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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.
Martin T. Palou Ľubomír Bágeľ Vladimír Živica Marta Kuliffayová Tomáš Ifka 《Journal of Thermal Analysis and Calorimetry》2013,113(1):385-394
Various hydrothermal curing regimes were used to investigate the hydration and physical characteristics of two kinds of inorganic binder composites: high alumina cement–silica fume–Portland cement and high alumina cement–silica fume–sodium polyphosphate. Simultaneous thermal analysis (DTA and TG) was used to identify temperature ranges of thermal decomposition of cured samples and to characterize the nature of hydrate products. Two kinds of products are formed. The first ones consist of C3AH6, AH3, calcium carbonate (C–C) as a product of carbonation, and C3AH1.5 resulted from the partial decomposition of C3AH6 under higher hydrothermal pressure. The second ones are the products formed by acid–base reaction between monocalcium aluminate and sodium polyphosphate to form NaCaPO4·xH2O and Al2O3·xH2O that could convert to chemically bonded ceramic binders like hydroxyapatite (Ca5(PO4)3OH) and gibbsite (Al(OH)3). These two hydroceramic products formed under these conditions act also as binder and could be useful as cement binders for the protection of petroleum, gas, or geothermal wells. Mercury intrusion porosimeter was used for the estimation of the pore structure parameters of the composites. It turned up that longer curing time coupled with higher hydrothermal pressure has improved the pore structure of the first composite, while that of the second has remained unchanged. 相似文献
93.
A chemoselective method for the hydrosilylation of ketones has been developed, using the combination of triphenylsilane and a catalyst prepared from Ni(COD)2 and the simple N-heterocyclic carbene IMes. The most notable feature of this method is that free hydroxyls are largely unaffected, thus providing a simple one-step procedure for the conversion of hydroxyketones to mono-protected diols, wherein the protecting group is exclusively installed on the ketone-derived hydroxyl. The process is typically high yielding with both simple ketones and more complex hydroxyketone substrates. 相似文献
94.
Irene Maijó Núria Fontanals Francesc Borrull Christian Neusüß Marta Calull Carme Aguilar 《Electrophoresis》2013,34(3):374-382
The use of SPE coupled in‐line to CE using electrospray MS detection (in‐line SPE‐CE‐ESI‐MS) was investigated for the preconcentration and separation of four UV filters: benzophenone‐3, 2,2‐dihydroxy‐4‐methoxybenzophenone, 2,4‐dihydroxybenzophenone and 2‐phenylbenzimidazole‐5‐sulphonic acid. First, a CE‐ESI‐MS method was developed and validated using standard samples, obtaining LODs between 0.06 μg/mL and 0.40 μg/mL. For the in‐line SPE‐CE‐ESI‐MS method, three different sorbents were evaluated and compared: Oasis HLB, Oasis MCX, and Oasis MAX. For each sorbent, the main parameters affecting the preconcentration performance, such as sample pH, volume, and composition of the elution plug, and sample injection time were studied. The Oasis MCX sorbent showed the best performance and was used to validate the in‐line SPE‐CE‐ESI‐MS methodology. The LODs reached for standard samples were in the range between 0.01 and 0.05 ng/mL with good reproducibility and the developed strategy provided sensitivity enhancement factors between 3400‐fold and 34 000‐fold. The applicability of the developed methodology was demonstrated by the analysis of UV filters in river water samples. 相似文献
95.
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
96.
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
97.
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
98.
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
99.
Dr. Martha V. Escárcega‐Bobadilla Dr. Marta Martínez Belmonte Eddy Martin Eduardo C. Escudero‐Adán Prof. Dr. Arjan W. Kleij 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(8):2641-2648
A tetraoxo bis‐Zn(salphen) supramolecular host can bind various divalent metal salts, thereby providing access to trinuclear bifunctional systems that incorporate both Lewis acid sites and dynamically bound nucleophilic anions. The formation of these trinuclear species was investigated and their stability features were also determined. The application of these trinuclear complexes as bifunctional catalysts was evaluated in the formation of cyclic organic carbonates from epoxides and CO2. The catalytic data, in combination with control experiments, clearly demonstrate that these trinuclear compounds show much higher recycling potential compared to various control compounds and they can be used in up to five cycles without an observable loss in activity. Furthermore, this new recyclable catalytic system does not require any additives and can be applied under solvent‐free conditions. 相似文献
100.