Gisselrobles1309

This study investigated the influence of cation type on the sodium deactivation of Brazilian bentonite varieties. Four bentonite clays were studied, including three mixed-cationic and one magnesium. Swelling and the main exchangeable cations (Na+, K+, Mg2+ and Ca2+) were the main evaluation parameters in this study. Periodic washes of the sodium-activated bentonites were performed based on the hypothesis that a possible desorption of the cations (primarily Na+) could cause the deactivation. Sodium activation was monitored using XRD measurements and an increase in swelling. Sodium deactivation was observed and monitored via a decrease in swelling. Positive and negative effects, caused by the proportions of the cations and the dominance of Mg2+, were emphasized by the set of cationically different samples applied in this study, which helped to answer the influence of main exchangeable cations, specially Mg2+, on the deactivation process.In this work, we propose a mathematical model describing thermal behavior and heating process optimization of solid fuel bread ovens. selleck chemicals llc Numerical simulation leads to temperature profiles of the oven. The design and implementation of an operating prototype permits us to obtain, with type K thermocouples, experimental temperature profiles in some points of the oven. There is a good agreement between the experimental results and those obtained from the numerical simulation of the proposed model. A permanent temperature value of 220 °C is reached in the baking chamber. It is obtained that the energy efficiency of the oven is 49%. Making use of the objective gain function, it is found that the optimal parameters of the oven are the following 50 W as optimum operating value of the electric power of the blower, 3 m2 as the optimum operating value of the total surface of the baking chamber; and 0.67 as the optimum operating value of the filling factor between the heating chamber and the baking chamber. The developed model serves to better understand the operation, the optimization and to rationally manage energy expenditure related to solid fuel bread ovens in developing countries.Four new compounds, (+)-(2S)-desmosdumosone (1), (+)-(2R)-7,8-dimethoxy-5-hydroxyflavanone (7), (+)-(2R)-7-methoxychamanetin (9), and (+)-(1'R,2'R)-phebalosin (18), and 25 known compounds were isolated from the twig and leaf extracts of Desmos dumosus. Compounds (±)-7 and (±)-9 were isolated as racemates and their enantiomers were separated by chiral HPLC. Their structures were elucidated by spectroscopic methods as well as comparisons made from the literature. The absolute configuration of (+)-(1'R,2'R)-18 was established by X-ray diffraction analysis using Cu Kα radiation and electronic circular dichroism (ECD) spectoscopy. In contrast, the absolute configuration of compounds (+)-(2S)-1, (+)-(2R)-7, and (+)-(2R)-9 were identified by comparing their ECD spectra and specific rotations with those of reported known compounds. Compounds 9, 11, 13, 14, 22, 25, and 28 showed α-glucosidase inhibitory activities with IC50 values ranging from 5.3-52.7 μM, much better than that of standard control (acarbose, IC50 value 83.5 μM). Compound 13 was the most active with an IC50 value of 5.3 μM.Since July 2018 several drugs have been recalled due to contamination with N-nitrosodimethylamine (NDMA), a probable human carcinogen. Dimethylamine (DMA) and nitrite are precursors in the formation of NDMA. In this study, ion chromatography (IC) methods were developed for the determination of these two precursors in drug substances and drug products. Two methods were developed to determine DMA in two drug products using a cation exchange separation coupled to suppressed conductivity detection. The limit of detection of DMA is less then 1 μg/g of active pharmaceutical ingredient (API) for both methods. Nitrite was determined using an anion exchange separation coupled with UV absorbance detection. The limit of detection of nitrite was 0.918 μg/g API. The developed methods were successfully applied to DMA and nitrite determinations in five drug products including metformin, losartan, ranitidine, Nytol, and Benadyrl, and two drug substances (APIs), losartan potassium and metformin hydrochloride. Some samples contained nitrite and DMA at detectable levels. Dimethylamine and nitrite recovery from pharmaceutical samples ranged from 96.0-104 %. The developed methods should be useful for the rapid screening and quantification of nitrite and DMA in pharmaceuticals and in-process samples to assess the likelihood of NDMA formation. The methods for DMA should be applicable to other amines to assess the likelihood of the formation of other nitrosamines in pharmaceutical products.[This corrects the article DOI 10.1016/j.heliyon.2020.e04928.].The Old Historical Wall, located in Bo Yang, Songkhla Province, Thailand, is an archaeological icon believed to have been constructed during the reign of Rama III, as indicated in the royal archives, around 1837-1840 CE. However, the recorded age is the result of unofficial documentation. The establishment was based on speculation from circumstantial evidence and local stories. The wall is made of bricks that underwent a heating process before being used for the construction. We therefore propose the use of the thermoluminescence technique for dating the wall. The samples include brick rubble from three excavation sites next to the wall. To determine the age, we estimate the radiation dose rate and the accumulated dose for each sample. The dose rate of the sample is determined using gamma spectroscopy with a high-purity germanium detector. For the accumulated dose, we employ the additive dose method using Co-60 with a dose range of 0-100 Gy. Glow curves are then deconvoluted using the general-order kinetics model. The results yield three superposition glow peaks at three different temperature ranges. Plateau tests are also carried out to find a proper temperature for dating purposes. Comparing the plateau test and the result of deconvolution, we find that the glow curve temperature suitable for dating was within 200-310 °C. The accumulated doses are then evaluated using the area under the curve of the peak temperature. The date is then determined as the ratio between the accumulated dose and the dose rate. The results indicate that the age is approximately 174-192 years, so that the wall was built around 1827-1841 CE, with one standard deviation interval. The duration is in agreement with the recorded age of the wall inscribed in the country's historical archives.