Melt processed blends of poly(styrene-co-acrylonitrile) and poly(phenylene ether) compatibilized with polystyrene-b-polybutadiene-b-poly(methyl methacrylate) triblock terpolymers

Polystyrene-b-polybutadiene-b-poly(methyl methacrylate) triblock terpolymers (SBM) with equal (symmetric) and different (asymmetric) block lengths were used to compatibilize polymer blends based on poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and poly(styrene-co-acrylonitrile) (SAN). First, the rheological behavior of the individual components and their binary mixtures was investigated. Based on the results, samples of PPE, SAN and SBM in weight ratios of 32/48/20 were melt blended and the morphology development during melt processing was investigated. It was found that a raspberry morphology, i.e. dispersion of PPE in SAN with rubbery PB domains at the PPE/SAN interface, could be achieved with a symmetric SBM with under sufficiently high shear rate, while a symmetric SBM with did not yield the desired morphology. Asymmetric SBMs with long PS blocks dissolved in the PPE phase did not display the expected compatibilization effect. In order to obtain a raspberry morphology with asymmetric copolymers it is suggested to pre-blend the SBM with SAN before adding the PPE. Finally it is shown that a commercial PPE containing High Impact Polystyrene (HIPS) as a toughness modifier can be compatibilized with SAN by melt processing using a symmetric SBM triblock terpolymer with      

Scholarly collaboration between Europe and Israel: A scientometric examination of a changing landscape

In this paper we examine various aspects of the scientific collaboration between Europe and Israel, and show that the traditional collaboration patterns of Israel (preference towards collaboration with the US) is changing, and the collaboration with the EU countries is growing.     

CHROMagar Candida medium as a practical tool for the differentiation and presumptive identification of yeast species isolated from salads

CHROMagar Candida medium was used to study the diversity of yeast biota of salad samples, and to presumptively identify the isolates. This medium was originally developed for the selective isolation and presumptive identification of some clinically important yeast species such as Candida albicans, Candida tropicalis, Candida krusei, and Candida glabrata on the basis of differences in colour and surface of colonies. Ninety three yeast strains representing 33 species from the culture collection and 39 fresh isolates from different mayonnaise-based mixed salads showed a wide range of hue of colony colours ranging from white to yellow, orange, red, pink, purple, blue, green, etc., as well as different morphological appearances on the CHROMagar Candida medium. Therefore, CHROMagar Candida medium facilitates the detection of mixtures of yeast species from different samples on a single isolation plate and this medium can be a practical method for the differentiation and rapid presumptive identification of many yeast species occurring frequently in different kind of foods.     

Abiotic Stress Response of Near-Isogenic Spring Durum Wheat Lines under Different Sowing Densities

A detailed study was made of changes in the plant development, morphology, physiology and yield biology of near-isogenic lines of spring durum wheat sown in the field with different plant densities in two consecutive years (2013–2014). An analysis was made of the drought tolerance of isogenic lines selected for yield QTLs (QYld.idw-2B and QYld.idw-3B), and the presence of QTL effects was examined in spring sowings. Comparisons were made of the traits of the isogenic pairs QYld.idw-3B++ and QYld.idw-3B−− both within and between the pairs. Changes in the polyamine content, antioxidant enzyme activity, chlorophyll content of the flag leaf and the normalized difference vegetation index (NDVI) of the plot were monitored in response to drought stress, and the relationship between these components and the yield was analyzed. In the case of moderate stress, differences between the NIL++ and NIL−− pairs appeared in the early dough stage, indicating that the QYld.idw-3B++ QTL region was able to maintain photosynthetic activity for a longer period, resulting in greater grain number and grain weight at the end of the growing period. The chlorophyll content of the flag leaf in phenophases Z77 and Z83 was significantly correlated with the grain number and grain weight of the main spike. The grain yield was greatly influenced by the treatment, while the genotype had a significant effect on the thousand-kernel weight and on the grain number and grain weight of the main spike. When the lines were compared in the non-irrigated treatment, significantly more grains and significantly higher grain weight were observed in the main spike in NIL++ lines, confirming the theory that the higher yields of the QYld.idw-3B++ lines when sown in spring and exposed to drought stress could be attributed to the positive effect of the “Kofa” QTL on chromosome 3B.     

Parallel models for arborescent polyisobutylene synthesized in batch reactor

A mathematical model is developed for estimating kinetic parameters that influence the production of arborescent polyisobutylene via carbocationic copolymerization of inimer (IM) and isobutylene. Six different propagation rate constants arise due to the two types of vinyl groups and three types of carbocations. These six parameters are estimated using parallel simulation systems in PREDICI that track (1) functional groups, (2) internal and dangling segments in the polymer, and (3) concentrations of IM and polymer molecules. Parameter estimates obtained using the proposed model result in a better fit to literature data than was obtained using a previous model that neglected two types of propagations reactions. Predictions from the proposed model are consistent with Monte Carlo simulations for molecular weight distribution of the internal and dangling segments. © 2014 American Institute of Chemical Engineers AIChE J, 61: 253–265, 2015     

Astrophysics publications on arXiv,Scopus and Mendeley: a case study

In this study we examined a sample of 100 European astrophysicists and their publications indexed by the citation database Scopus, submitted to the arXiv repository and bookmarked by readers in the reference manager Mendeley. Although it is believed that astrophysicists use arXiv widely and extensively, the results show that on average more items are indexed by Scopus than submitted to arXiv. A considerable proportion of the items indexed by Scopus appear also on Mendeley, but on average the number of readers who bookmarked the item on Mendeley is much lower than the number of citations reported in Scopus. The comparisons between the data sources were done based on the authors and the titles of the publications.     

Ellipsometric study of SixC films: Analysis of Tauc-Lorentz and Gaussian oscillator models

In this study, the suitability of Tauc-Lorentz and Gaussian oscillator models to describe amorphous silicon-carbon alloys of various compositions was tested. The dependence of the model parameters on the composition showed that the amplitude and broadening of both oscillators behave similarly and significant differences can only be observed in the oscillators’ position in case of high broadening parameter values. It was shown that this difference originates from the different mathematical forms of the oscillators and from the high broadening values. Sensitivity analysis of the parameters showed that the models became less sensitive to their parameters with large broadening values. Furthermore the model parameters were correlated to the various types of chemical bonding present within the samples.     

Characterization of pulsed laser deposited hydrogenated amorphous silicon films by spectroscopic ellipsometry

The wide absorption band of hydrogenated amorphous silicon (a-Si:H) is being realized as a key component of solar cells on glass. In this study, a-Si:H films were prepared by reactive pulsed laser deposition onto silicon and glass substrates. Ellipsometry showed that the optical properties of the films are effectively independent on the choice of substrate. According to the optical properties, the character of the films changes from amorphous silicon to dielectric as the hydrogen background pressure increases from 0 to 25 Pa. This observation was attributed to oxygen incorporation indicated by Rutherford Backscattering Spectrometry. Furthermore, a refractive index gradient in depth was revealed, which was attributed to the oxygen concentration gradient.