Controlled release systems (CRS), unlike the conventional formulations, facilitate a gradual and controlled discharge of the pesticides, reducing the losses by evaporation and leaching and minimizing ...pesticide pollution. In this study, carbofuranan insecticide−nematicide identified as a groundwater pollutantwas incorporated in alginate-based granules to obtain controlled release properties. The effect on carbofuran release rate caused by the incorporation of bentonite, activated carbon, and different mixtures of both sorbents in alginate basic formulation was studied by immersion of the granules in water. The water uptake, sorption capacity of the sorbent, permeability, and time taken for 50% of the active ingredient to be released into water, T 50, were calculated by the comparison of the preparations. T 50 values were higher for those formulations containing bentonite and/or activated carbon (T 50 values range from 14.76 h for the alginate formulation containing only bentonite as the sorbent to 29.5 weeks for the alginate formulation containing only activated carbon as the sorbent) than for the preparation without these sorbents (11.72 h). On the basis of a parameter of an empirical equation used to fit the insecticide−nematicide release data, it appears that the release of carbofuran from the various formulations into water is controlled by a diffusion mechanism. The sorption capacity of the sorbents for carbofuran was the most important factor modulating carbofuran release. In addition, it was observed that there is a linear correlation of the T 50 values and the content of activated carbon in dry granules. Keywords: Carbofuran; controlled release; activated carbon; bentonite; sorption
An improved analytical method was developed which may be applied to quality control of stevioside and rebaudioside A contents in dried leaves of Stevia rebaudiana before processing; in a selective ...sampling program searching for plants of higher yield in diterpene glycosides content; or when a large number of samples are sent to the laboratory for analysis. The procedure developed involves two steps: solvent extraction followed by an isocratic HPLC analysis. The sample, 1 g of dried leaves of S. rebaudiana, is ground and solvent-extracted with EtOH 70% (w/w) in Erlenmeyer flasks by shaking for 30 min in a 70 °C water bath. After the extract was cooled, it was filtered and analyzed by HPLC using an NH2 column (250 × 4.6 mm) and a mixture of acetonitrile/water (80:20, v/v) as mobile phase, pH 5 adjusted with acetic acid. The detection was in the UV range at 210 nm (0.04 AUFS). Quantitation was performed by means of an external standard calibration curve for each analyte which had been obtained from standard solutions of pure stevioside and rebaudioside A. Working under these conditions there were no observed interference effects. The method saves time in sample preparation, and reduces sample handling and chromatographic analysis time, while having little loss of precision coefficient of variation (CV%) between 1.8% and 3.0% and recovery between 98.5% and 100.5%. The method was applied to 30 samples of S. rebaudiana from Misiones (Northeastern Argentina), and the stevioside content found ranged between 3.78 and 9.75% (weight) whereas Rebaudioside A content ranged between 1.62 and 7.27% (weight). Keywords: Sweetener, Stevia rebaudiana, stevioside, rebaudioside A, HPLC analysis
The aim of this study was to clarify whether the C3A content of cement had a significant effect on electrochemical chloride extraction (ECE) treatment efficiency. It is known that a higher C3A ...content in a cement gives it superior chloride complexing ability resulting in the formation of an 'insoluble' calcium chloro aluminate compound. ECE was applied using cylindrical specimens made from concrete containing two levels of C3A (4.3% and 9.05%). Specimens were 5 cm in diameter and 10 cm in height. Steel was placed in the axial direction with an embedded length of 7 cm. These specimens were immersed in an NaCl solution and dried in a stream of air at 40 deg C for 10 months. The corrosion was monitored by half-cell potential and polarization resistance measurements. After steel depassivation, ECE was applied for 20, 30, 40 and 50 days using a constant current density of 1 A/m2 of steel. At the end of the treatment, the specimens were maintained at 20 deg C and 70% RH in order to observe the evolution of the steel (electrochemical measurements). The results show that, after 30 days of treatment, the chloride content remained constant in the specimen. This was probably due to OH(-) ion formation on the steel. The OH- ions 'contribute'to the current transport, decreasing the ECE efficiency. Concerning the C3A content, ECE efficiency was slightly affected by C3A because only a part of the bound chloride ions was released. From the point of view of corrosion, half-cell potential showed a shift in the positive direction, indicating little corrosion activity at 20 deg C and 70% RH. However, polarization resistance measurements showed that 2 months post treatment corrosion rates were significant, although the corrosion rate decreased from 6 muA/cm2 to 2.5 muA/cm2.
The objective was to characterize testicular development in Blackbelly sheep, focusing primarily on Sertoli cell number. Lambs (
n
=
43) were allotted into eight groups, and surgically castrated at ...0, 3, 6, 9, 12, 15,18 or 21 weeks of age (
n
=
4–6 lambs per group). Testes were fixed and paraffin-embedded, cross-sections (5
μm) were stained and evaluated with quantitative morphometry techniques. Testis weight increased at a greater rate between 9 and 15 weeks of age, which was associated with remarkable changes in testicular histology, including increases in tubular tissue volume, and tubule diameter and length. Spermatogenesis started in a period between 9 and 12 weeks, lumen and elongated spermatids were observed for the first time at 12 weeks (78% of the tubules) and 15 weeks (37% of the tubules), respectively. Total number of Sertoli cells (mean
±
S.E.M.) increased steadily from birth (531
±
76
×
10
6) to 15 weeks (12,008
±
1722
×
10
6), with no changes afterwards. Sertoli cell number per gram of testicular tissue decreased as lambs were older, with the most remarkable change occurring between Weeks 9 and 12. An early increase in serum LH was observed at 6 weeks of age, with testosterone (T) increasing at Weeks 12 and 21. In conclusion, Sertoli cells maintained the capacity of proliferating from birth to 15 weeks of age in Blackbelly sheep; furthermore, the period of accelerated testis growth was associated with increased serum T concentration and with important changes in testicular morphology, as a consequence of the beginning and establishment of spermatogenesis and Sertoli cell maturation.
Drylands (arid and semi-arid regions) are important regions in the world; they have been disregarded and considered poor undeveloped regions due to their ecological limitations. Farmers in these ...regions tend towards diversification of production systems in order to achieve livelihood security, and this phenomenon has not been extensively studied. The objective of this study was to create a typology of the production systems present in the Mexican north central drylands, using variables related to production, socioeconomics, and social capital. 1044 interviews were conducted in the semi-arid region of north central Mexico. Analysis of the data allowed for the observation of nine types of production systems distributed in three groups: Subsistence, commercial, and off-farm income systems. The differences observed within these systems are due to generational gaps, gender differences, market orientation, and social capital. It can be concluded that the diversification of the dryland production systems allows for an understanding of why generic public policies have failed to mitigate poverty in these regions. The implications of the study refer to the reconfiguration of Mexican policies for the development of the drylands.
•We propose a tracking-interface numerical method to analyze the dissolution of single bubbles rising in an isothermal liquid bath in the limit of small Weber numbers.•The key elements of the method ...are the use of a frame of reference moving with the bubble and the application of different meshes to solve the mechanical and massdiffusion problems.•The gas concentration in the atmosphere over the bath, determined by mass balance of species in the gas column, is shown to be an essential component of the global dissolution problem in steady regime.
The isothermal dissolution of small single rising bubbles in a low viscosity liquid is numerically and experimentally studied. We propose a tracking-interface numerical method to analyze the dissolution of single bubbles rising in an isothermal liquid bath in the limit of small Weber numbers. The key elements of the method are the use of a frame of reference moving with the bubble and the application of different meshes to solve the mechanical and mass-diffusion problems. In addition, the gas concentration in the atmosphere over the bath, determined by mass balance of species in the gas column, is shown to be an essential component of the global dissolution problem in steady regime. Comparison with small oxygen bubbles rising in water has been carried out with remarkable agreement.
The consumption of sweeteners has increased as a measure to reduce the consumption of calories and thus combat obesity and diabetes. Sweeteners are found in a large number of products, so chronic ...consumption has been little explored. The objective of the study was to evaluate the effect of chronic sweetener consumption on the microbiota and immunity of the small intestine in young mice. We used 72 CD1 mice of 21 days old, divided into 3 groups: (i) No treatment, (ii) Group A (6 weeks of treatment), and (iii) Group B (12 weeks of treatment). Groups A and B were divided into 4 subgroups: Control (CL), Sucrose (Suc), Splenda® (Spl), and Svetia® (Sv). The following were determined: anthropometric parameters, percentage of lymphocytes of Peyer’s patches and lamina propria, IL-6, IL-17, leptin, resistin, C-peptide, and TNF-α. From feces, the microbiota of the small intestine was identified. The BMI was not modified; the mice preferred the consumption of Splenda® and Svetia®. The percentage of CD3+ lymphocytes in Peyer’s patches was increased. In the lamina propria, Svetia® increased the percentage of CD3+ lymphocytes, but Splenda® decreases it. The Splenda® and Svetia® subgroups elevate leptin, C-peptide, IL-6, and IL-17, with reduction of resistin. The predominant genus in all groups was Bacillus. The chronic consumption of sweeteners increases the population of lymphocytes in the mucosa of the small intestine. Maybe, Bacillus have the ability to adapt to sweeteners regardless of the origin or nutritional contribution of the same.
Aloe barbadensis Miller, known as Aloe Vera, requires limited irrigation depending on the capacity of the soil to retain humidity, since it is a CAM species and thus naturally adapted to conditions ...of dryness and high temperatures. Therefore, we postulated that plants of Aloe Vera plants under conditions of water deficit should improve their water use efficiency (WUE) by performing osmotic adjustment (OA) with a temporal correlation between WUE and OA. The objective of the investigation was to determine the effect of water restriction on the WUE and OA of
A. barbadensis under different water treatments. 18-month old Aloe Vera plants were cultivated in pots with a soil substrate that was a mixture of equal parts of sand and organic matter with 18% of FC and 9% of permanent wilting point. To determine the effects of the soil humidity on plant WUE and OA, four treatments were arranged in a complete random design with four repetitions; these were 100%, 75%, 50% and 25% of FC, which correspond to an evatranspiration of 11.4, 9.6, 4.0 and 1.7
L per plant, respectively. The water treatments were maintained by frequent irrigation. The following variables were determined: dry matter, leaf water potential, relative water content (RWC), amount of gel produced, sap flow, proline content, soluble and total sugars and oligo and polyfructans. Aloe Vera increased WUE with increasing water deficit; the sap flow rate decreased with water restrictions, and the plants performed osmotic adjustment by increasing the synthesis of proline, soluble and total sugars as well as the amounts of oligo and polyfructans, mainly polymers of β-(2
→
6) kestotriose, changing from the inulin type to the neofructan type. The plants most and less irrigated (100% and 25% of FC) were the groups with lowest WUE. The plants irrigated with 75% of FC presented the best WUE in terms of dry mass and amount of gel produced by a litre of supplied water.
Composites that incorporate an electrically conducting filler, the hydrochloric polyaniline (PANI-Cl), into hydroxy-terminated polydimethylsiloxane (HO-PDMS) matrix were evaluated for DC electrical, ...mechanical, thermal, morphological and piezo-resistive properties. The main focus of the study was on the electrical–mechanical behavior of these composites in view of possible piezo-resistive sensor application. The percolation threshold of conductivity was determined to be around 11.5 wt% of PANI-Cl. Compression/expansion cyclic experiments showed that the filler content modified the stiffness, the magnitude of Mullins effect and the hysteresis behavior in elastomeric composites. The piezo-resistive response of composites differed depending on the sample composition and also, on the strain rate. Composites with concentration above the percolation threshold exhibited at least three-order change of its electrical resistance in a narrow interval of maximum 2% of deformation. The piezo-resistive sensitivity and the reproducibility of response suggested the possibility to use this material as a transducer in an electromechanical device.
PDF
