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  • 1
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    Bioresorbable optical sensor systems for monitoring of intracranial pressure and temperature (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉Continuous measurements of pressure and temperature within the intracranial, intraocular, and intravascular spaces provide essential diagnostic information for the treatment of traumatic brain injury, glaucoma, and cardiovascular diseases, respectively. Optical sensors are attractive because of their inherent compatibility with magnetic resonance imaging (MRI). Existing implantable optical components use permanent, nonresorbable materials that must be surgically extracted after use. Bioresorbable alternatives, introduced here, bypass this requirement, thereby eliminating the costs and risks of surgeries. Here, millimeter-scale bioresorbable Fabry-Perot interferometers and two dimensional photonic crystal structures enable precise, continuous measurements of pressure and temperature. Combined mechanical and optical simulations reveal the fundamental sensing mechanisms. In vitro studies and histopathological evaluations quantify the measurement accuracies, operational lifetimes, and biocompatibility of these systems. In vivo demonstrations establish clinically relevant performance attributes. The materials, device designs, and fabrication approaches outlined here establish broad foundational capabilities for diverse classes of bioresorbable optical sensors.〈/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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    Asymmetric photon transport in organic semiconductor nanowires through electrically controlled exciton diffusion (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018-03-17
    Description: The ability to steer the flow of light toward desired propagation directions is critically important for the realization of key functionalities in optical communication and information processing. Although various schemes have been proposed for this purpose, the lack of capability to incorporate an external electric field to effectively tune the light propagation has severely limited the on-chip integration of photonics and electronics. Because of the noninteractive nature of photons, it is only possible to electrically control the flow of light by modifying the refractive index of materials through the electro-optic effect. However, the weak optical effects need to be strongly amplified for practical applications in high-density photonic integrations. We show a new strategy that takes advantage of the strong exciton-photon coupling in active waveguides to effectively manipulate photon transport by controlling the interaction between excitons and the external electric field. Single-crystal organic semiconductor nanowires were used to generate highly stable Frenkel exciton polaritons with strong binding and diffusion abilities. By making use of directional exciton diffusion in an external electric field, we have realized an electrically driven asymmetric photon transport and thus directional light propagation in a single nanowire. With this new concept, we constructed a dual-output single wire–based device to build an electrically controlled single-pole double-throw optical switch with fast temporal response and high switching frequency. Our findings may lead to the innovation of concepts and device architectures for optical information processing.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Carbon dots in zeolites: A new class of thermally activated delayed fluorescence materials with ultralong lifetimes (2017)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2017-05-27
    Description: Thermally activated delayed fluorescence (TADF) materials are inspiring intensive research in optoelectronic applications. To date, most of the TADF materials are limited to metal-organic complexes and organic molecules with lifetimes of several microseconds/milliseconds that are sensitive to oxygen. We report a facial and general "dots-in-zeolites" strategy to in situ confine carbon dots (CDs) in zeolitic matrices during hydrothermal/solvothermal crystallization to generate high-efficient TADF materials with ultralong lifetimes. The resultant CDs@zeolite composites exhibit high quantum yields up to 52.14% and ultralong lifetimes up to 350 ms at ambient temperature and atmosphere. This intriguing TADF phenomenon is due to the fact that nanoconfined space of zeolites can efficiently stabilize the triplet states of CDs, thus enabling the reverse intersystem crossing process for TADF. Meanwhile, zeolite frameworks can also hinder oxygen quenching to present TADF behavior at air atmosphere. This design concept introduces a new perspective to develop materials with unique TADF performance and various novel delayed fluorescence–based applications.
    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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    In situ recombination junction between p-Si and TiO2 enables high-efficiency monolithic perovskite/Si tandem cells (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018
    Description: 〈p〉Increasing the power conversion efficiency of silicon (Si) photovoltaics is a key enabler for continued reductions in the cost of solar electricity. Here, we describe a two-terminal perovskite/Si tandem design that increases the Si cell’s output in the simplest possible manner: by placing a perovskite cell directly on top of the Si bottom cell. The advantageous omission of a conventional interlayer eliminates both optical losses and processing steps and is enabled by the low contact resistivity attainable between n-type TiO〈sub〉2〈/sub〉 and Si, established here using atomic layer deposition. We fabricated proof-of-concept perovskite/Si tandems on both homojunction and passivating contact heterojunction Si cells to demonstrate the broad applicability of the interlayer-free concept. Stabilized efficiencies of 22.9 and 24.1% were obtained for the homojunction and passivating contact heterojunction tandems, respectively, which could be readily improved by reducing optical losses elsewhere in the device. This work highlights the potential of emerging perovskite photovoltaics to enable low-cost, high-efficiency tandem devices through straightforward integration with commercially relevant Si solar cells.〈/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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    Gate-controlled VO2 phase transition for high-performance smart windows (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉Vanadium dioxide (VO〈sub〉2〈/sub〉) is a promising material for developing energy-saving "smart windows," owing to its infrared thermochromism induced by metal-insulator transition (MIT). However, its practical application is greatly limited by its relatively high critical temperature (~68°C), low luminous transmittance (2 film. With a solid electrolyte layer assisting gating treatment, we modulated the insertion/extraction of hydrogen into/from the VO〈sub〉2〈/sub〉 lattice at room temperature, causing tristate phase transitions that enable control of light transmittance. The dramatic increase in visible/infrared transmittance due to the phase transition from the metallic (lightly H-doped) to the insulating (heavily H-doped) phase results in an increased solar energy regulation ability up to 26.5%, while maintaining 70.8% visible luminous transmittance. These results break all previous records and exceed the theoretical limit for traditional VO〈sub〉2〈/sub〉 smart windows, making them ready for energy-saving utilization.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    A natural product that lowers cholesterol as an antagonist ligand for FXR (2002)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2002-05-04
    Description: Extracts of the resin of the guggul tree (Commiphora mukul) lower LDL (low-density lipoprotein) cholesterol levels in humans. The plant sterol guggulsterone [4,17(20)-pregnadiene-3,16-dione] is the active agent in this extract. We show that guggulsterone is a highly efficacious antagonist of the farnesoid X receptor (FXR), a nuclear hormone receptor that is activated by bile acids. Guggulsterone treatment decreases hepatic cholesterol in wild-type mice fed a high-cholesterol diet but is not effective in FXR-null mice. Thus, we propose that inhibition of FXR activation is the basis for the cholesterol-lowering activity of guggulsterone. Other natural products with specific biologic effects may modulate the activity of FXR or other relatively promiscuous nuclear hormone receptors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Urizar, Nancy L -- Liverman, Amy B -- Dodds, D'Nette T -- Silva, Frank Valentin -- Ordentlich, Peter -- Yan, Yingzhuo -- Gonzalez, Frank J -- Heyman, Richard A -- Mangelsdorf, David J -- Moore, David D -- New York, N.Y. -- Science. 2002 May 31;296(5573):1703-6. Epub 2002 May 2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular and Cellular Biology, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11988537" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Binding Sites ; Caco-2 Cells ; Carrier Proteins/genetics/metabolism ; Cells, Cultured ; Chenodeoxycholic Acid/pharmacology ; Cholesterol/*metabolism ; Cholesterol, Dietary/administration & dosage ; DNA/metabolism ; DNA-Binding Proteins/*antagonists & inhibitors/chemistry/genetics/*metabolism ; Hepatocytes/metabolism ; Histone Acetyltransferases ; Humans ; *Hydroxysteroid Dehydrogenases ; Hypolipidemic Agents/metabolism/*pharmacology ; Ligands ; Liver/metabolism ; *Membrane Glycoproteins ; Mice ; Nuclear Receptor Coactivator 1 ; Pregnenediones/metabolism/*pharmacology ; Promoter Regions, Genetic ; Protein Structure, Tertiary ; Receptors, Cytoplasmic and Nuclear/antagonists & inhibitors/genetics/metabolism ; Receptors, Steroid/antagonists & inhibitors/metabolism ; Transcription Factors/*antagonists & inhibitors/chemistry/genetics/*metabolism ; Transcriptional Activation/drug effects ; Transfection ; Tumor Cells, Cultured
    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 cellular striptease act (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-12-29
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Werb, Z -- Yan, Y -- CA72006/CA/NCI NIH HHS/ -- HD26732/HD/NICHD NIH HHS/ -- New York, N.Y. -- Science. 1998 Nov 13;282(5392):1279-80.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Anatomy, University of California, San Francisco, CA 94143-0452, USA. zena@itsa.ucsf.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9867633" target="_blank"〉PubMed〈/a〉
    Keywords: ADAM Proteins ; Animals ; Catalytic Domain ; Cell Adhesion Molecules/metabolism ; Cell Membrane/*metabolism ; Growth Substances/metabolism ; L-Selectin/metabolism ; Ligands ; Membrane Proteins/*metabolism ; Metalloendopeptidases/chemistry/*metabolism ; Mice ; Models, Biological ; Receptor, Epidermal Growth Factor/metabolism ; Tumor Necrosis Factor-alpha/*metabolism
    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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  • 8
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    In situ recombination junction between p-Si and TiO2 enables high-efficiency monolithic perovskite/Si tandem cells (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018-12-15
    Description: Increasing the power conversion efficiency of silicon (Si) photovoltaics is a key enabler for continued reductions in the cost of solar electricity. Here, we describe a two-terminal perovskite/Si tandem design that increases the Si cell’s output in the simplest possible manner: by placing a perovskite cell directly on top of the Si bottom cell. The advantageous omission of a conventional interlayer eliminates both optical losses and processing steps and is enabled by the low contact resistivity attainable between n-type TiO 2 and Si, established here using atomic layer deposition. We fabricated proof-of-concept perovskite/Si tandems on both homojunction and passivating contact heterojunction Si cells to demonstrate the broad applicability of the interlayer-free concept. Stabilized efficiencies of 22.9 and 24.1% were obtained for the homojunction and passivating contact heterojunction tandems, respectively, which could be readily improved by reducing optical losses elsewhere in the device. This work highlights the potential of emerging perovskite photovoltaics to enable low-cost, high-efficiency tandem devices through straightforward integration with commercially relevant Si solar cells.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    HAIRY MERISTEM with WUSCHEL confines CLAVATA3 expression to the outer apical meristem layers (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2018-08-03
    Description: The control of the location and activity of stem cells depends on spatial regulation of gene activities in the stem cell niche. Using computational and experimental approaches, we have tested and found support for a hypothesis for gene interactions that specify the Arabidopsis apical stem cell population. The hypothesis explains how the WUSCHEL gene product, synthesized basally in the meristem, induces CLAVATA3 -expressing stem cells in the meristem apex but, paradoxically, not in the basal domain where WUSCHEL itself is expressed. The answer involves the activity of the small family of HAIRY MERISTEM genes, which prevent the activation of CLAVATA3 and which are expressed basally in the shoot meristem.
    Keywords: Botany, Development
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    Mechanism of two classes of cancer mutations in the phosphoinositide 3-kinase catalytic subunit (2007)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2007-07-14
    Description: Many human cancers involve up-regulation of the phosphoinositide 3-kinase PI3Kalpha, with oncogenic mutations identified in both the p110alpha catalytic and the p85alpha regulatory subunits. We used crystallographic and biochemical approaches to gain insight into activating mutations in two noncatalytic p110alpha domains-the adaptor-binding and the helical domains. A structure of the adaptor-binding domain of p110alpha in a complex with the p85alpha inter-Src homology 2 (inter-SH2) domain shows that oncogenic mutations in the adaptor-binding domain are not at the inter-SH2 interface but in a polar surface patch that is a plausible docking site for other domains in the holo p110/p85 complex. We also examined helical domain mutations and found that the Glu545 to Lys545 (E545K) oncogenic mutant disrupts an inhibitory charge-charge interaction with the p85 N-terminal SH2 domain. These studies extend our understanding of the architecture of PI3Ks and provide insight into how two classes of mutations that cause a gain in function can lead to cancer.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Miled, Nabil -- Yan, Ying -- Hon, Wai-Ching -- Perisic, Olga -- Zvelebil, Marketa -- Inbar, Yuval -- Schneidman-Duhovny, Dina -- Wolfson, Haim J -- Backer, Jonathan M -- Williams, Roger L -- GM55692/GM/NIGMS NIH HHS/ -- MC_U105184308/Medical Research Council/United Kingdom -- New York, N.Y. -- Science. 2007 Jul 13;317(5835):239-42.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17626883" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Motifs ; Amino Acid Sequence ; Animals ; *Catalytic Domain ; Cattle ; Cell Line ; Cell Transformation, Neoplastic ; Crystallography, X-Ray ; Dimerization ; Humans ; Models, Molecular ; Molecular Sequence Data ; *Mutation ; Neoplasms/*genetics ; Phosphatidylinositol 3-Kinases/antagonists & ; inhibitors/chemistry/*genetics/*metabolism ; Protein Structure, Secondary ; Protein Structure, Tertiary ; src Homology Domains
    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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