排序方式: 共有20条查询结果,搜索用时 15 毫秒
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Lo Gorton Arne Torstensson Hans Jaegfeldt Gillis Johansson 《Journal of Electroanalytical Chemistry》1984,161(1):103-120
Meldola Blue (7-dimethylamino-1,2-benzophenoxazine) can be adsorbed on graphite to give chemically modified electrodes. The electrochemical redox reactions of the phenoxazine are fairly reversible at low coverages with an E′o of ?175 mV vs. SCE at pH 7.0. The electrode was most stable in acid solutions, at pH 6.0 its electrochemical activity decreased by 15% during 2h. The adsorbed compound mediated electron transfer in the electrocatalytic oxidation of the nicotinamide coenzymes (NADH and NADPH). The formation of a charge transfer complex between Meldola Blue and the coenzyme is demonstrated by experiments with a rotating disk electrode. The complex decomposes in a rate limiting step (k+2=30 s?1) to the oxidized coenzyme and the reduced Meldola Blue. The latter can be reoxidized in a fast electrochemical step. The overall result is an electrocatalytic oxidation at a voltage which is about 500 mV lower than at an unmodified electrode. 相似文献
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Y. Gell J. R. Torstensson H. Wilhelmsson B. Levush 《Applied physics. B, Lasers and optics》1982,27(1):15-18
Exact expressions are derived for the gain of a free-electron laser based on a uniform longitudinal magnetic field configuration operating in the single-particle, low-gain regime. The gain is calculated for different parameters of the system. For strong enough a field, the gain decreases with an increase of the amplitude, becoming negative when passing a threshold value, which depends on the system parameters. Implications regarding the saturation of the lasing process are discussed. 相似文献
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A controlled-potential coulometric iodometric method previously developed for the accurate determination of small amounts of nitrite has been extended for the determination of nitrate after its reduction on a coppered cadmium reductor. The conditions for quantitative reduction have been investigated with respect to type of reductor and pH. Nitrate-nitrogen in the range 0.01-100 mug ml may be determined with high accuracy in less than 10 min, including the reduction step. The method has been applied with good results to a large variety of samples such as meat products, juices and waste waters. 相似文献
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M. Bengtsson F. Malamas A. Torstensson O. Regnell G. Johansson 《Mikrochimica acta》1985,87(3-4):209-221
Summary
Trace Metal Ion P reconcentration for Flame Atomic Absorption by an Immobilized N,N,N-tri-(2-pyridylmetkyl)ethylene diamine (TriPEN) Chelate Ion Exchanger in a Flow Injection System
Chelating groups of N,N,N-tri-(2-pyridyl-methyl)ethyIene diamine (TriPEN) were synthesized on the surface of porous glass. A 100l column of the chelate ion exchanger was incorporated into a flow injection manifold with a flame atomic absorption spectrometer. Metal ions from samples (<1 ml to>80 ml) were retained on the chelate ion exchanger until an injection of acid displaced them into the flame. A peak-shaped absorbance curve was recorded. The use of immobilized TriPEN for preconcentration of metals from dilute solution and for matrix modifications was demonstrated. 相似文献
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Ulf Torstensson 《International Journal of Mathematical Education in Science & Technology》2013,44(4):363-365
In normal samples, the sample variance and sample mean are independent random variables, and the sample variance has, when properly normalized, a X2‐distribution. This paper gives elementary proofs by induction for these two facts. 相似文献
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Torstensson LG 《Talanta》1973,20(12):1319-1328
A controlled-potential electroanalytical method has been devised for the accurate determination of small amounts of thiols. An adequate excess of iodine is generated, the sample is added and the unreacted iodine is then electrolytically reduced. The iodine consumed is calculated from the measured number of coulombs. Amounts of thiols in the range 0·2–5 mg may be determined with an error of ± 0.05 %. A coulometric cell has been constructed which permits very high electrolysis rates, owing to efficient stirring by a large rotating platinum electrode combined with a high electrode-area to solution-volume ratio. A constant of 0·11 sec−1 is found for the reduction of iodine. The necessity of careful control of background currents and current efficiency in coulometric determinations is discussed. 相似文献
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一、TheProblem .Letf(x) =ax2 bx c ax2 px q,wherea >0 ,b2 - 4ac≤ 0andp2 - 4aq≤ 0 .OurProblemis“Whetherdoesminx∈Rf(x)exis?Moreover ,,ifminx∈Rf(x)exists,thenminx∈Rf(x)=?andinthiscasex =?” .Naturally ,weknowthatminx∈Rf(x)existsfromtheknowledgeofmathematicalanalysis.Also,wecangivethe… 相似文献
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New methods for determination of glyphosate and (aminomethyl)phosphonic acid in water and soil 总被引:2,自引:0,他引:2
New methods were developed to determine glyphosate, N-(phosphonomethyl)glycine, and its major metabolite, (aminomethyl)phosphonic acid in groundwater and soil. The methods involve ligand-exchange, anion-exchange and derivatisation and final identification and quantification by GC-MS. The limits of quantification in this experiment were 0.1 microg l(-1) for both compounds in water and 0.006 microg g(-1) for both compounds in soil. Decomposition in soil and occurrence in groundwater of the herbicide glyphosate was studied after its application for weed control on a Swedish railway embankment. 相似文献