Science,16,2021,vol. 372, No.6539.

Science 202 1 April 16 Volume 372, No.6539.

palaeontology

Absolute abundance and preservation rate of Tyrannosaurus rex

Absolute abundance and fossil preservation rate of Tyrannosaurus rex

Authors: Charles Marshall, Daniel v Latorre, Connor j Wilson, tanner m frank, etc.

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Combined with our rich knowledge of Tyrannosaurus rex, the population variables and preservation rate of postlarvae Tyrannosaurus rex are calculated. We estimate that its abundance is 20,000 individuals at any one time, and it has lasted for 65,438+027,000 generations. The total number of Tyrannosaurus Rex once lived is 2.5 billion individuals, and the fossil recovery rate is 65,438+0/80 million individuals, or 65,438+0/65,438+in the most abundant fossil places. The uncertainty of these values spans more than two orders of magnitude, mainly because of the change of density-weight relationship, not the change of paleontological input variables.

Physics physics

Realization of remote solid-state quantum bit multi-node quantum network

Realization of remote solid-state quantum bit polymorphic quantum network

Authors: M. Pompili, S.L.N. Hermans, S.Baier, H.K.C. Beukers, etc.

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The remote quantum node based on diamond communication qubits is combined into a scalable phase stability architecture, supplemented by powerful memory qubits and local quantum logic. In addition, we realize real-time communication across the network and feed-forward gate operation. We demonstrate two quantum network protocols without post-selection: the distribution of real multi-body entangled states on three nodes and the entanglement exchange through an intermediate node. Our work has established a key platform for exploring, testing and developing multi-node quantum network protocols and quantum network control stacks.

Band gap magnetic ground state in candidate quantum spin liquid κ-(BEDT-TTF)2Cu2(CN)3

Band gap magnetic ground state of quantum spin liquid candidate κ-(BEDT-TTF)2Cu2(CN)3

Author: Bj? Rn Miksch, Andrej Pustogow, Mojtaba Javaheri Rahim, Andrey A. Bardin, etc.

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This is consistent with the formation of the ground state of valence bond solid. We find that when the intrinsic spin forms singlet state, the contribution of impurities to ESR response is dominant. The detection of electrons directly shows the key role of defects in the low-energy properties of quantum spin systems without magnetic order.

materials science

Nematicity and Competitive Order of Superconducting Magic Horn Graphene

Linear and Competitive Order of Superconducting Magic Horn Graphene

Authors: Daniel Raton-Roeglin, Noah Yuan Fuqing, et al.

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E in pairs, at least two cones. Only two Weir cones of semi-metal are ideal Weir semi-metal (IWSM). Here, we report the experiment of realizing IWSM band by designing three-dimensional spin-orbit coupling of ultra-cold atoms. The topological Weyl point is clearly measured by virtual slice imaging technology in equilibrium state, and further analyzed in quenching dynamics. The realization of IWSM band opens up a way to study all kinds of strange phenomena that are difficult to obtain in solids.

environmental sciences

The carbon loss of wildfire in northern forest is offset by the increase of deciduous tree dominance.

The carbon loss caused by wildfires in the northern forest is offset by the increase of deciduous trees.

Authors: Michelle C. Mack, Sans J. Walker, Jill F. johnstone, Heather D. Alexander, etc.

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Compensation for greater burning of soil carbon in a ten-year time scale. The severe burning of organic soil shifted the tree advantage from the slow-growing black spruce to the fast-growing deciduous broad-leaved trees, resulting in a net increase of carbon storage by five times during the disturbance period. In the future, the reduction of forest fire activities dominated by fallen leaves in the north may increase the retention time of this carbon in the landscape, thus reducing the feedback to climate warming.