An automated HPLC determination of meticlorpindol in eggs with UV absorbance detection, using on-line dialysis and pre-concentration as sample clean-up; occurrence in and carry over to eggs

Summary A fully automated HPLC determination of the coccidiostat meticlorpindol in whole egg, egg white and yolk is described. The sample homogenate is dialysed online against water. The dialysate is concentrated on-line on a short reversed-phase (RP) column. The contents of this column are transferred to the reversed-phase analytical column by means of the mobile phase. Meticlorpindol is detected using an absorbance detector at 270 nm. Linear calibration graphs are obtained in the range 40–900 ng/g in whole egg and egg white (detection limit 10 ng/g) and 80–1800 ng/g in yolk (detection limit 20 ng/g). Out of 111 commercially obtained egg samples 12 contained meticlorpindol with levels varying from 10 to 433 ng/g. A group of laying hens, kept in cages, received 10 mg/kg of Lerbek (meticlorpindol and methylbenzoquate; Dow Chemical) in the feed for 10 days. Meticlorpindol residues in the eggs rose to a level of 622 ng/g. Meticlorpindol was found in the eggs until 6 days after withdrawal of the medicated feed. Another group received 110 mg/kg in the feed. Meticlorpindol residues rose to levels of 4480 ng/g in the eggs, 5880 ng/g in the egg white and 2660 ng/g in the yolk. Meticlorpindol was found in the eggs and the egg white until 14 days and in the yolk until 8 days after withdrawal of the medicated feed.

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Eine automatisierte HPLC-Methode zur Bestimmung von Meticlorpindol in Eiern mit UV-Detektion und Probenaufarbeitung mit direkter Dialyse und direkter Vorkonzentrierung; Übertragung (Carry-over) und Vorkommen in Eiern

Zusammenfassung Mit dem beschriebenen Verfahren können Rückstände von Meticlorpindol in Eiern, Eiklar und Dotter automatisch bestimmt werden. Homogenisierte Proben werden gegen Wasser dialysiert. Das Dialysat wird an einer Vorkonzentrierungssäule konzentriert. Mit der mobilen Phase wird das Konzentrat auf die analytische Säule gebracht. Der Nachweis wird mit einem UV-Absorption-Detektor ausgeführt (Wellenlänge 270 nm). Der Zusammenhang zwischen Meßwert und Meticlorpindolgehalt ist linear in dem Bereich von 40 bis 900 ng/g Meticlorpindol in Vollei und Eiklar (Nachweisgrenze etwa 10 ng/g) und von 80 bis 1800 ng/g in Dotter (Nachweisgrenze etwa 20 ng/g). Bei der Untersuchung von 111 Handelsproben wurden in 12 Proben Rückstände von Meticlorpindol nachgewiesen mit Konzentrationen zwischen 10 und 433 ng/g. Eine Gruppe von Legehennen erhielt 10 mg/kg Lerbek (Meticlorpindol und Methylbenzoquate; Dow Chemical) im Futter während 10 Tagen. Die Eier wiesen bis zum 6. Tag nach dem Absetzen des Futterzusatzes nachweisbare Meticlorpindol-Rückstände auf (Höchstgehalt 622 ng/g in Vollei). Eine zweite Gruppe erhielt 110 mg/kg im Futter. In den Volleiproben und Eiklarproben dieser Gruppe konnten bis zum 14. Tag nach dem Absetzen Rückstände von Meticlorpindol nachgewiesen werden (Höchstgehalte 4480 und 5880 ng/g), in den Dotterproben bis zum 8. Tag (Höchstgehalt 2660 ng/g).

     

Morphology and properties of NR/EPDM rubber blends filled with small amounts of titania nanoparticles

This article describes the results of an investigation on the influence of titania nanoparticles on the morphology and properties of vulcanized natural rubber (NR)/ethylene‐propylene‐diene monomer (EPDM) blends. The samples were prepared through roll‐milling and melt‐pressing and diphenyl guianidine was used as vulcanization accelerator. The transmission electron microscopy (TEM) and X‐ray diffraction (XRD) results show that the titania particles are concentrated in the NR phase, and that the presence of titania in EPDM seems to initiate the formation of crystals in the rubber phase. From the dynamic mechanical analysis (DMA) and tensile testing results it is clear that the presence of titania particles inhibited the vulcanization process in both the investigated rubbers, and that the mechanical properties of the nanocomposites were influenced by the interaction between the nanoparticles and the rubber, the reduced vulcanization of the two rubber phases, and the development of crystallinity in EPDM. The thermogravimetric (TGA) results show improved thermal stability of EPDM, and of the EPDM phase in the blend, for the samples containing titania nanoparticles. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

Substructure-based virtual screening for adenosine A2A receptor ligands

A virtual ligand-based screening approach was designed and evaluated for the discovery of new A(2A) adenosine receptor (AR) ligands. For comparison and evaluation, the procedures from a recently published virtual screening study that used the A(2A) AR X-ray crystal structure for the target-based discovery of new A(2A) ligands were largely followed. Several screening models were constructed by deriving the distinguishing structural features from selected sets of A(2A) AR antagonists, so-called frequent substructure mining. The best model in statistical terms was subsequently applied to large-scale virtual screens of a commercial vendor library. This resulted in the selection of 36 candidates for acquisition and testing. Of the selected candidates, eight compounds significantly inhibited radioligand binding at A(2A) AR (>30%) at 10 μM, corresponding to a "hit rate" of 22%. This hit rate is quite similar to that of the referenced target-based virtual screening study, while both approaches yield new, non-overlapping sets of ligands.     

Investigations on vinylene carbonate. IV. Radiation induced graft copolymerization of vinylene carbonate and N-vinyl-N-methylacetamide onto polyethylene films

Graft copolymerization of binary mixtures of vinylene carbonate (VCA) and N-vinyl–N–methylacetamide (VIMA) onto low density polyethylene (LDPE) films was studied by the mutual γ-irradiation technique. Sufficient amounts of functionally active VCA groups could be grafted onto the surface and the hydrophilicity of the surface was also improved. The grafting of VCA onto polyethylene films in the binary solutions was found to be promoted by the presence of VIMA, thus showing a positive synergism. The VCA content in the graft copolymers was always higher than in the copolymers obtained by homogeneous copolymerization using the same monomer feed composition. The monomer reactivity ratios, as well as a preferential partitioning of the monomers surrounding the polymeric substrate, were considered to explain the grafting reactions in the binary systems.     

Reduced percolation concentration in polypropylene/expanded graphite composites: Effect of viscosity and polypyrrole

With the goal to obtain material combining electrical and thermal conductivity at low filler loadings, composites based on polypropylenes (PP) and expanded graphite (EG) have been prepared. The effects of matrix viscosity and of coating the EG particles with polypyrrole (PPy, EG/PPy = 37.5/62.5 by weight) on the EG dispersibility and formation of percolation structures have been analyzed. When increasing the EG amount from 6 to 8 wt %, the electrical conductivity of PP/EG composites increased by 7–9 orders of magnitude, independent of matrix viscosity. When EG‐PPy is added, percolation was observed between 8 and 12 wt % EG‐PPy (3 and 4.5 wt % EG) in case of PP with higher viscosity and 6 wt % EG (2.25 wt % EG) in case of PP with lower viscosity, exhibiting a strong synergistic effect of EG and PPy in the latter case. In contrast, PPy does not contribute to reduction of thermal percolation concentration. Thermal percolation is observed at 8 wt % EG in PP/EG composites, but no percolation was found in PP/EG‐PPy composites with EG‐PPy contents of up to 20 wt %, corresponding to 7.5 wt % EG. Analyzing the melt rheology it becomes clear that the contribution of PPy to the formation of a filler network is strongly dependent on the matrix viscosity. The comparison of thermal, electrical and rheological percolation reveals that PPy participates in electron transport reducing the electrical percolation but not to heat transport. Overall, we found a good correlation between electrical, thermal, and melt rheological percolation concentrations. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41994.     

High‐Performance Carbon Nanotube‐Reinforced Bioplastic

The inherent properties of poly(lactide), a biocompatible and biodegradable polymer, are concurrently improved by the incorporation of a small amount of surface functionalized carbon nanotubes. A new method has been used to functionalize the CNTs' outer surface with hexadecylamine. A composite of PLA with functionalized CNTs has been prepared by melt‐extrusion. FT‐IR spectroscopy, Raman spectroscopy, DSC, and optical microscopy are used to investigate the thermal and mechanical property improvement mechanism in f‐CNTs containing PLA composite.

     

The Global Biogeochemical Silicon Cycle

Silicon is one of the most important elements in the current age of the anthropocene. It has numerous industrial applications, and supports a high-tech multi-billion Euro industry. Silicon has a fascinating biological and geological cycle, interacting with other globally important biogeochemical cycles. In this review, we bring together both biological and geological aspects of the silicon cycle to provide a general, comprehensive review of the cycling of silicon in the environment. We hope this review will provide inspiration for researchers to study this fascinating element, as well as providing a background environmental context to those interested in silicon.     

A connectionist approach to processing dimensional interaction

The difference between integral and separable interaction of dimensions is a classic problem in cognitive psychology (Garner 1970, American Psychologist, 25: 350-358, Shepard 1964, Journal of Mathematical Psychology, 1: 54-87) and remains an essential component of most current experimental and theoretical analyses of category learning (e.g. Ashby and Maddox 1994, Journal of Mathematical Psychology, 38: 423-466, Goldstone 1994, Journal of Experimental Psychology: General , 123: 178-200, Kruschke 1993, Connection Science, 5: 3-36, Melara et al. 1993, Journal of Experimental Psychology: Human Perception & Performance, 19: 1082-1104, Nosofsky 1992, Multidimensional Models of Perception and Cognition, Hillsdale NJ: Lawrence Erlbaum). So far the problem has been addressed through post hoc analysis in which empirical evidence of integral and separable processing is used to fit human data, showing how the impact of a pair of dimensions interacting in an integral or a separable manner enters into later learning processes. In this paper, we argue that a mechanistic connectionist explanation for variations in dimensional interactions can provide a new perspective through exploration of how similarities between stimuli are transformed from physical to psychological space when learning to identify, discriminate and categorize them. We substantiate this claim by demonstrating how even a standard backpropagation network combined with a simple image-processing Gabor filter component provides limited but clear potential to process monochromatic stimuli that are composed of integral pairs of dimensions differently from monochromatic stimuli that are composed of separable pairs of dimensions. Interestingly, the responses from Gabor filters are shown already to capture most ofthe dimensional interaction, which in turn can be operated upon by the neural network during a given learning task. In addition, we introduce a basic attention mechanism to back-propagation that gives it the ability to attend selectively to relevant dimensions and illustrate how this serves the model in solving a filtration versus condensation task (Kruschke 1993, Connection Science, 5: 3-36). The model may serve as a starting point in characterizing the general properties of the human perceptual system that causes some pairs of physical dimensions to be treated as integrally interacting and other pairs as separable. An improved understanding of these properties will aid studies in perceptual and category learning, selective attention effects and influences of higher cognitive processes on initial perceptual representations.     

Inverse gas chromatography for the determination of the dispersive surface free energy and acid–base interactions of a sheet molding compound. I. Matrix material and glass

Sheet molding compound is a material composed of a polyester thermosetting matrix with a thermoplastic, an inorganic filler, a metal oxide, reinforcement fibers, and material performance enhancers embedded in the crosslinked matrix. To achieve the optimum mechanical properties required for the composite material, the surface free energy of the polyester composite needs to be understood. In this study, the composite matrix and glass reinforcement fibers are compared with respect to their surface free energy and acid–base characteristics on the basis of inverse gas chromatography measurements. The inverse gas chromatography results for the matrix and glass are compared to previous results found for sized and unsized cellulosic fibers. The inverse gas chromatography data are used to assess chemical modifications performed on the biobased fibers to predict improvements in the fiber/matrix interaction, and this provides inferences on the overall composite cohesion. Our results show first that any fiber reinforcement system for the polyester composite material has to be acidic to promote good adhesion as the matrix system is very basic and second that the individual dispersive surface energies of the components of the matrix interact in a weighted average to determine the overall surface energy of the composite. Also, a commercial glass reinforcement sized for polyester has been found to have a lower interaction parameter than literature values for cellulosic fibers. This finding suggests that cellulosic fibers might have an advantage in competing with a conventional glass‐fiber reinforcement system in fiber/matrix bonding for sheet molding compound composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008