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51.
Efstathios Laskos Pygmalion S. Lianis Nestor A. Rodios 《Journal of heterocyclic chemistry》1994,31(2):425-430
The title compounds 2 are prepared from the reaction of 1-(N, N-diaroyl)amino-5-bromomethyl-1,2,3-triazoles with aromatic amines. The fragmentation pattern upon electron impact at 70 eV of compounds 2 is studied. The molecular ion peak is present in all the spectra examined. Besides the [M-28]++, there is also a more abundant [M-29]+ peak, corresponding to a N2H loss of the molecular ion. The ion Ar2NH = CH2 is the base or the most prominent peak. 相似文献
52.
1-(N-Phenacylidene)amino-1,2,3-triazoles 3 react with propionylchloride and phenoxyacetylchloride in the presence of triethylamine to give trans- ( 5 ) and cis- ( 6 ) 1-(1,2,3-triazol-1-yl)-4-aroylaztidin-2-ones in a 1:1 ratio, on the contrary to the 1-(N-arylidene)amino-1,2,3-triazoles, which do not give any reaction product with the same acid chlorides. The spectroscopic characteristics of these new N-triazolyl-β-lactams are also discussed. 相似文献
53.
P. Robouch G. Arana M. Eguskiza S. Pommé N. Etxebarria 《Journal of Radioanalytical and Nuclear Chemistry》2000,245(1):195-197
The concepts of the Guide to the expression of Uncertainties in Measurements for chemical measurements (GUM) and the recommendations of the Eurachem document "Quantifying Uncertainty in Analytical Methods" are applied to set up the uncertainty budget for k
0-NAA. The "universally applicable spreadsheet technique", described by Kragten, is applied to the k
0-NAA basic equations for the computation of uncertainties. The variance components — individual standard uncertainties — highlight the contribution and the importance of the different parameters to be taken into account. 相似文献
54.
Joaquim J. Moura Ramos Joo F. Mano David Lacey G. Nestor 《Journal of Polymer Science.Polymer Physics》1996,34(12):2067-2075
The molecular relaxation mechanisms in the glass transition region and in the liquid crystalline phase exhibited by two side-chain liquid crystalline polysiloxanes have been studied by Thermally Stimulated Discharge Currents. These results were compared with those previously obtained by dielectric relaxation spectroscopy. It was observed that two relaxation mechanisms were present in the liquid crystalline phase, and we suggest that these might correspond to the motions of the mesogenic moieties in the liquid crystalline phase. © 1996 John Wiley & Sons, Inc. 相似文献
55.
Carlos García Gorka Arana Nestor Etxebarria Luis A. Fernández 《Mikrochimica acta》2001,136(1-2):15-21
The analysis of mixtures of four phenolic compounds in an on-line system using UV-visible measurements with a fibre optic
probe is discussed in this work. The aim of this system is to provide accurate real time concentration profiles in order to
monitor the transport of phenols across a solid supported liquid membrane in both the feed and stripping phases. Different
calibration models are taking into account the pH of the solution, using experimental designs and the first derivative in
combination with different multivariate approaches like multiple linear regression (MLR), inverted least squares (ILS) and
partial least squares regression (PLS). The comparison of all these combinations is carried out by means of the predictive
residual error sum of squares (PRESS) evaluated from an independent set of spectra. From this comparison it is concluded that
a PLS model using first derivative spectra offers the most accurate and robust prediction in the permeation experiments. Additionally,
the stability of the model and the figures of merit obtained are also discussed.
Received July 22, 1999. Revision October 23, 2000. 相似文献
56.
Savaissou Nestor Souleymanou Abbagari Alphonse Houwe Mustafa Inc Gambo Betchewe Serge Y Doka 《理论物理通讯》2020,72(6):65501
This paper studies chirped optical solitons in nonlinear optical fibers. However, we obtain diverse soliton solutions and new chirped bright and dark solitons, trigonometric function solutions and rational solutions by adopting two formal integration methods. The obtained results take into account the different conditions set on the parameters of the nonlinear ordinary differential equation of the new extended direct algebraic equation method. These results are more general compared to Hadi et al(2018 Optik 172 545–53) and Yakada et al(2019 Optik197 163108). 相似文献
57.
Gorka Arana Nestor Etxebarria Luis Angel Fernández 《Analytical and bioanalytical chemistry》1994,349(10-11):703-707
The potentiometric determination of the protonation constants of phenol, 2-chlorophenol, 2-nitrophenol, 2,4-dichlorophenol and 2-methylphenol in 1.0 mol/L NaCl at 25°C is presented. An automated system has been used in the experiments. The determination of the constants has been carried out using both graphical and numerical methods. 相似文献
58.
R. Pérez-Olmos M. B. Etxebarria J. L. F. C. Lima M. C. B. S. M. Montenegro 《Analytical and bioanalytical chemistry》1998,362(2):230-233
A high dispersion FIA system with a fluoride selective and a double junction reference electrode in cascade arrangement was developed for the determination of the fluoride content in chromium electroplating baths. The analyses of seven synthetic baths prepared in the laboratory and two samples provided by the industry gave results with a mean recovery value of 100.5%, and a mean variation coefficient of 1.6%. These data were better than those obtained by the EDTA complexometric titration, the reference technique, with a mean recovery of 94.0% and a mean variation coefficient of 7.5%. The sampling rate for the FIA manifold was 20 samples per hour. 相似文献
59.
A new photoacoustic method for obtaining nonradiative decay rates in ion doped solids with a simple de-excitation scheme is theoretically investigated. From the theory developed, a relation between the amplitude ratio of the first and second harmonics of the photoacoustic signal and the spontaneous decay rate is predicted. 相似文献
60.
The pyrolysis of di-tert-butyl sulfide has been investigated in static and stirred-flow systems at subambient pressures. The rate of consumption of the sulfide was measured in some experiments, and the rate of pressure increase was followed in others. The results suggest that the reaction is essentially homogeneous in a seasoned reactor and proceeds through a free radical mechanism. In the initial stages, the decomposition rate follows first-order kinetics, and the rate coefficient in the absence of an inhibitor is given by between 360 and 413°C. The stoichiometry of the uninhibited reaction at 380°C and 50% decomposition is approximately between 360 and 413°C. The stoichiometry of the uninhibited reaction at 380°C and 50% decomposition is approximately. 相似文献