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661.
J. P. Gonçalves R. D. Toledo Filho E. M. R. Fairbairn 《Journal of Thermal Analysis and Calorimetry》2008,94(2):511-516
This paper reports an experimental study on the magnesium sulphate resistance of mortar specimens incorporating 0, 10 and
20% of metakaolin (MK). The evidence of the attack was evaluated through the content of calcium hydroxide (portlandite) and
formation of magnesium hydroxide (brucite) by thermal analysis (thermogravimetric and derivative thermogravimetric analysis).
The mechanical degradation of the mortar specimens was evaluated through splitting tensile tests after 200 days of exposition
to the magnesium solution. The addition of metakaolin resulted in a reduction in the content of calcium hydroxide and in a
smaller formation of brucite in comparison with reference mixture. A tensile strength loss of about 7% was observed for the
metakaolin mortars submitted to the magnesium solution attack for 200 days. 相似文献
662.
Stability studies on nifedipine tablets using thermogravimetry and differential scanning calorimetry
R. O. C. Filho P. I. B. M. Franco E. C. Conceição M. I. G. Leles 《Journal of Thermal Analysis and Calorimetry》2008,93(2):381-385
A formulation of nifedipine tablets was prepared in the present research. The tablets were conditioned in amber-colored glass
containers and placed in a climatized room at 40°C and relative humidity of 75% for 180 days. Differential scanning calorimetry
(DSC) and thermogravimetry (TG) were used in order to evaluate the thermal properties of nifedipine, the excipients and two
well-known nifedipine degradation products. The results demonstrated that there is no evidence on the interaction between
nifedipine and excipients, or degradation products. 相似文献
663.
Carneiro Jaqueline Dallagnol Juliana C. C. Veiga Andressa Noseda Miguel D. Duarte Maria Eugnia R. Filho Marco A. Carvalho Ducatti Diogo R. B. Gonalves Alan G. Murakami Fbio S. 《Journal of Thermal Analysis and Calorimetry》2022,147(12):6755-6764
Journal of Thermal Analysis and Calorimetry - Porphyrins have exquisite photophysical and electronic properties that enable their use in photodynamic therapy. Even though the thermodynamic behavior... 相似文献
664.
Maria Conceição M. Torres José Gustavo L. Almeida Raimundo Braz‐Filho Edilberto R. Silveira Otília Deusdênia L. Pessoa 《Magnetic resonance in chemistry : MRC》2012,50(1):74-78
From the leaves of Solanum campaniforme, two new spirosolane alkaloids β‐acetoxyl‐(25S)‐22βN‐spirosol‐4‐en‐3‐one (1) and β‐hydroxyl‐(25S)‐22βN‐spirosol‐4‐en‐3‐one (4) were isolated along with two other known alkaloids of the same class (25S)‐22βN‐spirosol‐1,4‐dien‐3‐one (2) and (25S)‐22βN‐spirosol‐4‐en‐3‐one (3), which are reported for the first time as natural products. The structures of all alkaloids were established after an extensive analysis by 1D and 2D NMR spectroscopy (COSY, HSQC, HMBC and NOESY) as well as HRESIMS. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
665.
Alexsandro Fernandes Marinho Eduardo de Jesus Oliveira Josean Fechine Tavares Raimundo Braz Filho Jose Maria Barbosa‐Filho 《Magnetic resonance in chemistry : MRC》2013,51(5):312-315
des‐7′‐O‐methylroraimine (compound 1) and epi‐des‐7′‐O‐methylroraimine (compound 2), two new isomeric bisbenzylisoquinoline alkaloids were isolated and characterized as a mixture from the rhizomes of Cissampelos sympodialis Eichl. The unambiguous structural elucidation of both isomers was performed with the aid of HR‐ESI‐MS, FT‐IR, and NMR techniques including COSY, HMQC, HMBC, and NOESY. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
666.
The Fokker-Planck equation is useful to describe stochastic processes. Depending on the force acting in the system, the solution of this equation becomes complicated and approximate or numerical solutions are needed. The relation with the Schrödinger equation allows building a method to obtain solutions of the Fokker-Planck equation. However, this approach has been limited to the study of confined potentials, restricting its applicability. In this work, we suggest a general treatment for non-confining potentials through the use of series of functions based on the solution of the Schrödinger equation, with part of discrete spectrum and part of continuum spectrum. Two examples, the Rosen-Morse potential and a limited harmonic potential, are analyzed using the suggested approach. 相似文献
667.
Patricia Bogalhos Lucente Fregolente Gláucia Maria F. Pinto Maria Regina Wolf-Maciel Rubens Maciel Filho 《Applied biochemistry and biotechnology》2010,160(7):1879-1887
Distilled glycerides are obtained through distillation of the system mono-diglycerides which is produced from the esterification
reaction between a triglyceride with glycerol. In this work, monoglycerides (MG) and diglycerides (DG) are produced through
lipase-catalyzed glycerolysis of soybean oil using Candida antarctica B in a solvent-free system. To separate the products of the reaction in order to obtain essentially MG and an oil of DG,
it is necessary to use a suitable process in order to preserve the stability of the components and to keep the products free
of inappropriate solvents. So, after 24 h of enzymatic reaction, the mixture of acylglycerols and fatty acids was distilled
into a centrifugal molecular distiller, since it provides a free solvent and lower temperature environment to increase the
desired product concentration. Starting from a material with 25.06% of triglycerides (TG), 46.63% of DG, 21.72% of MG, 5.38%
of free fatty acids (FFA), and 1.21% of glycerol, the MG purity in the distillate stream was 80% at evaporator temperature
(T
E) equal to 250 °C and feed flow rate (Q) equal to 10.0 mL/min. At these conditions, the MG recovery was 35%. The material collected in the residue stream presented
DG-enriched oil with TG unhydrolyzed, residual MG, and low acidity (29.83% of TG, 53.20% of DG, 15.64% of MG, and 1.33% of
FFA), which is suitable to replace TG oil in the human diet. 相似文献
668.
669.
A simple and rapid method based on solid-phase micro extraction (SPME) technique followed by gas chromatography-mass spectrometry with selected ion monitoring (GC-MS, SIM) was developed by the simultaneous determination of 16 pesticides of seven different chemical groups [Six organophosphorus (trichlorfon, diazinon, methyl parathion, malathion, fenthion and ethyon), three pyrethroids (bifenhin, permethrin, cypermethrin), two imidazoles (imazalil and prochloraz), two strobilurins (azoxystrobin and pyraclostrobin), one carbamate (carbofuran), one tetrazine (clofentezine), and one triazole (difenoconazole)] in water. The pesticides extraction was done with direct immersion mode (DI-SPME) of the polyacrilate fiber (PA 85 µm). The extraction temperature was adjusted to 50 °C during 30 min, while stirring at 250 rpm was applied. After extraction, the fiber was introduced in the GC injector for thermal desorption for 5 min. at 280 °C. The method was validated using ultra pure water samples fortified with pesticides at different concentration levels and shows good linearity in the concentrations between 0.05 and 250.00 ng mL− 1. The LOD and LOQ ranged, from 0.02 to 0.30 ng mL− 1 and 0.05 to 1.00 ng mL− 1, respectively. Intra-day and inter-day precisions were determined in two concentration levels (5.00 and 50.00 ng mL− 1). Intra-day relative standard deviation (%R.S.D.) ranged between 3.6 and 13.6%, and inter-day (%R.S.D.) ranged between 6.3 and 18.5%. Relative recovery tests were carried out spiking the ultra pure sample with standards in three different concentration levels 0.20, 5.00 and 50.00 ng mL− 1. The recovery at 0.20 ng mL− 1 level varied from 86.4 ± 9.4% to 108.5 ± 10.5%, at 5.00 ng mL− 1 level varied from 77.5 ± 10.8% to 104.6 ± 9.6% and at 50.00 ng mL− 1 level varied from 70.2 ± 4.6% to 98.4 ± 8.5%. The proposed SPME method was applied in twenty-six water samples collected in the “Platô de Neópolis”, State of Sergipe, Brazil. Methyl parathion was detected in five samples with an average concentration of 0.17 ng mL− 1 and bifenthrin, pyraclostrobin and azoxystrobin residues were found in three samples with average concentrations of 2.28, 3.12 and 0.15 ng mL− 1, respectively. 相似文献
670.
Luiza Placidina da Luz Pedro José Sanches Filho Elina Bastos Caramão 《Microchemical Journal》2010,96(1):161-166
This paper describes the extraction and analysis of Polyaromatic Hydrocarbons (PAHs) in five points of the Patos Lagoon Estuary. These points were in the area named “colony Z3”, which is a craft fishermen community in Pelotas City (southern Brazil). Samples were collected in July of 2007, and the concentrations of 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) were determined by gas chromatography coupled to a mass spectrometry detector (GC/MS). The PAH concentrations ranged from 4.7 to 112.5 µg kg− 1 dry weight. Sediment samples with the highest PAH concentrations appeared at point 2, which is a pier. The correlation between the total organic material (TOM) and the total PAH concentration suggests that TOM plays an important role in controlling the PAH levels in sediments. According to the observed ratios of individual PAHs, the contamination in the studied areas originated both from high-temperature pyrolytic processes and petrogenic sources. The levels of PAHs at the studied sites in the Z3 colony (Patos Lagoon) were low enough that they should not exert adverse biological effects. 相似文献