Correlation of spatially resolved photoluminescence and viscoelastic mechanical properties of encapsulating EVA in differently aged PV modules

The photoluminescence of ethylene vinyl acetate (EVA) in aged photovoltaic modules shows specific spatial patterns on the scale of the cells in the module that depend on the aging conditions. It is the aim of this work to investigate the correlation of these photoluminescence patterns to the viscoelastic mechanical properties of the encapsulating EVA. For this, the degradation under various conditions of two specimen sets of polycrystalline silicon photovoltaic mini‐modules, comprising EVA as encapsulating polymer, is investigated using spatially resolved, ultraviolet‐excited photoluminescence. Samples of the encapsulation EVA are systematically extracted from the modules for spatially resolved dynamic mechanical characterization. A correlation between the spatial distribution of the photoluminescence intensity and the values of storage modulus and loss factor of the EVA is found. An increase in the values for storage modulus and a decrease of the loss factor of the EVA from the edge of the cell towards the center are observed for all samples. We conclude that diffusion‐limited oxidation must be considered for aging studies of the encapsulation EVA and that photoluminescence detection can reveal the scale on which such diffusion processes occur. Copyright © 2016 John Wiley & Sons, Ltd.     

Evaluation of contaminant removal of reverse osmosis and advanced oxidation in full-scale operation by combining passive sampling with chemical analysis and bioanalytical tools

Advanced water treatment of secondary treated effluent requires stringent quality control to achieve a water quality suitable for augmenting drinking water supplies. The removal of micropollutants such as pesticides, industrial chemicals, endocrine disrupting chemicals (EDC), pharmaceuticals, and personal care products (PPCP) is paramount. As the concentrations of individual contaminants are typically low, frequent analytical screening is both laborious and costly. We propose and validate an approach for continuous monitoring by applying passive sampling with Empore disks in vessels that were designed to slow down the water flow, and thus uptake kinetics, and ensure that the uptake is only marginally dependent on the chemicals' physicochemical properties over a relatively narrow molecular size range. This design not only assured integrative sampling over 27 days for a broad range of chemicals but also permitted the use of a suite of bioanalytical tools as sum parameters, representative of mixtures of chemicals with a common mode of toxic action. Bioassays proved to be more sensitive than chemical analysis to assess the removal of organic micropollutants by reverse osmosis, followed by UV/H?O? treatment, as many individual compounds fell below the quantification limit of chemical analysis, yet still contributed to the observed mixture toxicity. Nonetheless in several cases, the responses in the bioassays were also below their quantification limits and therefore only three bioassays were evaluated here, representing nonspecific toxicity and two specific end points for estrogenicity and photosynthesis inhibition. Chemical analytical techniques were able to quantify 32 pesticides, 62 PCPPs, and 12 EDCs in reverse osmosis concentrate. However, these chemicals could explain only 1% of the nonspecific toxicity in the Microtox assay in the reverse osmosis concentrate and 0.0025% in the treated water. Likewise only 1% of the estrogenic effect in the E-SCREEN could be explained by the quantified EDCs after reverse osmosis. In comparison, >50% of the estrogenic effect can typically be explained in sewage. Herbicidal activity could be fully explained by chemical analysis as the sampling period coincided with an illegal discharge and two herbicides dominated the mixture effect. The mass balance of the reverse osmosis process matched theoretical expectations for both chemical analysis and bioanalytical tools. Overall the investigated treatment train removed >97% estrogenicity, >99% herbicidal activity, and >96% baseline toxicity, confirming the suitability of the treatment train for polishing water for indirect potable reuse. The product water was indistinguishable from local tap water in all three bioassays. This study demonstrates the suitability and robustness of passive sampling linked with bioanalytical tools for semicontinuous monitoring of advanced water treatment with respect to micropollutant removal.     

Mixed oxide coatings for optics

Material mixtures offer new possibilities for synthesizing coating materials with tailored optical and mechanical properties. We present experimental results on mixtures of HfO2, ZrO2, and Al2O3, pursuing applications in UV coating technology, while the mixtures are prepared by magnetron sputtering, ion beam sputtering, plasma ion-assisted deposition (PIAD), and electron beam evaporation without assistance. The properties investigated include the refractive index, optical gap, thermal shift, and mechanical stress. The first high reflectors for UV applications have been deposited by PIAD.     

Charakterisierung der Dispersionsgüte von Carbon Nanotubes in Polymer‐Nanokompositen

A practical overview of possibilities and limits to characterize the state of dispersion of carbon nanotubes (CNT) in polymer based nanocomposites is given. The most important and widely available methods are discussed with practical employment in mind. One focus is the quantitative characterization of the state of dispersion in solid samples using microscopy techniques such as optical microscopy or transmission electron microscopy. For dispersions of CNTs in aqueous media, solvents or monomers a sedimentation analysis is presented. This way dispersability and dispersion state of CNTs can be assessed. Indirect methods such as electrical conductivity measurements and rheological tests, dynamic differential scanning calorimetry and mechanical test are discussed.     

One-sided monte carlo tolerance limit factors in the case of the random effects one-way layout-an algorithm for application in statistical quality control

Assuming the statistical model of the random effects one-way layout under the usual conditions (normality and independence) and considering a realization of this model, the present paper treats the problem of the computation of one-sided tolerance limits for the corresponding defining random variable on the basis of the Monte Carlo method. Since subpopulations occurring in this scope can be considered as batches and since the model under consideration is sometimes called ‘cluster sampling model’, it is obvious that the present problem has important applications in the field of statistical quality control.—The Monte Carlo approach together with its realization by a computer program for the determination of such tolerance limit factors proved elementary and effective. In particular, in the important cases of limited sampling information (costs), this approach led to more realistic values in comparison, with other approaches. An additional problem occurring in connection with simultaneous statistical inference was solved by means of the Bonferroni inequality. Finally, the paper contains a computer program (FORTRAN 77) the applicability and use of which is shown by numerical examples.     

Catalytic Carbon Monoxide Oxidation Using Bio-Templated Platinum Clusters

The catalytic properties of highly dispersed, bacterial surface layer supported nanoscale platinum clusters immobilized at alumina particles are studied with respect to carbon monoxide oxidation. Compared to samples prepared from platinum impregnated alumina, the templated metal clusters are catalytically active at lower temperatures. The catalytic behaviour of the samples is discussed with respect to their cluster morphology studied by TEM.     

HPLC with light scatter detector and chemometric data evaluation for the analysis of cocoa butter and vegetable fats

High performance liquid chromatography equipped with an evaporative light scatter detector was carried out in order to proof the authenticity of cocoa butter. Signals of 17 characteristic triglycerides have been used to develop two chemometric models. PLS was applied for quantitation while neural nets were used for classification. The sample pool was divided in a training set of 18 and a prediction set of 14 samples. The samples included mixtures of several vegetable fats with cocoa butter. A 15 × 4 × 1 feed forward net could be trained and within the prediction set only 2 samples were not correctly assigned. A PLS model with 9 factors was applied and the mean prediction error was found to be 2.5%. The small number of samples was found to be sufficient to show the potential of this data evaluation. Results are expected to improve with a greater data pool.     

Enzymatic production and physicochemical characterization of uncommon wax esters and monoglycerides

Wax esters from fatty alcohols and uncommon fatty acids were synthesized in yields up to 90% when commercially available microbial lipases fromRhizomucor miehei (Lipozyme^™) andCandida antarctica (SP 435) were used with limited water content in nonpolar solvents under mild conditions. The corresponding fatty acids were prepared by chemical conversion of naturally occurring resources (agricultural surpluses). Also, when phenylboronic acid was added as solubilizing agent in a nonpolar solvent, the direct enzymatic monoacylation of glycerol with uncommon fatty acids was successful. The measurement of π/A-isotherms by means of a Langmuir film balance indicated medium film pressures, medium or large molecular areas, and interesting phase behavior. The monolayer of a wax ester at the air/water interface could be directly visualized by Brewster angle microscopy.     

3-Methylarginine from Pseudomonas syringae pv. syringae 22d/93 suppresses the bacterial blight caused by its close relative Pseudomonas syringae pv. glycinea

The epiphyte Pseudomonas syringae pv. syringae 22d/93 (Pss22d) produces a toxin that strongly inhibits the growth of its relative, the plant pathogen P. syringae pv. glycinea. The inhibition can be overcome by supplementing the growth medium with the essential amino acid, L-arginine; this suggests that the toxin acts as an inhibitor of the arginine biosynthesis. The highly polar toxin was purified by bioassay-guided fractionation using ion-exchange chromatography and subsequent RP-HPLC fractionation. The structure of the natural product was identified by HR-ESI-MS, HR-ESI-MS/MS, and NMR spectroscopy experiments as 3-methylarginine. This amino acid has previously only been known in nature as a constituent of the peptide lavendomycin from Streptomyces lavendulae. Results of experiments in which labeled methionine was fed to Pss22d indicated that the key step in the biosynthesis of 3-methylarginine is the introduction of the methyl group by a S-adenosylmethionine (SAM)-dependent methyltransferase. Transposon mutagenesis of Pss22d allowed the responsible SAM-dependent methyltransferase of the 3-methylarginine biosynthesis to be identified.