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111.
J. F. van Staden A. E. Joubert H. R. van Vliet 《Fresenius' Journal of Analytical Chemistry》1986,325(2):150-152
Summary An automated method for the determination of nitrate-nitrogen in surface, ground and domestic water based on flow-injection spectrophotometry is described. Nitrate is reduced to nitrite with a copperised cadmium tube in the reaction manifold. Nitrite is diazotised with sulphanilamide and the product is coupled with N-(1-naphthyl)ethylenediammonium dichloride to form a highly coloured azo dye, which is measured at 520 nm. A copper tube, incorporated into the reaction manifold before the copperised cadmium tube not only improves accuracy in the long run, but also extended the lifetime of the copperised cadmium tube. The sampling rate is 50 samples per hour. The method is suitable for the determination of nitrate-nitrogen with a coefficient of variation of better than 1.5%.
Fließinjektionsbestimmung von Nitrat in natürlichen Wässern mit Hilfe von Cu- und Cu/Cd-Röhren im Reaktionssystem
Zusammenfassung Ein automatisiertes Verfahren zur Bestimmung von Nitrat-Stickstoff in Oberflächen-, Grund- und Leitungswasser mit Hilfe der Fließinjektions-Spektral-photometrie wird beschrieben. Dabei wird Nitrat im Reaktionssystem in einer verkupferten Cadmiumröhre zu Nitrit reduziert; das Nitrit wird mit Sulfanilamid diazotiert und mit N-(1-Naphthyl)-ethylendiammoniumdichlorid zu einem intensiv gefärbten Azofarbstoff gekoppelt, der bei 520 nm gemessen wird. Eine Kupferröhre, die vor die verkupferte Cadmiumröhre im Reaktionssystem geschaltet wird, verbessert die Genauigkeit und verlängert die Lebensdauer der Cu/ Cd-Röhre. Je Stunde werden 50 Proben verarbeitet. Das Verfahren ist zur Nitratstickstoff-Bestimmung mit einem Variationskoeffizienten besser als 1,5% geeignet.相似文献
112.
113.
Joubert DP 《The Journal of chemical physics》2007,127(24):244104
The optimized effective potential (OEP) equation can be used in a numerically efficient self-consistent form to solve for the density functional exchange and correlation potentials, as shown in a recent paper of Kummel and Perdew [Phys. Rev. Lett. 90, 43004 (2003)]. The uniqueness of an iterative solution of the OEP equation has not yet been adequately addressed. In this paper, it is shown that no nonconstant multiplicative potentials that can contaminate an iterative solution of the OEP equation exist and, hence, that formally the exact exchange-correlation potential determined form of the OEP equation is unique to within a constant. 相似文献
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116.
Preliminary investigation on propylene copolymers with odd carbon number olefin are reviewed. Additional experimental data presents propylene copolymers with 1-heptene and 1-nonene having higher impact strength and lower tensile strength values than copolymers of propylene and 1-pentene.Thermoanalysis shows that the melting temperatures of the different copolymers decreases with increasing comonomer content. Slight changes were observed between the different propylene/1-heptene copolymer melting and propylene/1-pentene while the 1-nonene copolymers show broadening of the melting curves as the comonomer content increases. It was highlighted that the source of novelty for these polymers is the comonomer type and content. 相似文献
117.
Ni boracite crystals with the general formula Ni3B7I1—x(OH)xO13 have been prepared by hydrothermal synthesis. The experimental conditions are given along with some characteristics of the crystals obtained. 相似文献
118.
Samuel Noirault Eric Quarez Yves Piffard Olivier Joubert 《Solid State Ionics》2009,180(20-22):1157-1163
Ba2(In1 − xMx)2O5 − y / 2(OH)y□1 − y / 2 (y ≤ 2; M = Sc3+ 0 ≤ x < 0.5 and M = Y3+ 0 ≤ x < 0.35) compounds were prepared by reacting Ba2(In1 − xMx)2O5 phases with water vapor. This reaction is reversible. Analyses of the hydration process by TG and XRD studies show that the thermal stability of hydrated phases increases when x increases and that the incorporation of water is not a single-phase reaction inducing either a crystal system or space group modification. Fully hydrated (y = 2) and dehydrated (y = 0) samples have been stabilized at room temperature and characterized for all compositions. In wet air, all phases show a proton contribution to the total conductivity at temperatures between 350 and 600 °C. At a given temperature, proton conductivity increases with the substitution ratio and reaches at 350 °C, 5.4 10− 3 S cm− 1 for Ba2(In0.65Sc0.35)2O4.2□0.2(OH)1.6. 相似文献
119.
Let G = (V, E) be a graph. A set S í V{S \subseteq V} is a total restrained dominating set if every vertex is adjacent to a vertex in S and every vertex of V − S is adjacent to a vertex in V − S. The total restrained domination number of G, denoted by γ
tr
(G), is the smallest cardinality of a total restrained dominating set of G. We show that if δ ≥ 3, then γ
tr
(G) ≤ n − δ − 2 provided G is not one of several forbidden graphs. Furthermore, we show that if G is r − regular, where 4 ≤ r ≤ n − 3, then γ
tr
(G) ≤ n − diam(G) − r + 1. 相似文献
120.