Allelochemical Potential of Metopium brownei

Metopium brownei is a tree that grows in coastal tropical forests along the Gulf of Mexico and in the Yucatan Peninsula. This medicinal species produces a strongly irritant exudate, and sometimes forms pure populations favored by fire. The bioactivity of the aqueous leachates, organic extracts (leaves, bark, and wood), and mixtures of urushiols and flavonoids from M. brownei were evaluated on the growth of two plants: Amaranthus hypochondriacus and Echinochloa crusgalli, and four phytopathogenic fungi: Fusarium oxysporum, Helminthosporium sp., Alternaria sp., and Pythium sp. Alkylcatechols (urushiols) were isolated from an acetone extract of the bark. Dihydroquercetin and eriodictyol were isolated from the chloroform–methanol extract of the wood. In addition, masticadienoic acid was isolated from the leaves. The aqueous leachates, organic extracts, and the mixtures of flavonoids and urushiols were inhibitory to the growth of test plants and phytopathogenic fungi. The allelochemical role of the bioactive compounds from M. brownei is discussed in relation with other results reported in some studies on Anacardiaceae family and M. brownei.     

Thermochromic and/or photochromic properties of electrospun cellulose acetate microfibers for application as sensors in smart packing

There is growing demand for smart materials whose chemical structure, shape, and/or color, among other properties could be modified for use in applied packaging in the food industry, pharmacy, textiles, and so forth. These variations results from external stimuli, whether chemical, physical, and/or environmental (humidity, heat, light, and so forth), which has created promising materials for use in various areas of engineering, such as the production of ultrasensitive sensors with the capacity that the said variations are perceptible to the naked eye. The production of nanostructured sensor membranes obtained by electrospinning is one interesting alternative that has been attracting the attention of researchers in recent years. However, many studies related to the application of photosensors supported in electrospun cellulose acetate (CA) have not been found in the literature. Among the most used materials in electrospinning, CA stands out due to its wide availability and low cost that reflects in several applications. Two commercial sensitive pigments were used, a thermosensitive and a photosensitive one, in concentrations between 0 and 10% (m/v), to evaluate the best amount in the nanosensors they could be seen through naked eye. Variation on the fibers morphology was characterized by scanning electron microscopy. The stability and thermal transitions were evaluated using thermogravimetric analysis/differential thermogravimetric analysis and differential scanning calorimetry. The composition of chemical fibers was studied using FTIR-ATR. Finally, the thermal and/or UV light response was performed by qualitative test.     

Allelopathic potential ofIpomoea tricolor (Convolvulaceae) in a greenhouse experiment

The allelopathic potential ofIpomoea tricolor, a plant used in Mexican agriculture to control weeds, and tricolorin A, the major phytogrowth inhibitor present in the so-called resin glycosides of this plant, have been evaluated by testing leachates of the plant and the compound on the germination and radicle growth ofAmaranthus hypochondriacus, Echinochloa crusgalli, Senna uniflora, I. tricolor, andI. purpurea. The allelopathic potential ofI. tricolor was evaluated in a greenhouse experiment with dryI. tricolor mixed with sterile and nonsterile soil in pots.A. hypochondriacus was sown in pots containingI. tricolor, 2-chloro-4-(ethylamino)-6-(isopropylamino)-1,3,5 triazine (Gesaprim) or 1-glyphosphate, and the glyphosphate salt of isopropylamine (Faena), two different commercial herbicides used as a comparison toI. tricolor. Number and dry weights of different monocotyledonous and dicotyledonous weeds andA. hypochondriacus growing in the different treatments were measured.Ipomoea and Faena herbicide had a similar inhibitory effect on monocots.     

Effect of phytotoxic resin glycoside on activity of H+-ATPase from plasma membrane

A resin glycoside mixture isolated fromIpomoea tricolor inhibited radicle growth ofEchinochloa crusgalli. The effect of the resin was tested on the activity of the plasma membrane H⁺-ATPase fromE. crusgalli. For this purpose, plasma membrane vesicles were purified by the method of aqueous two-phase partitioning. The resin glycoside inhibited by 30% the activity of the plasma membrane ATPase. The same result was obtained with the purified main component of the resin. This indicates that the plasma membrane ATPase can be one of the cellular targets of the resin. Hence it is possible that the mechanism of action of the resin involves an inhibition of the plasma membrane ATPase.     

Effects of concentrated electrolytes administered via a paste on fluid, electrolyte, and acid base balance in horses

OBJECTIVES: To test effectiveness of an electrolyte paste in correcting fluid, electrolyte and acid base alterations in response to furosemide administration. ANIMALS: 6 Standardbreds. PROCEDURES: Horses received electrolyte paste or water only (control). The paste was given orally 3 hours after furosemide administration (1 mg/kg of body weight, IM). Water was given ad libitum soon after the paste and 3 hours after furosemide administration to treated and control groups, respectively. Paste Na+, K+, and Cl- composition was approximately 2,220, 620, and 2,840 mmol, respectively. The PCV and plasma concentrations of total protein ([TP]), [Na+], [K+], [Cl-]), and bicarbonate ([HCO3-]) were determined, and urinary fluid and electrolyte excretion, fecal water, and body weight changes were measured. RESULTS: At the end of a 6-hour period, the paste-treated group had higher water consumption, which resulted in lower plasma [TP]; net electrolyte losses also were substantially less. With paste administration, [Na+] was approximately 2 mmol/L above a prefurosemide value of 137.3 mmol/L; control horses had values similar to the prefurosemide value. Plasma [Cl-] remained at the prefurosemide value, but values in control horses decreased by 7 mmol/L with water consumption. Plasma [K+] remained approximately 0.8 mmol/L below prefurosemide values in both groups. Venous [HCO3-] returned to prefurosemide values after paste administration, but alkalosis persisted in control horses after consumption of water only. Body weight loss was less after paste administration. CONCLUSIONS: Administration of electrolyte paste is advantageous over water alone in restoring fluid, electrolyte, and acid base balance after fluid and electrolyte loss attributable to furosemide administration.     

Modelling and control of synchronous generators for wide‐range variable‐speed wind turbines

The modelling and control of a wide‐range variable speed wind turbine based on a synchronous generator are presented. Two different methods to control the operation of the synchronous generator are investigated, i.e. load angle control and instantaneous vector control. The dynamic performance characteristics of these control strategies are evaluated and compared using three model representations of the generator: a non‐reduced order model including both stator and rotor transients, a reduced order model with stator transients neglected, and a steady‐state model that neglects generator electrical dynamics. Assessment on the performance of grid‐side controller is shown during network fault and frequency variation. A simplified wind turbine model representation is also developed and proposed for large‐scale power system studies. Simulation results in Matlab/Simulink are presented and discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Pectin-derived oligosaccharides increase color and anthocyanin content in Flame Seedless grapes

BACKGROUND: Grapes grown in warm weather do not develop a desirable red color and require the use of products to enhance berry color. Pectin‐derived oligosaccharides (PDOs) have been shown to have a role in various responses including plant defense, growth and development. In this work a mixture of PDOs with 3–20 degrees of polymerization was applied to Vitis vinifera cv. Flame Seedless grapes under field conditions and compared to the effects of ethephon (an ethylene‐releasing compound). The effect of treatments on grape color, anthocyanin content and phenylalanine ammonia lyase (PAL) mRNA levels was evaluated. RESULTS: PDOs treatment increased berry color measured by the Color Index of Red Grapes (CIRG) and anthocyanin content, compared to ethephon and untreated berries (control); 1.5, 1 and 0.5 mg mL^?1 PDOs increased berry color by 30%, 27% and 26%, respectively, when compared to control berries. Levels of PAL mRNA accumulating in berries treated with PDOs were elevated within the first 24 h of treatment. CONCLUSIONS: PDOs enhanced the color and anthocyanin content of Flame Seedless grape berries possibly due by the induction of PAL mRNA expression. The results demonstrated that PDOs can be used to improve fruit quality aspects such as berry skin color. Copyright © 2011 Society of Chemical Industry     

Risk evaluation and management to reaching a suggested FSO in a steam meal

Steam meals are ready-to-eat meals composed of raw and semi-cooked ingredients, which get cooked while microwave heating. In this study, an Indian style meal was selected, Chicken Tandoori, from two different producers. These meals were first evaluated with the Risk Ranger^® to identify the main foodborne pathogens risks, which were Listeria monocytogenes, Salmonella Typhimurium and Bacillus cereus. Thereafter, quantitative microbiology was applied using different models and verified with growth and inactivation challenge tests. It was observed that the gamma model and the ComBase program^® showed very similar results. However, in some cases the results obtained with the challenge tests showed different results. The information gathered was used to create different scenarios which indicate how to manage the risks by setting Performance Objectives during the different stages of the food chain of this product and hence reaching a suggested Food Safety Objective.     

Effect of drying conditions on the retention of phenolic compounds,anthocyanins and antioxidant activity of roselle (Hibiscus sabdariffa L.) added to yogurt

To evaluate the use of lixiviate roselle calyxes as an alternative source of bioactive compounds, they were subjected to dehydration in a vibrofluidised bed dryer after which some chemical parameters such as the retention of monomeric anthocyanins (MA), phenolic compounds, polymeric colour and antioxidant activity were determined. Drying curves showed both a constant drying period and a decreasing falling rate period. The different drying conditions showed significant differences in the chemical parameters. Using the dry residue with the best bioactive compounds content, it was possible to develop a dairy beverage (yogurt). The results confirmed that lixiviated roselle calyxes could be a competitive alternative for traditional products, such as grapes or bilberries, in terms on their antioxidant activity and stability when it is added as a source of bioactive compounds.     

Recommender system in collaborative learning environment using an influence diagram

Giving useful recommendations to students to improve collaboration in a learning experience requires tracking and analyzing student team interactions, identifying the problems and the target student. Previously, we proposed an approach to track students and assess their collaboration, but it did not perform any decision analysis to choose a recommendation for the student. In this paper, we propose an influence diagram, which includes the observable variables relevant for assessing collaboration, and the variable representing whether the student collaborates or not. We have analyzed the influence diagram with two machine learning techniques: an attribute selector, indicating the most important attributes that the model uses to recommend, and a decision tree algorithm revealing four different scenarios of recommendation. These analyses provide two useful outputs: (a) an automatic recommender, which can warn of problematic circumstances, and (b) a pedagogical support system (decision tree) that provides a visual explanation of the recommendation suggested.