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A Historical Sedimentary Record of Mercury in a Shallow Eutrophic Lake: Impacts of Human Activities and Climate Change

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Engineering 2019年第2期5卷 296-304页

作者： Hanxiao Zhang Shouliang Huo Kevin M. Yeager Beidou Xi Jingtian Zhang fengchang wu State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental Science Beijing 100012 China Department of Earth and Environmental Sciences University of Kentucky Lexington KY 40506 USA

Mercury and its derivatives are hazardous environmental pollutants and could affect the aquatic ecosystems and human health by biomagnification. Lake sediments can provide important historical information regarding changes in pollution levels and thus trace anthropogenic or natural influences. This research investigates the 100-year history of mercury (Hg) deposition in sediments from Chao Lake, a shallow eutrophic lake in China. The results indicate that the Hg deposition history can be separated into three stages (pre-1960s, 1960s–1980s, and post-1980s) over the last 100 years. Before the 1960s, Hg concentrations in the sediment cores varied little and had no spatial difference. Since the 1960s, the concentration of Hg began to increase gradually, and showed a higher concentration of contamination in the western half of the lake region than in the eastern half of the lake region due to all kinds of centralized human-input sources. The influences of anthropogenic factors and hydrological change are revealed by analyzing correlations between Hg and heavy metals (Fe, Co, Cr, Cu, Mn, Pb, and Zn), stable carbon and nitrogen isotopes (d13C and d15N), nutrients, particle sizes, and meteorological factors. The results show that Hg pollution intensified after the 1960s, mainly due to hydrological change, rapid regional development and urbanization, and the proliferation of anthropogenic Hg sources. Furthermore, the temperature, wind speed, and evaporation are found to interactively influence the environmental behaviors and environmental fate of Hg.

关键词： Lake sediment Mercury Vertical distribution Anthropogenic activities

A novel Ag/ZnO core-shell structure for efficient sterilization synergizing antibiotics and subsequently removing residuals

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Green Energy & Environment 2024年第2期9卷 366-377页

作者： Wenmei Han Wenli Wang Jie Fan Runping Jia Xuchun Yang Tong wu Qingsheng wu School of Chemical Science and Engineering Shanghai Key Laboratory of Chemical Assessment and SustainabilityInstitute of Advanced StudyTongji UniversityShanghai200092China College of Textile and Clothing Engineering China National Textile and Apparel Council Key Laboratory of Natural DyesSoochow UniversitySuzhou215123China Department of Urology Shanghai First People’s HospitalSchool of MedicineShanghai Jiaotong UniversityShanghai200080China School of Materials Science and Engineering Shanghai Institute of TechnologyShanghai201418China

The massive use of antibiotics has led to the aggravation of bacterial resistance and also brought environmental pollution problems.This poses a great threat to human health.If the dosage of antibiotics is reduced by increasing its bactericidal performance,the emergence of drug resistance is certainly delayed,so that there's not enough time for developing drug resistance during treatment.Therefore,we selected typical representative materials of metal Ag and semiconductor ZnO nano-bactericides to design and synthesize Ag/ZnO hollow core-shell structures(AZ for short).Antibiotics are grafted on the surface of AZ through rational modification to form a composite sterilization system.The research results show that the antibacterial efficiency of the composite system is significantly increased,from the sum(34.7%+22.8%-57.5%)of the antibacterial efficiency of AZ and gentamicin to 80.2%,net synergizes 22.7%,which fully reflects the effect of 1+1>2.Therefore,the dosage of antibiotics can be drastically reduced in this way,which makes both the possibility of bacterial resistance and medical expenses remarkably decrease.Subsequently,residual antibiotics can be degraded under simple illumination using AZ-self as a photocatalyst,which cuts off the path of environmental pollution.In short,such an innovative route has guiding significance for drug resistance.

关键词： Ag/ZnO hollow Core-shell structures Antibiotics Gentamycin Synergistic sterilization Photodegradation

Matched Volterra reduced-order model for an airfoil undergoing periodic translation

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Chinese Journal of Aeronautics 2024年第1期37卷 19-23页

作者： Lianrui NIE Ziniu wu Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China

This paper is devoted to application of the Reduced-Order Model(ROM)based on Volterra series to prediction of lift and drag forces due to airfoil periodic translation in transonic flow region.When there is large amplitude oscillation of the relative Mach number,as appeared in helicopter rotor movement in forward flight,the conventional Volterra ROM is found to be unsatisfactory.To cover such applications,a matched Volterra ROM,inspired from previous multistep nonlinear indicial response method based on Duhamel integration,is thus considered,in which the step motions are defined inside a number of equal intervals with both positive and negative step motions to match the airfoil forward and backward movement,and the kernel functions are constructed independently at each interval.It shows that,at least for the translation movement considered,this matched Volterra ROM greatly improves the accuracy of prediction.Moreover,the matched Volterra ROM,with the total number of step motions and thus the computational cost close to those of the conventional Volterra ROM method,has the additional advantage that the same set of kernels can match various translation motions with different starting conditions so the kernels can be predesigned without knowing the specific motion of airfoil.

关键词： Airfoil periodic translation Lift and drag Reduced-order model Transonic flow Unsteady flow

High-dimensional robust inference for censored linear models

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Science China Mathematics 2024年第4期67卷 891-918页

作者： Jiayu Huang Yuanshan wu School of Mathematics and Statistics Wuhan UniversityWuhan 430072China School of Statistics and Mathematics Zhongnan University of Economics and LawWuhan 430073China

Due to the direct statistical interpretation,censored linear regression offers a valuable complement to the Cox proportional hazards regression in survival analysis.We propose a rank-based high-dimensional inference for censored linear regression without imposing any moment condition on the model error.We develop a theory of the high-dimensional U-statistic,circumvent challenges stemming from the non-smoothness of the loss function,and establish the convergence rate of the regularized estimator and the asymptotic normality of the resulting de-biased estimator as well as the consistency of the asymptotic variance estimation.As censoring can be viewed as a way of trimming,it strengthens the robustness of the rank-based high-dimensional inference,particularly for the heavy-tailed model error or the outlier in the presence of the response.We evaluate the finite-sample performance of the proposed method via extensive simulation studies and demonstrate its utility by applying it to a subcohort study from The Cancer Genome Atlas(TCGA).

关键词： censoring mechanism heavy-tailed distribution non-smooth loss function outlier rank regression

Space-time estimates of the 3D bipolar compressible Navier-Stokes-Poisson system with unequal viscosities

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Science China Mathematics 2024年第5期67卷 1059-1084页

作者： Zhigang wu Weike Wang Department of Mathematics Donghua UniversityShanghai 201620China School of Mathematical Sciences Shanghai Jiao Tong UniversityShanghai 200240China Shanghai Frontier Science Center of Modern Analysis(CMA-Shanghai) Shanghai Jiao Tong UniversityShanghai 200240China

The space-time behavior for the Cauchy problem of the 3D compressible bipolar Navier-Stokes-Poisson(BNSP)system with unequal viscosities is given.The space-time estimate of the electric field▽φ=▽(-△)^(-1)(n-Zρ)is the most important in deducing generalized Huygens’principle for the BNSP system and it requires proving that the space-time estimate of n-Zρonly contains the diffusion wave due to the singularity of the operator▽(-△)^(-1).A suitable linear combination of unknowns reformulating the original system into two small subsystems for the special case(with equal viscosities)in wu and Wang(2017)is crucial for both linear analysis and nonlinear estimates,especially for the space-time estimate of▽φ.However,the benefits from this reformulation will no longer exist in general cases.Here,we study an 8×8 Green’s matrix directly.More importantly,each entry in Green’s matrix contains wave operators in the low-frequency part,which will generally produce Huygens’wave;as a result,one cannot achieve the space-time estimate of n-Zρthat only contains the diffusion wave as before.We overcome this difficulty by taking a more detailed spectral analysis and developing new estimates arising from subtle cancellations in Green’s function.

关键词： Green's function bipolar Navier-Stokes-Poisson system unequal viscosities

A level line of the Gaussian free field with measure-valued boundary conditions

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Science China Mathematics 2024年第2期67卷 367-404页

作者： Titus Lupu Hao wu Laboratoire de Probabilités Statistique et ModélisationSorbonne Universitéand UniversitéParis CitéCNRSParis F-75005France Yau Mathematical Sciences Center Tsinghua UniversityBeijing 100084China

In this article, we construct samples of Schramm-Loewner-evolution-like curves out of samples ofthe conformal loop ensemble and Poisson point processes of Brownian excursions. We show that the laws of thesecurves depend continuously on the intensity measure of the Brownian excursions. Using such a construction ofcurves, we extend the notion of level lines of the Gaussian free field to the case where the boundary conditionis measure-valued.

关键词： Schramm-Loewner evolution conformal loop ensemble Brownian excursion Gaussian free field

Iron-Catalyzed Reductive C(aryl)—Si Cross-Coupling of Diaryl Ethers with Chlorosilanes

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Chinese Journal of Chemistry 2024年第6期42卷 578-584页

作者： Pei Liu Baowei wu Xuefeng Cong Jie Kong School of Chemistry and Chemical Engineering Northwestern Polytechnical UniversityXi'anShaanxi710072 China Institute of Molecular Plus Department of Chemistry and Haihe Laboratory of Sustainable Chemical TransformationsTianjin University92 Weijin RoadTianjin300072 China

The reductive cross-coupling between C(aryl)—O and Si—Cl bonds is of much importance as a valuable strategy for the construction of C(aryl)—Si bonds but has remained a great challenge.Herein,we report a reductive cross-coupling of diaryl ethers and chlorosilanes via strong electrophilic C(aryl)—O and Si—Cl bonds cleavage by iron catalysis,which constitutes an efficient protocol for the synthesis of a range of functionalized arylsilanes.The combination of low cost FeCl2 as the precatalyst and iPrMgCl as the reductant shows high activity in the successive cleavage of unactivated C(aryl)—O bonds of diaryl ethers and strong electrophilic Si—Cl bonds of chlorosilanes,allowing their cross-coupling in a reductive fashion.The low-valent iron species generated in situ by reduction of FeCl2 with iPrMgCl was proposed,which prefers to initially cleavage the C(aryl)—O bond of diaryl ethers with the chelation help of an o-amide auxiliary.

关键词： Cross-coupling Diaryl ethers Chlorosilanes C—O bond cleavage Iron catalyst 3d transition metals Selectivity Regioselectivity

“If I Do not Go to Work, They Will Die!” Dual Roles of Older-Adult Personal Support Workers' Contributions During the COVID-19 Pandemic

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International Journal of Disaster Risk Science 2024年第2期15卷 226-238页

作者： Haorui wu Mandy Yung School of Social Work Faculty of Health Dalhousie University

When COVID-19 devastated older-adult organizations(long-term care homes and retirement homes), most public attention was directed toward the older-adult residents rather than their service providers. This was especially true in the case of personal support workers, some of whom are over the age of 55, putting them in two separate categories in the COVID-19 settings:(1) a vulnerable and marginalized group who are disproportionately impacted by COVID-19; and(2) essential healthcare workers. Since the current disaster-driven research, practice, and policy have primarily focused on generalized assumptions that older-adults are a vulnerable, passive, and dependent group rather than recognizing their diversity, expertise, assets, and experiences, this study aimed to identify their contributions from the perspective of older-adult personal support worker(OAPSW). This qualitative study conducted in-depth interviews, inviting 15 OAPSWs from the Greater Toronto Area, Canada. This study uncovered the OAPSWs' contribution at three levels: individual(enhancing physical health, mental health, and overall well-being), work(improving working environment and service and supporting co-workers), and family(protecting their nuclear and extended families). The outcomes inform the older-adult research, practice, policy, public discourse, and education by enhancing the appreciation of older-adults' diverse strengths and promoting their engagement and contributions in disaster settings.

关键词： Canada COVID-19 Individual-work-family triangulation Older-adult personal support workers

Palladium-Catalyzed anti-Markovnikov Halosulfonamidation of Unactivated Alkene

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Chinese Journal of Chemistry 2024年第5期42卷 464-470页

作者： Bowen Wang Jianxiao Li Wanqing wu Huanfeng Jiang State Key Laboratory of Pulp and Paper Engineering Key Laboratory of Functional Molecular Engineering of Guangdong ProvinceSchool of Chemistry and Chemical EngineeringSouth China University of TechnologyGuangzhouGuangdong510641 China

Palladium-catalyzed regioselective amination of unactivated alkene remains a challenge and is of great interest.Herein,a three-component coupling of unactivated alkene,sulfonamide,and N-halo compounds accessing vicinal haloamine has been conceived.This aminohalogenation represents a modular and regioselective strategy.The electrophilic halogenating agent enables regioselective anti-Markovnikov aminopalladation and facilitates subsequent halogenation events.And this protocol is characterized by gram-scale syntheses and late-stage functionalizations.Of note,the recovered byproduct phthalimide allows for reusing by conversion to the starting material.

关键词： Unactivated alkene anti-Markovnikov aminopalladation Vicinal haloamine Palladium catalysis Halosulfonamidation Selectivity N-Halo compounds