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61.
Complete classification of formally real fields with 8 square classes with respect to the behaviour of quadratic forms is given. Two fields F and K are equivalent with respect to quadratic forms if the quadratic form schemes of the two fields are isomorphic or in other words, if the Witt rings W(F) and W(K) are isomorphic. It is shown here that for formally real fields with 8 square classes there are exactly seven possible quadratic form schemes and for each of the seven schemes a formally real field with 8 square classes and the given scheme is constructed. 相似文献
62.
The paper is concerned with the modelling and numerical simulation of fibre-composite plates in the nonlinear range due to large strains and damage. The layer-wise approach is applied. Each layer is treated as elastic-brittle and assumed to be orthotropic in the local material coordinate system. The appearance of damage is controlled according to the failure criteria [1,2,3,4]. When the failure condition is satisfied, the mechanical properties of the material are modified appropriately, depending on the type of damage (fibre breakage, matrix crack, fibre-matrix shear). We have programmed the model as a user subroutine within the ABAQUS environment and carried out a number of numerical simulations. The obtained numerical results are compared with the experimental data available in the literature [3]. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
63.
Competition between Nucleophilic Substitution of Halogen (SNAr) versus Substitution of Hydrogen (SNArH)—A Mass Spectrometry and Computational Study 下载免费PDF全文
Kacper Błaziak Prof. Mieczysław Mąkosza Prof. Witold Danikiewicz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(16):6048-6051
The mechanism of intramolecular gas‐phase reactions of N‐(2‐X‐5‐nitrophenyl)‐N‐methylacetamide carbanions (X=H, F, Cl) has been studied using negative ion electrospray mass spectrometry ((?)ESI‐MS) technique and modelled computationally. It was proven that all three anions form cyclic σH adducts, which undergo elimination of water. In the case of X=F, formation of the σF adduct, leading to SNAr reaction, was a competing process. This is the first proof that also in the gas phase formation of σH adduct proceeds faster than σX adduct and only when X=F, rates of these two processes are comparable. The experimental results are in full agreement with quantum chemical calculations. 相似文献
64.
Henryk Foks Danuta Pancechowska-Ksepko Mieczysław Janowiec Zofia Zwolska Ewa Augustynowicz-Kopeé 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2291-2297
1,1-bis-methylthio-2-nitro-ethene was used as a substrate to the syntheses of new heterocyclic compounds. In the reactions, with 1-phenylpiperazine—the corresponding diaminonitroethane 1 , 1,3-diaminonitropropane, and 1,3-diaminonitropropanol—the nitromethylenotetrahydropyrimidine derivatives 2 and 3 were prepared, whereas, with o-phenylenediamine—2-nitromethyleno-benzimidazole 4 were obtained. In the condensation reactions of compounds 2 , 3 , and 4 with benzoyl isothiocyanate, the products 5 , 6 , and 7 were obtained, and afterwards two of them, 5 and 6 , were transformed into the isothiazolines 8 and 9 . 1,1-bis-(4-phenylpiperazino)-2-nitroethane ( 1 ) was exposed to the action of phenyl isothiocyanate and the derivative obtained ( 10 ) was transformed, in the reaction with phenacylbromide, in to benzoylonitrothiophene 11 . The diazo compounds 12 , 13 , and 14 were obtained in the reactions of nitromethylenotetrahydropyrimidines 2 and 3 and of 2-nitromethylenobenzimidazole 4 with benzenediazonium chloride. The derivatives obtained were tested in vitro for their tuberculostatic activity. The compounds 7 (MIC 8–32 μg/mL) and 14 (MIC 16–63 μg/mL) appeared to be the most active compounds. 相似文献
65.
Mieczysław S. Sokołowski Leszek Konopski 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2311-2327
Reaction of 2-chlorovinyldichloroarsine (Lewisite-1) with alcohols, thiols, diols, and hydroxy thiols in water at 40°C has been examined. The expected derivatization products, dialkyl 2-chlorovinylarsonites or corresponding arsonodithiolites, were obtained with alcohols and thiols, whereas reactions with bifunctional diols and hydroxythiols produced analogous cyclic esters. All derivatives may be easily detected using gas chromatography. This reaction was found useful to easily transform bis(2-hydroxyethyl) sulfide (thiodiglycol), a sulfur mustard decomposition product, to a stable eight-membered cyclic arsonite derivative. After extraction with dichloromethane, the derivative may be easily and selectively detected using GC/MS at a 100 ppb level thiodiglycol content in water matrices, eliminating tedious evaporation of water and then silylation. This method may be applied to analyze Chemical Weapons Convention related environmental water samples. 相似文献
66.
The synthesis of diethyl [2-(2-alkyl-3-oxo-2,3-dihydro-1H-isoindol-1-yl)ethyl]phosphonates and diethyl [3-(2-alkyl-3-oxo-2,3-dihydro-1H-isoindol-1-yl)propyl]phosphonates, via metallation (sec-BuLi) of N-substituted isoindolin-1-ones and then the reaction of the generated lithiated species 4 with diethyl vinylphosphonate or diethyl 3-bromopropylphosphonate, respectively, is described. 相似文献
67.
Abstract Barbier-type reductive coupling of allylic bromides and organotin compounds can be carried out in liquid ammonia (?33°C) using commercial zinc powder. This procedure provide a new simple and environment-friendly method for the synthesis of allylstannanes and distannanes. 相似文献
68.
Mieczysław Jaroniec Anna Deryło Adam Marczewski 《Monatshefte für Chemie / Chemical Monthly》1983,114(4):393-397
Correlation between parameters obtained from the signle-solute and bisolute adsorption data by means of theLangmuir-Freundlich equation has been studied. 相似文献
69.
Adam Bieniek Jan Epsztajn Mieczysław W. Płotka 《Monatshefte für Chemie / Chemical Monthly》2003,134(4):533-538
Summary. A convenient two step protocol preparation of ortho-phenylthiomethyl aromatic carboxylic acids from aromatic carboxylic acids anilides is reported. The phenylthiolation of phthalides
with benzenethiol as a key step is described.
Corresponding author. E-mail: epsztajn@krysia.uni.lodz.pl
Received June 21, 2002; accepted July 9, 2002 相似文献
70.
JPC – Journal of Planar Chromatography – Modern TLC - Tea is one of the most popular beverages in the world. The exact composition of tea depends on the manufacturing process. Our goal... 相似文献