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91.
Joël Delville 《Applied Scientific Research》1994,53(3-4):263-281
Experiments are performed in an incompressible plane turbulent mixing layer, using various hot wire rake configurations. From these experiments, the Proper Orthogonal Decomposition is applied for kernels where the space-time correlation tensor is evaluated over different spatial meshes and velocity components configurations. The resulting decompositions are then discussed in terms of characterization of the organization of the flow for various scalar or vectorial approaches of the POD. An incrtial range law is evidenced. The instantaneous contribution of the first modes of the POD to the organization of the flow is analyzed. A dynamical behavior for the organization of the flow is observed from the correlation between the first two modes contribution. 相似文献
92.
Summary A thin layer chromatographic method for a qualitative screening-test and a quantitative analysis of 2,4,6-TNT, biodegradation products, octogen and hexogen in ammunition wastes was developed using both polar and non-polar modified sorbents. For enrichment a solidphase extraction on LiChrolut® EN followed by removal with methanol/acetonitrile (11 v/v) was chosen. To imitate real samples, spiked tap water samples of known composition were used. 相似文献
93.
Sousa Pedrares A Teng W Ruhlandt-Senge K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(9):2019-2024
Novel magnesium pyridine-2-thiolates were prepared by using alkane elimination chemistry. The resulting complexes display a metal coordination environment composed of sulfur/nitrogen bonding from the intramolecularly stabilized mercaptopyridine ligand, in addition to coordination by the oxygen centers from two THF donors. The compounds are well-suited model compounds for the magnesium centers in Photosystem I, in which magnesium, situated in the central chlorophyll ligand, is bound to sulfur from a nearby methionine residue. All compounds were characterized by (1)H, (13)C NMR, and IR spectroscopy, in addition to Xray crystallography. 相似文献
94.
Masataka Hiraide Kennich Ishikawa Zuo Sheng Chen Hiroshi Kawaguchi 《Mikrochimica acta》1994,117(1-2):7-13
Coprecipitation first with magnesium hydroxide, next with tin(IV) hydroxide is developed for the determination of traces of beryllium in sea-water. To a 200-ml sample is added a sodium hydroxide solution to form magnesium hydroxide at pH 11.5, on which beryllium is quantitatively coprecipitated. The precipitate is separated by centrifugation and dissolved in 2 ml of 12 mol/l hydrochloric acid. The resulting solution (ca. 10 ml) is mixed with 2 mg of tin (IV) carrier and the pH is adjusted to 5.0 to collect the beryllium on tin (IV) hydroxide, leaving magnesium ions in the solution. The tin (IV) hydroxide is centrifuged, dissolved in 0.1 ml of 5 mol/l hydrobromic acid, and then diluted to 1 ml with water. Magnesium is so added as to be 500 g/ml for increasing the sensitivity about four times, and the beryllium in the solution is determined by graphite furnace atomic absorption spectrometry. The experiments with synthetic seawater samples showed that pg — g amounts of beryllium can be coprecipitated on the metal hydroxides and beryllium at the low ng/1 level can be determined with reasonable precision (RSD < 10%). The detection limit of the proposed method is 0.5 ng/l of beryllium in seawater. 相似文献
95.
Saeed Yousefinejad Fatemeh Honarasa Samira Akbari Mohsen Nekoeinia 《液相色谱法及相关技术杂志》2020,43(15-16):580-588
AbstractSeparation of amino acids (AAs) and their simple and inexpensive determination/identification is an interesting topic in biological and protein science, different food industries, and drug factories. Also, the presentation of the chromatographic behavior of compounds in a predictive model can be effective to estimate the structural/chemical properties of analyte and mobile phases. In this work for the first time, retardation factor (RF) of 42 AAs in reversed-phase thin layer chromatography (RP-TLC) was modeled. Acetonitrile-sodium azide solution and 1,2 dioxane-sodium azide solution were two mobile phases which have been studied in this work. Results showed that the values of RF are correlated with the structural properties of AAs and these properties had some similarities and differences in two noted mobile phases. For the TLC data in two mobile phases, five parametric linear models were suggested (R2train = 0.93 and 0.97; R2test = 0.93 and 0.99). The models were also evaluated with different statistical approaches. It was shown that increasing the sum of geometrical distances between N and O in AAs causes decreasing their RF in RP-TLC using both mobile phases. Other structural effects of AAs on their separation in the desired RP-TLC system were also discussed. 相似文献
96.
Dusanka Ž. Obadović Anikó Vajda Maya Garić A. Bubnov Vera Hamplová M. Kašpar Katalin Fodor-Csorba 《Journal of Thermal Analysis and Calorimetry》2005,80(2):519-523
Summary Thermal properties of a homologous series of ferroelectric liquid crystals S-(-)-[4-(2-n-alkoxy-propionyloxy)]biphenyl-4'-[n-alkoxy-(3,5-dimethyl)]benzoate have been investigated by polarizing optical microscopy and differential scanning calorimetry.
The mesophases were identified and confirmed by X-ray too. Three binary mixtures were prepared from the individual homologues.
In one of the mixtures (Mix1), the ferroelectric SmC* phase has broadened and became enantiotropic. This mesophase remained
monotropic in the other two mixtures (Mix2, Mix3). The chiral nematic N* phase did not appear in Mix1, but remained monotropic
for the other two mixtures. Two molecular parameters, the layer spacing and the average intermolecular distance have been
calculated from the X-ray results for the homologues and their mixtures. An intercalated tail-to-tail packing of molecules
was found both in the single compounds and their mixtures resulting in the layer spacing about half of the molecular length
of the single compounds. 相似文献
97.
The relationship between the current and the bulk concentration of complex ions during concurrent specific adsorption of an electrochemically active complex ion and a complexing ligand is considered. The effect of parameters that characterize adsorption of such ions and the structure of the electrical double layer on this relationship is analyzed.__________Translated from Elektrokhimiya, Vol. 41, No. 7, 2005, pp. 817–822.Original Russian Text Copyright © 2005 by Rogozhnikov. 相似文献
98.
2型糖尿病患者血清钙镁与甲状腺激素含量变化及临床意义 总被引:1,自引:0,他引:1
为了监测 2型糖尿病人血清钙、镁和甲状腺激素含量 ,分析其临床意义及相关性 ,应用放射免疫分析法测定了 1 1 5例 2型糖尿病及 1 5 0例健康人血清甲状腺激素含量。同时用美国杜邦RXL自动生化仪测定了其血清钙、镁含量。结果表明 ,在 2型糖尿病伴有明显并发症者血镁、FT3水平明显降低 (P <0 0 5 ) ,钙镁两种元素与甲状腺激素水平无明显相关性。 2型糖尿病患者适当补镁对预防其并发症是有益的 ,测定FT3 等可作为判断 2型糖尿病严重程度和估计预后的参考指标。 相似文献
99.
3He/4He ratios in samples of sea water obtained at depths from surface to 300 m in the upper layer of the Western Pacific Ocean were measured by a mass spectrometer VG5400. The lateral and vertical distribution of He isotopes in the studied area was discussed in detail on the basis of 3He/4He ratios. Excess and depleted 3He. in relation to δ3He value of surface water in equilibrium with air has been discussed in the area, which may be mainly attributed to the incorporation of the North Pacific Intermediate Water with the Equatorial Upwelling and the exchange of water masses between the South China Sea and the Western Pacific, respectively. The present work in Western Pacific has also indicated that He isotopes may be used as a tracer for mixing processes of water masses and oceanic circulation. 相似文献
100.
薄层色谱法在香兰素合成中的应用 总被引:3,自引:0,他引:3
应用薄层色谱法对愈创木酚、3-甲氧基-4-羟基扁桃酸和香兰素进行了分析,以硅胶GF254作为吸附剂,从几种溶剂系统中选出氯仿:乙酸乙酯:正丙醇:冰乙酸:水=20:1:1:1:2溶液作为展开剂。建立了 香兰素的薄层扫描定量分析方法,测定波长为500nm,参比波长为570nm,线性范围为0.31-6.2μg。 相似文献