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11.
Role of elemental fluorine in nuclear field 总被引:1,自引:0,他引:1
The preparation of fluorine gas by Henri Moissan by electrolysis of molten fluorides can be considered as one of the most important discoveries during the last centuries. Indeed, in addition to its use in many industrial fields (microelectronic, surface cleaning, pharmacology, medicine, …), fluorine gas is strongly involved in nuclear field for the preparation of UF6. The latter allows the natural uranium enrichment via the gaseous diffusion process. Due to the increase of the energy demand in industrialised and emergent countries, the production of UF6 and consequently of F2 should increase drastically during the next decades. The aim of this paper is to summarise the evolution of the process to produce fluorine from its discovery to the present process. Few aspects on the researches done for a better understanding of the fluorine evolution reaction are presented. The use of fluorine in the nuclear field is also discussed. 相似文献
12.
The electrochemical phase isolation (EPI) is described as a preparation method for determining specific precipitations in solid materials in microamounts and microdimensions. Fundamental criteria are examined as a function of the main parameter (polarization current) on the system Fe3C in a Fe-matrix. The influence of the electrolyte composition on the electrochemical behaviour of the matrix, on the one hand, and of the phase, on the other hand, are investigated and utilized. 相似文献
13.
In contrast to normal cells, the glycoprotein profile on epithelial tumor cells is distinctly altered. Due to an incomplete formation of the glycan side-chains resulting from a premature sialylation, additional peptide epitopes become accessible to the immune system in mucin-type glycoproteins on tumor cells. These tumor-associated structure alterations constitute the basis for a selective immunological attack on cancer cells. For the construction of immunostimulating antigens, glycopeptide partial structures from the mucins MUC1 and MUC4 carrying the tumor-associated sialyl-T(N), alpha2,6-sialyl-T and alpha2,3-sialyl-T antigens have been synthesized. Employing different linkers such as the allylic HYCRON or the fluoride-sensitive PTMSEL anchor, the antigenic glycopeptide structures were constructed on the solid phase utilizing pre-assembled glycosyl amino acid building blocks prepared in solution by convergent chemical or chemoenzymatic strategies. The proliferation of cytotoxic T cells has been induced applying a construct composed of a sialyl-T(N) MUC1-glycopeptide conjugated with a tetanus toxin T cell peptide epitope. 相似文献
14.
15.
乌江流域沉积岩风化过程中稀土元素的富集与释放 总被引:1,自引:0,他引:1
以乌江流域石灰岩、白云质灰岩、白云岩、硅质岩、页岩和砂岩等沉积岩的13条风化剖面为对象,运用R型分层聚类分析和质量平衡计算方法,研究了这些岩石风化过程中稀土元素(REE)的富集与释放及其对植物生长和河水REE分布的影响,目的是为河水物质来源研究和为农业生产提供依据。结果表明:(1)乌江流域石灰土中REE的富集程度显著高于各自母岩、黄壤、上陆壳(UCC)、中国土壤(CS)和世界土壤(WS);(2)沉积岩风化过程中REE的富集特征和机制可能与母岩中REE分布特征以及风化剖面中有机质、铁(氢)氧化物和粘土矿物的吸附有关;(3)沉积岩风化过程中释放的REE可为植物吸收利用;(4)石灰岩等沉积岩风化过程中REE和F。等元素的释放对河水溶解态REE的分布有重要影响。 相似文献
16.
Jijun Tang Jianwei Xie Lei Guo Yan Yan Ningsheng Shao 《Frontiers of Chemistry in China》2007,2(4):431-435
Aptamers which specifically recognize targets are selected from random oligonucleotide library using systematic evolution
of ligands by exponential enrichment (SELEX). In this paper, capillary electrophoresis (CE) as a separation approach has been
introduced to SELEX procedure. The high efficiency of CE gives rise to greatly shorten the selection procedure. The results
from enzyme-linked assay and dot blot experiment show that an enrichment pool has been obtained after four rounds selection,
which can specifically recognize ricin.
__________
Translated from Chemical Journal of Chinese Universities, 2006, 27(10): 1,840–1,843 [译自: 高等学校化学学报] 相似文献
17.
Lim LW Hirose K Tatsumi S Uzu H Mizukami M Takeuchi T 《Journal of chromatography. A》2004,1033(2):205-212
An on-line sample enrichment system was designed using monolithic precolumns in microcolumn LC. The monolithic ODS capillary columns were prepared via in situ sol-gel processes. The enrichment efficiency of the monolithic columns was tested by using phthalates as the analytes. The relative standard deviations (n = 6) for the retention time, peak area and peak height were between 0.4 and 1.2%, 0.9 and 5.5% and 0.4 and 3.9%, respectively. The system was linear (R2 > 0.99) within the working sample concentration and sample volume ranges. Comparing to 0.2 microl injection with a typical sample injector, the theoretical plate number of a same separation column was increased by 3-6-fold when the precolumn unit was used for sample injection. The recoveries of the analytes were between 88 and 120%, and the sample volume that could be injected into the system was increased up to 5000-fold. The limits of detection were improved by more than 2000-fold and were between 0.21 and 0.87 ng ml(-1) even with a UV absorbance detector. This system was applied to the determination of phthalates contained in laboratory distilled water and tap water samples. 相似文献
18.
19.
Effect of pressure on oxygen enrichment of liquid crystalline cellulose ether membranes at elevated temperature 总被引:1,自引:0,他引:1
Cholesteric liquid crystalline triheptyl cellulose (THC)/ethyl cellulose binary blend membranes were prepared and the effect of pressure on their oxygen enrichment at elevated temperature was investigated using a constant pressure-variable volume method. The oxygen enrichment increased with the increase of transmembrane pressure difference or with slight increase of the THC content in the blend membranes. The oxygen concentration through the membranes increased linearly with decreasing pressure ratio. Air was directly separated through a 17 m-thick THC/EC(1.5/98.5) membrane to prepare an oxygen-enriched air containing 39.5% oxygen at the flux of 6.99×10–4 cm3 (STP)/s.cm2 at the pressure difference of 0.43 MPa and 85 °C. 相似文献
20.
水中痕量镉的准液膜富集 总被引:4,自引:0,他引:4
准液膜法是在液膜法基础上提出的新分离方法,它保持了液膜法分离富集的高效能,但省去了液膜法的制乳与破乳过程,使操作更为简便易行。本文用此法富集了水及废水中痕量镉,富集倍数可达230倍,镉的回收率在97%以上。 相似文献