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  • 1
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    Nanoscale magnetic imaging of ferritins in a single cell (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2019
    Beschreibung: 〈p〉The in situ measurement of the distribution of biomolecules inside a cell is one of the important goals in life science. Among various imaging techniques, magnetic imaging (MI) based on the nitrogen-vacancy (NV) center in diamond provides a powerful tool for the biomolecular research, while the nanometer-scale MI of intracellular proteins remains a challenge. Here, we use ferritin as a demonstration to realize the MI of endogenous proteins in a single cell using the NV center as the sensor. With the scanning, intracellular ferritins are imaged with a spatial resolution of ca. 10 nm, and ferritin-containing organelles are colocalized by correlative MI and electron microscopy. The approach paves the way for nanoscale MI of intracellular proteins.〈/p〉
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
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    Direct observation of valley-coupled topological current in MoS2 (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2019
    Beschreibung: 〈p〉The valley degree of freedom of electrons in two-dimensional transition metal dichalcogenides has been extensively studied by theory (〈cross-ref type="bib" refid="R1"〉〈i〉1〈/i〉〈/cross-ref〉–〈cross-ref type="bib" refid="R4"〉〈i〉4〈/i〉〈/cross-ref〉), optical (〈cross-ref type="bib" refid="R5"〉〈i〉5〈/i〉〈/cross-ref〉–〈cross-ref type="bib" refid="R9"〉〈i〉9〈/i〉〈/cross-ref〉), and optoelectronic (〈cross-ref type="bib" refid="R10"〉〈i〉10〈/i〉〈/cross-ref〉–〈cross-ref type="bib" refid="R13"〉〈i〉13〈/i〉〈/cross-ref〉) experiments. However, generation and detection of pure valley current without relying on optical selection have not yet been demonstrated in these materials. Here, we report that valley current can be electrically induced and detected through the valley Hall effect and inverse valley Hall effect, respectively, in monolayer molybdenum disulfide. We compare temperature and channel length dependence of nonlocal electrical signals in monolayer and multilayer samples to distinguish the valley Hall effect from classical ohmic contributions. Notably, valley transport is observed over a distance of 4 μm in monolayer samples at room temperature. Our findings will enable a new generation of electronic devices using the valley degree of freedom, which can be used for future novel valleytronic applications.〈/p〉
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    A molecular perovskite solid solution with piezoelectricity stronger than lead zirconate titanate (2019)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2019
    Beschreibung: 〈p〉Piezoelectric materials produce electricity when strained, making them ideal for different types of sensing applications. The most effective piezoelectric materials are ceramic solid solutions in which the piezoelectric effect is optimized at what are termed morphotropic phase boundaries (MPBs). Ceramics are not ideal for a variety of applications owing to some of their mechanical properties. We synthesized piezoelectric materials from a molecular perovskite (TMFM)〈i〉〈sub〉x〈/sub〉〈/i〉(TMCM)〈sub〉1–〈/sub〉〈i〉〈sub〉x〈/sub〉〈/i〉CdCl〈sub〉3〈/sub〉 solid solution (TMFM, trimethylfluoromethyl ammonium; TMCM, trimethylchloromethyl ammonium, 0 ≤ 〈i〉x〈/i〉 ≤ 1), in which the MPB exists between monoclinic and hexagonal phases. We found a composition for which the piezoelectric coefficient 〈i〉d〈/i〉〈sub〉33〈/sub〉 is ~1540 picocoulombs per newton, comparable to high-performance piezoelectric ceramics. The material has potential applications for wearable piezoelectric devices.〈/p〉
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Extraordinary tensile strength and ductility of scalable nanoporous graphene (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2019
    Beschreibung: 〈p〉While the compressive strength-density scaling relationship of ultralight cellular graphene materials has been extensively investigated, high tensile strength and ductility have not been realized in the theoretically strongest carbon materials because of high flaw sensitivity under tension and weak van der Waals interplanar bonding between graphene sheets. In this study, we report that large-scale ultralight nanoporous graphene with three-dimensional bicontinuous nanoarchitecture shows orders of magnitude higher strength and elastic modulus than all reported ultralight carbon materials under both compression and tension. The high-strength nanoporous graphene also exhibits excellent tensile ductility and work hardening, which are comparable to well-designed metamaterials but until now had not been realized in ultralight cellular materials. The excellent mechanical properties of the nanoporous graphene benefit from seamless graphene sheets in the bicontinuous nanoporosity that effectively preserves the intrinsic strength of atomically thick graphene in the three-dimensional cellular nanoarchitecture.〈/p〉
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Synthesis of stable and low-CO2 selective {varepsilon}-iron carbide Fischer-Tropsch catalysts (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2018-10-13
    Beschreibung: The Fe-catalyzed Fischer-Tropsch (FT) reaction constitutes the core of the coal-to-liquids (CTL) process, which converts coal into liquid fuels. Conventional Fe-based catalysts typically convert 30% of the CO feed to CO 2 in the FT unit. Decreasing the CO 2 release in the FT step will reduce costs and enhance productivity of the overall process. In this context, we synthesize phase-pure (')-Fe 2 C catalysts exhibiting low CO 2 selectivity by carefully controlling the pretreatment and carburization conditions. Kinetic data reveal that liquid fuels can be obtained free from primary CO 2 . These catalysts displayed stable FT performance at 23 bar and 235°C for at least 150 hours. Notably, in situ characterization emphasizes the high durability of pure (')-Fe 2 C in an industrial pilot test. These findings contribute to the development of new Fe-based FT catalysts for next-generation CTL processes.
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
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    Routine allomaternal nursing in a free-ranging Old World monkey (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2019
    Beschreibung: 〈p〉While regular allomaternal nursing (suckling) has been documented in a number of rodent and carnivore species, as well as in some prosimians, New World monkeys, and humans, it is not common in Old World monkeys and apes. Here, we present a detailed field study of allomaternal nursing in golden snub-nosed monkeys (〈i〉Rhinopithecus roxellana〈/i〉, Colobinae). We found that more than 87% of infants were nursed by females other than their mothers. Allomaternal nursing was largely confined to the first 3 months of an infant’s life and occurred predominantly between related females who nursed each other’s offspring in a reciprocal manner. Allomaternal nursing enhanced infant survivorship and did not have a negative impact on the future reproductive success of allonursers. Our findings expand the taxonomic distribution of allomaternal nursing and provide fresh insight into the possible factors driving evolution of allomaternal nursing behavior in primates, including humans.〈/p〉
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
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    Phenylacetonitrile in locusts facilitates an antipredator defense by acting as an olfactory aposematic signal and cyanide precursor (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2019
    Beschreibung: 〈p〉Many aggregating animals use aposematic signals to advertise their toxicity to predators. However, the coordination between aposematic signals and toxins is poorly understood. Here, we reveal that phenylacetonitrile (PAN) acts as an olfactory aposematic signal and precursor of hypertoxic hydrogen cyanide (HCN) to protect gregarious locusts from predation. We found that PAN biosynthesis from phenylalanine is catalyzed by 〈i〉CYP305M2〈/i〉, a novel gene encoding a cytochrome P450 enzyme in gregarious locusts. The RNA interference (RNAi) knockdown of 〈i〉CYP305M2〈/i〉 increases the vulnerability of gregarious locusts to bird predation. By contrast, the elevation of PAN levels through supplementation with synthetic PAN increases the resistance of solitary locusts to predation. When locusts are attacked by birds, PAN is converted to HCN, which causes food poisoning in birds. Our results indicate that locusts develop a defense mechanism wherein an aposematic compound is converted to hypertoxic cyanide in resistance to predation by natural enemies.〈/p〉
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
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    Synthesis of stable and low-CO2 selective {varepsilon}-iron carbide Fischer-Tropsch catalysts (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2018
    Beschreibung: 〈p〉The Fe-catalyzed Fischer-Tropsch (FT) reaction constitutes the core of the coal-to-liquids (CTL) process, which converts coal into liquid fuels. Conventional Fe-based catalysts typically convert 30% of the CO feed to CO〈sub〉2〈/sub〉 in the FT unit. Decreasing the CO〈sub〉2〈/sub〉 release in the FT step will reduce costs and enhance productivity of the overall process. In this context, we synthesize phase-pure (')-Fe〈sub〉2〈/sub〉C catalysts exhibiting low CO〈sub〉2〈/sub〉 selectivity by carefully controlling the pretreatment and carburization conditions. Kinetic data reveal that liquid fuels can be obtained free from primary CO〈sub〉2〈/sub〉. These catalysts displayed stable FT performance at 23 bar and 235°C for at least 150 hours. Notably, in situ characterization emphasizes the high durability of pure (')-Fe〈sub〉2〈/sub〉C in an industrial pilot test. These findings contribute to the development of new Fe-based FT catalysts for next-generation CTL processes.〈/p〉
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
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    Evidence for Majorana bound states in an iron-based superconductor (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2018
    Beschreibung: 〈p〉The search for Majorana bound states (MBSs) has been fueled by the prospect of using their non-Abelian statistics for robust quantum computation. Two-dimensional superconducting topological materials have been predicted to host MBSs as zero-energy modes in vortex cores. By using scanning tunneling spectroscopy on the superconducting Dirac surface state of the iron-based superconductor FeTe〈sub〉0.55〈/sub〉Se〈sub〉0.45〈/sub〉, we observed a sharp zero-bias peak inside a vortex core that does not split when moving away from the vortex center. The evolution of the peak under varying magnetic field, temperature, and tunneling barrier is consistent with the tunneling to a nearly pure MBS, separated from nontopological bound states. This observation offers a potential platform for realizing and manipulating MBSs at a relatively high temperature.〈/p〉
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
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    Evidence for Majorana bound states in an iron-based superconductor (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2018-10-19
    Beschreibung: The search for Majorana bound states (MBSs) has been fueled by the prospect of using their non-Abelian statistics for robust quantum computation. Two-dimensional superconducting topological materials have been predicted to host MBSs as zero-energy modes in vortex cores. By using scanning tunneling spectroscopy on the superconducting Dirac surface state of the iron-based superconductor FeTe 0.55 Se 0.45 , we observed a sharp zero-bias peak inside a vortex core that does not split when moving away from the vortex center. The evolution of the peak under varying magnetic field, temperature, and tunneling barrier is consistent with the tunneling to a nearly pure MBS, separated from nontopological bound states. This observation offers a potential platform for realizing and manipulating MBSs at a relatively high temperature.
    Schlagwort(e): Physics
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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