Temperature-dependent photoabsorption cross-sections of cyanoacetylene and diacetylene in the mid- and vacuum-UV: Application to Titan's atmosphere     

T. Ferradaz  Y. Bénilan  M. Schwell  H.-W. Jochims 《Planetary and Space Science》2009,57(1):10-81

Cyanoacetylene (HC₃N) and diacetylene (C₄H₂) play an important role in the photochemistry of Titan's atmosphere, in part because of their strong absorption between 110 and 180 nm. Accurate photoabsorption cross-sections at temperatures representative of Titan's atmosphere are required to interprete Cassini observations and to calculate photolysis rates used in photochemical models. Using synchrotron radiation as a tunable vacuum ultraviolet (VUV) light source, we have measured absolute photoabsorption cross-sections of C₄H₂ and HC₃N with a spectral resolution of 0.05 nm in the region between 80 and 225 nm and at different temperatures between 173 and 295 K. The measured cross-sections are used to model transmission spectra of Titan atmosphere in the VUV.  相似文献   

X-ray absorption contrast images of binary chemical reactions     

D. Walker  O.T. Lord  M.J. Walter  S.M. Clark   《Chemical Geology》2009,260(3-4):211-220

Low-divergence synchrotron-sourced X-rays enable a radiographic imaging scheme for full characterization of binary chemical reactions and characterization by type of more complex reactions, in situ, in diamond anvil cells (DAC). Spatially resolved reactants are induced to react by laser heating of their interface. The spatially intermediate products are observed through X-ray absorption contrast. Limits to the technique include the ability to maintain controlled experiment geometry during compression and the ability to resolve chemical differences between reactants and products by X-ray absorption. The ability to make in situ observations at experimental pressure and temperature obviates the problem with quenching techniques for capturing liquid compositions in experiments with dimensions smaller than the diffusion length during quenching time. Partially molten Fe-alloy systems, of poor quenchability, are examined at DAC pressures and temperatures for relevance to Earth's core constitution and evolution. Determinations of eutectic melting in Fe–FeS match known results. Of the probable light elements that may alloy with Fe in the Earth's liquid outer core, Fe–FeS experiments show only modest quenching problems, but C and Si alloy experiments are highly vulnerable to quenching artifacts. The observed reactivity of FeS, Fe₃C, FeSi, and FeO(OH) with Fe in DAC makes the observed non-reactivity between Fe and FeO more significant, reducing the probability that oxygen alone is the major alloy in Earth's molten outer core.  相似文献   

The High-Resolution Solar Reference Spectrum between 250 and 550 nm and its Application to Measurements with the Ozone Monitoring Instrument     

Marcel Dobber  Robert Voors  Ruud Dirksen  Quintus Kleipool  Pieternel Levelt 《Solar physics》2008,249(2):281-291

We have constructed a new high resolution solar reference spectrum in the spectral range between 250 and 550 nm. The primary use of this spectrum is for the calibration of the Dutch – Finnish Ozone Monitoring Instrument (OMI), but other applications are mentioned. The incentive for deriving a new high resolution solar reference spectrum is that available spectra do not meet our requirements on radiometric accuracy or spectral resolution. In this paper we explain the steps involved in constructing the new spectrum, based on available low and high resolution spectra and discuss the main sources of uncertainty. We compare the result with solar measurements obtained with the OMI as well as with other UV-VIS space-borne spectrometers with a similar spectral resolution. We obtain excellent agreement with the OMI measurements, which indicates that both the newly derived solar reference spectrum and our characterization of the OMI instrument are well understood. We also find good agreement with previously published low resolution spectra. The absolute intensity scale, wavelength calibration and representation of the strength of the Fraunhofer lines have been investigated and optimized to obtain the resulting high resolution solar reference spectrum.  相似文献   

Prevalence of Bacillus sp. among the biofilm forming community on Ti surface in marine environment     

PRIYA Chokkalingam  ARAVIND Ganessin  THILAGARAJ Wilson Richard 《海洋学报(英文版)》2017,36(6):89-94

Prevalence of bacterial species involved in biomineralization of manganese on titanium (Ti) surfaces in marine environment was revealed in this research work. This study involves one year sea water exposure of Ti and their periodical biofilm characterization was carried out to quantify the manganese oxidizing bacterial (MOB) presence in the biofilm formed on titanium surfaces. The total viable count study of Ti coupons exposed to sea water for one year resulted in 60% of the MOB in overall biofilm population. The biochemical characterization of MOB isolates were performed for the genus level identification of the seven bacterial isolates. Further, the seven strains were subjected to 16S rRNA gene sequencing. Evolutionary analysis was performed using MEGA 7 to obtain closely related strains within the groups. The manganese oxidizing ability of the bacterial isolates were determined with Leucoberbelin Blue Assay (LBB) and Atomic Absorption Spectroscopy studies (AAS). The results show that among the isolated marine MOB species, Bacillus sp. and Leptothrix sp. have the maximum Mn oxidizing property. The microtitre plate assay was performed to determine the biofilm forming ability of the isolated marine MOB species. All the results have confirmed the prevalence of Bacillus sp. among the biofilm colonizers on Ti surfaces when exposed in sea water.  相似文献   

基于能量方程的建筑结构半主动控制   总被引：4，自引：2，他引：2  

涂文戈  邹银生 《地震工程与工程振动》2005,25(3):145-151

基于地震作用下结构的能量响应方程,本文提出根据结构吸收能量、相对动能和变形能的变化(对时间的一次导数)进行结构的“开-关”半主动减震的控制律;在物理坐标系中对这3种控制律的动力特征和控制效果,以及作动器参数的选取进行了分析。本文针对建筑结构进行了数值仿真。计算结果表明,本文提出的控制律可以有效地减小了结构的位移响应,对随机不确定的地震波均具有良好的减震效果,适应性强,而且控制器参数合理。其中根据结构变形能推导的控制律的半主动控制效果优于其它2种控制律。  相似文献   

Interaction between Microbes DNA and Atrazine in Black Soil Analyzed by Spectroscopy          下载免费PDF全文

Ying Zhang  Huosheng Guo  Dongfang Meng  Yang Wang  Po‐keung Wong 《洁净——土壤、空气、水》2015,43(6):867-871

  相似文献   

岩土介质中锰的吸附、解吸行为研究   总被引：1，自引：0，他引：1  

于晓英  邹胜章 《地下水》2009,31(3):82-84

通过吸附、物理解吸及化学解吸试验,模拟地下水污染特征,进而研究地下水重金属污染作用机理.结果表明,供试土壤对锰具有较强吸附能力,其吸附以化学吸附为主,占总吸附量的 90.94%.供试土壤对其吸持能力较强,不易于其迁移,但很容易造成土壤富集,通过植被进入生态系统,危害人体健康.  相似文献   

氯化钯作基体改进剂石墨炉原子吸收光谱法测定土壤中的铍   总被引：1，自引：1，他引：0  

姚朝英  任兰 《岩矿测试》2012,31(6):975-979

铍是一种对人体有害的金属元素,土壤中铍的测定目前尚无国家标准方法.本文采用盐酸-硝酸-氢氟酸体系微波消解、石墨炉原子吸收光谱法测定土壤样品中的铍,实验了钯、硝酸铝、硝酸镁、钙盐的增敏效果.结果表明,以氯化钯为基体改进剂,灰化温度和原子化温度分别提高到1100℃和2650℃,原子化峰形尖锐,背景吸收很小,提高了测定灵敏度;其他三种基体改进剂虽然也能提高测定灵敏度,但背景吸收较大.采用优化的实验条件,Fe、Mg、K、Na、Ca、Ti、Cu、Ba、Mn、Zn、Pb、Sr等共存元素对测定不产生干扰.铍的浓度在0 ～4.00 μg/L范围内线性良好,方法检出限为0.01 μg/g,精密度(RSD,n=6)为3.5％ ～6.7％,实际土壤样品的加标回收率为84.0％ ～ 113.0％,土壤国家标准物质的测定值在标准值的误差范围内.本法与萃取光度法、电感耦合等离子体发射光谱/质谱法相比,操作简便,分析成本较低.  相似文献   

Intra-plant differences in seaweed nutritional quality and chemical defenses: Importance for the feeding behavior of the intertidal amphipod Orchestoidea tuberculata     

Cristian Duarte  Karin Acuña  Jorge M. Navarro  Iván Gómez 《Journal of Sea Research》2011,66(3):215-221

As a result of their morphological complexity, large macroalgae show intra-thallus variations in their nutritional composition and secondary metabolite content, which influences the trophic ecology of herbivorous invertebrates, and ultimately their fitness. In this study, we evaluated for the first time the variability in nutritional quality (protein content, carbohydrates, lipids, and total organic matter), secondary metabolites (phlorotannins), and structure (shape and toughness) between blades and stipes of the macroalgae Durvillaea Antarctica. Specifically, we looked at their effect on feeding preference, rate of consumption, absorption efficiency, and growth rate of the amphipod Orchestoidea tuberculata, one of the most abundant organisms on Chilean sandy beaches. Proteins, carbohydrates, total organic matter and phlorotannin contents were significantly higher in blades than in stipes. Preference experiments revealed that the amphipods preferred blades when fresh pieces of blades and stipes were offered at the same time. Similar results were found when artificial food (in which structures of both parts of the alga were standardized) was offered, suggesting that shape and toughness of the two different parts of the alga did not influence preference patterns of O. tuberculata. Absorption efficiency of O. tuberculata was higher on blades compared to stipes. When the amphipods were kept with each of the algal parts separately (i.e. no choice), they consumed a significantly higher amount of stipe, which suggests that O. tuberculata used food quantity to compensate for the lower nutritional quality of stipes. The higher nutritional values of blades compared to stipes appears to explain observed preference patterns by O. tuberculata. Phlorotannin content did not appear to inhibit blade consumption, suggesting that the nutritional quality of the food could be more important than chemical defense in determining food choice in O. tuberculata. Growth did not differ between the amphipods maintained with either blades or stipes (i.e. no choice), which is consistent with the hypothesis of compensatory feeding. To conclude, O. tuberculata can actively select specific parts of an alga and this selection appears to be based on nutritional quality. The capacity for using different feeding strategies allow O. tuberculata, in some cases, to successfully exploit food types with different nutritional qualities.  相似文献   

聚氨酯泡塑富集硫脲解脱-石墨炉原子吸收光谱法测定地质样品中金铂   总被引：5，自引：4，他引：1  

刘向磊  文田耀  孙文军  姚维利  王腾飞  吴俊文 《岩矿测试》2013,32(4):576-580

泡沫塑料常用于富集常规地质样品中的铂族元素,而富集后往往用高温灰化法解脱,此法操作繁琐,温度过高易使铂配合物分解为王水难以提取的不溶性残渣,导致测试结果不稳定、效率低;单独使用20 g/L硫脲溶液解脱,测试结果的重现性差。本文对此方法进行改进,采用50%王水封闭溶解试样,氯化亚锡还原,聚氨酯泡塑富集,20 g/L硫脲-20%盐酸溶液解脱,石墨炉原子吸收光谱法测定金和铂。在盐酸-氯化亚锡体系中,吸附温度为20℃,振荡时间为30 min时,金和铂的回收率均在95%以上,金和铂的检出限分别为0.23 ng/g和0.39 ng/g,精密度(RSD,n=10)分别为1.8%～10.3%和1.3%～13.3%。经国家一级标准物质验证,测定值和标准值基本相符。该方法泡塑解脱时无需高温灰化,用王水多次提取,在100℃沸水浴中即可一次完成,样品处理快捷。与高温灰化法相比,提取温度大为降低,分析流程简单,显著提高了单次测样量,且干扰小、空白值低,可以满足除王水难溶的铂矿种外大部分地质样品快速测定的需要。  相似文献