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研究首次揭示地球早期微生物对地球轨道周期变化的响应 快报文章
地球科学快报,2022年第21期
作者:  张树良
Microsoft Word(14Kb)  |  收藏  |  浏览/下载:658/0  |  提交时间:2022/11/10
microbial community  earth's orbital cycles  orbital driven paleoenvironmental changes  paleoenvironment evolution  
PERSIANN-CDR based characterization and trend analysis of annual rainfall in Rio De Janeiro State, Brazil 期刊论文
ATMOSPHERIC RESEARCH, 2020, 238
作者:  Sobral, Bruno Serafini;  de Oliveira-Junior, Jose Francisco;  Alecrim, Fabiano;  Gois, Givanildo;  Muniz-Junior, Joao Gualberto;  de Bodas Terassi, Paulo Miguel;  Pereira-Junior, Edson Rodrigues;  Lyra, Gustavo Bastos;  Zeri, Marcelo
收藏  |  浏览/下载:19/0  |  提交时间:2020/08/18
Orbital products  Rainfall variability  Climate change  Trend  
Vertical angular momentum constraint on lunar formation and orbital history 期刊论文
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2020, 117 (27) : 15460-15464
作者:  Tian, ZhenLiang;  Wisdom, Jack
收藏  |  浏览/下载:25/0  |  提交时间:2020/06/29
moon formation  orbital evolution  angular momentum  
Methane, Monsoons, and Modulation of Millennial-Scale Climate 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (9)
作者:  Thirumalai, Kaustubh;  Clemens, Steven C.;  Partin, Judson W.
收藏  |  浏览/下载:19/0  |  提交时间:2020/07/02
methane  monsoon  modulation  orbital forcing  millennial-scale climate variability  late Pleistocene  
Laser spectroscopy of pionic helium atoms 期刊论文
NATURE, 2020, 581 (7806) : 37-+
作者:  Shang, Jian;  Ye, Gang;  Shi, Ke;  Wan, Yushun;  Luo, Chuming;  Aihara, Hideki;  Geng, Qibin;  Auerbach, Ashley;  Li, Fang
收藏  |  浏览/下载:36/0  |  提交时间:2020/07/03

Charged pions(1) are the lightest and longest-lived mesons. Mesonic atoms are formed when an orbital electron in an atom is replaced by a negatively charged meson. Laser spectroscopy of these atoms should permit the mass and other properties of the meson to be determined with high precision and could place upper limits on exotic forces involving mesons (as has been done in other experiments on antiprotons(2-9)). Determining the mass of the pi(-) meson in particular could help to place direct experimental constraints on the mass of the muon antineutrino(10-13). However, laser excitations of mesonic atoms have not been previously achieved because of the small number of atoms that can be synthesized and their typically short (less than one picosecond) lifetimes against absorption of the mesons into the nuclei(1). Metastable pionic helium (pi He-4(+)) is a hypothetical(14-16) three-body atom composed of a helium-4 nucleus, an electron and a pi(-) occupying a Rydberg state of large principal (n approximate to 16) and orbital angular momentum (l approximate to n - 1) quantum numbers. The pi He-4(+) atom is predicted to have an anomalously long nanosecond-scale lifetime, which could allow laser spectroscopy to be carried out(17). Its atomic structure is unique owing to the absence of hyperfine interactions(18,19) between the spin-0 pi(-) and the He-4 nucleus. Here we synthesize pi He-4(+) in a superfluid-helium target and excite the transition (n, l) = (17, 16) -> (17, 15) of the pi(-)-occupied pi He-4(+) orbital at a near-infrared resonance frequency of 183,760 gigahertz. The laser initiates electromagnetic cascade processes that end with the nucleus absorbing the pi(-) and undergoing fission(20,21). The detection of emerging neutron, proton and deuteron fragments signals the laser-induced resonance in the atom, thereby confirming the presence of pi He-4(+). This work enables the use of the experimental techniques of quantum optics to study a meson.


Long-lived pionic helium atoms (composed of a helium-4 nucleus, an electron and a negatively charged pion) are synthesized in a superfluid-helium target, as confirmed by laser spectroscopy involving the pion-occupied orbitals.


  
African climate response to orbital and glacial forcing in 140,000-y simulation with implications for early modern human environments 期刊论文
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2020, 117 (5) : 2255-2264
作者:  Kutzbach, John E.;  Guan, Jian;  He, Feng;  Cohen, Andrew S.;  Orland, Ian J.;  Chen, Guangshan
收藏  |  浏览/下载:33/0  |  提交时间:2020/05/13
paleoclimate  Africa  climate modeling  glacial and orbital forcing  human dispersal  
Actinide 2-metallabiphenylenes that satisfy Huckel's rule 期刊论文
NATURE, 2020, 578 (7796) : 563-+
作者:  Achar, Yathish Jagadheesh;  Adhil, Mohamood;  Choudhary, Ramveer;  Gilbert, Nick;  Foiani, Marco
收藏  |  浏览/下载:15/0  |  提交时间:2020/07/03

Aromaticity and antiaromaticity, as defined by Huckel'  s rule, are key ideas in organic chemistry, and are both exemplified in biphenylene(1-3)-a molecule that consists of two benzene rings joined by a four-membered ring at its core. Biphenylene analogues in which one of the benzene rings has been replaced by a different (4n + 2) pi-electron system have so far been associated only with organic compounds(4,5). In addition, efforts to prepare a zirconabiphenylene compound resulted in the isolation of a bis(alkyne) zirconocene complex instead(6). Here we report the synthesis and characterization of, to our knowledge, the first 2-metallabiphenylene compounds. Single-crystal X-ray diffraction studies reveal that these complexes have nearly planar, 11-membered metallatricycles with metrical parameters that compare well with those reported for biphenylene. Nuclear magnetic resonance spectroscopy, in addition to nucleus-independent chemical shift calculations, provides evidence that these complexes contain an antiaromatic cyclobutadiene ring and an aromatic benzene ring. Furthermore, spectroscopic evidence, Kohn-Sham molecular orbital compositions and natural bond orbital calculations suggest covalency and delocalization of the uranium f(2) electrons with the carbon-containing ligand.


The synthesis of uranium- and thorium-containing metallabiphenylenes demonstrates the ability of the actinides to stabilize aromatic/antiaromatic structures where transition metals have failed.


  
Eastern Mediterranean summer temperatures since 730 CE from Mt. Smolikas tree-ring densities 期刊论文
CLIMATE DYNAMICS, 2019
作者:  Esper, Jan;  Klippel, Lara;  Krusic, Paul J.;  Konter, Oliver;  Raible, Christoph C.;  Xoplaki, Elena;  Luterbacher, Juerg;  Buentgen, Ulf
收藏  |  浏览/下载:20/0  |  提交时间:2020/02/17
Temperature reconstruction  Pinus heldreichii  Maximum latewood density  Medieval warm period  Orbital forcing  Greece  
Modeling the late Pliocene global monsoon response to individual boundary conditions 期刊论文
CLIMATE DYNAMICS, 2019, 53: 4871-4886
作者:  Zhang, Ran;  Jiang, Dabang;  Zhang, Zhongshi;  Yan, Qing;  Li, Xiangyu
收藏  |  浏览/下载:16/0  |  提交时间:2019/11/27
Late Pliocene  Global monsoon  North Africa  Asia  Orbital parameters  
Orbital and millennial northern mid-latitude westerlies over the last glacial period 期刊论文
CLIMATE DYNAMICS, 2019, 53: 3315-3324
作者:  Li, Yun;  Song, Yougui;  Yin, Qiuzhen;  Han, Li;  Wang, Yixuan
收藏  |  浏览/下载:20/0  |  提交时间:2019/11/27
Orbital  Millennial  Northern westerlies  AMOC  Precession