检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

海洋放射性监测技术——现在与未来

核化学与放射化学 2012年第2期34卷 65-73页

作者：刘广山厦门大学环境与生态学院福建厦门361005

海洋放射性监测是测定海洋中的放射性核素,围绕采样—制样—测量—数据分析这样一个过程实施。测量对象的放射性水平决定了所能利用的仪器设备、采样量、采样方法和制样方法。海洋的放射性是低水平或极低水平的,所以低本底测量仪器和大... 详细信息

海洋放射性监测是测定海洋中的放射性核素,围绕采样—制样—测量—数据分析这样一个过程实施。测量对象的放射性水平决定了所能利用的仪器设备、采样量、采样方法和制样方法。海洋的放射性是低水平或极低水平的,所以低本底测量仪器和大体积采样是海洋放射性监测的主要特点。有2条途径解决目前存在的大体积采样和样品处理的困难。一种是发展自动采样和制样系统,单核素快速富集可能是可行的技术路线。另一种是发展质谱学方法,特别是加速器质谱学方法,可以成十倍或百倍地减小样品需要量,可以极大地减小采样和制样工作的困难。浮标技术结合现代通信方法可能是核工厂和核电厂环境监测的自动化方法。走航测量可能是核事故后高放射性水团追踪的有效方法。这2种技术都是海洋放射性监测有待发展的技术,或等待填补的空白。

关键词：放射性海洋计数方法质谱法样品处理

AMS Measurement of ^(53)Mn at CIAE

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2011年第7期28卷 69-72页

作者： DONG Ke-Jun HE Ming LI Chao-Li HU Hao liu guang-shan CHEN Zhi-Gang LI Zhen-Yu WU Shao-Yong liu Jian-Cheng YOU Qu-Bo JIN Chun-Sheng WANG Xiang-Gao SHEN Hong-Tao GUAN Yong-Jing YUAN Jian JIANG shan China Institute of Atomic Energy P.O.Box 275(50)Beijing 102413 College of Oceanography and Environmental Science Xiamen UniversityXiamen 361005 College of Physics Science and Technology Guangxi UniversityNanning 530004 College of Physics and Technology Guangxi Normal UniversityGuilin 541004

The long-lived isotope ^(53)Mn cosmogenically produced in situ is a very useful indicator for geochronological dating.A new ^(53)Mn accelerator−mass-spectrometry(AMS)measurement method is developed based on the HI-13 Tandem Accelerator andΔE−Q3D detection system at China Institute of Atomic *** performance of ^(53)Cr isobar separation and suppression is tested by a series of ^(53)Mn standards and commercial MnO *** results show that theΔE−Q3D detection system brought about an overall suppression factor of more than 107 for the interfering isobar ^(53)Cr.

关键词： system separation Q3D

基于镭同位素分布的黄海和东海垂直混合速率计算

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

地球物理学报 2010年第8期53卷 1976-1984页

作者：刘广山门武纪丽红近海海洋环境科学国家重点实验室厦门大学海洋与环境学院厦门361005 国家海洋局大气化学与全球变化重点实验室第三海洋研究所厦门361005

在黄海和东海采样测定了水体中的镭同位素分布,用平流扩散模型描述镭同位素分布,最小二乘方法计算了垂直涡动扩散系数和上升流或下降流流速.结果给出北黄海中部、南黄海中部、浙江沿岸和台湾北部海域存在上升流,流速分别为0.46×10^(-3... 详细信息

在黄海和东海采样测定了水体中的镭同位素分布,用平流扩散模型描述镭同位素分布,最小二乘方法计算了垂直涡动扩散系数和上升流或下降流流速.结果给出北黄海中部、南黄海中部、浙江沿岸和台湾北部海域存在上升流,流速分别为0.46×10^(-3)cm·s^(-1)、0.17×10^(-3)～1.39×10^(-3)cm·s^(-1)、2.02×10^(-3)～3.04×10^(-3)cm·s^(-1)和1.06×10^(-3)～2.51×10^(-3)cm·s^(-1).北黄海中部和东海东北部存在下降流.流速分别为-2.30×10^(-3)cm·s^(-1)和-0.61×10^(-3)～-2.10×10^(-3)cm·s^(-1) .计算同时给出的垂直涡动扩散系数为5.84～48.2 cm^2·s^(-1),平均值为22.3 cm^2·s^(-1).北黄海和浙江沿岸上升流流速与文献的结果一致;北黄海中部存在下降流与文献的结论一致.本研究结果与文献结果一致是对所建立的方法的肯定,也是对文献研究结果的支持.

关键词：镭同位素涡动扩散上升流下降流

The burden of upper motor neuron involvement is correlated with the bilateral limb involvement interval in patients with amyotrophic lateral sclerosis:a retrospective observational study

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第5期20卷 1505-1512页

作者： Jieying Wu shan Ye Xiangyi liu Yingsheng Xu Dongsheng Fan Department of Neurology Peking University Third HospitalBeijingChina Beijing Municipal Key Laboratory of Biomarker and Translational Research in Neurodegenerative Diseases BeijingChina Key Laboratory for Neuroscience National Health Commission/Ministry of EducationPeking UniversityBeijingChina

Amyotrophic lateral sclerosis is a rare neurodegenerative disease characterized by the involvement of both upper and lower motor *** bilateral limb involvement significantly affects patients'daily lives and may lead them to be confined to ***,the effect of upper and lower motor neuron impairment and other risk factors on bilateral limb involvement is *** address this issue,we retrospectively collected data from 586 amyotrophic lateral sclerosis patients with limb onset diagnosed at Peking University Third Hospital between January 2020 and May 2022.A univariate analysis revealed no significant differences in the time intervals of spread in different directions between individuals with upper motor neuron-dominant amyotrophic lateral sclerosis and those with classic amyotrophic lateral *** used causal directed acyclic graphs for risk factor determination and Cox proportional hazards models to investigate the association between the duration of bilateral limb involvement and clinical baseline characteristics in amyotrophic lateral sclerosis *** factor analyses revealed that higher upper motor neuron scores(hazard ratio[HR]=1.05,95%confidence interval[CI]=1.01–1.09,P=0.018),onset in the left limb(HR=0.72,95%CI=0.58–0.89,P=0.002),and a horizontal pattern of progression(HR=0.46,95%CI=0.37–0.58,P<0.001)were risk factors for a shorter interval until bilateral limb *** results demonstrated that a greater degree of upper motor neuron involvement might cause contralateral limb involvement to progress more quickly in limb-onset amyotrophic lateral sclerosis *** findings may improve the management of amyotrophic lateral sclerosis patients with limb onset and the prediction of patient prognosis.

关键词： amyotrophic lateral sclerosis bilateral limb involvement Cox proportional hazards regression model horizontal spread restricted cubic spline analysis time interval upper motor neuron vertical spread

Unraveling brain aging through the lens of oral microbiota

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第7期20卷 1930-1943页

作者： Qinchao Hu Si Wang Weiqi Zhang Jing Qu guang-Hui liu State Key Laboratory of Membrane Biology Institute of ZoologyChinese Academy of SciencesBeijingChina Hospital of Stomatology Guanghua School of StomatologyGuangdong Provincial Key Laboratory of StomatologySun Yat-sen UniversityGuangzhouGuangdong ProvinceChina Advanced Innovation Center for Human Brain Protection and National Clinical Research Center for Geriatric Disorders Xuanwu HospitalCapital Medical UniversityBeijingChina Aging Translational Medicine Center International Center for Aging and CancerBeijing Municipal Geriatric Medical Research CenterXuanwu HospitalCapital Medical UniversityBeijingChina CAS Key Laboratory of Genomic and Precision Medicine Beijing Institute of GenomicsChinese Academy of Sciences and China National Center for BioinformationBeijingChina University of Chinese Academy of Sciences BeijingChina Institute for Stem Cell and Regeneration Chinese Academy of SciencesBeijingChina Aging Biomarker Consortium BeijingChina State Key Laboratory of Stem Cell and Reproductive Biology Institute of ZoologyChinese Academy of SciencesBeijingChina Beijing Institute for Stem Cell and Regenerative Medicine BeijingChina

The oral cavity is a complex physiological community encompassing a wide range of *** of oral microbiota can lead to various oral infectious diseases,such as periodontitis and tooth decay,and even affect systemic health,including brain aging and neurodegenerative *** studies have highlighted how oral microbes might be involved in brain aging and neurodegeneration,indicating potential avenues for intervention *** this review,we summarize clinical evidence demonstrating a link between oral microbes/oral infectious diseases and brain aging/neurodegenerative diseases,and dissect potential mechanisms by which oral microbes contribute to brain aging and *** also highlight advances in therapeutic development grounded in the realm of oral microbes,with the goal of advancing brain health and promoting healthy aging.

关键词： Alzheimer's disease brain aging multiple sclerosis neurodegeneration neurodegenerative diseases oral microbiota Parkinson's disease periodontitis bacteria Porphyromonas gingivalis

在线全文

学校读者我要写书评

暂无评论

中国东海的^(224)Ra

地球科学（中国地质大学学报） 2011年第6期36卷 999-1008页

作者：门武刘广山陈敏黄奕普厦门大学海洋与环境学院福建厦门361005 国家海洋局海洋大气化学与全球变化重点实验室福建厦门361005

用锰纤维富集—射气法测量了东海水体中的224 Ra,研究了东海夏季和冬季水体中224 Ra的水平与垂直分布,夏季224 Ra比活度为详细信息

用锰纤维富集—射气法测量了东海水体中的224 Ra,研究了东海夏季和冬季水体中224 Ra的水平与垂直分布,夏季224 Ra比活度为

关键词：东海 224Ra 水体混合上升流海洋地质地球化学

微量Ag对ZL114A铝合金组织和力学性能的影响

在线全文

学校读者我要写书评

暂无评论

材料工程 2021年第1期49卷 82-88页

作者：吴桢陆政刘闪光罗传彪中国航发北京航空材料研究院北京100095 北京市先进铝合金材料及应用工程技术研究中心北京100095

利用万能电子拉伸试验机、光学显微镜、扫描电子显微镜、球差校正场发射透射电子显微镜等研究微量Ag元素对ZL114A铝合金力学性能和显微组织的影响。结果表明:随着Ag含量的增加,合金的抗拉强度、屈服强度提高,伸长率无明显变化;当Ag含量... 详细信息

利用万能电子拉伸试验机、光学显微镜、扫描电子显微镜、球差校正场发射透射电子显微镜等研究微量Ag元素对ZL114A铝合金力学性能和显微组织的影响。结果表明:随着Ag含量的增加,合金的抗拉强度、屈服强度提高,伸长率无明显变化;当Ag含量提高到0.55%(质量分数)时,ZL114A铝合金的峰时效抗拉强度从351MPa提高到369MPa,屈服强度从309MPa提高到328MPa,伸长率从2.36%提高到2.93%。ZL114A合金组织的α-Al枝晶和共晶Si无明显变化;Ag含量的提高,促进了GP区形核质点数量增加,引起了β″数量密度增加。在高角度环形暗场扫描透射(HAADF-STEM)模式下观察到Ag原子分布在β″相中,抑制了Mg原子和Si原子在β″相中扩散,导致β″相尺寸减小。

关键词： ZL114A铝合金 Ag 力学性能显微组织 β″相

Simulations of electron zebra stripes in the inner radiation belt using a composite empirical electric field model

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2025年第1期68卷 27-38页

作者： Ziyang WANG Ying liu Qiugang ZONG Hong ZOU Yuguang YE Xuzhi ZHOU Chao YUE shan WANG Institute of Space Physics and Applied Technology Peking University State Key Laboratory of Lunar and Planetary Science Macau University of Science and Technology

The phenomenon termed “zebra stripes” manifests as regular patterns in the energy-space(L shell) spectrum of energetic electrons(ranging from tens to hundreds ke V) within the inner radiation belt. These structures exhibit drift-periodic behavior and commonly arise from large-scale electric field perturbations near the substorm onsets. In this study, we introduce a composite electric field model and replicate the formation, structure, and evolution of zebra stripes using a bounce-averaged test particle code under this electric field model. High-resolution measurements of energetic electrons obtained from the Van Allen Probes and the recently launched Macao Science Satellites-1 are used as initial conditions and served to validate our test particle simulations. Comparative analyses between observed data and simulations demonstrate our test particle method's efficacy in capturing zebra stripes' general behavior. Moreover, the composite model proves capable of reproducing realistic variations in the electric field within the inner radiation belt to a certain extent. Nevertheless, subtle differences emerge in the flux strength and the positions of stripes. These disparities primarily stem from limitations inherent in the electric field model and the initial conditions of the simulation. Acknowledging that the model represents an average case, it is conceivable that real-world scenarios may deviate from the average, thereby introducing variations in the observed phenomena.

关键词： Zebra stripes Inner radiation belt Large-scale electric fields Van Allen Probes Macao Science Satellite

^(129)I的海洋放射年代学及其他应用研究进展

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

台湾海峡 2010年第1期29卷 140-147页

作者：刘广山纪丽红厦门大学海洋学系福建厦门361005

应用129I的海洋学研究可分为3个方面:(1)人工129I的年代学,利用人工放射性在沉积物岩心中的记录,包括以核试验全球最大沉降年1963年为参考时间和利用切尔诺贝利核电站事故发生的1986年作为参考时间的年代测定.(2)利用宇生129I的年代学,... 详细信息

应用129I的海洋学研究可分为3个方面:(1)人工129I的年代学,利用人工放射性在沉积物岩心中的记录,包括以核试验全球最大沉降年1963年为参考时间和利用切尔诺贝利核电站事故发生的1986年作为参考时间的年代测定.(2)利用宇生129I的年代学,测年体系主要有地热流体、天然气水合物和石油地质体系.(3)利用核燃料后处理厂排放的129I进行的海洋环流与混合研究.核试验和核事故释放的129I测定的是现代沉积物年代,测年时间尺度为50a.人们提出人类利用原子能之前地球表层初始129I丰度为1.5×10-12,并以该值作为利用宇生129I估算年代的初始丰度值.半衰期和丰度探测下限水平允许宇生129I可测年的时间尺度为80Ma.本文综述了以上几方面的研究进展.海洋多金属结核和结壳的生长速率为毫米每兆年量级,一块1～10cm大小的多金属结核和结壳所能涵盖的时间尺度约为10～100Ma,刚好是129I测年的时间尺度,所以本文提出了多金属结核和结壳可能是合适的129I测年介质的观点.

关键词：海洋化学 129I 年代学人工放射性核素宇生放射性核素综述