Characterization of Anacardium occidentale exudate polysaccharide

The composition, structure and molar mass distribution of Anacardium occidentale exudate polysaccharide of Brazilian origin was investigated. The composition from gas–liquid chromatography (GLC) and ¹³C NMR was 72% β-D -galactopyranose, 14% α-D -glucopyranose, 4·6% α-L -arabinofuranose, 3·2% α-L -rhamnopyranose and 4·5% β-D -glucuronic acid. A thorough analysis of high resolution ¹³C NMR spectra from intact, partially hydrolysed and Smith-degraded polysaccharide enabled reliable chemical shift assignments to be made, and indicated the presence of three types of unit within the branched galactan core: linked at C-1 and C-3, at C-1 and C-6, and at C-1, C-3 and C-6. The polysaccharide was fractionated with respect to molar mass using water/ethanol as a solvent/non-solvent system. The polysaccharide and fractions were characterized by gel permeation chromatography (GPC), intensity light scattering, dilute solution viscometry and sedimentation velocity. The intrinsic viscosity in 0·1M aqueous NaCl at 25°C was found to depend on molar mass according to: [η]/(cm³g^-1)=0·052M^0·42. The molar mass distribution for the whole polysaccharide, determined by GPC using a universal calibration, exhibited two main peaks at 28000 and 67000gmol^-1, together with traces of much higher molar mass material. © 1998 SCI.     

Olefinreaktionen in Gegenwart wolfram- und molybdänhaltiger Katalysatorsysteme vom Ziegler-Natta-Typ

Reactions of Alkenes in the Presence of Tungsten- and Molybdenum-containing Ziegler-Natta-Catalysts In connection with investigations of reactions of alkenes under the conditions of metathesis we studied the reactions of a mixture of 2-pentene/toluene in presence of the catalytic systems WCl₆/EtAlCl₂ and MoCl₅/EtAlCl₂ in homogeneous liquid phase. Alkylation of toluene, metathesis of 2-pentene and also indirect isomerisation of double bonds have been determined in dependence of the molar proportions of 2-pentene/MeCl_x, toluene/2-pentene, and MeCl_x/EtAlCl₂, the addition order (“formation”) of reactants, the “building time” of catalytic system and the reaction time. Compositions of the reaction mixtures have been determined by GLC.     

Preparation,structure, and properties of montmorillonite/cellulose II/natural rubber nanocomposites

In this work, sodium montmorillonite clay was added, as filler, to nanocomposites of natural rubber (NR) and cellulose II (regenerated cellulose) in amounts varying from 0 to 5 phr (per hundred resin). Natural rubber (NR)/cellulose II/montmorillonite nanocomposites were prepared by co‐coagulating NR latex, montmorillonite aqueous suspension and cellulose xanthate. The clay was previously exfoliated in water, and the resulting suspension was then added to the mixture of NR latex with cellulose xanthate. Morphological, rheometric, mechanical, and dynamic mechanical properties were evaluated, and an increase in these properties was observed upon the addition of cellulose and clay nanomaterials to the rubber matrix. The results show the advantage in using cellulose as a nanopolymer as well as MMT as nanofiller. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Styrene–butadiene rubber/cellulose II/clay nanocomposites prepared by cocoagulation—mechanical properties

In this work, nanocomposites of styrene butadiene rubber (SBR), cellulose II, and clay were prepared by cocoagulation of SBR latex, cellulose xanthate, and clay aqueous suspension mixtures. The incorporated amount of cellulose II was 15 phr, and the clay varied from 0 to 7 phr. The influence of cellulose II and clay was investigated by rheometric, mechanical, physicochemical, and morphological properties. From the analysis of transmission electron microscopy (TEM), dispersion in nanometric scale (below 100nm) of the cellulosic and mineral components throughout the elastomeric matrix was observed. XRD analysis suggested that fully exfoliated structure could be obtained by this method when low loading of silicate layers (up to 5 phr) is used. The results from mechanical tests showed that the nanocomposites presented better mechanical properties than SBR gum vulcanizate. Furthermore, 5 phr of clay is enough to achieve the best tensile properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Imazalil Degradation upon Applying Ozone—Transformation Products,Kinetics, and Toxicity of Treated Aqueous Solutions

The elimination of the pesticide imazalil (IMZ) spiked into ultrapure water as well as into wastewater applying ozone (O₃) and the identification of transformation products was investigated. O₃ under hydroxyl radical suppression conditions reacted rapidly with the aliphatic double bond or the imidazole ring in IMZ, yielding several transformation products by partial oxidation. The structures of four oxidation products not yet described were characterized and identified after liquid chromatography coupled with high resolution, high mass accuracy, mass and tandem mass spectrometry (LC/MS and -MSⁿ) in ultrapure water. For two identified transformation products, generated via direct ozone attack on IMZ, formation pathways were proposed. In wastewater, only two of those transformation products were observed. Kinetics studies for the reaction of IMZ with O₃, evaluated by the competition kinetic method, resulted in a second-order rate constant k_O3,IMZ ～ (1.02 ± 0.03)?×?10⁵ M^?1 s^?1 at pH 6.6 ± 0.2, indicating that IMZ is completely transformed during the ozonation process. Tests of acute toxicity were performed applying a solution of IMZ in ultrapure water or treated wastewater to Daphnia magna. In both cases the decrease of toxicity was observed after ozone treatment.     

Functionally Graded Ceramics Fabricated with Side‐by‐Side Tape Casting for Use in Magnetic Refrigeration

Functionally graded ceramic tapes have been fabricated by a side‐by‐side tape casting technique. This study shows the possibility and describes the main principles of adjacent coflow of slurries resulting in formation of thin plates of graded ceramic material. Results showed that the small variations of solvent and binder system concentrations have a substantial effect on slurry viscosity. Varying these parameters showed that side‐by‐side tape casting with a well‐defined interface area is possible for slurries with viscosities above 3500 mPa s at a casting shear rate of 3.3 s^?1. As it was expected, the choice of de‐bindering and sintering regimes significantly influences crack formation, and a three‐step heating programme was found to result in tapes of the highest quality. The interface regions of green graded tapes were investigated structurally by scanning electron microscopy; for a distinct identification of the interface region and analysing the degree of cross‐interface diffusion, the isothermal entropy change was measured by a vibrating sample magnetometer as the magnetic transition temperature (Curie temperature) is very sensitive to the dopant level in ceramics. Also the purpose of developing this graded ceramic tape casting was applications of these specific magnetocaloric properties within the magnetic refrigeration technology.     

Measurements of normal boiling points of fatty acid ethyl esters and triacylglycerols by thermogravimetric analysis

At present, a large number of studies of biodiesel production process using simulation packages are being developed. In these studies, vegetable oils and biodiesels are characterized in the software through representative compounds because of they are not in the compounds database of commercial simulators. With the aim to achieve a successfully characterization in these kinds of software, some properties of the substances must be available. The normal boiling point (NBP) is the most important property due to the fact that this property along with group contribution methods allows other properties calculation such as, e.g., critical properties and temperature dependency properties. In this work, a thermogravimetric analysis (TGA) method for rapid measurement of normal boiling points of two triacylglycerols and four ethyl esters, i.e., triolein, tripalmitin, ethyl oleate, ethyl palmitate, ethyl linoleate and ethyl ricinoleate, was used. Nowadays, in the open literature exists few data available about ethyl esters properties; hence, the results obtained here will contribute in the proposal, analysis, and evaluation of ethyl esters (biodiesel) virtual plants using reliable simulation packages. In addition, a more accurate characterization of compounds and therefore more accurate simulation results can be obtained when they are used.     

Kinetic and stoichiometric characterisation of streptavidin-binding aptamers

Aptamers are oligonucleotide ligands that are selected for high-affinity binding to molecular targets. Only limited knowledge relating to relations between structural and kinetic properties that define aptamer-target interactions is available. To this end, streptavidin-binding aptamers were isolated and characterised by distinct analytical techniques. Binding kinetics of five broadly similar aptamers were determined by surface plasmon resonance (SPR); affinities ranged from 35-375 nM with large differences in association and dissociation rates. Native mass spectrometry showed that streptavidin can accommodate up to two aptamer units. In a 3D model of one aptamer, conserved regions are exposed, strongly suggesting that they directly interact with the biotin-binding pockets of streptavidin. Mutational studies confirmed both conserved regions to be crucial for binding. An important result is the observation that the most abundant aptamer in our selections is not the tightest binder, emphasising the importance of having insight into the kinetics of complex formation. To find the tightest binder it might be better to perform fewer selection rounds and to focus on post-selection characterisation, through the use of complementary approaches as described in this study.     

Effect of a new fermented soy milk product on serum lipid levels in normocholesterolemic adult men

This study was undertaken to verify the effect of a daily intake of a new fermented soy milk produced with Enterococcus faecium and Lactobacillus jugurti on the serum lipid levels in normocholesterolemic middle-aged men. The study was randomized, double-blind and placebo-controlled and was performed for a period of 6 weeks. Forty-four normocholesterolemic healthy, male volunteers, aged 40-55 years old were randomly separated in two groups: The F-group received 200 ml of the fermented product daily and the P-group received 200 ml of placebo (chemically fermented). The blood samples were drawn initially and after 3 and 6 weeks and serum values for total cholesterol, HDL-cholesterol and triglyceride were determined. The LDL-cholesterol value was estimated. No significant changes in the fermented group (F) were observed for total cholesterol, LDL-cholesterol or triglyceride levels, while the HDL-cholesterol level was significantly higher (p < or = 0.05) after 6 weeks. The total cholesterol and LDL-cholesterol levels were significantly higher (p < or = 0.05) in the placebo group (P), but no changes were found for the HDL-cholesterol and triglyceride levels during the experimental period. In conclusion, the intake of 200 ml/day of the fermented soy milk, produced with E. faecium and L. jugurti, for 6 weeks, did not affect the serum total cholesterol and LDL-cholesterol, and led an increase of 10% in the HDL-cholesterol level.