Seed compositional studies of some species of Papilionoideae (Leguminosae) native to Argentina

Seeds of 17 wild leguminous species belonging to the Papilionoideae subfamily were analysed for their proximate, fatty acid and sterol compositions. Centrosema virginianum, Tipuana tipu, Adesmia volckmanni and some species of Desmodium contained high amounts (>300 g kg^?1) of protein. Geoffroea decorticans and Clitoria cordobensis were noteworthy for their high oil content (>350 g kg^?1). The seed lipids had a high proportion of unsaturated (oleic and linoleic mainly) fatty acids. Linolenic acid had the highest value in Adesmia volckmanni (25.4% of total fatty acids). β‐Sitosterol was the major component of the sterol fraction. Chemical analyses indicated that all species studied are suitable sources of animal feed. © 2002 Society of Chemical Industry     

Epitaxial growth of Dy2O3 thin films on epitaxial Dy-germanide films on Ge(0 0 1) substrates

Ultra-thin films of Dy are grown on Ge(0 0 1) substrates by molecular beam deposition near room temperature and immediately annealed for solid phase epitaxy at higher temperatures, leading to the formation of DyGe_x films. Thin films of Dy₂O₃ are grown on the DyGe_x film on Ge(0 0 1) substrates by molecular beam epitaxy. Streaky reflection high energy electron diffraction (RHEED) patterns reveal that epitaxial DyGe_x films grow on Ge(0 0 1) substrates with flat surfaces. X-ray diffraction (XRD) spectrum suggests the growth of an orthorhombic phase of DyGe_x films with (0 0 1) orientations. After the growth of Dy₂O₃ films, there is a change in RHEED patterns to spotty features, revealing the growth of 3D crystalline islands. XRD spectrum shows the presence of a cubic phase with (1 0 0) and (1 1 1) orientations. Atomic force microscopy image shows that the surface morphology of Dy₂O₃ films is smooth with a root mean square roughness of 10 Å.     

Removal of dyes from water using chitosan hydrogel/SiO2 and chitin hydrogel/SiO2 hybrid materials obtained by the sol-gel method

This work describes the synthesis of chitosan hydrogel/SiO(2) and chitin hydrogel/SiO(2) hybrid mesoporous materials obtained by the sol-gel method for their use as biosorbents. Their adsorption capabilities against four dyes (Remazol Black B, Erythrosine B, Neutral Red and Gentian Violet) were compared in order to evaluate chitin as a plausible replacement for chitosan considering its efficiency and lower cost. Both chitin and chitosan were used in the form of hydrogels. This allowed full compatibility with the ethanol release from tetraethoxysilane. The hybrid materials were characterized by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Nitrogen Adsorption Isotherms and (13)C solid-state Nuclear Magnetic Resonance. Adsorption experimental data were analyzed using Langmuir, Freundlich and Dubinin-Radushkevich isotherm models along with the evaluation of adsorption energy and standard free energy (ΔG(0)). The adsorption was observed to be pH dependent. The main mechanism of dye adsorption was found to be a spontaneous charge associated interaction, except for EB adsorption on chitin/SiO(2) matrix, which showed to involve a lower energy physical adsorption interaction. Aside from highly charged dyes the chitin containing matrix has similar or higher adsorption capacity than the chitosan one.     

RAPD-based screening for spore-forming bacterial populations in Uruguayan commercial powdered milk

The occurrence of spore-forming bacteria in powdered milk is of concern to the dairy industry due to potential deleterious effects including those resulting from proteolytic and lipolytic activities. Twenty-two powdered milk samples representative of spring and summer production obtained from Uruguayan retail stores were analyzed for type and number of thermophilic and spore-forming bacterial species. Bacillus licheniformis isolates were found to be the most prominent milk powder contaminant followed by Anoxybacillus flavithermus representing 71.5 to 84% of the total microflora. Geobacillus stearothermophilus, however, was not found. B. licheniformis strains F and G were both found in this study but strain F was the prevalent isolate representing 98.9% of the total isolates of this species. A. flavithermus isolates corresponded to strain C in accordance with 16S rRNA gene sequence analysis, however, in contrast with other reports, the RAPD profiles showed three characteristic bands at approximately 650, 1000 and 1650 bp, but lacking a band at 1250 bp. A third group of isolates was identified corresponding to members of a Bacillus subtilis group and Bacillus megaterium. Isolates designated B. licheniformis, A. flavithermus, B. megaterium and the B. subtilis group represented 89.1 to 93.6% of those analyzed, and depended on previous heat treatment and incubation temperatures of the plates. The remaining isolates were Bacillus pumilus and unidentified spore-formers.     

Chemical composition of Arbequina virgin olive oil in relation to extraction and storage conditions

The chemical composition of virgin olive oils from Arbequina olives cultivated in Córdoba (Argentina) was studied in relation to the oil extraction system and production year. Significant variations were found between oils obtained by pressure (PEOs) and centrifugation (CEOs) systems. PEOs were characterised by higher values of acidity, pigments and oleic acid, while CEOs showed greater phenol content. Moreover, a significant effect of crop year was observed. Arbequina oils produced in Córdoba contained lower amounts of oleic acid but higher amounts of phenolic compounds than Arbequina oils produced in Spain. A storage stability test was carried out in order to study the combined effects of oil extraction system and storage conditions (packaging material and illumination) on quality indices related to oxidative stability. Multivariate analysis applied to the chemical data emphasised the differences between PEOs and CEOs, indicating that variations due to extraction system were greater than those due to illumination condition and package type. Cluster analysis of oils from each extraction system stressed the influence of illumination condition on the oxidative stability of olive oils, showing increased amounts of secondary oxidation products in oils exposed to light. Glass and tin packages appear to be the most appropriate containers for maintaining the quality of olive oils, but this supposition is strongly dependent on the type of oil (PEO or CEO) and its initial chemical properties. Copyright © 2006 Society of Chemical Industry     

Controlling the Degree of Dispersion of Aluminum Hydroxide Suspensions by Steric Stabilization

Eighty-eight percent hydrolyzed polyvinyl alcohol was effective in dispersing an amorphous carbonate-containing aluminum hydroxide suspension. It is believed that the polyvinyl acetate units are adsorbed, providing an anchor for the highly hydrated polyvinyl alcohol units. Hydroxypropyl cellulose did not exhibit steric stablization, probably because it is too soluble to be significantly adsorbed.     

The Neumann series as a fundamental solution of the two-dimensional convection–diffusion equation with variable velocity

The fundamental solution of the two-dimensional convection–diffusion equation with variable coefficients and its adjoint equation are obtained in complex form in terms of the unknown density of two equivalent uniquely solvable Volterra integral equations of the second kind whose analytical solutions are given explicitly as convergent Neumann series. The Volterra integral equations are obtained by integrating the complex form of the original differential equations, without additional change of variables as proposed by previously authors. In the numerical examples, cases corresponding to non-self-adjoint operators are considered. As a validation, the proposed approach is used to derive the fundamental solution of the adjoint to the convection–diffusion equation with constant velocity. In this case, the series solution can be evaluated analytically. For more general velocity fields, the recursive terms of the series can be evaluated by symbolic computation or numerical integration.     

Phenolic characterisation of red wines from different grape varieties cultivated in Mendoza province (Argentina)

BACKGROUND: Knowledge of the chemical composition of wine and its association with the grape variety/cultivar is of paramount importance in oenology and a necessary tool for marketing. Phenolic compounds are very important quality parameters of wines because of their impact on colour, taste and health properties. The aim of the present work was to study and describe the non‐flavonoid and flavonoid composition of wines from the principal red grape varieties cultivated in Mendoza (Argentina). RESULTS: Sixty phenolic compounds, including phenolic acids/derivatives, stilbenes, anthocyanins, flavanols, flavonols and dihydroflavonols, were identified and quantified using high‐performance liquid chromatography with diode array detection coupled with electrospray ionisation mass spectrometry (HPLC‐DAD/ESI‐MS). Marked quantitative differences could be seen in the phenolic profile among varieties, especially in stilbenes, acylated anthocyanins and other flavonoids. CONCLUSION: The polyphenolic content of Malbec wines was higher compared with the other red varieties. Dihydroflavonols represent a significant finding from the chemotaxonomic point of view, especially for Malbec variety. This is the first report on the individual phenolic composition of red wines from Mendoza (Argentina) and suggests that anthocyanins, flavanols and phenolic acids exert a great influence on cultivar‐based differentiation. Copyright © 2011 Society of Chemical Industry     

Electric‐Field‐Induced Alignment of Block Copolymer/Nanoparticle Blends

External electric fields readily align birefringent block‐copolymer mesophases. In this study the effect of gold nanoparticles on the electric‐field‐induced alignment of a lamellae‐forming polystyrene‐block‐poly(2‐vinylpyridine) copolymer is assessed. Nanoparticles are homogeneously dispersed in the styrenic phase and promote the quantitative alignment of lamellar domains by substantially lowering the critical field strength above which alignment proceeds. The results suggest that the electric‐field‐assisted alignment of nanostructured block copolymer/nanoparticle composites may offer a simple way to greatly mitigate structural and orientational defects of such films under benign experimental conditions.