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Equilibrium thallium isotope fractionation and its constraint on Earth’s late veneer

Acta Geochimica 2019年第4期38卷 459-471页

作者： Tong Fang Yun liu State Key Laboratory of Ore Deposit Geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081People's Republic of China University of Chinese Academy of Sciences No.19(A) Yuquan RoadShijingshan DistrictBeijing 100049People's Republic of China CAS Center for Excellence in Comparative Planetology HefeiPeople's Republic of China

Equilibrium isotope fractionation of thallium(Tl) includes the traditional mass-dependent isotope fractionation effect and the nuclear volume effect(NVE). The NVE dominates the overall isotope fractionation, especially at high temperatures. Heavy Tl isotopes tend to be enriched in oxidized Tl^3+-bearing species. Our NVE fractionation results of oxidizing Tl^+ to Tl^3+ can explain the positive enrichments observed in ferromanganese sediments. Experimental results indicate that there could be0.2–0.3 e-unit fractionation between sulfides and silicates at 1650 ℃. It is consistent with our calculation results,which are in the range of 0.17–0.38 e-unit. Importantly,Tl’s concentration in the bulk silicate Earth(BSE) can be used to constrain the amount of materials delivered to Earth during the late veneer accretion stage. Because the Tl concentration in BSE is very low and its Tl isotope composition is similar with that of chondrites, suggesting either no Tl isotope fractionation occurred during numerous evaporation events, or the Tl in current BSE was totally delivered by late veneer. If it is the latter, the Tl-contentbased estimation could challenge the magnitude of late veneer which had been constrained by the amount of highly siderophile elements in BSE. Our results show that the lateaccreted mass is at least five-times larger than the previously suggested magnitude, i.e., 0.5 wt% of current Earth’s mass. The slightly lighter 205 Tl composition of BSE relative to chondrites is probable a sign of occurrence of Tlbearing sulfides, which probably were removed from the mantle in the last accretion stage of the Earth.

关键词： Equilibrium Tl isotope fractionation Nuclear volume effect Tl fractionations between silicates and sulfides Late veneer First-principles calculation

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On the Error Estimate of the Harmonic B_z Algorithm in MREIT from Noisy Magnetic Flux Field

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Chinese Annals of Mathematics,Series B 2014年第3期35卷 319-336页

作者： Qun CHEN Jijun liu College of Mathematics and Statistics Nanjing University of Information Science and Technology Corresponding author. Department of Mathematics Southeast University

Abstract Magnetic resonance electrical impedance tomography （MREIT, for short） is a new medical imaging technique developed recently to visualize the cross-section conduc- tivity of biologic tissues. A new MREIT image reconstruction method called harmonic Bz algorithm was proposed in 2002 with the measurement of Bz that is a single component of an induced magnetic flux density subject to an injection current. The key idea is to solve a nonlinear integral equation by some iteration process. This paper deals with the convergence analysis as well as the error estimate for noisy input data Bz, which is the practical situation for MREIT. By analyzing the iteration process containing the Laplacian operation on the input magnetic field rigorously, the authors give the error estimate for the iterative solution in terms of the noisy level 6 and the regularizing scheme for determining ABz approximately from the noisy input data. The regularizing scheme for computing the Laplacian from noisy input data is proposed with error analysis. Our results provide both the theoretical basis and the implementable scheme for evaluating the reconstruction accuracy using harmonic Bz algorithm with practical measurement data containing noise.

关键词： MREIT Image reconstruction Iteration Error estimate

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Recent Progress of Magnetically Actuated DNA Micro/Nanorobots

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Cyborg and Bionic Systems 2022年第1期2022卷 43-54页

作者： Fengyu liu Xiaoming liu Qiang Huang Tatsuo Arai Key Labraoryof Bmetic Robts and Sym Minsry of EduationState KeyLaboratoryofInteligent Controlandcisnof Complex SystemBejing Advanced Innovation Center for Intlligent Robots and Systems and School of Mechatron ical Engineering Bejing Institute of TechnologyBeijing 100081China Center for Neuroscience and Biomedical Enginring The University of Eletro-CommunicationsTokyo 182-8585 Japan

In the past few decades,the field of DNA origami based micro/nanotechnology has developed dramatically and spawned attention increasingly,as its high integrality,rigid structure,and excellent resistance ability to enzyme *** two-dimensional and three-dimensional DNA nanostructures coordinated with optical,chemical,or magnetic triggers have been designed and assembled,extensively used as versatile templates for molecular robots,nanosensors,and intracellular drug *** magnetic field has been widely regarded as an ideal driving and operating system for micro/nanomaterials,as it does not require high intensity lasers like light control,nor does it need to change the chemical composition similar to chemical ***,we review the recent achievements in the induction and actuation of DNA origami-based nanodevices that respond to magnetic *** magnetic actuation-based DNA nanodevices were regularly combined with magnetic beads or gold nanopartides and applied to generate single stranded scaffolds,assemble various DNA nanostructures,and purify specific DNA ***,they also produced artificial magnetism or moved regularly driven by *** fields to explain deeper scientific issues.

关键词： resistance magnetic versatile

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Biological analysis of woodpecker’s brain after impact experiments

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Science China(Technological Sciences) 2021年第5期64卷 1101-1106页

作者： XU Peng NI YiKun liu JingLong ZHANG WeiRong liu SiJian WANG LiZhen FAN YuBo Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education Beijing Advanced Innovation Centre for Biomedical EngineeringSchool of Biological Science and Medical EngineeringBeihang UniversityBeijing 100083China

Woodpeckers can withstand a fierce impact during *** studies have focused on the biomechanical analysis of the pecking process,the properties of the beak and hyoid bone of woodpecker;however,the biological characteristics of the woodpecker brain are also important in resisting impact *** employed impact experiments and biological analysis in normal and injured brains to reveal the impact-resistant biological characteristics of woodpecker brains,as well as the impact energy’s biological effects on the woodpecker *** hoopoe,which has a similar size but only a slight pecking behavior,was selected as the control group to compare brain morphology and neuronal cells differences in normal brains between woodpecker and hoopoe by sectioning and staining.A loading device was designed to conduct a quantifiable impact energy to the woodpeckers’*** groups of woodpeckers were impacted with the same energy on the forehead,beak,tempus and occiput,*** changes in the injured brains were evaluated by Nissl staining and enzyme-linked immunosorbent *** results showed that:(1)woodpeckers had a larger cerebellum and a higher density of Nissl bodies than hoopoe;(2)Nissl apoptosis appeared in the brain samples after the forehead and the occiput impact experiments,but no obvious Nissl body apoptosis was observed after impact on the tempus and the beak;(3)β-amyloid protein accumulated in the normal status woodpecker *** study reveals that:woodpecker brain morphology is well-adapted to impact,woodpecker heads display location-dependent protective performance,with beak and tempus regions having a better protective performance than the forehead and occiput,Nissl apoptosis appears in injured woodpecker brains,and that the accumulation ofβ-amyloid protein does not show a direct relationship with the injury state of woodpecker’s brain tissue in our study.

关键词： woodpecker biomechanics impact experiments impact resistance biological analysis

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Permethrin resistance variation and susceptible reference line isolation in a field population of the mosquito, Culex quinquefasciatus （Diptera： Culicidae）

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Insect Science 2014年第5期21卷 659-666页

作者： Ting Yang Nannan liu Department of Entomology and Plant Pathology Auburn University Auburn AL 36849 USA

This study examines the genetic variations and mechanisms involved in the development of permethrin resistance in individual mosquitoes from a field population of Culex quinquefasciatus, HAmCq^G0, and characterizes susceptible reference lines of mosquitoes with a similar genetic background to the field HAmCq^G0 strain. Six upregulated cytochrome P450 genes, CYP9M10, CYP9J34, CYP6P14, CYP9J40, CYP6AA7, and CYP4C52v1, previously identified as being upregulated in the larvae of resistant HAmCq68 mosquitoes were examined in the larvae of 3 strains （susceptible S-Lab, parental HAmCq^G0 and permethrin-selected highly resistant HAmCq68） and 8 HAmCq^G0 single- egg raft colonies, covering a range of levels of susceptibility/resistance to perrnethrin and exhibiting different variations in the expression of A and/or T alleles at the L-to-F kdr locus of the sodium channel. The 2 lines with the lowest tolerance to permethrin and bearing solely the susceptible A allele at the L-to-F kdr locus of the sodium channels, from colonies Cx_SERC5 and Cx_SERC8, showed lower or similar levels of all 6 of the P450 genes tested compared with the S-Lab strain, suggesting that these 2 lines could be used as the reference mosquitoes in future studies characterizing insecticide resistance in HAmCq mosquitoes. This study also provides a detailed investigation of the mechanisms involved in insecticide resistance in individuals within a population： individuals with elevated levels of resistance to permethrin all displayed one or more potential resistance mechanisms-either elevated levels of P450 gene expression, or L-to-F mutations in the sodium channel, or both.

关键词： Culex quinquefasciatus permethrin resistance single-egg raft colony susceptibility

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Cohen-Fischman-Westreich's Double Centralizer Theorem for Almost-Triangular Hopf Algebras

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Chinese Annals of Mathematics,Series B 2016年第4期37卷 483-494页

作者： Guohua liu Xiaofan ZHAO Department of Mathematics Southeast University College of Mathematics and Information Science Henan Normal University

In this paper, the authors study the Cohen-Fischman-Westreich's double centralizer theorem for triangular Hopf algebras in the setting of almost-triangular Hopf algebras.

关键词： Schur's double centralizer theorem Cohen-Fischman-Westreich's doublecentralizer theorem Almost-triangular Hopf algebra R-Lie algebra

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TOPOLOGY DESCRIPTION FUNCTION BASED METHOD FOR MATERIAL DESIGN

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Acta Mechanica Solida Sinica 2006年第2期19卷 95-102页

作者： Cao Xianfan liu Shutian State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanics Dalian University of Technology Dalian 116024 China

The purpose of this paper is to investigate the application of topology description function （TDF） in material design. Using TDF to describe the topology of the microstructure, the formulation and the solving technique of the design problem of materials with prescribed mechanical properties are presented. By presenting the TDF as the sum of a series of basis functions determined by parameters, the topology optimization of material microstructure is formulated as a size optimization problem whose design variables are parameters of TDF basis functions and independent of the mesh of the design domain. By this method, high quality topologies for describing the distribution of constituent material in design domain can be obtained and checkerboard problem often met in the variable density method is avoided. Compared with the conventional level set method, the optimization problem can be solved simply by existing optimization techniques without the process to solve the ＇Hamilton-Jacobi-type＇ equation by the difference method. The method proposed is illustrated with two 2D examples. One gives the unit cell with positive Poisson＇s ratio, the other with negative Poisson＇s ratio. The examples show the method based on TDF is effective for material design.

关键词： topology optimization topology description function material design

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Ab initio investigation on the structures and spectra of the firefly luciferin

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Science China Chemistry 2007年第6期50卷 725-730页

作者： liu YaJun FANG WeiHai College of Chemistry Beijing Normal University Beijing 100875 China College of Chemistry Beijing Normal University Beijing 100875 China

The ground state (S0) geometry of the firefly luciferin (LH2) was optimized by both DFT B3LYP and CASSCF methods. The vertical excitation energies (Tv) of three low-lying states (S1, S2, and S3) were calculated by TD-DFT B3LYP//CASSCF method. The S1 geometry was optimized by CASSCF method. Its Tv and the transition energy (Te) were calculated by MS-CASPT2//CASSCF method. Both the TD-DFT and MS-CASPT2 calculated S1 state Tv values agree with the experimental one. The IPEA shift greatly affects the MS-CASPT2 calculated Tv values. Some important excited states of LH2 and oxyluciferin (oxyLH2) are charge-transfer states and have more than one dominant configuration, so for deeply researching the firefly bioluminescence, the multireference calculations are desired.

关键词： firefly luciferin, TD-DFT, CASSCF, CASPT2

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A geometric heat flow for vector fields

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Science China Mathematics 2015年第4期58卷 673-688页

作者： LI Yi liu KeFeng Department of Mathematics Shanghai Jiao Tong University Department of Mathematics University of California at Los AngelesLos Angeles CA 90095-1555 USA Center of Mathematical Sciences Zhejiang University

We introduce and study a geometric heat flow to find Killing vector fields on closed Riemannian manifolds with positive sectional curvature. We study its various properties, prove the global existence of the solution to this flow, discuss its convergence and possible applications, and its relation to the Navier-Stokes equations on manifolds and Kazdan-Warner-Bourguignon-Ezin identity for conformal Killing vector fields. We also provide two new criterions on the existence of Killing vector fields. A similar flow to finding holomorphic vector fields on K¨ahler manifolds will be studied by Li and liu(2014).

关键词： geometric heat flow Killing vector fields Yano's theorem Navier-Stokes equations KazdanWarner-Bourguignon-Ezin identity

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LOCAL BENDING OF THIN FILM ON VISCOUS LAYER

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Acta Mechanica Solida Sinica 2010年第2期23卷 106-114页

作者： Yin Zhang Yun liu State Key Laboratory of Nonlinear Mechanics (LNM) Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China Faculty of Information and Automation Kunming University of Science and Technology Kunming 650051 China

Effects of deposition layer position film are systematically investigated. Because the and number/density on local bending of a thin deposition layer interacts with the thin film at the interface and there is an offset between the thin film neutral surface and the interface, the deposition layer generates not only axial stress but also bending moment. The bending moment induces an instant out-of-plane deflection of the thin film, which may or may not cause the socalled local bending. The deposition layer is modeled as a local stressor, whose location and density are demonstrated to be vital to the occurrence of local bending. The thin film rests on a viscous layer, which is governed by the Navier-Stokes equation and behaves like an elastic foundation to exert transverse forces on the thin film. The unknown feature of the axial constraint force makes the governing equation highly nonlinear even for the small deflection chse. The constraint force and film transverse deflection are solved iteratively through the governing equation and the displacement constraint equation of immovable edges. This research shows that in some special cases, the deposition density increase does not necessarily reduce the local bending. By comparing the thin film deflections of different deposition numbers and positions, we also present the guideline of strengthening or suppressing the local bending.

关键词： local bending deposition layer/dot thin film viscous layer constraint

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