保持空间分布特征的散列式居民地综合选取方法     

高凯  杨敏  张跃鹏 《测绘科学技术学报》2015,(6):626-630

中小比例尺地形图上存在大量由不依比例尺"房屋群"构成的散列式居民地,综合选取时除考虑单个房屋专题重要性外,还要保持各房屋群的分布特征。将基于Vorinoi图模型的点群化简算法应用到散列式居民地选取中,在综合选取的两个主要过程(选取定额模型和结构化选取方法)中综合考虑分布密度、分布范围等分布结构信息和专题属性信息。实验分析表明,该方法保留重要居民地的同时,能够较好地保持原有的空间分布特征。  相似文献   

Effects of Monochromatic UV-Visible Light and Sunlight on Fe(III)-Catalyzed Oxidation of Dissolved Sulfur Dioxide     

Yuegang?ZuoEmail author  Jian?Zhan  Taixing?Wu 《Journal of Atmospheric Chemistry》2005,50(2):195-210

The effect of UV-visible light and natural sunlight on the Fe(III)-catalyzed oxidation of dissolved sulfur dioxide has been studied under the conditions representative for those of acidified atmospheric liquids. The experimental results have shown that both sunlight and UV-visible light enhance the rate of Fe(III)-catalyzed oxidation of aqueous sulfite with wavelength ranging from 300 to 575 nm. The light enhanced oxidation is mainly due to photochemical formation of OH radicals from Fe(OH)²⁺ complexes in the wavelength region below 420 nm and SO₃^•− free radicals from Fe(III) sulfite complexes above 420 nm in the absence of organic ligands. Like the Fe(III)-catalyzed thermal chemical oxidation, the Fe(III)-catalyzed photochemical oxidation is also first order with respect to sulfite ion concentration. The sunlight irradiation can increase the Fe(III)-catalyzed oxidation of S(IV) over 45%. The presence of organic complex ligands, such as oxalate, can completely inhibit the Fe-catalyzed oxidation of S(IV) in the dark. However, the photolysis of Fe(III)-oxalato complexes generates oxalate free radicals, leading to the formation of H₂O₂ and OH radicals and the oxidation of S(IV). The rate of Fe(III)-catalyzed oxidation of S(IV) species is found to increase with increasing light intensity. The effects of sunlight on the Fe(III)-catalyzed oxidation of S(IV) should be taken into account when predicting the daytime rates of sulfuric acid formation in atmospheric water droplets.  相似文献   

Hydroxyl Radical Concentrations Estimated from Measurements of Trichloroethylene during the EASE/ACSOE Campaign at Mace Head, Ireland during July 1996     

R. G. Derwent  N. Carslaw  P. G. Simmonds  M. Bassford  S. O'Doherty  D. B. Ryall  M. J. Pilling  A. C. Lewis  J. B. McQuaid 《Journal of Atmospheric Chemistry》1999,34(2):185-205

During the EASE/OXICOA campaign of the NERC ACSOE programme, trichloroethylene and a wide range of man-made halocarbons and radiatively-active trace gases were monitored with high precision and high frequency throughout July 1996 at Mace Head on the Atlantic Ocean coast of Ireland. Trichloroethylene concentrations in concert with many other trace gases became elevated as regionally-polluted and photochemically-aged air masses reached Mace Head. However, as the anticyclonic air masses retreated during 19 and 20 July, trace gas concentrations remained elevated for a significant period. During this 2–4 day period, trichloroethylene concentrations decayed significantly, though the concentrations of the other more chemically-inert trace gases did not. A detailed interpretation of this behaviour using a Lagrangian dispersion model has allowed the estimation of average and peak OH radical concentrations of 3 and 9×10⁶ molecule cm^-3, respectively, during the travel from the source areas in the U.K. and the low countries out to Mace Head. Using a simple box model, the available Mace Head measurements, when combined into a detailed chemical mechanism, generated OH radical concentrations which peaked at 7×10⁶ molecule cm^-3, in close agreement with the estimates based on trichloroethylene decay.  相似文献   

贻贝棘尾虫年轻与衰老无性系抗氧化能力的比较     

邱子健  单志新  史新柏  付桂荣 《海洋与湖沼》1999,30(5):519-524

贻贝棘尾虫采自黑龙江省帽儿山南山水库附近水塘,于１９９５年９月在本系实验室通过接合生殖得到的接合后体,克隆培养作为无性系;采用１９８８年９月以来实验室保存培养的去小核无性系为衰老无性系。  相似文献   

菲对斜生栅藻(Scenedesmus obliquus)自由基的诱导及胁迫效应     

蒋丽娟  尹颖  杨柳燕  尹大强  王晓蓉  郭红岩 《湖泊科学》2013,25(6):943-949

通过静态模拟实验,研究不同浓度(0.005、0.01、0.025、0.05和0.1 mg/L)菲暴露96 h后,对斜生栅藻的生长、自由基含量、抗氧化系统以及脂质过氧化产物(MDA)的影响.结果表明,0.01 mg/L菲开始对藻细胞生长产生显著抑制作用,在此浓度下电子自旋共振检测到的自由基信号(g=2.0033,幅宽10.15 mT)显著增强;在浓度设置范围内,超氧化物酶歧化酶、过氧化物酶、谷胱甘肽-S-转移酶活性均被显著诱导,显示出抗氧化系统的应激机制.谷胱甘肽和MDA含量均在0.025 mg/L时被显著诱导.这说明斜生栅藻对菲暴露比较敏感,0.01 mg/L即已显示胁迫效应,自由基的诱导是斜生栅藻产生损伤的重要原因,藻细胞的生长量是比较敏感的损伤指标.  相似文献   

小球藻EC04产胞内多糖条件优化及抗氧化活性研究     

杨海燕  李洁琼  刘红全  黄小燕  许钟涛  罗远康  禤金彩  龙寒 《热带海洋学报》2019,38(6):98-104

小球藻胞内多糖等活性物质具有多种重要生物活性和生理功能。为提高小球藻EC04胞内多糖的产率, 采用单因素实验和L₉(3 ⁴)正交实验优化对其培养条件进行优化。在暗光比12∶12、温度24±1℃和2000Lux光照条件下, EC04产胞内多糖的最佳条件为: MgSO₄·7H₂O浓度112.5mg·L ^-1, K₂HPO₄浓度60mg·L ^-1, NaNO₃浓度1.2g·L ^-1, 维生素B₁浓度0.5mg·L ^-1, 维生素B₁₂浓度0.1μg·L ^-1。在此条件下, EC04产糖率为271.74mg·g ^-1, 细胞密度为48.027×10 ⁶cells·mL ^-1, 与基础培养基相比分别提高了97.49%和34.91%。添加VB₁、VB₁₂等也在不同程度上影响小球藻胞内多糖产率。对所提取胞内多糖进行抗氧化活性初探, 结果表明其具有一定的自由基的清除能力, 对DPPH·(1-二苯基-2-三硝基苯肼)和·OH(羟自由基)的最大清除率分别达到了82.32%和64.27%。  相似文献   

Observations of the Oh Radio Lines of Comets at Nançay – Recent Developments     

Crovisier  Jacques  Colom  Pierre  Gérard  Éric  Bockelée-Morvan  Dominique 《Earth, Moon, and Planets》2002,90(1-4):369-370

The 18 cm lines of OH have been observed in more than 70 comets withthe Nançay radio telescope since 1974. The observations made from1982 to 1999 are now organized in a data base. The Nançay radiotelescope has been recently upgraded, and observations since 2000 aremade with a sensitivity increased by about a factor of two. Twelvecomets were observed from July 2000 to May 2002.  相似文献   

Study on the Free Radical Scavenging Activity of Sea Cucumber （Paracaudina chinens vat.） Gelatin Hydrolysate     

ZENG Mingyong XIAO Feng ZHAO Yuanhui LIU Zunying LI Bafang DONG Shiyuan 《中国海洋大学学报(英文版)》2007,6(3):255-258

Gelatin from the sea cucumber （Paracaudina chinens var.） was hydrolyzed by bromelain and the hydrolysate was found to have a high free radical scavenging activity. The hydrolysate was fractionated through an ultrafiltration membrane with 5 kDa molecular weight cutoff （MWCO）. The portion （less than 5 kDa） was further separated by Sephadex G-25. The active peak was collected and assayed for free radical scavenging activity. The scavenging rates for superoxide anion radicals （O2·^-） and hydroxyl radicals （·OH） of the fraction with the highest activity were 29.02% and 75.41%, respectively. A rabbit liver mitochondrial free radical damage model was adopted to study the free radical scavenging activity of the fraction. The results showed that the sea cucumber gelatin hydrolysate can prevent the damage of rabbit liver and mitochondria.  相似文献   

群的根性的一个问题   总被引：1，自引：1，他引：0  

李雪梅 《成都信息工程学院学报》2007,22(2):281-282

假设（R）是群的根性,N是群G的正规子群,记N^-/N＝RR（G/N）.主要利用群的根性的性质来解决哪种根性具有特征性质N1N2^-＝N1^-N2^-这个问题.  相似文献   

Conversion rates of surface HO_x radicals in Beijing City     

Ren Xin-rong  Wang Li-xin  Wang Hui-xiang  Miao Guo-fang 《中国地理科学(英文版)》2004,14(1):34-38

Surface OH radical concentration in Beijing City was measured by impregnated filter trapping technique-high performance liquid chromatography (IFT-HPLC). The observed concentration of OH radical showed obvious diurnal and seasonal variations, with maximum readings at noon or afternoon, ∼80×10⁶OH/cm³ in summer and ∼20×10⁶-40×10⁶OH/cm³ in fall. On the basis of measured data, the reaction rates related to the photochemical process of HO_X (OH+HO₂) were derived and characteristics of atmospheric chemical processes in the city were analyzed. The results showed that conversion rates of atmospheric OH and HO₂ in the summer of Beijing City were about 700×10⁶ molecule/(cm³·s) and 600×10⁶molecule/(cm³·s), respectively. And the net production of OH in the air of the city mainly originate from the photolysis of the gaseous HNO₂, and the main sink of OH were the photochemical reactions with VOCs, NO₂, HCHO and CO. It was different from the clean area. Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 40075026) Biography: REN xin-rong (1973 -), male, a native of Zhejiang Province, Ph. D., now a postdoctorship in Pennsylvania State University, USA, specialized in the reaction kinetics of atmospheric environment. E-mail: ren@essc.psu.edu  相似文献