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Theoretical Investigation on Regioselectivities of Diels-Alder Reactions by Conjugated Effect

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Chinese Journal of Chemistry 2020年第12期38卷 1696-1702页

作者： zhen-zhen xu Jian zhao dong-xia zhao zhong-zhi yang Jiangxi Province Key Laboratory of the Causes and Control of Atmospheric Pollution and School of Chemistry Biology and Materials ScienceEast China University of TechnologyNonchangJiangxi 330013China School of Chemistry and Chemical Engineering Liaoning Normal UniversityDalianLiaoning 116029China

of main observation and conclusion The regioselectivities of 76 Diels-Alder reactions between unsymmetrical dienes and dienophiles were investigated by local softness and generalized local softness at atomic and chemical bond view,respectively,where the reactivity descriptors were calculated by finite difference approximation and ABEEMan *** on local HSAB principle and matching criterion of local softness,reasonable explanation and prediction on regioselectivities of all reactions through ABEEMan model have been obtained,which are in agreement with the experimental ***,at n-bond level,while the 1-substituents of dienes were NH2/NMe2,and NEt2/because of the p-R conjugated effect between the lone pairs of Natom and the conjugated n-bond of the four double-bonded carbon atoms in diene,it made the dienophile not easy to approach diene by Manner A,hence,Manner B can forecast the ortho regioisomer as main product well,and Manner A *** to the other reactions,both Manner A and Manner B can predict their *** can be seen that the ABEEMan model can take the effect of the chemical environment on the reaction reactivity into account richly,especially the system includes n-bond and lone ***,the results through the finite difference approximation are not reasonable.

关键词： reactivity conjugated approximation

10B-doped MCP detector developed for neutron resonance imaging at Back-n white neutron source

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Nuclear Science and Techniques 2024年第8期35卷 58-68页

作者： Qiang Li Li‑Jiao Wang Jing‑Yu Tang xiang‑Biao Qiu zhen Chen Mao‑Yuan zhao Chang‑Jun Ning Kai Pan Wei xu Tao Li Su‑Peng Lu Han Yi Rui‑Rui Fan Chang‑Qing Feng Rong Zhang xiao‑yang Sun Qi An Hao‑Fan Bai Jiang‑Bo Bai Jie Bao Ping Cao Qi‑Ping Chen Yong‑Hao Chen Zeng‑Qi Cui An‑Chuan Fan Fan‑zhen Feng Min‑Hao Gu Chang‑Cai Han Zi‑Jie Han Guo‑Zhu He Yong‑Cheng He yang Hong Yi‑Wei Hu Han‑Xiong Huang Wei Jiang zhi‑Jie Jiang zheng‑Yao Jin Ling Kang Bo Li Gong Li xiao Li yang Li Jie Liu Rong Liu Shu‑Bin Liu Yi‑Na Liu Guang‑Yuan Luan Jie Ren zhi‑Zhou Ren Xi‑Chao Ruan zhao‑Hui Song Kang Sun zhi‑Xin Tan Sheng‑Da Tang Jin‑Cheng Wang Peng‑Cheng Wang zhao‑Hui Wang zhong‑Wei Wen xiao‑Guang Wu xuan Wu Cong xia Yong‑Ji Yu Guo‑Hui Zhang Hang‑Chang Zhang Lin‑Hao Zhang Qi‑Wei Zhang xian‑Peng Zhang Yu‑Liang Zhang Yue Zhang zhi‑Yong Zhang zhi‑Hao Zhou Ke‑Jun Zhu Chong Zou Institute of High Energy Physics Chinese Academy of Sciences(CAS)Beijing 100049China Spallation Neutron Source Science Center Dongguan 523803China State Key Laboratory of Particle Detection and Electronics Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China dongguan Songshan Lake Future School Dongguan 523808China School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230027China State Key Laboratory of Particle Detection and Electronics University of Science and Technology of ChinaHefei 230026China North Night Vision Science and Technology(Nanjing)Research Institute Co.Ltd Nanjing 211106China Department of Modern Physics University of Science and Technology of ChinaHefei 230026China State Key Laboratory of Nuclear Physics and Technology School of PhysicsPeking UniversityBeijing 100871China Institute of Modern Physics Fudan UniversityShanghai 200433China Key Laboratory of Nuclear Data China Institute of Atomic EnergyBeijing 102413China China Academy of Engineering Physics Institute of Nuclear Physics and ChemistryMianyang 621900China USTC archaeometry lab University of Science and Technology of ChinaHefei 230026China Northwest Institute of Nuclear Technology Xi’an 710024China University of Chinese Academy of Sciences Beijing 100049China China Shipbuilding Trading Co. LtdBeijing 100044China

Neutron resonance imaging(NRI)has recently emerged as an appealing technique for neutron *** complexity surpasses that of conventional transmission imaging,as it requires a high demand for both a neutron source and ***,the progression of NRI technology has been sluggish since its inception in the 1980s,particularly considering the limited studies analyzing the neutron energy range above *** white neutron source(Back-n)at the China Spallation Neutron Source(CSNS)provides favorable beam conditions for the development of the NRI technique over a wide neutron energy range from eV to ***-sensitive microchannel plates(MCP)have emerged as a cutting-edge tool in the field of neutron detection owing to their high temporal and spatial resolutions,high detection efficiency,and low *** this study,we report the development of a 10B-doped MCP detector,along with its associated electronics,data processing system,and NRI experiments at the *** heavy elements such as gold,silver,tungsten,and indium can be easily identified in the transmission images by their characteristic resonance peaks in the 1–100 eV energy range;the more difficult medium-weight elements such as iron,copper,and aluminum with resonance peaks in the 1–100 keV energy range can also be *** particular,results in the neutron energy range of dozens of keV(Aluminum)are reported here for the first time.

关键词： Neutron resonance imaging 10B doped MCP detector White neutron source Sample nuclide identification

Synthesis and insecticidal activities of novel bridged-neonicotinoids

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Chinese Chemical Letters 2017年第8期28卷 1743-1745页

作者： dong-dong Zhang Shu-xia Cui zhi-Ping xu dong-Mei Li zhong-zhen Tian Shandong Provincial Key Laboratory of Fluorine Chemistry and Chemical Materials School of Chemistry and Chemical Engineering University of Jinan Shanghai Key Laboratory of Chemical Biology School of Pharmacy East China University of Science and Technology

A series of novel bridged-neonicotinoid analogues were designed and synthesized, which were constructed by starting material 8 with cyclopentenone or cyclohexenone in the presence of catalyst aluminium chloride. All of the compounds were characterized and confirmed by^1H NMR,^（13）C NMR, HRMS and IR. The bioassay tests showed that compounds 5 and 6a showed higher bioactivities than imidacloprid against Aphis craccivora.

关键词： Neonicotinoid Bridged compound Insecticidal activity Michael addition Resistance

双季稻复种冬季马铃薯提高真菌α多样性和腐生真菌相对丰度促进秸秆腐解

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植物营养与肥料学报 2024年第6期30卷 1075-1091页

作者：田茂平姜东海邱智容苗旭晨夏银行陈涛张振华赵紫薇湖南农业大学资源学院湖南长沙410128 衡阳市气象局湖南衡阳421000

【目的】秸秆还田是提高土壤肥力和作物产量的有效途径,复种模式影响土壤真菌群落结构和功能,进而影响秸秆在土壤中的降解程度。通过研究不同复种模式下秸秆的降解特征,为提高秸秆还田效益提供依据。【方法】培养试验的土壤取自3个三熟... 详细信息

【目的】秸秆还田是提高土壤肥力和作物产量的有效途径,复种模式影响土壤真菌群落结构和功能,进而影响秸秆在土壤中的降解程度。通过研究不同复种模式下秸秆的降解特征,为提高秸秆还田效益提供依据。【方法】培养试验的土壤取自3个三熟复种地块:稻—稻—紫云英(RRA)、稻—稻—油菜(RRO)、稻—稻—马铃薯(RRP),和两个两熟复种地块:稻—稻—冬板田(RRN)、稻—稻—冬泡田(RRI),采集时间均为早稻扬花期。每个土壤均设不添加和添加秸秆(0.5 g秸秆与80 g风干土混合)两个处理,然后置于250 mL棕色瓶中厌氧培养120天。在培养期内,定期取样检测CO_(2)排放量,破坏性采集土样测定土壤微生物生物量碳、氮含量和4种秸秆降解酶活性,利用扩增子高通量测序技术分析真菌群落结构。【结果】与两熟复种模式相比,三熟复种模式提高了土壤微生物生物量碳、氮含量以及β-葡萄糖苷酶、β-纤维二糖苷酶、β-木糖苷酶和漆酶活性。三熟与两熟复种土壤之间真菌群落结构存在差异,RRP地块土壤真菌ASV数目、Chao1、ACE和Shannon指数,以及分解半纤维素、纤维素和木质素等有机物质的无茎真菌属(Acaulium)、被孢霉属(Mortierella)、粉枝孢属(Oidiodendron)的相对含量显著高于两熟地块。共现性网络分析发现,与RRN相比,RRO和RRP复种模式增加了土壤真菌网络的复杂性,提高了网络中子囊菌门、壶菌门等具有秸秆分解潜力的关键物种的数量。冗余分析及回归分析等发现,全磷是复种系统中影响土壤真菌群落结构及秸秆降解酶类活性的最重要的环境因子。【结论】相比于冬闲两熟复种模式,三熟复种模式可增加微生物生物量,提高秸秆降解酶活性,同时提高真菌α多样性以及增加腐生真菌的相对丰度,进而更有效地促进秸秆的分解。双季稻结合冬季复种马铃薯是促进还田秸秆腐解、提升土壤肥力的有效复种模式。

关键词：复种模式秸秆分解秸秆分解酶活性真菌群落结构α多样性腐生真菌

Incidence and prognosis of olfactory and gustatory dysfunctions related to SARS-CoV-2 Omicron strain infection in China:A national multicenter survey of 35,566 individuals

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World Journal of Otorhinolaryngology-Head and Neck Surgery 2024年第2期10卷 113-120页

作者： Meng-Fan Liu Rui-xia Ma xian-Bao Cao Hua Zhang Shui-Hong Zhou Wei-Hong Jiang Yan Jiang Jing-Wu Sun Qin-Tai yang xue-zhong Li Ya-Nan Sun Li Shi Min Wang Xi-Cheng Song Fu-Quan Chen xiao-Shu Zhang Hong-Quan Wei Shao-Qing Yu dong-dong Zhu Luo Ba zhi-Wei Cao xu-Ping xiao Xin Wei zhi-Hong Lin Feng-Hong Chen Chun-Guang Shan Guang-Ke Wang Jing Ye Shen-Hong Qu Chang-Qing zhao zhen-Lin Wang Hua-Bin Li Feng Liu xiao-Bo Cui Sheng-Nan Ye zheng Liu Yu xu xiao Cai Wei Huang Ru-Xin Zhang Yu-Lin zhao Guo-dong Yu Guang-Gang Shi Mei-Ping Lu yang Shen Yu-Tong zhao Jia-Hong Pei Shao-Bing Xie Long-Gang Yu Ye-Hai Liu Shao-Wei Gu Yu-Cheng yang Lei Cheng Jian-Feng liu Graduate School of Beijing University of Chinese Medicine BeijingChina Department of Otorhinolaryngology Head and Neck Surgery China-Japan Friendship HospitalBeijingChina Department of Otorhinolaryngology Head and Neck Surgery The First People's Hospital of YinchuanYinchuanChina Department of Otorhinolaryngology The First People's Hospital of Yunnan ProvinceKunmingChina Department of Otorhinolaryngology The First Affiliated Hospital of Xinjiang Medical UniversityUrumqiChina Department of Otorhinolaryngology Head and Neck Surgery The First Affiliated Hospital of Zhejiang University School of MedicineHangzhouChina Department of Otorhinolaryngology Head and Neck Surgery Xiangya Hospital Central South UniversityChangshaChina Department of Otorhinolaryngology Head and Neck Surgery The Affiliated Hospital of Qingdao UniversityQingdaoChina Department of Otorhinolaryngology Head and Neck Surgery The First Affiliated Hospital of USTCHefeiChina Department of Otorhinolaryngology Head and Neck Surgery The Third Affiliated Hospital of Sun Yat-sen UniversityGuangzhouChina Department of Otorhinolaryngology Head and Neck Surgery Qilu Hospital of Shandong UniversityJinanChina Department of Otorhinolaryngology Head and Neck Surgery The Second Affiliated Hospital of Harbin Medical UniversityHarbinChina Department of Otolaryngology The Second Hospital of Shandong UniversityShandong UniversityJinanChina Department of Otorhinolaryngology Head and Neck Surgery Peking University People's HospitalBeijingChina Department of Otorhinolaryngology Head and Neck Surgery Yantai Yuhuangding HospitalQingdao UniversityYantaiChina Department of Otorhinolaryngology Head and Neck Surgery Xijing HospitalThe Fourth Military Medical UniversityXi'anChina Gansu Provincial Center for Disease Control and Prevention LanzhouChina Department of Otorhinolaryngology Head and Neck Surgery The First Affiliated Hospital of China Medical UniversityShenyangChina Department of Otorhinolaryngology Head and Neck Surgery Tongji Hospit

Objective:This cross-sectional study aimed to determine the epidemiology of olfactory and gustatory dysfunctions related to COVID-19 in ***:This study was conducted by 45 tertiary Grade-A hospitals in *** and offline questionnaire data were obtained from patients infected with COVID-19 between December 28,2022,and February 21,*** collected information included basic demographics,medical history,smoking and drinking history,vaccination history,changes in olfactory and gustatory functions before and after infection,and other postinfection symptoms,as well as the duration and improvement status of olfactory and gustatory ***:Complete questionnaires were obtained from 35,566 *** overall incidence of olfactory and taste dysfunction was 67.75%.Being female or being a cigarette smoker increased the likelihood of developing olfactory and taste *** received four doses of the vaccine or having good oral health or being a alcohol drinker decreased the risk of such *** infection,the average olfactory and taste VAS scores were 8.41 and 8.51,respectively;after infection,they decreased to 3.69 and 4.29 and recovered to 5.83 and 6.55 by the time of the *** median duration of dysosmia and dysgeusia was 15 and 12 days,respectively,with 0.5%of patients having symptoms lasting for more than 28 *** overall self-reported improvement rate was 59.16%.Recovery was higher in males,never smokers,those who received two or three vaccine doses,and those that had never experienced dental health issues,or chronic accompanying ***:The incidence of dysosmia and dysgeusia following infection with the SARS-CoV-2 virus is high in *** and prognosis are influenced by several factors,including sex,SARS-CoV-2 vaccination,history of head-facial trauma,nasal and oral health status,smoking and drinking history,and the persistence of accompanying symptoms.

关键词： epidemiologic studies incidence olfactory disorders prognosis SARS-CoV-2 taste disorders

Searching for^(76)Ge neutrinoless double beta decay with the CDEX-1B experiment

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Chinese Physics C 2024年第10期48卷 11-22页

作者： Bing-Tao Zhang Jun-zheng Wang Li-Tao yang Qian Yue Ke-Jun Kang Yuan-Jing Li Hai-Peng An C.Greeshma Jian-Ping Chang Yun-Huan Chen Jian-Ping Cheng Wen-Han Dai zhi Deng Chang-Hao Fang Xin-Ping Geng Hui Gong Qiu-Ju Guo xu-Yuan Guo Li He Sheng-Ming He Jin-Wei Hu Han-Xiong Huang Tu-Chen Huang Hai-Tao Jia Xi Jiang S.Karmakar Hao-Bin Li Jian-Min Li Jin Li Qian-Yun Li Ren-Ming-Jie Li xue-Qian Li Yu-Lan Li Yi-Fan Liang Bin Liao Fong-Kay Lin Shin-Ted Lin Jia-xuan Liu Shu-Kui Liu Yan-dong Liu Yu Liu Yuan-Yuan Liu zhong-zhi Liu Hao Ma Yu-Cai Mao Qi-Yuan Nie Jin-Hua Ning Hui Pan Ning-Chun Qi Jie Ren Xi-Chao Ruan Ze She Manoj Kumar Singh Tian-Xi Sun Chang-Jian Tang Wei-You Tang yang Tian Guang-Fu Wang Li Wang Qing Wang Yu-Feng Wang Yun-xiang Wang Henry-Tsz-King Wong Shi-Yong Wu Yu-Cheng Wu Hao-yang Xing Rui xu Yin xu Tao xue Yu-Lu Yan Nan Yi Chun-xu Yu Hai-Jun Yu Jian-Feng Yue Ming Zeng zhi Zeng Feng-Shou Zhang Lei Zhang zhen-Hua Zhang zhen-Yu Zhang Kang-Kang zhao Ming-Gang zhao Ji-Fang Zhou Zu-Ying Zhou Jing-Jun Zhou Key Laboratory of Particle and Radiation Imaging(Ministry of Education)and Department of Engineering Physics Tsinghua UniversityBeijing 100084 Department of Physics Tsinghua UniversityBeijing 100084 Institute of Physics Academia SinicaTaipei 11529 NUCTECH Company Beijing 100084 YaLong River Hydropower Development Company Chengdu 610051 College of Nuclear Science and Technology Beijing Normal UniversityBeijing 100875 College of Physics Sichuan UniversityChengdu 610065 School of Physics Peking UniversityBeijing 100871 Department of Nuclear Physics China Institute of Atomic EnergyBeijing 102413 Sino-French Institute of Nuclear and Technology Sun Yat-sen UniversityZhuhai 519082 School of Physics Nankai UniversityTianjin 300071 Department of Physics Banaras Hindu UniversityVaranasi 221005 Department of Physics Beijing Normal UniversityBeijing 100875

We operated a p-type point contact high purity germanium(PPCGe)detector(CDEX-1B,1.008 kg)in the China Jinping Underground Laboratory(CJPL)for 500.3 days to search for neutrinoless double beta(0νββ)decay of^(76)Ge.A total of 504.3 kg⋅day effective exposure data was *** anti-coincidence and the multi/single-site event(MSE/SSE)discrimination methods were used to suppress the background in the energy region of interest(ROI,1989–2089 keV for this work)with a factor of 23.A background level of 0.33 counts/(keV⋅kg⋅yr)was *** lower limit on the half life of^(76)Ge 0νββdecay was constrained as T_(1/2)^(0ν)>1.0×10^(23)yr(90%C.L.),corresponding to the upper limits on the effective Majorana neutrino mass:<3.2–7.5 eV.

关键词： neutrinoless double beta decay CDEX point-contact germanium detector ^(76)Ge

还田方式对绿肥油菜腐解特征与土壤养分含量的影响

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中国土壤与肥料 2024年第1期 182-191页

作者：王贞元徐志辉赵劲飞韩苏建张全忠席琳乔廖结安刘新英苏广东塔里木大学机械电气化工程学院新疆阿拉尔843300 新疆维吾尔自治区普通高等学校现代农业工程重点实验室新疆阿拉尔843300 塔里木大学动物科学学院新疆阿拉尔843300

为了明确果园绿肥在不同机械方式还田后腐解特征与土壤养分的变化规律,为南疆果园绿肥短期内高效还田、充分利用提供理论参考,在南疆香梨园行间种植油菜绿肥进行田间小区试验,设置4个处理(3种机械还田方式):旋耕机浅旋还田(T1-t1)、正... 详细信息

为了明确果园绿肥在不同机械方式还田后腐解特征与土壤养分的变化规律,为南疆果园绿肥短期内高效还田、充分利用提供理论参考,在南疆香梨园行间种植油菜绿肥进行田间小区试验,设置4个处理(3种机械还田方式):旋耕机浅旋还田(T1-t1)、正常旋耕还田(T2-t2)、绿肥粉碎旋耕一体机还田(T3-t3)和1个对照(CK),探究不同还田方式下油菜的腐解、养分变化特征及土壤养分的变化规律。结果表明:3种还田处理下油菜的腐解特征和碳氮的释放规律相似,整体都表现为前期快、后期逐渐缓慢的趋势,其中t3处理相较其他处理更有利于油菜的腐解及养分的释放,且利用一级动力学方程能够很好地拟合相关规律;3种还田方式下土壤pH值呈现先降低后升高的趋势,其余指标均呈先升高再降低的趋势,各指标相较第0 d增降幅度大小依次为速效钾>碱解氮>有效磷>有机质>pH值,T1、T2、T3处理下土壤各指标均与CK存在显著性差异(P<0.05),其中T3处理下土壤各指标增降幅度较为明显,且整个试验期内3个处理下土壤各指标间均存在一定的相关性。综上说明,在短期内T3-t3的还田方式下油菜的腐解及其对土壤养分的影响较其他两个处理更为显著,研究结果可作为南疆果园绿肥高效还田的主要机械还田方式。

关键词：绿肥油菜还田方式腐解特征土壤性状

Overexpression of Myocardin-related transcription factor-A attenuated middle cerebral artery occlusion/reperfusion-induced apoptosis via the Mcl-1/Cyt C/cleaved caspase 3 pathway

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Journal of Innovative Optical Health Sciences 2019年第6期12卷 199-209页

作者： zhi-Jun Yu Jing Du Wei Zhang Shu-Qi zhao Wei dong Shi-Qiang xu Ling Hu zhen-Li Min Qiong Yuan Chunxiang Zhang xia-Min Hu New Drugs Innovation Institute Wuhan University of Science and Technology Wuhan 430065 P.R.China Shanghai University of Medicine and Health Sciences Shanghai 200000 P.R.China Department of Rehabilitation Medicine China Resources&WISCO General Hospital Wuhan 430080 P.R.China Department of Biomedical Engineering School of Medicine and School of Engineering The University of Alabama at Birmingham Birmingham AL 35294USA Department of Pharmacy Wuhan Asia Heart Hospital WuhanHubei Province 430000P.R.China Hubie Provincial Key Laboratory of Occupational Hazard Identication and Control Wuhan University of Science and Technology Wuhan 430065 P.R.China

To investigate the effect of Myocardin related transcription factor A(MRTF-A)on apoptosis induced by ischemic/reperfusion(I/R),middle cerebral artery occlusion/reperfusion(MCAO/R)in rats were applied to mimic I/*** neurological deficit score,cerebral infarct size,cortical neuron apoptosis and cleaved caspase 3 level were evaluated to determine the effect and the level of apoptosis by TTC straining,terminal deoxynucleotidyl transferase dUTP nick end labeling(TUNEL)straining,Western blot and immunofuorescence *** myeloid cell leukemia-1(Mcl-1)expression,release of cytochrome C(Cyt C)and its colocalization with apoptotic pro-tease activating factor-1(Apaf-1)were analyzed by quantitative real-time PCR(qRT-PCR),Western blot,and immunofuorescence *** results showed that MRTF-A over-expression could decrease the neurological deficit score and reduce cerebral infarct size(P<0.01 versus Sham).In the MRTF-A-I/R group,TUNEL-positive cells and apoptosis ratio(%)(51.61±6.17%)were significantly decreased compared to the Neg-I/R group(76.45±8.77%)at 24 h ***,the cleaved caspase 3 expression revealed a similar trend while the expression of Mcl-1 was the ***,MRTF-A overexpression significantly enhanced Mcl-1 fAuorescence intensity,which up-regulated the mRNA and protein level(P<0.05or P<0.01 versus Neg-I/R).Furthermore,MRTF-A overexpression markedly inhibited the release of Cyt C,and decreased the colocalization with Apaf-1 in the cytoplasm(P<0.05 or P<*** Neg-I/R).All the data indicated that MRTF-A overexpression could improve the neu-rological function against cerebral I/R-induced apoptosis since underlying mechanism might be involved in the Mc-1/Cyt C/cleaved caspase 3 signaling pathway.

关键词： Stroke animal model immunofuorescence staining laser scanning confocal microscope

Risk assessment and ranking of pesticide residues in Chinese pears

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Journal of Integrative Agriculture 2015年第11期14卷 2328-2339页

作者： LI zhi-xia NIE Ji-yun YAN zhen xu Guo-feng LI Hai-fei KUANG Li-xue PAN Li-gang XIE Han-zhong WANG Cheng LIU Chuan-de zhao xu-bo GUO Yong-ze Institute of Pomology Chinese Academy of Agricultural Sciences/Laboratory of Quality & Safety Risk Assessment for Fruit (Xingcheng)Ministry of Agriculture Beijing Research Center for Agricultural Standards and Testing zhengzhou Institute of Pomology Chinese Academy of Agricultural Sciences Institute of Quality Standards & Testing Technology for Agro-Products Xinjiang Academy of Agricultural Sciences Yantai Academy of Agricultural Sciences Northwest A&F University Institute of Tianjin Agriculture Quality Standard and Testing Technology

The presence of pesticide residues in pears is a serious health concern. This study presents the results from a 2-year investigation （2013-2014） that used gas chromatography, GS/MS and UPLC/MS-MS to measure the levels of 104 pesti- cides in 310 pear samples. In 93.2% of the samples, 43 pesticides were detected, of which the maximum residue levels （MRLs） were exceeded in 2.6% of the samples. Multiple residues （two to eight compounds） were present in 69.7% of the samples; one sample contained nine pesticides and one sample contained 10. Only 6.8% of the samples did not contain residues. To assess the health risks, the pesticide residue data have been combined with daily pear consumption data for children and adult populations. A deterministic model was used to assess the chronic and acute exposures based on the Joint Meeting on Pesticide Residues （JMPR） method. A potential acute risk was demonstrated for children in the case of bifenthrin, which was found to be present at 105.36% of the acute reference dose （ARfD） value. The long- term exposure of the Chinese consumer to pesticide residues through the consumption of raw pears was far below the acceptable daily intake （ADI） criterion. Additionally, the matrix ranking scheme was used to classify risk subgroups of pesticides and pear samples. In general, 95.5% of samples were deemed to be safe and nine pesticides were classified as being of a relatively high risk. The findings indicated that the occurrence of pesticide residues in pears should not be considered a serious public health problem. Nevertheless, a more detailed study is required for vulnerable consumer groups, especially children. Continuous monitoring of pesticides in pears and tighter regulation of pesticide residue standards are recommended.

关键词： pear pesticide residue risk assessment intake risk ranking