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171.
Maciej Walcerz Ewa Bulska Adam Hulanicki 《Fresenius' Journal of Analytical Chemistry》1993,346(6-9):622-626
Summary A detailed study of interfering processes in the determination of As, Sb and Se using a twin-channel hydride generation flow-system is presented. The influence of As, Sb, Se and Sn on all three studied elements has a similar character and occurs in the gas phase only. In the presence of bismuth and tellurium interferences occur also in the liquid phase. It was found that arsenic and antimony may influence the analytical signals of elements with analytical lines in the range from 190 to 235 nm by non-specific absorption due to molecular band spectra.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday 相似文献
172.
Ewa Schab-Balcerzak Lukasz Grobelny Andrzej Miniewicz 《European Polymer Journal》2006,42(10):2859-2871
A new family of functionalized semiaromatic polyimides has been developed. Cycloaliphatic-aromatic polyimides, derived from the polycondensation of 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA) with various diamines bearing azobenzene group, have been prepared and characterized. Molecular structural characterization for the resulting polymers has been achieved by 13C NMR, 1H NMR, FTIR and UV-visible spectroscopies. Light-induced optical anisotropy, in novel azobenzene functionalized polyimides, has been studied by holographic polarization grating recording performed at 514.5 nm line of Ar+ laser. Two-wave mixing technique has been employed to inscribe the gratings in these polymers. Formation of gratings has been investigated with two s-s and s-p polarized writing beams. The kinetics of grating recording observed within the studied polymers is discussed in relation to their structure. 相似文献
173.
Wojciech Kroszczyski Ewa Olszewska Piotr Saaski Janusz Jurczak 《Helvetica chimica acta》2004,87(6):1488-1492
A simple and effective method to deprotect of sterically hindered steroid esters is described. Deprotection was carried out in MeOH in the presence of a catalytic amount of Et3N under high‐pressure conditions. Enzymatic, anionite, and high‐pressure methods are compared. 相似文献
174.
The hexatic smectic B (Hex B) phase is commonly encountered among hydrogen-bonded liquid crystal materials. Among enaminoketone and Schiff's base compounds, twenty homologous series (c. 102 compounds) exhibiting orthogonal mono-or bi-layer hexatic phases were identified by combined microscopy and DSC. Phase transitions from crystal B (CrB) of Sf to Hex B as well as from Hex B to Sf, Sa or Sc phases were observed within the range 50 to 190°C. Temperature ranges of the Hex B phase detectable by DSC varied from 0.2 to 20°C. Within two groups of three-ring enaminoketones, the formation of the Hex B phase was found to be controlled by both inductive and mesomeric components of the Hammett constants of the terminal substituents of the molecules. 相似文献
175.
176.
The supramolecular approach was applied to obtain a thermotropic liquid crystalline phase from the smallest possible molecules. Diaminobenzene derivatives are able to form smectic layers through a network of interconnected hydrogen bonded rings. The observed smectic A phase exhibits unusually small optical birefringence, comparable with that of lyotropic lamellar phases. 相似文献
177.
A graph is k-domination-critical if γ(G) = k, and for any edge e not in G, γ(G + e) = k ? 1. In this paper we show that the diameter of a domination k-critical graph with k ≧ 2 is at most 2k ? 2. We also show that for every k ≧ 2, there is a k-domination-critical graph having diameter [(3/2)k ? 1]. We also show that the diameter of a 4-domination-critical graph is at most 5. 相似文献
178.
This paper presents a comparative study of the use of two different methods of data analysis on a common set of data. The first is a method based on rough sets theory and the second is the location model method from the field of discriminant analysis. To investigate the comparative performance of these methods, a set of real medical data has been used. The data considered are of both discrete and continuous character. During the comparison, particular attention is paid to data reduction and to the derivation of decision rules and classification functions from the reduced set. 相似文献
179.
Summary A new chelate-forming resin was prepared from common anionexchanger Amberlyst A-26 and thoron. Thoron-loaded resin is stable and resistant to mineral acids. To differentiate the selectivity of thoron-loaded resin trien as competitive reagent was used. In the presence of trien thoron-loaded resin is almost selective for Fe(III) as a counter ion. The application of the resin to the analysis of iron in brass and the preconcentration and determination of iron in natural waters was described. 相似文献
180.
Zygmunt Eckstein Ewa Lipczyńska-Kochany Ewa Leszczyńska 《Monatshefte für Chemie / Chemical Monthly》1983,114(8-9):1009-1011
A series of new quinolinecarbohydroxamic acids has been prepared by treatment of corresponding methyl quinolinecarboxylates with hydroxylamine. 相似文献