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  • Proceedings of the National Academy of Sciences  (18)
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  • Proceedings of the National Academy of Sciences  (18)
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  • 1
    Online Resource
    Online Resource
    Zintl-phase Eu 2 ZnSb 2 : A promising thermoelectric material with ultralow thermal conductivity
    Proceedings of the National Academy of Sciences ; 2019
    In:  Proceedings of the National Academy of Sciences Vol. 116, No. 8 ( 2019-02-19), p. 2831-2836
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 116, No. 8 ( 2019-02-19), p. 2831-2836
    Abstract: Zintl compounds are considered to be potential thermoelectric materials due to their “phonon glass electron crystal” (PGEC) structure. A promising Zintl-phase thermoelectric material, 2-1-2–type Eu 2 ZnSb 2 ( P 6 3 / mmc ), was prepared and investigated. The extremely low lattice thermal conductivity is attributed to the external Eu atomic layers inserted in the [Zn 2 Sb 2 ] 2- network in the structure of 1-2-2–type EuZn 2 Sb 2 ( P 3 ¯ m 1 ) , as well as the abundant inversion domain boundary. By regulating the Zn deficiency, the electrical properties are significantly enhanced, and the maximum ZT value reaches ∼1.0 at 823 K for Eu 2 Zn 0.98 Sb 2 . Our discovery provides a class of Zintl thermoelectric materials applicable in the medium-temperature range.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1819157116
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2019
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
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  • 2
    Online Resource
    Online Resource
    Biomass smoke from southern Africa can significantly enhance the brightness of stratocumulus over the southeastern Atlantic Ocean
    Proceedings of the National Academy of Sciences ; 2018
    In:  Proceedings of the National Academy of Sciences Vol. 115, No. 12 ( 2018-03-20), p. 2924-2929
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 115, No. 12 ( 2018-03-20), p. 2924-2929
    Abstract: Marine stratocumulus clouds cover nearly one-quarter of the ocean surface and thus play an extremely important role in determining the global radiative balance. The semipermanent marine stratocumulus deck over the southeastern Atlantic Ocean is of particular interest, because of its interactions with seasonal biomass burning aerosols that are emitted in southern Africa. Understanding the impacts of biomass burning aerosols on stratocumulus clouds and the implications for regional and global radiative balance is still very limited. Previous studies have focused on assessing the magnitude of the warming caused by solar scattering and absorption by biomass burning aerosols over stratocumulus (the direct radiative effect) or cloud adjustments to the direct radiative effect (the semidirect effect). Here, using a nested modeling approach in conjunction with observations from multiple satellites, we demonstrate that cloud condensation nuclei activated from biomass burning aerosols entrained into the stratocumulus (the microphysical effect) can play a dominant role in determining the total radiative forcing at the top of the atmosphere, compared with their direct and semidirect radiative effects. Biomass burning aerosols over the region and period with heavy loadings can cause a substantial cooling (daily mean −8.05 W m −2 ), primarily as a result of clouds brightening by reducing the cloud droplet size (the Twomey effect) and secondarily through modulating the diurnal cycle of cloud liquid water path and coverage (the cloud lifetime effect). Our results highlight the importance of realistically representing the interactions of stratocumulus with biomass burning aerosols in global climate models in this region.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1713703115
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2018
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 3
    Online Resource
    Online Resource
    Phase-transition temperature suppression to achieve cubic GeTe and high thermoelectric performance by Bi and Mn codoping
    Proceedings of the National Academy of Sciences ; 2018
    In:  Proceedings of the National Academy of Sciences Vol. 115, No. 21 ( 2018-05-22), p. 5332-5337
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 115, No. 21 ( 2018-05-22), p. 5332-5337
    Abstract: Germanium telluride (GeTe)-based materials, which display intriguing functionalities, have been intensively studied from both fundamental and technological perspectives. As a thermoelectric material, though, the phase transition in GeTe from a rhombohedral structure to a cubic structure at ∼700 K is a major obstacle impeding applications for energy harvesting. In this work, we discovered that the phase-transition temperature can be suppressed to below 300 K by a simple Bi and Mn codoping, resulting in the high performance of cubic GeTe from 300 to 773 K. Bi doping on the Ge site was found to reduce the hole concentration and thus to enhance the thermoelectric properties. Mn alloying on the Ge site simultaneously increased the hole effective mass and the Seebeck coefficient through modification of the valence bands. With the Bi and Mn codoping, the lattice thermal conductivity was also largely reduced due to the strong point-defect scattering for phonons, resulting in a peak thermoelectric figure of merit ( ZT ) of ∼1.5 at 773 K and an average ZT of ∼1.1 from 300 to 773 K in cubic Ge 0.81 Mn 0.15 Bi 0.04 Te. Our results open the door for further studies of this exciting material for thermoelectric and other applications.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1802020115
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2018
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 4
    Online Resource
    Online Resource
    Nanofluid of graphene-based amphiphilic Janus nanosheets for tertiary or enhanced oil recovery: High performance at low concentration
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 28 ( 2016-07-12), p. 7711-7716
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 28 ( 2016-07-12), p. 7711-7716
    Abstract: The current simple nanofluid flooding method for tertiary or enhanced oil recovery is inefficient, especially when used with low nanoparticle concentration. We have designed and produced a nanofluid of graphene-based amphiphilic nanosheets that is very effective at low concentration. Our nanosheets spontaneously approached the oil–water interface and reduced the interfacial tension in a saline environment (4 wt % NaCl and 1 wt % CaCl 2 ), regardless of the solid surface wettability. A climbing film appeared and grew at moderate hydrodynamic condition to encapsulate the oil phase. With strong hydrodynamic power input, a solid-like interfacial film formed and was able to return to its original form even after being seriously disturbed. The film rapidly separated oil and water phases for slug-like oil displacement. The unique behavior of our nanosheet nanofluid tripled the best performance of conventional nanofluid flooding methods under similar conditions.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1608135113
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 5
    Online Resource
    Online Resource
    On the accuracy of official Chinese crop production data: Evidence from biophysical indexes of net primary production
    Proceedings of the National Academy of Sciences ; 2020
    In:  Proceedings of the National Academy of Sciences Vol. 117, No. 41 ( 2020-10-13), p. 25434-25444
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 117, No. 41 ( 2020-10-13), p. 25434-25444
    Abstract: With rapid economic growth and urbanization, self-sufficiency in crop production has become central to China’s agriculture policy. Accurate crop production statistics are essential for research, monitoring, and planning. Although researchers agree that China’s statistical authority has considerably modernized over time, China’s economic statistics have still been viewed as unreliable and often overstated to meet growth targets at different administrative levels. Recent increases in crop production reported by national statistics have also come under increasing scrutiny. This paper investigates crop production data quality from a planetary boundary perspective—comparing net primary production (NPP) harvested obtained from national statistics with satellite-driven NPP estimates that are supported by detailed observation of land cover, combined with observations on physical factors that limit plant growth. This approach provides a powerful means to check the plausibility of China’s grain production statistics at different administrative levels that can generate insights about their discrepancies and can contribute to improved crop production measurements. We find some evidence of potential misreporting problems from the lower administration level where the risk of manipulation of statistics is higher. We also find problems from provincial-level major grain producers. These values can also affect the national totals. Although the numbers are affected by large uncertainties, we find that improving the spatial resolution of key agricultural parameters can greatly improve the reliability of the indicator that in turn can help improve data quality. More reliable production data will be vital for relevant research and provide better insights into food security problems, the carbon cycle, and sustainable development.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1919850117
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    Matrix-transmitted paratensile signaling enables myofibroblast – fibroblast cross talk in fibrosis expansion
    Proceedings of the National Academy of Sciences ; 2020
    In:  Proceedings of the National Academy of Sciences Vol. 117, No. 20 ( 2020-05-19), p. 10832-10838
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 117, No. 20 ( 2020-05-19), p. 10832-10838
    Abstract: While the concept of intercellular mechanical communication has been revealed, the mechanistic insights have been poorly evidenced in the context of myofibroblast–fibroblast interaction during fibrosis expansion. Here we report and systematically investigate the mechanical force-mediated myofibroblast–fibroblast cross talk via the fibrous matrix, which we termed paratensile signaling. Paratensile signaling enables instantaneous and long-range mechanotransduction via collagen fibers (less than 1 s over 70 μm) to activate a single fibroblast, which is intracellularly mediated by DDR2 and integrin signaling pathways in a calcium-dependent manner through the mechanosensitive Piezo1 ion channel. By correlating in vitro fibroblast foci growth models with mathematical modeling, we demonstrate that the single-cell-level spatiotemporal feature of paratensile signaling can be applied to elucidate the tissue-level fibrosis expansion and that blocking paratensile signaling can effectively attenuate the fibroblast to myofibroblast transition at the border of fibrotic and normal tissue. Our comprehensive investigation of paratensile signaling in fibrosis expansion broadens the understanding of cellular dynamics during fibrogenesis and inspires antifibrotic intervention strategies targeting paratensile signaling.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1910650117
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
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  • 7
    Online Resource
    Online Resource
    Relationship between thermoelectric figure of merit and energy conversion efficiency
    Proceedings of the National Academy of Sciences ; 2015
    In:  Proceedings of the National Academy of Sciences Vol. 112, No. 27 ( 2015-07-07), p. 8205-8210
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 112, No. 27 ( 2015-07-07), p. 8205-8210
    Abstract: The formula for maximum efficiency ( η max ) of heat conversion into electricity by a thermoelectric device in terms of the dimensionless figure of merit ( ZT ) has been widely used to assess the desirability of thermoelectric materials for devices. Unfortunately, the η max values vary greatly depending on how the average ZT values are used, raising questions about the applicability of ZT in the case of a large temperature difference between the hot and cold sides due to the neglect of the temperature dependences of the material properties that affect ZT . To avoid the complex numerical simulation that gives accurate efficiency, we have defined an engineering dimensionless figure of merit ( ZT ) eng and an engineering power factor ( PF ) eng as functions of the temperature difference between the cold and hot sides to predict reliably and accurately the practical conversion efficiency and output power, respectively, overcoming the reporting of unrealistic efficiency using average ZT values.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1510231112
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2015
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 8
    Online Resource
    Online Resource
    Achieving high power factor and output power density in p-type half-Heuslers Nb 1-x Ti x FeSb
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 48 ( 2016-11-29), p. 13576-13581
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 48 ( 2016-11-29), p. 13576-13581
    Abstract: Improvements in thermoelectric material performance over the past two decades have largely been based on decreasing the phonon thermal conductivity. Enhancing the power factor has been less successful in comparison. In this work, a peak power factor of ∼106 μW⋅cm −1 ⋅K −2 is achieved by increasing the hot pressing temperature up to 1,373 K in the p-type half-Heusler Nb 0.95 Ti 0.05 FeSb. The high power factor subsequently yields a record output power density of ∼22 W⋅cm −2 based on a single-leg device operating at between 293 K and 868 K. Such a high-output power density can be beneficial for large-scale power generation applications.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1617663113
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 9
    Online Resource
    Online Resource
    n-type thermoelectric material Mg 2 Sn 0.75 Ge 0.25 for high power generation
    Proceedings of the National Academy of Sciences ; 2015
    In:  Proceedings of the National Academy of Sciences Vol. 112, No. 11 ( 2015-03-17), p. 3269-3274
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 112, No. 11 ( 2015-03-17), p. 3269-3274
    Abstract: Thermoelectric power generation is one of the most promising techniques to use the huge amount of waste heat and solar energy. Traditionally, high thermoelectric figure-of-merit, ZT , has been the only parameter pursued for high conversion efficiency. Here, we emphasize that a high power factor ( PF ) is equivalently important for high power generation, in addition to high efficiency. A new n-type Mg 2 Sn-based material, Mg 2 Sn 0.75 Ge 0.25 , is a good example to meet the dual requirements in efficiency and output power. It was found that Mg 2 Sn 0.75 Ge 0.25 has an average ZT of 0.9 and PF of 52 μW⋅cm −1 ⋅K −2 over the temperature range of 25–450 °C, a peak ZT of 1.4 at 450 °C, and peak PF of 55 μW⋅cm −1 ⋅K −2 at 350 °C. By using the energy balance of one-dimensional heat flow equation, leg efficiency and output power were calculated with T h = 400 °C and T c = 50 °C to be of 10.5% and 6.6 W⋅cm −2 under a temperature gradient of 150 °C⋅mm −1 , respectively.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1424388112
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2015
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 10
    Online Resource
    Online Resource
    Variants of mouse DNA polymerase κ reveal a mechanism of efficient and accurate translesion synthesis past a benzo[ a ]pyrene dG adduct
    Proceedings of the National Academy of Sciences ; 2014
    In:  Proceedings of the National Academy of Sciences Vol. 111, No. 5 ( 2014-02-04), p. 1789-1794
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 111, No. 5 ( 2014-02-04), p. 1789-1794
    Abstract: DNA polymerase κ (Polκ) is the only known Y-family DNA polymerase that bypasses the 10 S (+)- trans - anti -benzo[ a ]pyrene diol epoxide (BPDE)- N 2 -deoxyguanine adducts efficiently and accurately. The unique features of Polκ, a large structure gap between the catalytic core and little finger domain and a 90-residue addition at the N terminus known as the N-clasp, may give rise to its special translesion capability. We designed and constructed two mouse Polκ variants, which have reduced gap size on both sides [Polκ Gap Mutant (PGM) 1] or one side flanking the template base (PGM2). These Polκ variants are nearly as efficient as WT in normal DNA synthesis, albeit with reduced accuracy. However, PGM1 is strongly blocked by the 10 S (+)- trans - anti -BPDE- N 2 -dG lesion. Steady-state kinetic measurements reveal a significant reduction in efficiency of dCTP incorporation opposite the lesion by PGM1 and a moderate reduction by PGM2. Consistently, Polκ-deficient cells stably complemented with PGM1 GFP-Polκ remained hypersensitive to BPDE treatment, and complementation with WT or PGM2 GFP-Polκ restored BPDE resistance. Furthermore, deletion of the first 51 residues of the N-clasp in mouse Polκ (mPolκ 52–516 ) leads to reduced polymerization activity, and the mutant PGM2 52–516 but not PGM1 52–516 can partially compensate the N-terminal deletion and restore the catalytic activity on normal DNA. However, neither WT nor PGM2 mPolκ 52–516 retains BPDE bypass activity. We conclude that the structural gap physically accommodates the bulky aromatic adduct and the N-clasp is essential for the structural integrity and flexibility of Polκ during translesion synthesis.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1324168111
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2014
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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