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91.
José L. de la Fuente Marta Ruiz-Bermejo César Menor-Salván Susana Osuna-Esteban 《Journal of Thermal Analysis and Calorimetry》2013,111(3):1699-1706
This study presents the thermogravimetry (TG) of hydrophobic tholins, obtained from different simulation experiments of prebiotic synthesis carried out in a CH4/N2/H2 atmosphere with spark discharge activation of aqueous aerosols and liquid water. Differential thermal analysis and differential scanning calorimetry were also used to evaluate the thermal behaviour of these complex organic compounds that could play an important role in prebiotic chemistry. A coupled thermogravimetry-mass spectrometry system allowed us to analyse the principal volatile thermal decomposition and fragmentation products of the hydrophobic tholins under dynamic conditions and an inert atmosphere. During their thermal degradation, which occurs in two stages, a wide variety of hydrocarbon products including methane, vinyl monomers (such as ethylene and propylene), acetylene, oligomers, and some other unknown compounds are found. Besides, a thermally stable structure is present (graphitic structure) in these particular organic substances. Finally, data collected from TG experiments in an oxidative atmosphere showed significant differences at temperatures above 240 °C. According to these results, the different techniques of thermal analysis here applied have proved to be an adequate methodology for the study and characterization of these complex systems, structures of which remain controversial even in these days. 相似文献
92.
Marta Zalewska Agnieszka Gawin Milena Ściskalska Marcin Moczulski Halina Milnerowicz 《International journal of environmental analytical chemistry》2013,93(14-15):1422-1434
Metallurgy processes are associated with many hazardous and toxic factors, including heavy metals. Exposure to heavy metals can cause damage to different organs, which can be observed through variation in the concentration of proteins in serum. The aim of this study was to evaluate the changes in a serum protein profile of copper smelters exposed to As, Cd and Pb ions, and xenobiotics present in tobacco smoke. A 2.3-fold higher Pb concentration in the blood and a 2.8-fold greater As concentration have been observed in the urine of non-smoking smelters compared to a control group. In the blood of smoking smelters, Cd concentration was 2-fold higher than in non-smoking ones. Serum proteins were separated by capillary electrophoresis, and in the group of non-smoking smelters, a higher amount of α1-globulins was observed. In the group of smoking smelters, fewer α1-globulins were noted. Furthermore, a greater amount of α2-globulins in the serum of smoking and non-smoking workers in relation to the control group was revealed. A positive correlation between the concentration of Cd in the blood and the content of a fraction containing α1- and α2-globulins was revealed. Urine Cd concentration was found to be negatively associated with the α1- and α2-globulins fraction. Observed abnormalities in the proteins profiles of smelters can be important markers when assessing exposure to heavy metals and in the early diagnosis of diseases caused by them. 相似文献
93.
Jerzy Jabłoński Władysław Janusz Marta Szymula Jerzy Szczypa 《Journal of Dispersion Science and Technology》2013,34(6):663-681
The adsorption of metal ions at the stearic acid/electrolyte and nnonadccane-stearic acid mixture/electrolyte interface was investigated by means of the potentiometric titration, zeta potential and adsorption measurements. It was found that the studied colloidal suspensions exhibited an adsorption affinity towards multivalent metal ions. The adsorption of Ca2+, Cd2+ and Al3+ ions caused a strong decrease of surface charge density and zeta potential values in this systems. The adsorption reactions occur by way of cation exchange with protons from two surface carboxyl groups. Al high metal concentrations, in adsorption reactions there are involved also carboxyl groups from the subsurface layer. On the basis of the adsorption data, the cation surface complexation constants were calculated by Shindler's method. 相似文献
94.
Marta Rámirez Johnny Bullón José Andérez Isabel Mira Jean-Louis Salager 《Journal of Dispersion Science and Technology》2013,34(1-3):309-321
The research work on why and how distribution bimodality tends to reduce the viscosity of a particulate suspension is reviewed. The transfer of the corresponding concepts to emulsions requires some statistical tools, and becomes particularly easy with probability scale plotting which is reviewed. Viscosity reduction can be attained for different kinds of fine and coarse emulsion associations. The results are shown to depend on the characteristics of the base emulsions as well as on the way they are mixed. 相似文献
95.
Marta Menyhárt Katalin Kövér Ferenc Sztaricskai 《Journal of carbohydrate chemistry》2013,32(2-3):253-267
ABSTRACT Synthetic approaches to anthracycline antibiotic analogues in which the nitrogen atom of the carbohydrate portion is incorporated into a 1, 2, 3-triazolyl moiety were investigated. By using methyl 6-azido-2, 6-dideoxy-β-D--arabino-hexopyranoside and methyl 6-azido-2, 3, 6-tricdeoxy--α-L-arabino-hexopyranoside, the corresponding glycosides (16 a, b - 18 a, b) of carminomycinone and daunomycinone were prepared. The desired heterocyclic system was developed directly with the C-3′ and C-6′ azido anthracyclines by means of a cycloaddition process to give 7-0-[6′-(4, 5--dicarboethoxy-l, 2, 3-triazolyl)-2′, 6′-dideoxy-β-D-arabino--hexopyranosyl]-carminomycinone (23) and -daunomycinone (22), and 3′-(4, 5-dicarboethoxy - l, 2, 3-triazolyl)-4′ -epi-daunomycin (24). 相似文献
96.
Gaston Bocaz-BeneventiRosa Latorre Marta FarkováJosef Havel 《Analytica chimica acta》2002,452(1):47-63
The application of the combination of experimental design (ED) and artificial neural networks (ANNs) for the quantification of overlapped peaks in capillary zone electrophoresis is described. When the total separation cannot be achieved by separation techniques, the use of ED-ANN can be a suitable approach. The unstability of EOF causes peak shift that has to be corrected in order to apply ED-ANN methods. In this work, normalization procedure of electropherograms with consequent application of ANNs for quantification purpose was developed. Both, spectra and electropherograms can be used as multivariate data. In general, both kinds of data were found to be suitable for unresolved peaks quantification by ED-ANN approach. 相似文献
97.
Rosillo M Casarrubios L Domínguez G Pérez-Castells J 《Organic & biomolecular chemistry》2003,1(9):1450-1451
Starting from conveniently designed dienynes complexed to cobalt, a tandem RCM-intramolecular Pauson-Khand reaction yields tricyclic compounds. The methodology allows the synthesis of 6,5,5 and 7,5,5 systems. 相似文献
98.
Alvarez-Bercedo P Bond AD Haigh R Hopkins AD Lawson GT McPartlin M Moncrieff D Mosquera ME Rawson JM Woods AD Wright DS 《Chemical communications (Cambridge, England)》2003,(11):1288-1289
The reaction of CyPHNa with Sn(NMe2)2 in the presence of PMDETA (= (Me2NCH2CH2)2NMe) gives the title compound [(Sn(mu-PCy))3(Na x PMDETA)2] (1), containing an electron-deficient [(Sn(mu-PCy))]3(2-) dianion with a novel two-electron, three centre (2e-3c) bonding arrangement. 相似文献
99.
Barrett PA Boix T Puche M Olson DH Jordan E Koller H Camblor MA 《Chemical communications (Cambridge, England)》2003,(17):2114-2115
The new synthetic form of microporous crystalline silica, denoted as ITQ-12, shows a high potential for the separation of propane and propene from its mixtures. 相似文献
100.
Abstract. The aerobic oxidation of saturated long chain fatty acids to the lower aldehyde and CO2 catalyzed by the α-oxidase system of young leaves from germinating Pisum sativum results in concomitant excitation of the chloroplasts or/and fractions present in the α-oxidase preparation. The excitation is attested to by both chlorophyll emission and Hill activity. This is the first case of photobiochemistry without light within a natural system. 相似文献