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Assessments of the factors controlling latent heat flux and the coupling degree between an alpine wetland and the atmosphere on the Qinghai-Tibetan Plateau in summer 期刊论文
ATMOSPHERIC RESEARCH, 2020, 240
作者:  Chen, Jinlei;  Wen, Jun;  Kang, Shichang;  Meng, Xianhong;  Tian, Hui;  Ma, Xin;  Yuan, Yuan
收藏  |  浏览/下载:10/0  |  提交时间:2020/08/18
Wetlands  Latent heat  Coupling  Control factor  CLM  
The role of the surface evapotranspiration in regional climate modelling: Evaluation and near-term future changes 期刊论文
ATMOSPHERIC RESEARCH, 2020, 237
作者:  Garcia-Valdecasas Ojeda, Matilde;  Jose Rosa-Canovas, Juan;  Romero-Jimenez, Emilio;  Yeste, P.;  Gamiz-Fortis, Sonia R.;  Castro-Diez, Yolanda;  Jesus Esteban-Parra, Maria
收藏  |  浏览/下载:9/0  |  提交时间:2020/07/02
Surface evapotranspiration  Land-surface processes  Regional climate simulations  Weather research and forecasting  Iberian Peninsula  
Coupling delay controls synchronized oscillation in the segmentation clock 期刊论文
NATURE, 2020
作者:  Yoshioka-Kobayashi, Kumiko;  Matsumiya, Marina;  Niino, Yusuke;  Isomura, Akihiro;  Kori, Hiroshi;  Miyawaki, Atsushi;  Kageyama, Ryoichiro
收藏  |  浏览/下载:7/0  |  提交时间:2020/07/03

Individual cellular activities fluctuate but are constantly coordinated at the population level via cell-cell coupling. A notable example is the somite segmentation clock, in which the expression of clock genes (such as Hes7) oscillates in synchrony between the cells that comprise the presomitic mesoderm (PSM)(1,2). This synchronization depends on the Notch signalling pathway  inhibiting this pathway desynchronizes oscillations, leading to somite fusion(3-7). However, how Notch signalling regulates the synchronicity of HES7 oscillations is unknown. Here we establish a live-imaging system using a new fluorescent reporter (Achilles), which we fuse with HES7 to monitor synchronous oscillations in HES7 expression in the mouse PSM at a single-cell resolution. Wild-type cells can rapidly correct for phase fluctuations in HES7 oscillations, whereas the absence of the Notch modulator gene lunatic fringe (Lfng) leads to a loss of synchrony between PSM cells. Furthermore, HES7 oscillations are severely dampened in individual cells of Lfng-null PSM. However, when Lfng-null PSM cells were completely dissociated, the amplitude and periodicity of HES7 oscillations were almost normal, which suggests that LFNG is involved mostly in cell-cell coupling. Mixed cultures of control and Lfng-null PSM cells, and an optogenetic Notch signalling reporter assay, revealed that LFNG delays the signal-sending process of intercellular Notch signalling transmission. These results-together with mathematical modelling-raised the possibility that Lfng-null PSM cells shorten the coupling delay, thereby approaching a condition known as the oscillation or amplitude death of coupled oscillators(8). Indeed, a small compound that lengthens the coupling delay partially rescues the amplitude and synchrony of HES7 oscillations in Lfng-null PSM cells. Our study reveals a delay control mechanism of the oscillatory networks involved in somite segmentation, and indicates that intercellular coupling with the correct delay is essential for synchronized oscillation.


Monitoring cells of the mouse presomitic mesoderm using the Achilles reporter fused to HES7 sheds light on the mechanisms that underpin synchronous oscillations in the expression of clock genes between neighbouring cells.


  
Proton-assisted growth of ultra-flat graphene films 期刊论文
NATURE, 2020, 577 (7789) : 204-+
作者:  Yuan, Guowen;  Lin, Dongjing;  Wang, Yong;  Huang, Xianlei;  Chen, Wang;  Xie, Xuedong;  Zong, Junyu;  Yuan, Qian-Qian;  Zheng, Hang;  Wang, Di;  Xu, Jie;  Li, Shao-Chun;  Zhang, Yi;  Sun, Jian;  Xi, Xiaoxiang;  Gao, Libo
收藏  |  浏览/下载:8/0  |  提交时间:2020/07/03

Graphene films grown by chemical vapour deposition have unusual physical and chemical properties that offer promise for applications such as flexible electronics and high-frequency transistors(1-10). However, wrinkles invariably form during growth because of the strong coupling to the substrate, and these limit the large-scale homogeneity of the film(1-4,11,12). Here we develop a proton-assisted method of chemical vapour deposition to grow ultra-flat graphene films that are wrinkle-free. Our method of proton penetration(13-17) and recombination to form hydrogen can also reduce the wrinkles formed during traditional chemical vapour deposition of graphene. Some of the wrinkles disappear entirely, owing to the decoupling of van der Waals interactions and possibly an increase in distance from the growth surface. The electronic band structure of the as-grown graphene films shows a V-shaped Dirac cone and a linear dispersion relation within the atomic plane or across an atomic step, confirming the decoupling from the substrate. The ultra-flat nature of the graphene films ensures that their surfaces are easy to clean after a wet transfer process. A robust quantum Hall effect appears even at room temperature in a device with a linewidth of 100 micrometres. Graphene films grown by proton-assisted chemical vapour deposition should largely retain their intrinsic performance, and our method should be easily generalizable to other nanomaterials for strain and doping engineering.


  
Structural basis of DNA targeting by a transposon-encoded CRISPR-Cas system 期刊论文
NATURE, 2020, 577 (7789) : 271-+
作者:  Halpin-Healy, Tyler S.;  Klompe, Sanne E.;  Sternberg, Samuel H.;  Fernandez, Israel S.
收藏  |  浏览/下载:5/0  |  提交时间:2020/07/03

Bacteria use adaptive immune systems encoded by CRISPR and Cas genes to maintain genomic integrity when challenged by pathogens and mobile genetic elements(1-3). Type I CRISPR-Cas systems typically target foreign DNA for degradation via joint action of the ribonucleoprotein complex Cascade and the helicase-nuclease Cas3(4,5), but nuclease-deficient type I systems lacking Cas3 have been repurposed for RNA-guided transposition by bacterial Tn7-like transposons(6,7). How CRISPR- and transposon-associated machineries collaborate during DNA targeting and insertion remains unknown. Here we describe structures of a TniQ-Cascade complex encoded by the Vibrio cholerae Tn6677 transposon using cryo-electron microscopy, revealing the mechanistic basis of this functional coupling. The cryo-electron microscopy maps enabled de novo modelling and refinement of the transposition protein TniQ, which binds to the Cascade complex as a dimer in a head-to-tail configuration, at the interface formed by Cas6 and Cas7 near the 3'  end of the CRISPR RNA (crRNA). The natural Cas8-Cas5 fusion protein binds the 5'  crRNA handle and contacts the TniQ dimer via a flexible insertion domain. A target DNA-bound structure reveals critical interactions necessary for protospacer-adjacent motif recognition and R-loop formation. This work lays the foundation for a structural understanding of how DNA targeting by TniQ-Cascade leads to downstream recruitment of additional transposase proteins, and will guide protein engineering efforts to leverage this system for programmable DNA insertions in genome-engineering applications.


  
Transparent ferroelectric crystals with ultrahigh piezoelectricity 期刊论文
NATURE, 2020, 577 (7790) : 350-+
作者:  Qiu, Chaorui;  Wang, Bo;  Zhang, Nan;  Zhang, Shujun;  Liu, Jinfeng;  Walker, David;  Wang, Yu;  Tian, Hao;  Shrout, Thomas R.;  Xu, Zhuo;  Chen, Long-Qing;  Li, Fei
收藏  |  浏览/下载:16/0  |  提交时间:2020/07/03

Transparent piezoelectrics are highly desirable for numerous hybrid ultrasound-optical devices ranging from photoacoustic imaging transducers to transparent actuators for haptic applications(1-7). However, it is challenging to achieve high piezoelectricity and perfect transparency simultaneously because most high-performance piezoelectrics are ferroelectrics that contain high-density light-scattering domain walls. Here, through a combination of phase-field simulations and experiments, we demonstrate a relatively simple method of using an alternating-current electric field to engineer the domain structures of originally opaque rhombohedral Pb(Mg1/3Nb2/3)O-3-PbTiO3 (PMN-PT) crystals to simultaneously generate near-perfect transparency, an ultrahigh piezoelectric coefficient d(33) (greater than 2,100 picocoulombs per newton), an excellent electromechanical coupling factor k(33) (about 94 per cent) and a large electro-optical coefficient gamma(33) (approximately 220 picometres per volt), which is far beyond the performance of the commonly used transparent ferroelectric crystal LiNbO3. We find that increasing the domain size leads to a higher d(33) value for the [001]-oriented rhombohedral PMN-PT crystals, challenging the conventional wisdom that decreasing the domain size always results in higher piezoelectricity(8-10). This work presents a paradigm for achieving high transparency and piezoelectricity by ferroelectric domain engineering, and we expect the transparent ferroelectric crystals reported here to provide a route to a wide range of hybrid device applications, such as medical imaging, self-energy-harvesting touch screens and invisible robotic devices.


  
Characterising the levels and sources of the historical metal contamination in the atmosphere of Montreal (Canada) from 1973 to 2013 by coupling chemistry and Lead and Osmium isotope ratios 期刊论文
ATMOSPHERIC RESEARCH, 2020, 235
作者:  Bagur, M.;  Widory, D.
收藏  |  浏览/下载:0/0  |  提交时间:2020/07/02
Interactions between Moisture and Tropical Convection. Part I: The Coevolution of Moisture and Convection 期刊论文
JOURNAL OF THE ATMOSPHERIC SCIENCES, 2020, 77 (5) : 1783-1799
作者:  Wolding, Brandon;  Dias, Juliana;  Kiladis, George;  Ahmed, Fiaz;  Powell, Scott W.;  Maloney, Eric;  Branson, Mark
收藏  |  浏览/下载:8/0  |  提交时间:2020/07/02
Clouds  Convection  Cloud parameterizations  Convective parameterization  Model errors  Tropical variability  
Interactions between Moisture and Tropical Convection. Part II: The Convective Coupling of Equatorial Waves 期刊论文
JOURNAL OF THE ATMOSPHERIC SCIENCES, 2020, 77 (5) : 1801-1819
作者:  Wolding, Brandon;  Dias, Juliana;  Kiladis, George;  Maloney, Eric;  Branson, Mark
收藏  |  浏览/下载:11/0  |  提交时间:2020/07/02
Convective adjustment  Convective clouds  Large-scale motions  Waves  atmospheric  Intraseasonal variability  Tropical variability  
Estimating the Shallow Convective Mass Flux from the Subcloud-Layer Mass Budget 期刊论文
JOURNAL OF THE ATMOSPHERIC SCIENCES, 2020, 77 (5) : 1559-1574
作者:  Vogel, Raphaela;  Bony, Sandrine;  Stevens, Bjorn
收藏  |  浏览/下载:7/0  |  提交时间:2020/07/02
Cumulus clouds  Marine boundary layer  Mixed layer  Mass fluxes  transport  Dropsondes  Large eddy simulations