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研究人员利用最新气候模型预测西北太平洋大尺度大气环流模式及相关温度与降水 快报文章
地球科学快报,2023年第19期
作者:  王立伟
Microsoft Word(13Kb)  |  收藏  |  浏览/下载:473/0  |  提交时间:2023/10/10
weather patterns  atmospheric circulation patterns  
地震震源性质控制近源地震辐射模式对于地震频率的依赖性 快报文章
地球科学快报,2022年第1期
作者:  王晓晨
Microsoft Word(13Kb)  |  收藏  |  浏览/下载:726/0  |  提交时间:2022/01/11
Earthquake Source Complexity  Near-Source Radiation Patterns  
挪威非盈利组织探讨G20国家食品消费对气候的影响 快报文章
气候变化快报,2020年第16期
作者:  曾静静
Microsoft Word(16Kb)  |  收藏  |  浏览/下载:387/0  |  提交时间:2020/08/19
Food Consumption Patterns  National Dietary Guidelines (NDGs)  G20 Countries  
The timing and effect of the earliest human arrivals in North America 期刊论文
NATURE, 2020
作者:  Lorena Becerra-Valdivia;  Thomas Higham
收藏  |  浏览/下载:28/0  |  提交时间:2020/08/09

The peopling of the Americas marks a major expansion of humans across the planet. However, questions regarding the timing and mechanisms of this dispersal remain, and the previously accepted model (termed '  Clovis-first'  )-suggesting that the first inhabitants of the Americas were linked with the Clovis tradition, a complex marked by distinctive fluted lithic points(1)-has been effectively refuted. Here we analyse chronometric data from 42 North American and Beringian archaeological sites using a Bayesian age modelling approach, and use the resulting chronological framework to elucidate spatiotemporal patterns of human dispersal. We then integrate these patterns with the available genetic and climatic evidence. The data obtained show that humans were probably present before, during and immediately after the Last Glacial Maximum (about 26.5-19 thousand years ago)(2,3)but that more widespread occupation began during a period of abrupt warming, Greenland Interstadial 1 (about 14.7-12.9 thousand years beforead 2000)(4). We also identify the near-synchronous commencement of Beringian, Clovis and Western Stemmed cultural traditions, and an overlap of each with the last dates for the appearance of 18 now-extinct faunal genera. Our analysis suggests that the widespread expansion of humans through North America was a key factor in the extinction of large terrestrial mammals.


A Bayesian age model suggests that human dispersal to the Americas probably began before the Last Glacial Maximum, overlapping with the last dates of appearance for several faunal genera.


  
Spatial Dependence of Floods Shaped by Spatiotemporal Variations in Meteorological and Land-Surface Processes 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (13)
作者:  Brunner, Manuela, I;  Gilleland, Eric;  Wood, Andy;  Swain, Daniel L.;  Clark, Martyn
收藏  |  浏览/下载:19/0  |  提交时间:2020/06/16
spatial dependence  extremes  flood  precipitation  weather patterns  co-occurrence  
Is the cold region in Northeast China still getting warmer under climate change impact? 期刊论文
ATMOSPHERIC RESEARCH, 2020, 237
作者:  Zhou, Zhaoqiang;  Shi, Haiyun;  Fu, Qiang;  Li, Tianxiao;  Gan, Thian Yew;  Liu, Suning;  Liu, Kang
收藏  |  浏览/下载:10/0  |  提交时间:2020/07/02
Global warming hiatus  Temperature trend  Cross wavelet analysis  Large-scale climate patterns  Northeast China  
Nearest neighbours reveal fast and slow components of motor learning 期刊论文
NATURE, 2020, 577 (7791) : 526-+
作者:  Kollmorgen, Sepp;  Hahnloser, Richard H. R.;  Mante, Valerio
收藏  |  浏览/下载:5/0  |  提交时间:2020/07/03

A new method for analysing change in high-dimensional data is based on nearest-neighbour statistics and is applied here to song dynamics during vocal learning in zebra finches, but could potentially be applied to other biological and artificial behaviours.


Changes in behaviour resulting from environmental influences, development and learning(1-5) are commonly quantified on the basis of a few hand-picked features(2-4,6,7) (for example, the average pitch of acoustic vocalizations(3)), assuming discrete classes of behaviours (such as distinct vocal syllables)(2,3,8-10). However, such methods generalize poorly across different behaviours and model systems and may miss important components of change. Here we present a more-general account of behavioural change that is based on nearest-neighbour statistics(11-13), and apply it to song development in a songbird, the zebra finch(3). First, we introduce the concept of '  repertoire dating'  , whereby each rendition of a behaviour (for example, each vocalization) is assigned a repertoire time, reflecting when similar renditions were typical in the behavioural repertoire. Repertoire time isolates the components of vocal variability that are congruent with long-term changes due to vocal learning and development, and stratifies the behavioural repertoire into '  regressions'  , '  anticipations'  and '  typical renditions'  . Second, we obtain a holistic, yet low-dimensional, description of vocal change in terms of a stratified '  behavioural trajectory'  , revealing numerous previously unrecognized components of behavioural change on fast and slow timescales, as well as distinct patterns of overnight consolidation(1,2,4,14,15) across the behavioral repertoire. We find that diurnal changes in regressions undergo only weak consolidation, whereas anticipations and typical renditions consolidate fully. Because of its generality, our nonparametric description of how behaviour evolves relative to itself-rather than to a potentially arbitrary, experimenter-defined goal(2,3,14,16)-appears well suited for comparing learning and change across behaviours and species(17,18), as well as biological and artificial systems(5).


  
Archimedean lattices emerge in template-directed eutectic solidification 期刊论文
NATURE, 2020, 577 (7790) : 355-+
作者:  Subbaraman, Nidhi;  Viglione, Giuliana
收藏  |  浏览/下载:9/0  |  提交时间:2020/07/03

Template-directed assembly has been shown to yield a broad diversity of highly ordered mesostructures(1),(2), which in a few cases exhibit symmetries not present in the native material(3-5). However, this technique has not yet been applied to eutectic materials, which underpin many modern technologies ranging from high-performance turbine blades to solder alloys. Here we use directional solidification of a simple AgCl-KCl lamellar eutectic material within a pillar template to show that interactions of the material with the template lead to the emergence of a set of microstructures that are distinct from the eutectic'  s native lamellar structure and the template'  s hexagonal lattice structure. By modifying the solidification rate of this material-template system, trefoil, quatrefoil, cinquefoil and hexafoil mesostructures with submicrometre-size features are realized. Phase-field simulations suggest that these mesostructures appear owing to constraints imposed on diffusion by the hexagonally arrayed pillar template. We note that the trefoil and hexafoil patterns resemble Archimedean honeycomb and square-hexagonal-dodecagonal lattices(6), respectively. We also find that by using monolayer colloidal crystals as templates, a variety of eutectic mesostructures including trefoil and hexafoil are observed, the former resembling the Archimedean kagome lattice. Potential emerging applications for the structures provided by templated eutectics include non-reciprocal metasurfaces(7), magnetic spin-ice systems(8,9), and micro- and nano-lattices with enhanced mechanical properties(10,11).


  
Cortical pattern generation during dexterous movement is input-driven 期刊论文
NATURE, 2020, 577 (7790) : 386-+
作者:  Cyranoski, David
收藏  |  浏览/下载:9/0  |  提交时间:2020/07/03

The motor cortex controls skilled arm movement by sending temporal patterns of activity to lower motor centres(1). Local cortical dynamics are thought to shape these patterns throughout movement execution(2-4). External inputs have been implicated in setting the initial state of the motor cortex(5,6), but they may also have a pattern-generating role. Here we dissect the contribution of local dynamics and inputs to cortical pattern generation during a prehension task in mice. Perturbing cortex to an aberrant state prevented movement initiation, but after the perturbation was released, cortex either bypassed the normal initial state and immediately generated the pattern that controls reaching or failed to generate this pattern. The difference in these two outcomes was probably a result of external inputs. We directly investigated the role of inputs by inactivating the thalamus  this perturbed cortical activity and disrupted limb kinematics at any stage of the movement. Activation of thalamocortical axon terminals at different frequencies disrupted cortical activity and arm movement in a graded manner. Simultaneous recordings revealed that both thalamic activity and the current state of cortex predicted changes in cortical activity. Thus, the pattern generator for dexterous arm movement is distributed across multiple, strongly interacting brain regions.


  
Localization and delocalization of light in photonic moire lattices 期刊论文
NATURE, 2020, 577 (7788) : 42-+
作者:  Wang, Peng;  Zheng, Yuanlin;  Chen, Xianfeng;  Huang, Changming;  Kartashov, Yaroslav V.;  Torner, Lluis;  Konotop, Vladimir V.;  Ye, Fangwei
收藏  |  浏览/下载:13/0  |  提交时间:2020/07/03

Moire lattices consist of two superimposed identical periodic structures with a relative rotation angle. Moire lattices have several applications in everyday life, including artistic design, the textile industry, architecture, image processing, metrology and interferometry. For scientific studies, they have been produced using coupled graphene-hexagonal boron nitride monolayers(1,2), graphene-graphene layers(3,4) and graphene quasicrystals on a silicon carbide surface(5). The recent surge of interest in moire lattices arises from the possibility of exploring many salient physical phenomena in such systems  examples include commensurable-incommensurable transitions and topological defects(2), the emergence of insulating states owing to band flattening(3,6), unconventional superconductivity(4) controlled by the rotation angle(7,8), the quantum Hall effect(9), the realization of non-Abelian gauge potentials(10) and the appearance of quasicrystals at special rotation angles(11). A fundamental question that remains unexplored concerns the evolution of waves in the potentials defined by moire lattices. Here we experimentally create two-dimensional photonic moire lattices, which-unlike their material counterparts-have readily controllable parameters and symmetry, allowing us to explore transitions between structures with fundamentally different geometries (periodic, general aperiodic and quasicrystal). We observe localization of light in deterministic linear lattices that is based on flatband physics(6), in contrast to previous schemes based on light diffusion in optical quasicrystals(12), where disorder is required(13) for the onset of Anderson localization(14) (that is, wave localization in random media). Using commensurable and incommensurable moire patterns, we experimentally demonstrate the twodimensional localization-delocalization transition of light. Moire lattices may feature an almost arbitrary geometry that is consistent with the crystallographic symmetry groups of the sublattices, and therefore afford a powerful tool for controlling the properties of light patterns and exploring the physics of periodic-aperiodic phase transitions and two-dimensional wavepacket phenomena relevant to several areas of science, including optics, acoustics, condensed matter and atomic physics.