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71.
72.
The degradation process of TEOS-PDMS Ormosils containing different amounts of γ -APS has been studied by means of DTA, TG, FTIR and 29Si-NMR measurements. It has been found that the amount of γ -APS improved the thermal properties of Ormosil materials. The increase in γ -APS content causes the increment on the decomposition temperatures and activation energies of the studied Ormosils. These results have been attributed to the favourable effect of γ -APS in the copolymerisation reaction between TEOS and PDMS molecules. 29Si-NMR analyses have shown that the incorporation of γ -APS increases the concentration of D(Q) units in the Ormosil structure, i.e., increases the number of TEOS molecules bonded to PDMS ones. Initial decomposition temperature (IDT), temperature of maximum weight loss rate (Tmax), integral procedure decomposition temperature (IPDT) and activation energy values (E) were calculated from different equations which described the degradation of these materials. Addition of 10 wt% γ -APS produced an increase of 63∘C in the IDT and of 115 and 110∘C, respectively, for Tmax and IPDT (up to 478 and 610∘C) compared to the free γ -APS Ormosil. Activation energy values also rise up to 69.4 kJ⋅ mol−1 by introducing 10 wt% of γ -APS. 相似文献
73.
74.
David Kessel Kevin M. Smith R. K. Pandey F.-Y. Shiau Barbara Henderson 《Photochemistry and photobiology》1993,58(2):200-203
Abstract— Biophysical and photobiological properties of a group of bacteriochlorins were compared with efficacy of these products for photodynamic therapy of murine tumors. Predictive factors for selective photosensitization in vivo include affinity binding to lipoproteins greater than albumin, extinction coefficient at the wavelength of irradiation and tumor/skin distribution. Efficacy was correlated with circulating plasma levels of the different sensitizers but not with the photodynamic therapy response in cell culture. 相似文献
75.
Laila Čakare Marija Kosec Barbara Malič 《Journal of Sol-Gel Science and Technology》2000,19(1-3):603-606
PbZrO3 (PZ) thin films have been prepared by 2-methoxyethanol route from lead oxide or lead acetate and zirconium n-butoxide. The use of lead oxide as lead source and the seeding layer of TiO2 on Pt/TiO2/SiO2/Si substrate facilitate the formation of the perovskite phase. 相似文献
76.
María Beatriz de la Calle Guntiñas Michiel Ceulemans Claudia Witte Ryszard Łobiński Freddy C. Adams 《Mikrochimica acta》1995,120(1-4):73-82
A method is presented for the selective determination of the volatile selenium species dimethylselenide and dimethyldiselenide, using a commercially available purge-and-trap injection system coupled to capillary gas chromatography-microwave induced plasma-atomic emission spectrometry. The efficiency of the purging step was evaluated and the parameters affecting the purge and trap processes were optimized. The method was applied to the determination of volatile selenium compounds in lake water. Relative detection limits of 2ng/l for dimethylselenide and dimethyldiselenide, corresponding to an absolute detection limit of 10 pg, were achieved. 相似文献
77.
Corona-Avendaño S Rojas-Hernández A Romero-Romo MA Pardavé MP Ramírez-Silva MT 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):3139-3144
Noradrenaline is a catecholamine which has been largely recognised to play a very important role in biological systems. In view of the neurotransmitter's alleged importance, this work aimed at showing the influence of time on its spectral behaviour using different analytical methods and determining its acidity constants through spectrophotometric titration and by the so-called point-by-point analysis, where the samples are freshly prepared for each pH value investigated at the instant required. Because the catecholamines are light-sensitive and likely to react with the oxygen in the surrounding air, both methods used preclude its incidence onto the samples being analysed under the presence of a nitrogen atmosphere maintained over the solutions. The constants obtained through point-by-point analysis were log beta1 = 30.71+/-0.16, log beta2 = 22.00+/-0.15 and log beta3 = 11.69+/-0.16. 相似文献
78.
Applied Biochemistry and Biotechnology - Biological systems can convert renewable resources, including lignocellulosic biomass, starch crops, and carbon dioxide, into fuels, chemicals, and... 相似文献
79.
A simple technique is described for the routine simultaneous capillary electrophoretic determination of 6 cations in wine. Separation was achieved on a fused silica capillary column with a UV-Cat-1, alpha-hydroxysobutyric acid and 18-crown-6-ether buffer at pH 4.5 and indirect UV detection at 214 nm. The content of magnesium, sodium, potassium, calcium, manganese, and lithium was determined. The method is quantitative, with recoveries in the 92-102% range, and linear over more than one order of magnitude. The precision is better than 2.5-3.4%. The method is sensible, with detection limits between 0.01 and 0.06 mg/L. Twenty-five red wines with a Certified Brand of Origin from Galicia (north-western Spain) were analyzed by the proposed method. Various wines showed very similar electrophoretic profiles, but significant quantitative differences were observed. 相似文献
80.
F. Garcias J. A. Alonso M. Barranco J. M. López A. Mañanes J. Németh 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1994,31(4):275-277
The competition experimentally observed between asymmetric fission and neutral monomer evaporation as dissociation channels of excited doubly charged sodium clusters has been investigated by means of an axially symmetric, fully selfconsistent Kohn-Sham method. Ellipsoidal equilibrium configurations for parent and daughter clusters have been considered using a deformed jellium model.This paper was originally submitted in connection with the 2nd. Int. Conference on Atomic and Nuclear Clusters held in Santorini from 28. June–2. July 1993 and is published here as a regular article after an independent refereeing procedure according to the standards of Z. Phys. D 相似文献