排序方式: 共有34条查询结果,搜索用时 31 毫秒
31.
Anissa Khelfa Gisèle Finqueneisel M. Auber J. V. Weber 《Journal of Thermal Analysis and Calorimetry》2008,92(3):795-799
The influence of different inorganic salts (MgCl2, ZnCl2, NiCl2 and H2PtCl6) on the primary mechanisms of cellulose thermal degradation has been conducted by using thermogravimetric (TG-DTG) and pyrolysis-mass
spectrometry (Py-MS) analysis at low heating rate (10°C min-1) from ambient temperature to 500°C. The results clearly demonstrate
that the used salts influence the primary degradation mechanisms. Furthermore, we can assume that some inorganic salts could
be considered as specific catalysts and some others as inhibitors. MgCl2 promotes selectively initial low temperature dehydration as observed both by TG and Py-MS. ZnCl2 strongly changes the thermal behaviour of impregnated sample. The maximum mass loss rate temperature is shifted to lower
temperature and on the basis of our results we can conclude that ZnCl2 acts as catalyst in all primary degradation mechanisms. NiCl2 and H2PtCl6 do not modify significantly the cellulose thermal behaviour but change the composition of both produced gases and liquids
suggesting that these minerals catalyse some secondary reactions. 相似文献
32.
Flow-injection methylene blue-based spectrophotometric method for the determination of peroxide values in edible oils 总被引:3,自引:0,他引:3
A flow-injection method for measuring the peroxide value (PV, mequiv. O2 kg−1) in edible oils is described. The technique is based on spectrophotometric monitoring at 660 nm of methylene blue (MB), generated from leucomethylene blue (LMB) oxidation with peroxides present in oil samples. After being optimized, the method was validated in terms of linearity, precision sensitivity and recovery.Linear calibration graph was obtained in the range 0.1-5 mequiv. O2 kg−1, with a detection limit (S/N = 3) of 0.014 mequiv. O2 kg−1. The precision of the method (R.S.D., n = 9) for within and between-days is better than 1.5% and 2.2%, respectively at 0.4 mequiv. O2 kg−1. The method was applied successfully to the determination of PV in six edible oil samples, and compared to the classical official method. Using the linear regression test, Student's t-test and variance ratio F-test, there was no significant difference between the compared methods. The proposed method is accurate, simple, cheap and could be used to control edible oil rancidity with a high sample throughputs (30 samples h−1). 相似文献
33.
Fatima Ezzahra El oumari Dalila Bousta Hamada Imtara Anissa Lahrichi Radouane Elhabbani Ghita El mouhri Omkulthom Al kamaly Asmaa Saleh Mohammad Khalid Parvez Andriy Grafov Tarik Sqalli Houssaini 《Molecules (Basel, Switzerland)》2022,27(13)
Ethnobotanical studies have reported the traditional medicinal uses of Acacia senegal (L.) Willd. and Argania spinosa (L.) Skeels against kidney stone formation and other chronic kidney diseases. The present work is undertaken to study the litholytic activity and the inhibiting activity of calcium oxalate crystallization by bioactive compounds identified in Argania spinosa (L.) Skeels press-cake (residue of Argan oil) and in Acacia senegal (L.) Willd. The litholytic activity was studied in vitro on cystine and uric acid stones using a porous bag and an Erlenmeyer glass. The study of the inhibiting activity of calcium oxalate crystallization, was based on temporal measurements of the optical density, registered at a 620 nm wavelength for 30 min using an ultraviolet–visible spectrophotometer. The silylation method was performed to identify phytochemicals, followed by gas chromatography coupled with mass spectrophotometry (GC/MS) analysis. The results show significant litholytic activity of Argania Spinosa press-cake hydro-ethanolic extract on uric acid and cystine stones, respectively, with dissolution rates (DR) of 86.38% and 60.42% versus 3.23% and 9.48% for the hydro-ethanolic extract of Acacia senegal exudate. Furthermore, the percentages of nucleation inhibition are 83.78% and 43.77% (p ˂ 0.05) for Argania spinosa and Acacia senegal, respectively. The results point to the detection of 17 phytochemicals in Argania spinosa press-cake extract, the majority of which are phenolic acids and have potent anti-urolithiatic action. 相似文献
34.
Dr. Ram Kumar Dr. Yang Song Anissa Ghoridi Dr. Philippe Boullay Prof. Gwenaelle Rousse Prof. Christel Gervais Dr. Cristina Coelho Diogo Dr. Houria Kabbour Dr. Capucine Sassoye Patricia Beaunier Dr. Victor Castaing Dr. Bruno Viana Dr. Maria Luisa Ruiz Gonzalez Prof. José Gonzalez Calbet Prof. Christel Laberty-Robert Dr. David Portehault 《Angewandte Chemie (International ed. in English)》2023,62(26):e202303487
Mixed-anion compounds widen the chemical space of attainable materials compared to single anionic compounds, but the exploration of their structural diversity is limited by common synthetic paths. Especially, oxychlorides rely mainly on layered structures, which suffer from low stability during photo(electro)catalytic processes. Herein we report a strategy to design a new polar 3D tetrahedral framework with composition Zn4Si2O7Cl2. We use a molten salt medium to enable low temperature crystallization of nanowires of this new compound, by relying on tetrahedral building units present in the melt to build the connectivity of the oxychloride. These units are combined with silicon-based connectors from a non-oxidic Zintl phase to enable precise tuning of the oxygen content. This structure brings high chemical and thermal stability, as well as strongly anisotropic hole mobility along the polar axis. These features, associated with the ability to adjust the transport properties by doping, enable to tune water splitting properties for photoelectrocatalytic H2 evolution and water oxidation. This work then paves the way to a new family of mixed-anion solids 相似文献