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  • 11
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    Overcoming the electroluminescence efficiency limitations of perovskite light-emitting diodes (2016)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2016-01-20
    Description: Organic-inorganic hybrid perovskites are emerging low-cost emitters with very high color purity, but their low luminescent efficiency is a critical drawback. We boosted the current efficiency (CE) of perovskite light-emitting diodes with a simple bilayer structure to 42.9 candela per ampere, similar to the CE of phosphorescent organic light-emitting diodes, with two modifications: We prevented the formation of metallic lead (Pb) atoms that cause strong exciton quenching through a small increase in methylammonium bromide (MABr) molar proportion, and we spatially confined the exciton in uniform MAPbBr3 nanograins (average diameter = 99.7 nanometers) formed by a nanocrystal pinning process and concomitant reduction of exciton diffusion length to 67 nanometers. These changes caused substantial increases in steady-state photoluminescence intensity and efficiency of MAPbBr3 nanograin layers.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cho, Himchan -- Jeong, Su-Hun -- Park, Min-Ho -- Kim, Young-Hoon -- Wolf, Christoph -- Lee, Chang-Lyoul -- Heo, Jin Hyuck -- Sadhanala, Aditya -- Myoung, NoSoung -- Yoo, Seunghyup -- Im, Sang Hyuk -- Friend, Richard H -- Lee, Tae-Woo -- New York, N.Y. -- Science. 2015 Dec 4;350(6265):1222-5. doi: 10.1126/science.aad1818. Epub 2015 Dec 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang, Gyungbuk 790-784, Republic of Korea. ; Advanced Photonics Research Institute (APRI), Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712, Republic of Korea. ; Department of Chemical Engineering, College of Engineering, Kyung Hee University, 1 Seochon-dong, Giheung-gu, Youngin-si, Gyeonggi-do 446-701, Republic of Korea. ; Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK. ; Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea. ; Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang, Gyungbuk 790-784, Republic of Korea. Department of Chemical Engineering, Division of Advanced Materials Science, School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Nam-Gu, Pohang, Gyungbuk 790-784, Republic of Korea. twlee@postech.ac.kr taewlees@gmail.com.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26785482" target="_blank"〉PubMed〈/a〉
    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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  • 12
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    Doridosine: a new hypotensive N-methylpurine riboside from the nudibranch Anisodoris nobilis (1980)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1980-01-11
    Description: A new N-methylpurine riboside (doridosine), probably N1-Methylisoguanosine, was isolated from the digestive glands of a nudibranch. Doridosine produces prolonged hypotension and bradycardia in anesthetized rats, decreases the rate and the amplitude of contraction of guinea pig atria in vitro, and causes the heart rate in anesthetized mice to be reduced by 50 percent for many hours after which the animals recover completely.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fuhrman, F A -- Fuhrman, G J -- Kim, Y H -- Pavelka, L A -- Mosher, H S -- New York, N.Y. -- Science. 1980 Jan 11;207(4427):193-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7350655" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antihypertensive Agents/*isolation & purification ; Guanosine/*analogs & derivatives/isolation & purification/pharmacology ; Guinea Pigs ; Heart Rate/drug effects ; Mice ; Mollusca/analysis ; 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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  • 13
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    Chiral recognition by nucleosides and nucleotides: resolution of helicenes by high-performance liquid chromatography (1981)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1981-09-18
    Description: Chiral recognition by nucleosides and nucleotides coated on silica gel was studied by high-performance liquid chromatography. Helicenes, which are chiral polyaromatic hydrocarbons, were used as probes. Stereoselectivity was detected when the nucleobase was a purine (adenosine 3', 5'-monophosphate, an guanosine), but was not detected with the pyrimidine derivative uridine. For a given nucleobase (adenine), all changes in the ribose moiety affected the resolution factors, which ranged between 1.03 and 1.074. These results might be relevant to the enantioselectivity of carcinogenic metabolites of polyaromatic hydrocarbons.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kim, Y H -- Tishbee, A -- Gil-Av, E -- New York, N.Y. -- Science. 1981 Sep 18;213(4514):1379-81.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7268441" target="_blank"〉PubMed〈/a〉
    Keywords: Chemistry, Physical ; Chromatography, High Pressure Liquid ; *Nucleosides ; *Nucleotides ; Physicochemical Phenomena ; *Polycyclic Compounds ; Stereoisomerism
    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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  • 14
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    Selective control of electron and hole tunneling in 2D assembly (2017)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2017-04-20
    Description: Recent discoveries in the field of two-dimensional (2D) materials have led to the demonstration of exotic devices. Although they have new potential applications in electronics, thermally activated transport over a metal/semiconductor barrier sets physical subthermionic limitations. The challenge of realizing an innovative transistor geometry that exploits this concern remains. A new class of 2D assembly (namely, "carristor") with a configuration similar to the metal-insulator-semiconductor structure is introduced in this work. Superior functionalities, such as a current rectification ratio of up to 400,000 and a switching ratio of higher than 10 6 at room temperature, are realized by quantum-mechanical tunneling of majority and minority carriers across the barrier. These carristors have a potential application as the fundamental building block of low–power consumption electronics.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 15
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    Acupuncture attenuates alcohol dependence through activation of endorphinergic input to the nucleus accumbens from the arcuate nucleus (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉A withdrawal-associated impairment in β-endorphin neurotransmission in the arcuate nucleus (ARC) of the hypothalamus is associated with alcohol dependence characterized by a chronic relapsing disorder. Although acupuncture activates β-endorphin neurons in the ARC projecting to the nucleus accumbens (NAc), a role for ARC β-endorphin neurons in alcohol dependence and acupuncture effects has not been examined. Here, we show that acupuncture at Shenmen (HT7) points attenuates behavioral manifestation of alcohol dependence by activating endorphinergic input to the NAc from the ARC. Acupuncture attenuated ethanol withdrawal tremor, anxiety-like behaviors, and ethanol self-administration in ethanol-dependent rats, which are mimicked by local injection of β-endorphin into the NAc. Acupuncture also reversed the decreased β-endorphin levels in the NAc and a reduction of neuronal activity in the ARC during ethanol withdrawal. These results suggest that acupuncture may provide a novel, potential treatment strategy for alcohol use disorder by direct activation of the brain pathway.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 16
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    Edge-selenated graphene nanoplatelets as durable metal-free catalysts for iodine reduction reaction in dye-sensitized solar cells (2016)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2016-06-19
    Description: Metal-free carbon-based electrocatalysts for dye-sensitized solar cells (DSSCs) are sufficiently active in Co(II)/Co(III) electrolytes but are not satisfactory in the most commonly used iodide/triiodide (I – /I 3 – ) electrolytes. Thus, developing active and stable metal-free electrocatalysts in both electrolytes is one of the most important issues in DSSC research. We report the synthesis of edge-selenated graphene nanoplatelets (SeGnPs) prepared by a simple mechanochemical reaction between graphite and selenium (Se) powders, and their application to the counter electrode (CE) for DSSCs in both I – /I 3 – and Co(II)/Co(III) electrolytes. The edge-selective doping and the preservation of the pristine graphene basal plane in the SeGnPs were confirmed by various analytical techniques, including atomic-resolution transmission electron microscopy. Tested as the DSSC CE in both Co(bpy) 3 2+/3+ (bpy = 2,2'-bipyridine) and I – /I 3 – electrolytes, the SeGnP-CEs exhibited outstanding electrocatalytic performance with ultimately high stability. The SeGnP-CE–based DSSCs displayed a higher photovoltaic performance than did the Pt-CE–based DSSCs in both SM315 sensitizer with Co(bpy) 3 2+/3+ and N719 sensitizer with I – /I 3 – electrolytes. Furthermore, the I 3 – reduction mechanism, which has not been fully understood in carbon-based CE materials to date, was clarified by an electrochemical kinetics study combined with density functional theory and nonequilibrium Green’s function calculations.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 17
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    Cortical layer-specific critical dynamics triggering perception (2019)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2019
    Description: 〈p〉Perceptual experiences may arise from neuronal activity patterns in mammalian neocortex. We probed mouse neocortex during visual discrimination using a red-shifted channelrhodopsin (ChRmine, discovered through structure-guided genome mining) alongside multiplexed multiphoton-holography (MultiSLM), achieving control of individually specified neurons spanning large cortical volumes with millisecond precision. Stimulating a critical number of stimulus-orientation-selective neurons drove widespread recruitment of functionally related neurons, a process enhanced by (but not requiring) orientation-discrimination task learning. Optogenetic targeting of orientation-selective ensembles elicited correct behavioral discrimination. Cortical layer–specific dynamics were apparent, as emergent neuronal activity asymmetrically propagated from layer 2/3 to layer 5, and smaller layer 5 ensembles were as effective as larger layer 2/3 ensembles in eliciting orientation discrimination behavior. Population dynamics emerging after optogenetic stimulation both correctly predicted behavior and resembled natural internal representations of visual stimuli at cellular resolution over volumes of cortex.〈/p〉
    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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  • 18
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    Dynamic assembly of liquid crystalline graphene oxide gel fibers for ion transport (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018
    Description: 〈p〉Colloidal dispersions with liquid crystallinity hold great promise for fabricating their superstructures. As an example, when graphene oxide (GO) sheets are assembled in the liquid crystalline state, they can turn into ordered macroscopic forms of GO such as fibers via the wet spinning process. Here, we report that by reinforcing intersheet interactions, GO liquid crystals (LCs) turn into mechanically robust hydrogels that can be readily drawn into highly aligned fibrillar structures. GO hydrogel fibers with highly aligned sheets (orientation factor, 〈i〉f〈/i〉 = 0.71) exhibit more than twice the ionic conductivity compared to those with partially aligned structures (〈i〉f〈/i〉 = 0.01). The hierarchically interconnected two-dimensional nanochannels within these neatly aligned GOLC hydrogel fibers may facilitate controlled transport of charge carriers and could be potentially explored as cables for interconnecting biosystems and/or human-made devices.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 19
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    Human-caused Indo-Pacific warm pool expansion (2016)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2016-07-03
    Description: The Indo-Pacific warm pool (IPWP) has warmed and grown substantially during the past century. The IPWP is Earth’s largest region of warm sea surface temperatures (SSTs), has the highest rainfall, and is fundamental to global atmospheric circulation and hydrological cycle. The region has also experienced the world’s highest rates of sea-level rise in recent decades, indicating large increases in ocean heat content and leading to substantial impacts on small island states in the region. Previous studies have considered mechanisms for the basin-scale ocean warming, but not the causes of the observed IPWP expansion, where expansion in the Indian Ocean has far exceeded that in the Pacific Ocean. We identify human and natural contributions to the observed IPWP changes since the 1950s by comparing observations with climate model simulations using an optimal fingerprinting technique. Greenhouse gas forcing is found to be the dominant cause of the observed increases in IPWP intensity and size, whereas natural fluctuations associated with the Pacific Decadal Oscillation have played a smaller yet significant role. Further, we show that the shape and impact of human-induced IPWP growth could be asymmetric between the Indian and Pacific basins, the causes of which remain uncertain. Human-induced changes in the IPWP have important implications for understanding and projecting related changes in monsoonal rainfall, and frequency or intensity of tropical storms, which have profound socioeconomic consequences.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 20
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    Cortical layer-specific critical dynamics triggering perception (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉Perceptual experiences may arise from neuronal activity patterns in mammalian neocortex. We probed mouse neocortex during visual discrimination using a red-shifted channelrhodopsin (ChRmine, discovered through structure-guided genome mining) alongside multiplexed multiphoton-holography (MultiSLM), achieving control of individually-specified neurons spanning large cortical volumes with millisecond precision. Stimulating a critical number of stimulus-orientation-selective neurons drove widespread recruitment of functionally-related neurons, a process enhanced by (but not requiring) orientation-discrimination task learning. Optogenetic targeting of orientation-selective ensembles elicited correct behavioral discrimination. Cortical layer specific-dynamics were apparent, as emergent neuronal activity asymmetrically propagated from layer-2/3 to layer-5, and smaller layer-5 ensembles were as effective as larger layer-2/3 ensembles in eliciting orientation discrimination behavior. Population dynamics emerging after optogenetic stimulation both correctly predicted behavior and resembled natural neural representations of visual stimuli.〈/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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