期刊文献+
共找到9篇文章
< 1 >
每页显示 20 50 100
Interaction of DNA with aromatic hydrocarbons fraction in atmospheric particulates of Xigu District of Lanzhou,China 被引量:1
1
作者 GAO Hong MA Min-quan +3 位作者 ZHOU Lei JIA Run-ping CHEN Xing-guo HU Zhi-de 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2007年第8期948-954,共7页
Voluminously epidemiological studies show that the relationships exist between the air pollution and human health and cancer. Aromatic hydrocarbons (AHs) in air form a large class of organic pollutants, which are wi... Voluminously epidemiological studies show that the relationships exist between the air pollution and human health and cancer. Aromatic hydrocarbons (AHs) in air form a large class of organic pollutants, which are widely in environment and many of them are known to be carcinogenic and/or mutagenic and contribute to ambient air pollution. In the past decades, bioassays mainly have been used to evaluate the toxicity of chemical mixtures in atmospheric particulates or aqueous environment. However, it is well known that the covalent complexes formed by carcinogens with DNA may be exert negative results in bioassay. So the main aim of this paper is to develop an evaluation method of toxicity effects of chemical mixtures in atmospheric particulates from chemical standpoint. In this study, the in vitro interaction of the AHs with DNA was investigated by absorption, fluorescence and resonance light scattering (RLS) spectroscopic techniques. The results showed that the AHs in the atmospheric particulates could combine with calf thymus DNA (ctDNA) and herring sperm DNA (hsDNA) without being activated or metabolized by organism, respectively. Intercalation may be present in the mechanism of interaction. The binding constants of the AHs with ctDNA and hsDNA were 2.5x102 and 2.0x103, respectively, which indicated that the interaction of the AHs with hsDNA is stronger than that with ctDNA. In addition, the relationships of dose-effect between the total mole concentration of chemical components and the ability of binding ctDNA and hsDNA were confirmed. This research made it possible to study the toxicity effects of chemical mixtures in atmospheric particulates by chemical method. It is believed that the composition and contents of unknown AHs and the interaction of DNA with AHs in atmospheric particulates of Xigu District of Lanzhou City, China are first reported in the past twenty years. 展开更多
关键词 atmospheric particulates aromatic hydrocarbons fraction interaction with DNA
下载PDF
Tunable optical filter using second-order micro-ring resonator 被引量:1
2
作者 Lin Deng Dezhao Li +3 位作者 Zilong Liu Yinghao Meng Xiaonan Guo Yonghui Tian 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第2期250-253,共4页
In this paper, we design and fabricate a silicon integrated optical filter consisting of two cascaded micro-ring resonators and two straight waveguides. Two micro-heaters are fabricated on the top of two micro-rings r... In this paper, we design and fabricate a silicon integrated optical filter consisting of two cascaded micro-ring resonators and two straight waveguides. Two micro-heaters are fabricated on the top of two micro-rings respectively, which are employed to modulate the micro-rings to perform the function of a tunable optical filter by the thermo–optic effect. The static response test indicates that the extinction ratio and 3-d B bandwidth are 29.01 d B and 0.21 nm respectively, the dynamic response test indicates that the 10%–90% rise and 90%–10% fall time of the filter are 16 μs and 12 μs, respectively,which can meet the requirements of optical communication and information processing. Finally, the power consumption of the device is also characterized, and the total power consumption is about 9.43 m W/nm, which has been improved efficiently. 展开更多
关键词 integrated optics wavelength filtering devices resonators photonic integrated circuits
下载PDF
STUDY ON THE COMPLICATED DYNAMICAL BEHAVIORS OF NONLINEAR ECOSYSTEMS(Ⅲ)
3
作者 Zan Ting-quan 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1991年第7期647-653,共7页
This paper is a continuous study of references[1-2].At first,we introduce the concept of assembles of ecosystems,and then discuss macro-and micro-synergetical methods for ecology study.Combining the two methods,by use... This paper is a continuous study of references[1-2].At first,we introduce the concept of assembles of ecosystems,and then discuss macro-and micro-synergetical methods for ecology study.Combining the two methods,by use of the macroscopic data(observable)outputted from the ecosystems,we can construct their GGLE,master their information changes between,before and after the generalized phase changes(e.g.community successions),and find out the action mechanisms of microscopic factors on macroscopic results.This may be a new approach to the study of action mechanisms of complex ecosystems. 展开更多
关键词 ECOSYSTEMS NONLINEARITY ASSEMBLE ATTRACTOR information SYNERGETICS
下载PDF
AN EXACT ANALYTIC METHOD APPLIED TO NONHOMOGENEOUS RING-AND STRINGER-STIFFENED CYLINDRICAL SHELLS
4
作者 叶开源 纪振义 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1989年第9期785-796,共12页
In this paper, the nonlinear axial symmetric deformation problem of nonhomogeneous ring- and stringer-stiffened shells is first solved by the exact analytic method. An analytic expression of displacements and stress r... In this paper, the nonlinear axial symmetric deformation problem of nonhomogeneous ring- and stringer-stiffened shells is first solved by the exact analytic method. An analytic expression of displacements and stress resultants is obtained and its convergence is proved. Displacements and stress resultants converge to exact solution uniformly. Finally, it is only necessary to solve a system of linear algebraic equations with two unknowns. Four numerical examples are given at the end of the paper which indicate that satisfactory results can be obtained by the exact analytic method. 展开更多
关键词 AN EXACT ANALYTIC METHOD APPLIED TO NONHOMOGENEOUS RING-AND STRINGER-STIFFENED CYLINDRICAL SHELLS
下载PDF
Iodomethane as an organocatalyst for the aerobic ortho-selective trifluoromethylation of pyridines
5
作者 Jianjin Yu Renqin Zhan +1 位作者 Chao-Jun Li Huiying Zeng 《Science China Chemistry》 SCIE EI CAS CSCD 2023年第1期133-138,共6页
Iodomethane is usually used as an electrophilic methylation reagent.Herein,we report its use as a C1 organocatalyst for the aerobic ortho-selective trifluoromethylation of pyridines in the absence of a transition meta... Iodomethane is usually used as an electrophilic methylation reagent.Herein,we report its use as a C1 organocatalyst for the aerobic ortho-selective trifluoromethylation of pyridines in the absence of a transition metal.Trifluoroacetic acid(TFA)was employed as an inexpensive,readily available trifluoromethyl source.The reaction efficiently produced a variety of trifluoromethylation products,with good functional group compatibility.Pyridine-containing drug molecules could also be selectively trifluoromethylated for late-stage functionalizations.Mechanistic studies showed that iodomethane selectively reacted with the pyridine starting material,rather than the pyridine product,to generate the corresponding N-methylpyridinium iodide.The decarboxylation of trifluoroacetic acid produced a trifluoromethyl anion,which added to the methylpyridinium iodide,and the subsequent aerobic rearomatization led to the generation of the ortho-trifluoromethylated product. 展开更多
关键词 iodomethane-catalysis TRIFLUOROMETHYLATION PYRIDINES transition-metal-free trifluoroacetic acid
原文传递
THE EFFECTS OF EXTERNAL FORCING,DISSIPATION AND NONLINEARITY ON THE SOLUTIONS OF ATMOSPHERIC EQUATIONS 被引量:9
6
作者 李建平 丑纪范 《Acta meteorologica Sinica》 SCIE 1997年第1期57-65,共9页
Based on the primitive equations of the atmosphere,we study the effects of external forcing. dissipation and nonlinearity on the solutions of stationary motion and non-stationary motion.The results show that the asymp... Based on the primitive equations of the atmosphere,we study the effects of external forcing. dissipation and nonlinearity on the solutions of stationary motion and non-stationary motion.The results show that the asymptotic behavior of solutions of the forced dissipative nonlinear system is essentially different from that of the adiabatic non-dissipative system,the adiabatic dissipative system,the diabatic non-dissipative system and the diabatic dissipative linear system,and that the joint action of external forcing,dissipation and nonlinearity is the source of multiple equilibria. From this we can conclude that the important actions of diabatic heating and dissipation must be considered in the models of the long-term weather and the climate. 展开更多
关键词 external forcing DISSIPATION NONLINEARITY operator equation asymptotic behavior ATTRACTOR
原文传递
Repair effect of thymine radical anion by echinocoside using pulse radiolysis 被引量:1
7
作者 李雯艳 郑荣梁 +2 位作者 赵松岭 姜岳 林念芸 《Science China(Life Sciences)》 SCIE CAS 1996年第5期544-550,共7页
Repair activities of thymine radical anion by echinocoside, isolated from Pedicularis plicata. were studied using pulse radiolysis technique. The thymine radical anion was produced by the reaction of hydrated electron... Repair activities of thymine radical anion by echinocoside, isolated from Pedicularis plicata. were studied using pulse radiolysis technique. The thymine radical anion was produced by the reaction of hydrated electron with thymine. Echinocoside. one of the polyphenols of phenylpropanoid glycoside, was added to the thymine aqueous solution saturated with N2. Kinetic analysis by transient absorption spectrum showed that thymine radical anion was formed at first, and then after several decades of microseconds of pulse radiolysis. the spectrum of thymine radical anion was changed to that of echinocoside radical anion. The evidence indicated that thymine radical anion was repaired through one-electron-transfer between the DNA base radical anion and echinocoside. The rate constant of electron transfer by echinocoside was 1.45× 109 dm3 · mol1 · s 1. 展开更多
关键词 echinocoside PULSE RADIOLYSIS THYMINE RADICAL anion.
原文传递
A Facile Approach for the Total Synthesis of(±)-Cembrene
8
作者 李卫东 李瀛 李裕林 《Chinese Science Bulletin》 SCIE EI CAS 1994年第4期350-352,共3页
Cembrene (1), a cembrene-type hydrocarbon diterpene, is the first discovered natural-ly occurring fourteen-membered macrocyclic diterpenoid, which has been found in manyspecies of plant pines. The total synthesis of l... Cembrene (1), a cembrene-type hydrocarbon diterpene, is the first discovered natural-ly occurring fourteen-membered macrocyclic diterpenoid, which has been found in manyspecies of plant pines. The total synthesis of l has been reported by Dauben, Kato 展开更多
关键词 DITERPENOID membered FACILE HYDROCARBON Cembrene SELECTIVITY CYCLIZATION STARTING consuming titanium
原文传递
SOME PROPERTIES OF THE SOLUTIONS OF THE LARGE-SCALE EQUATIONS OF ATMOSPHERE——NONLINEAR ADJUSTMENT PROCESS BY EXTERIOR STEADY SOURCES
9
作者 汪守宏 黄建平 丑纪范 《Science China Chemistry》 SCIE EI CAS 1990年第4期476-484,共9页
From the large-scale equations of atmospheric motion, we investigated the long-time behaviour of atmospheric system forcing by exterior steady sources. Firstly, we established the fundamental functional space and oper... From the large-scale equations of atmospheric motion, we investigated the long-time behaviour of atmospheric system forcing by exterior steady sources. Firstly, we established the fundamental functional space and operator equations, and then demonstrated the existence and uniqueness theorems of solutions. Based on these results, the existence of the bounded global absorbing set and invariant set in it were discussed. Finally, the nonlinear adjustment process to exterior sources was revealed. 展开更多
关键词 SOLUTIONS of ATMOSPHERE EQUATIONS NONLINEAR adjustment PROCESS absor BING set.
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部