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1.
The microstructural development during crystallization firing of a commercially-available dental-grade nanostructured lithia-zirconia glass-ceramic (Vita Suprinity® PC) was unraveled using a wide battery of ex-situ and in-situ characterization techniques. It was found that the milling blocks are slightly crystallized glass-ceramics, with a complex chemical composition and consisting of partially de-polymerized glass plus lithium silicate (Li2SiO3) nanocrystals. It was also found that during crystallization firing the glassy matrix first reacts with part of the Li2SiO3 to form lithium disilicate (Li2Si2O5) at ~810?820 °C, and then lithium orthophosphate (Li3PO4) precipitates from the glass. This results in glass-ceramics with abundant nanocrystals embedded in a sparse zirconosilicate glass matrix (containing many other cations subsumed) that, due to its high viscosity, inhibited crystal growth. Therefore, these dental glass-ceramics are not reinforced with zirconia (ZrO2) crystals unless over-fired above ~890 °C and at the expense of its singular nanostructure. Finally, this study opens doors for optimizing the clinical performance of these dental glass-ceramics via microstructural tailoring.  相似文献   
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A novel series of cleavable alkyltrimethylammonium surfactants with different hydrocarbon chain lengths (C8–16) were synthesized. A carbonate break site inserted between the polar head and the hydrocarbon chain makes these compounds hydrolyzable. The reagents used are renewable, (bio)degradable, or reusable. The hydrolysis of these cleavable surfactants will lead to the generation of fatty alcohols and choline, which is an essential biological nutrient. The surface activities in aqueous solution of the synthesized carbonates fulfill the requirement of being good surfactants. In addition, the cleavable compounds containing n-decyl and n-dodecyl chains showed similar or higher antimicrobial activities when compared to a non-cleavable analog.  相似文献   
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Monoacylglycerol (MAG) and diacylglycerol (DAG) are two natural components found in most edible oils and fats. Conventional synthesis of MAG and DAG is usually conducted by glycerolysis of triacylglycerol (TAG) at high temperatures (above 200°C) in the presence of an alkaline catalyst. In this work, the synthesis of MAG and DAG using enzymatic glycerolysis of olive oil was investigated using Tween 80 as surfactant, n-butanol as co-surfactant and the novel lipase in free/liquid formulation Lipozyme TL 100L as catalyst. Experimental design was used to evaluate the effect of enzyme load and reaction temperature on the feedstock conversion. Enzyme load and system temperature were significant variables in the statistical design and the best condition was found at 35°C, 7.5 vol% of Lipozyme TL 100L and glycerol to oil volumetric ratio of 2:1 with conversion of TAG at approximately 98% after 2 h of process. A mathematical model based on the Ping-Pong Bi-Bi mechanism was used to describe the reaction kinetics. The model adequately described the behavior of the system and can be a useful tool for the design of reactors in larger scales.  相似文献   
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The present study develops a new method for manganese (Mn) preconcentration and speciation in bioaccessible fraction (soluble and dialyzable fraction) of enteral nutrition formulas by cloud point extraction (CPE) and atomic absorption spectroscopy (AAS). For this purpose, a non-ionic surfactant (Triton X-100) and three chelating reagents [8-hydroxyquinoline (8-HQ); 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP); and ammonium pyrrolidine dithiocarbamate (APDC)] were used with different operating conditions. The results showed that an efficient extraction of ionic Mn could be achieved with the following conditions: pH?=?10; chelating reagent concentrations of [8-HQ]?=?0.36 M, [PMBP]?=?0.09 M, and [APDC]?=?0.09 M; surfactant Triton X-100 at 25% (w/v), and equilibration temperature-time of 85 °C and 30 min. Limits of detection and quantitation are 0.015 and 0.050 mg L?1 respectively. Furthermore, when analyzing the bioaccessible fraction of the enteral nutrition formulas, the proposed approach can be used to distinguish between ionic (free) Mn and Mn that has been previously bound to existing substances obtained from enzymatic digestion. These Mn speciation findings can be used to validate results obtained from the bioaccessibility assays.  相似文献   
5.
Cysteine is present in a large number of natural and synthetic (bio)molecules. Although the thiol side chain of Cys can be in a free form, in most cases it forms a disulfide bond either with a second Cys (bridge) or with another thiol, as in the case of protecting groups. Efficient reduction of these disulfide bridges is a requirement for many applications of Cys-containing molecules in the fields of chemistry and biochemistry. Here we review reducing methods for disulfide bonds, taking into consideration the solubility of the substrates when selecting the appropriate reducing reagent.  相似文献   
6.
Water contaminated by oil poses challenges to the management of water resources. Magnetic nanoparticles has been issue of different potential applications including remotion oil from water. Magnetic polystyrene–palygorskite nanocomposites were prepared by a heterogeneous phase polymerization for the removal of organic contaminants from water. The organo‐Fe3O4‐palygorskite nanoparticles were coated with polystyrene, forming water repellent and oil absorbing surfaces to promote the removal of oil from the surfaces of nanocomposites by applying an external magnetic field. X‐ray fluorescence, X‐ray diffraction, scanning electron microscopy, zeta potential and size distribution measurement, surface area determination by BET, density measurement by He pycnometry, carbon grade determination, thermogravimetric analysis, Fourier‐transform infrared spectroscopy, Raman spectroscopy, and evaluation of hydrophobicity by contact angle were used to characterize the nanoparticles. The magnetic nanocomposite obtained showed excellent hydrophobicity, around 78° contact angle. In addition, oil removal capability tests were also performed, according to which the preliminary results indicated removal of approximately 98% of oil in synthetic oily water samples. The oil–water separation using this magnetic nanocomposite provides a promising alternative strategy for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46162.  相似文献   
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ABSTRACT

Environmental research data usually present high variability because of the presence of outlier values. This study sought to apply the interval bootstrap method, as compared to Chebyshev’s Theorem, for the statistical assessment of environmental data with anomalous values. The results obtained showed that: (a) the bootstrap method is an excellent alternative in the assessment of environmental data with outliers; (b) the method percentile bootstrap (Boot-perc-s) presented the lower interval amplitude to the concentrations of 226Ra, and (c) Chebyshev’s Theorem presented the highest interval amplitude for the concentration of 226Ra.  相似文献   
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