetectors on foreign nanocavities (2017)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2017-07-08
    Description: Miniaturization of optoelectronic devices offers tremendous performance gain. As the volume of photoactive material decreases, optoelectronic performance improves, including the operation speed, the signal-to-noise ratio, and the internal quantum efficiency. Over the past decades, researchers have managed to reduce the volume of photoactive materials in solar cells and photodetectors by orders of magnitude. However, two issues arise when one continues to thin down the photoactive layers to the nanometer scale (for example, 〈50 nm). First, light-matter interaction becomes weak, resulting in incomplete photon absorption and low quantum efficiency. Second, it is difficult to obtain ultrathin materials with single-crystalline quality. We introduce a method to overcome these two challenges simultaneously. It uses conventional bulk semiconductor wafers, such as Si, Ge, and GaAs, to realize single-crystalline films on foreign substrates that are designed for enhanced light-matter interaction. We use a high-yield and high-throughput method to demonstrate nanometer-thin photodetectors with significantly enhanced light absorption based on nanocavity interference mechanism. These single-crystalline nanomembrane photodetectors also exhibit unique optoelectronic properties, such as the strong field effect and spectral selectivity.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 10
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    Segregation-induced ordered superstructures at general grain boundaries in a nickel-bismuth alloy (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-10-06
    Description: The properties of materials change, sometimes catastrophically, as alloying elements and impurities accumulate preferentially at grain boundaries. Studies of bicrystals show that regular atomic patterns often arise as a result of this solute segregation at high-symmetry boundaries, but it is not known whether superstructures exist at general grain boundaries in polycrystals. In bismuth-doped polycrystalline nickel, we found that ordered, segregation-induced grain boundary superstructures occur at randomly selected general grain boundaries, and that these reconstructions are driven by the orientation of the terminating grain surfaces rather than by lattice matching between grains. This discovery shows that adsorbate-induced superstructures are not limited to special grain boundaries but may exist at a variety of general grain boundaries, and hence they can affect the performance of polycrystalline engineering alloys.
    Keywords: Materials Science
    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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