Migration of antifog additives in agricultural films of low‐density polyethylene and ethylene‐vinyl acetate copolymers

In this work, polymer films of low density polyethylene and ethylene‐vinyl acetate copolymers containing two types of antifog additives (nonionic surfactants) were exposed to two simulated horticultural greenhouse environments, reproducing hot and cold climate conditions. The evolution of the antifog effect was visually observed and that of the additive concentration measured using Fourier transform infrared spectroscopy (FTIR). All the films studied showed good antifog properties, but in all cases, the duration of the antifog effect was longer in the hot‐climate test. From the FTIR, we can conclude that the additives studied showed a low migration rate and, therefore, when the antifog effect is lost, important quantities of the additive remain in the bulk. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The impact of metal transport processes on bioavailability of free and complex metal ions in methanogenic granular sludge

Bioavailability of metals in anaerobic granular sludge has been extensively studied, because it can have a major effect on metal limitation and metal toxicity to microorganisms present in the sludge. Bioavailability of metals can be manipulated by bonding to complexing molecules such as ethylenediaminetetraacetate (EDTA) or diethylenetriaminepentaacetate (DTPA). It has been shown that although the stimulating effect of the complexed metal species (e.g. [CoEDTA](2-)) is very fast, it is not sustainable when applied to metal-limited continuously operated reactors. The present paper describes transport phenomena taking place inside single methanogenic granules when the granules are exposed to various metal species. This was done using magnetic resonance imaging (MRI). The MRI results were subsequently related to technological observations such as changes in methanogenic activity upon cobalt injection into cobalt-limited up-flow anaerobic sludge blanket (UASB) reactors. It was shown that transport of complexed metal species is fast (minutes to tens of minutes) and complexed metal can therefore quickly reach the entire volume of the granule. Free metal species tend to interact with the granular matrix resulting in slower transport (tens of minutes to hours) but higher final metal concentrations.     

Real-time mapping of moisture migration in cereal based food systems with Aw contrast by means of MRI

The redistribution of water in prototype food systems, comprising phases with contrasting water activity (A_w), was investigated. To accomplish this task, MRI techniques adapted to migration rate were used. RARE and SPI measuring methods were used to monitor water redistribution in crunchy inclusions in water and biscuit shells with apple filling during storage, respectively. In the first case, fast migration, which typically last some tens of minutes, was monitored with a temporal resolution 3.5 min or better, while in the second case of slow migration it was monitored during 2 months with 10 days temporal resolution. 3D MR images with sub-millimeter resolution visualise the spatial redistribution of moisture and allow a quantification of its rate and extent of matrix swelling. Correlation with high resolution X-ray (XRT) images allows to identify structural elements responsible for unwanted fast hydration.     

The structural and hydration properties of heat-treated rice studied at multiple length scales

The impact of heat-treatment on structure and hydration properties of rice was studied at different length scales (μm–nm). Heat-treatment introduced micro- and macro-pores within rice kernels (μCT) and, within intact cell walls, disintegrated starch granules were observed (SEM, CSLM). In native kernels starch predominantly occurred as crystalline A-type starch and, upon heat treatment, amorphous and V-type starch appeared (XRD, ¹³C CP MAS NMR). Plasticization of amorphous starch by water was more pronounced for heat-treated than for native kernels (¹³C SPE MAS NMR). Within native kernels, more effective spin diffusion between water and starch chains was present (WISE-Exchange), confirming the inter-helical nanoscale order of amylose helices. Upon heat-treatment, this inter-helical nanoscale order was lost, as well as microscale granular compartmentalisation (TD NMR). These findings explain why, upon heat-treatment, vapour sorption is lower and starch is more prone to gelatinization (DSC).     

Fluconazole release through semi‐interpenetrating polymer network hydrogels based on chitosan,acrylic acid,and citraconic acid

Semi‐interpenetrating polymer network hydrogels with different compositions of chitosan (Cs), acrylic acid, and citraconic acid were synthesized via free‐radical polymerization with ethylene glycol dimethacrylate as a crosslinker. The variations of the swelling percentages of the hydrogels with time, temperature, and pH were determined, and Cs–poly(acrylic acid) (PAA) hydrogels were found to be most swollen at pH 7.4 and 37°C. Scanning electron micrographs of Cs–PAA and Cs–P(AA‐co‐CA)‐1 (Cs‐poly(acrylicacid‐co‐citraconir acid)^?1) were taken to observe the morphological differences in the hydrogels. Although the less swollen hydrogel, Cs–P(AA‐co‐CA)‐1, had a sponge‐type structure, the most swollen hydrogel, Cs–PAA, displayed a uniform porous appearance. Fluconazole was entrapped in Cs–P(AA‐co‐CA)‐1 and Cs–PAA hydrogels, and the release was investigated at pH 4.0 and 37°C. The kinetic release parameters of the hydrogels (the gel characteristic constant and the swelling exponent) were calculated, and non‐Fickian diffusion was established for Cs–PAA, which released fluconazole much more slowly than the Cs–P(AA‐co‐CA)‐1 hydrogel. A therapeutic range was reached at close to 1 h for both hydrogels. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Determination of phenolic acids and rutin in Heliotropium thermophilum by high-performance liquid chromatography with photodiode array detection

A novel and rapid method was validated for the determination of phenolics in plants by high-performance liquid chromatography coupled to photodiode array detection. The optimized method was employed for the quantification of phenolic acids and rutin present in Heliotropium thermophilum. Eight samples collected from two locations were analyzed. Additionally, temperature dependent changes in the phenolic composition of H. thermophilum samples was evaluated. A series of standards were used for identification that included gallic acid, protocatechuic acid, 4-hydroxybenzoic acid, chlorogenic acid, vanillic acid, caffeic acid, syringic acid, p-coumaric acid, rutin, ferulic acid, benzoic acid, 2-hydroxycinnamic acid, abscisic acid, and trans-cinnamic acid. Chromatographic separation was performed on C₈ column at 40°C with gradient elution. A phosphate buffer (20 mM, pH: 2.5) and acetonitrile mixture was used as the mobile phase with detection at 280 nm wavelength and a flow rate of 1.5 mL/min. The developed method was shown to be sensitive, accurate, and reproducible for the determination of phenolic acids and rutin in plants.     

The effect of the concentration of hydrochloric acid and acetic acid aqueous solution for fast hydrogen production from methanol solution of NaBH4

The semi-methanolysis reactions with hydrochloric acid and acetic acid were used for the hydrogen production from sodium borohydride (NaBH₄). The effects of the NaBH₄ concentration, hydrochloric acid and, acetic acid concentration, and temperature on the reactions were investigated. The maximum hydrogen production rates in the semi-methanolysis with 1 M hydrochloric acid and acetic acid were 4875 and 3960 ml min^?1, respectively. At the same time, the semi-methanolysis reactions with the acids are completed within 4 and 5 s, respectively. The power law kinetic model is performed for kinetic studies. Activation energies for the semi-methanolysis reactions of NaBH₄ in the presence of hydrochloric acid and acetic acid were found as 5.84 and 2.81 kJ mol^?1, respectively.     

Magnetic resonance in Hallevorden-Spatz disease

The Hallevorden-Spatz disease should be suspected in children or young people with motor, pyramidal or extrapyramidal symptomatology and deterioration of superior functions specially upon the existence of family history. Pathognomonic diagnosis may only be obtained by necropsy but magnetic resonance images, although not pathognomic, are sufficiently characteristics to strongly support the diagnosis. Four cases of Hallevorden-Spatz disease are presented with special emphasis on the MR images characteristic of this disease.     

Clock recovery based on a new type of selfpulsation in a 1.5 mu m two-section InGaAsP-InP DFB laser

Clock extraction from an optically or electrically injected 2/sup 23/-1 PRBS RZ data signal in a two-section ridge waveguide DFB laser with a new type of selfpulsation is demonstrated between 0.4 and 0.7 GHz. A locking range of 50 MHz is measured.<>