The thermo‐mechanical properties of organogels developed by a complex mixture of n‐alkanes present in candelilla wax (CW) were investigated and compared with the ones of organogels developed by a pure n‐alkane, dotriacontane (C32). In both cases, the liquid phase used was safflower oil high in triolein (SFO) and the variables studied were two levels of gelator concentration (1 and 3%), cooling rates of 1 and 10 °C/min, and two gel setting temperatures, 5 and 25 °C (Tset). Based on comparisons of the organogels made with C32, the presence of minor molecular components in CW had a profound effect on the crystal habit of the n‐alkanes in CW‐based organogels, and therefore on their physical properties. Thus, independent of the cooling rate and Tset, C32 showed a higher solubility and higher self‐assembly capability in the SFO than CW. Nevertheless, for the same gelator concentration and time‐temperature conditions, C32 organogels had lower G' profiles than CW organogels. Additionally, independent of the type of gelator, more stable organogel structures were developed at Tset = 5 °C and using the lower cooling rate. The rheological behavior of the organogels was explained considering the formation of a rotator phase by the n‐alkanes, its solid‐solid transition, and their dependence as a function of the cooling rate and Tset. The results here obtained showed that it is possible to gelate SFO through organogelation with CW and without the use of trans fats. 相似文献
Currently, electrospraying is a novel process for obtaining the nanoparticles from biopolymers. Zein nanoparticles have been obtained by this method and used to protect both hydrophilic and hydrophobic antioxidant molecules from environmental factors. The objective of this work was to prepare and characterize gallic acid‐loaded zein nanoparticles obtained by the electrospraying process to provide protection to gallic acid from environmental factors. Thus, it was related to the concentration of gallic acid in physicochemical and rheological properties of the electrosprayed solution, and also to equipment parameters, such as voltage, flow rate, and distance of the collector in morphology, and particle size. The physicochemical properties showed a relationship in the formation of a Taylor cone, in which at a low concentration of gallic acid (1% w/v), low viscosity (0.00464 ± 0.00001 Pa·s), and density (0.886 ± 0.00002 g/cm3), as well as high electrical conductivity (369 ± 4.3 µs/cm), forms a stable cone‐jet mode. The rheological properties and the Power Law model of the gallic acid‐zein electrosprayed solution demonstrated Newtonian behavior (n = 1). The morphology and size of the particle were dependent on the concentration of gallic acid. Electrosprayed parameters with high voltage (15 kV), low flow rate (0.1 mL/hr), and short distance (10 cm) exhibited a smaller diameter and spherical morphology. FT–IR showed interaction in the gallic acid‐loaded zein nanoparticle by hydrogen bonds. Therefore, the electrospraying process is a feasible technique for obtaining gallic acid‐loaded zein nanoparticles and providing potential protection to gallic acid from environmental factors. 相似文献
One important challenge in mathematics education is teaching modeling skills. We analyze the logs from a game-based learning system used in a massively multiplayer online tournament. Students had to detect an input–output pattern across 20 rounds. For each round, they received an input and had 2 minutes to predict the output by selecting a binary option (2 points if correct, ?1 otherwise), or writing a model (4 points if model prediction was correct, ?4 otherwise), or refraining (1 point). Thousands of 3rd to 10th grade students from hundreds of schools simultaneously played together on the web. We identified different types of players using cluster analysis. From 5th grade onwards, we found a cluster of students that wrote models with correct predictions. Half of the 7th to 10th grade students that detected patterns were able to express them with models. The analysis also shows diffusion within the teams of modeling strategies for simple patterns. 相似文献
Underground mine production scheduling determines when, if ever, activities associated with the extraction of ore should be executed. The accumulation of heat in the mine where operators are working is a major concern. At the time of this writing, production scheduling and ventilation decisions are not made in concert. Correspondingly, heat limitations are largely ignored. Our mixed-integer program maximizes net present value subject to constraints on precedence, and mill and extraction capacities with the consideration of heat using thermodynamic principles, while affording the option of activating refrigeration to mitigate heat accumulation. In seconds to hours, depending on the problem size (up to thousands of activities and 900 daily time periods), a corresponding methodology that exploits the mathematical problem structure provides schedules that maintain a safe working environment for mine operators; optimality gaps are no more than 15% and average less than half that for otherwise-intractable instances.
In order to compare intestinal morphology and function, diarrhea was produced in rats using laxatives in the diet. The 14 day study included two groups of rats with diarrhea (osmotic or secretory), two groups without diarrhea but with a degree of malnutrition which was similar to that seen in the rats with diarrhea (malnourished without diarrhea) and a well-nourished group (control). The inclusion of laxatives(lactose or bisoxatin acetate) cause a reduction in food intake, diarrhea an malnutrition. It also caused a reduction in dietary protein and fat digestibility which was proportional to the severity of diarrhea and more pronounced in secretory diarrhea. In the malnourished rats without diarrhea, malnutrition did not affect their absorptive function. Both in the rats with secretory and osmotic diarrhea an intestinal hypertrophy was observed. This hypertrophy was proportional to the severity of diarrhea and independent of its aetiology. In the intestines of the rats with both types of diarrhea there was inflammation, a greater number of mitotic figures but the flattening of the villi seen in the malnourished rats without diarrhea was not seen. In osmotic diarrhea there was, in addition, a patchy damage of the surface of the jejunal mucosa and an increment in the number of goblet cells, indicating a more severe intestinal deterioration. Since despite this greater deterioration, these rats absorbed more protein and fat we concluded that the alterations in intestinal morphology seen in this study was not predictive of intestinal function. The study also showed that diarrhea had a trophic effect on the intestine which did not occur in malnourished rats without diarrhea. 相似文献
Olive pomace wastes were used as precursors for the development of new biosorbents for heavy metals. Thermal and/or chemical treatments were addressed in terms of their effects on functional group properties and copper removal. Product development was guided by experimental characterization (potentiometric titrations, IR spectra, copper biosorption, total surface area) and theoretical modeling of acid-base properties. Olive pomace was characterized by negative charge due to dissociation of two weakly acidic sites (carboxylic and phenolic). After thermal treatment, a char-like material was obtained, characterized by basic sites with positive charge in the acidic pH range. Copper biosorption properties of this material were improved with respect to olive pomace due to the binding ability of pyrone-like sites. Both native and carbonized olive pomace samples were chemically treated by HNO(3). Experimental tests were performed according to factorial designs and analysis of variance was used to evaluate significant effects on copper removal of both oxidant concentration and temperature. Chemical treatment by HNO(3) of carbonized material developed negatively charged groups in the acidic pH range (carboxylic groups), but presented a decreased copper removal. Chemical treatment by HNO(3) of olive pomace without carbonization gave biosorbents with acid-base properties similar to those of native olive pomace, but with a significant increase of copper biosorption. Specific carboxylic-copper interactions indicated by IR spectra and increased surface area due to chemical treatment were simultaneously responsible for such improvement. 相似文献