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排序方式: 共有394条查询结果,搜索用时 468 毫秒
1.
Elena Kardash-Strochkova Yakov I. Tur’yan I. Kuselman Naphtali Brodsky 《Accreditation and quality assurance》2002,7(6):250-254
The results of two interlaboratory comparisons of acid number determinations in used motor oils are discussed. It is shown
that the comparability of the measurement results is not as good as that required by known standards for petroleum products.
The problem is motor oil contaminants which accumulated during use, and which are the source of a matrix effect in the acid
number determination. The standard methods’ drawbacks are analyzed and some improvements are proposed. Repeatability and accuracy
of the improved methods are evaluated.
Received: 11 December 2001 Accepted: 15 February 2002 相似文献
2.
3.
Jacek Doskocz Jadwiga Sołoducho Joanna Cabaj Mieczysław Łapkowski Sylwia Golba Krystyna Palewska 《Electroanalysis》2007,19(13):1394-1401
A convenient and higher yielding synthetic route to N‐alkyl‐bis(thiophene)phenothiazine derivatives is reported and their aggregation, electrochemical properties and polymerization are characterized. The key step in the synthesis of this group of compounds has been the Stille type coupling reaction between the N‐alkyldibromophenothiazine and tin derivatives of thiophene as the best way for preparation of conjugated N‐alkylphenothiazine derivatives. For this group of compounds we also present an electrochemical polymerization effect and widely adopted approach to prepare structurally ordered thin, electroconducting films by Langmuir–Blodgett technique. 相似文献
4.
A theorem of Birkhoff‐Frink asserts that every algebraic closure operator on an ordinary set arises, from some algebraic structure on the set, as the corresponding generated subalgebra operator. However, for many‐sorted sets, i.e., indexed families of sets, such a theorem is not longer true without qualification. We characterize the corresponding many‐sorted closure operators as precisely the uniform algebraic operators. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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6.
O. N. Lyubenko I. G. Ermolenko L. D. Patsenker Krasovitskii I. N. Tur 《Chemistry of Heterocyclic Compounds》2003,39(4):511-519
The behavior of dimethylamino-substituted 7H-benzo[de]pyrazolo[5,1-a]isoquinoline-7-ones, synthesized for the first time, under conditions of the Vilsmeier-Haack reaction. It has been shown that, on heating with POCl3 and DMF, they are converted by electrophilic substitution at the position ortho to the dimethylamino group, followed by cyclization of the iminium adduct to a quinazolinium salt. When an acetyl group is present, the Arnold reaction, leading to the formation of a chloroaryl, accompanies the heterocyclization. The rates and proportion of the reaction products depend on the position of the dimethyl groups relative to the pyrazole ring. 相似文献
7.
Oriňák Andrej Arlinghaus Heinrich Frank Vering Guido Justinová Martina Oriňáková Renáta Turčániová L’udmila Halama Maroš 《平面色谱法杂志一现代薄层色谱法》2003,16(1):23-27
JPC – Journal of Planar Chromatography – Modern TLC - Two interfaces have been tested for coupling thin-layer chromatography (TLC) with time-of-flight secondary-ion mass spectrometry... 相似文献
8.
A. N. Dovbnya K. V. Korytchenko M. A. Krasnogolovets Yu. Ya. Volkolupov Yu. D. Tur S. M. Shkirida A. I. Kosoi 《Technical Physics》2003,48(12):1586-1589
The influence of the discharge conditions on the dynamics of energy release is considered for pulsed arcs in air at initial pressures from 105 to 8×105 Pa and a low-voltage capacitor voltage of up to 400 V. A novel method for determining the resistance of the discharge channel in the final stage of a spark discharge is proposed. The method is applied to estimating the discharge channel parameters. 相似文献
9.
Jadwiga Frelek Günther Snatzke Wojciech J. Szczepek 《Fresenius' Journal of Analytical Chemistry》1993,345(11):683-687
Summary Bidentate complexes of dimolybdenum tetraacetate with 1,3-diaxial diols show Cotton effects around 490–540 nm (CD band I), 400–440 nm (II), 350–380 nm (III), 320 nm (IV) and 280 nm (V). The sign of the Cotton effect II can be predicted by a proposed sector rule. It seems that from the Cotton effects for cyclic 1,3-diols the absolute configurations or conformations can be obtained.A part of this material was presented at III-rd International Conference on CD Spectroscopy [1] 相似文献
10.
Jadwiga Walczak Elżbieta Tomaszewicz 《Journal of Thermal Analysis and Calorimetry》1995,43(1):319-322
The investigations of reaction between Ag2SO4 and Ag2S in air atmosphere have been carried. Results of DTA and X-ray phase powder diffraction of a reaction mixture have confirmed that in the Ag?O?S system exists a new phase. A formula of the phase is Ag2SO2. 相似文献