Dilute Solution Properties and Chain Dimensions of Poly(2-alkoxyethyl methacrylates)

The solution properties of poly(2-methoxyethyl methacrylate) (PMEMA), poly(2-ethoxyethyl methacrylate) (PEEMA) and poly- (2-n-butoxyethyl methacrylate) (PBEMA) have been compared. The respective 8-temperatures in n-butanol are 64, 38 and 17DC. From the relationships between intrinsic viscosity and molecular weight in a thermodynamically good solvent, methyl ethyl ketone (MEK), the respective characteristic ratios Coo = 11.1, 12.6, and 15.5 were estimated. The unperturbed dimensions of PBEMA depend on the nature of the solvent, being lower in n-butanol (12.3)than in MEK. The conformational properties of poly(2-alkoxyethyl methacrylates) resemble those of poly(n-alkyl methacrylates) with a comparable side-chain length

Source-based nomenclature for single-strand homopolymers and copolymers (IUPAC Recommendations 2016)

IUPAC recommendations on source-based nomenclature for single-strand polymers have so far addressed its application mainly to copolymers, non-linear polymers and polymer assemblies, and within generic source-based nomenclature of polymers. In this document, rules are formulated for devising a satisfactory source-based name for a polymer, whether homopolymer or copolymer, which are as clear and rigorous as possible. Thus, the source-based system for naming polymers is presented in a totality that serves as a user-friendly alternative to the structure-based system of polymer nomenclature. In addition, because of their widespread and established use, recommendations for the use of traditional names of polymers are also elaborated

Variation in Phenotype, Parasite Load and Male Competitive Ability across a Cryptic Hybrid Zone

BackgroundMolecular genetic studies are revealing an increasing number of cryptic lineages or species, which are highly genetically divergent but apparently cannot be distinguished morphologically. This observation gives rise to three important questions: 1) have these cryptic lineages diverged in phenotypic traits that may not be obvious to humans; 2) when cryptic lineages come into secondary contact, what are the evolutionary consequences: stable co-existence, replacement, admixture or differentiation and 3) what processes influence the evolutionary dynamics of these secondary contact zones?Methodology/principal findingsTo address these questions, we first tested whether males of the Iberian lizard Lacerta schreiberi from two highly genetically divergent, yet morphologically cryptic lineages on either side of an east-west secondary contact could be differentiated based on detailed analysis of morphology, coloration and parasite load. Next, we tested whether these differences could be driven by pre-copulatory intra-sexual selection (male-male competition). Compared to eastern males, western males had fewer parasites, were in better body condition and were more intensely coloured. Although subtle environmental variation across the hybrid zone could explain the differences in parasite load and body condition, these were uncorrelated with colour expression, suggesting that the differences in coloration reflect heritable divergence. The lineages did not differ in their aggressive behaviour or competitive ability. However, body size, which predicted male aggressiveness, was positively correlated with the colour traits that differed between genetic backgrounds.Conclusions/significanceOur study confirms that these cryptic lineages differ in several aspects that are likely to influence fitness. Although there were no clear differences in male competitive ability, our results suggest a potential indirect role for intra-sexual selection. Specifically, if lizards use the colour traits that differ between genetic backgrounds to assess the size of potential rivals or mates, the resulting fitness differential favouring western males could result in net male-mediated gene flow from west to east across the current hybrid zone.Devi Stuart-Fox, Raquel Godinho, Joëlle Goüy de Bellocq, Nancy R. Irwin, José Carlos Brito, Adnan Moussalli, Pavel Široký, Andrew F. Hugall and Stuart J. E. Bair

FEM optimization of a steel belt of OTR tyres

This paper deals with an FEM simulation of a steel belt of tyres. A belt is a part of a tyre that plays a very important role in all radial tyres especially in case of heavy-duty off-the-road (OTR)  ones. It is a composite composed of rubber material and a steel reinforcement. High peak stress inside this composite can initiate cracks, which subsequently lead to a complete tyre failure. In this work, the belt is extracted from the tyre and simulated separately in order to be able to cover individual cords. Belt behaviour under tension is studied and optimal cord distribution is proposed to decrease the risk of the failure. FEM software MSC Marc/Mentat is employed as a calculation tool. © 2020 Trans Tech Publications Ltd, Switzerland

A New Insight into the Stereoelectronic Control of the Pd-0-Catalyzed Allylic Substitution: Application for the Synthesis of Multisubstituted Pyran-2-ones via an Unusual 1,3-Transposition

Pyran-2-ones 3 undergo a novel Pd0 -catalyzed 1,3-rearrangement to afford isomers 6. The reaction proceeds via an η2 -Pd complex, the pyramidalization of which (confirmed by quantum chemistry calculations) offers a favorable antiperiplanar alignment of the Pd-C and allylic C-O bonds (C), thus allowing the formation of an η3 -Pd intermediate. Subsequent rotation and rate-limiting recombination with the carboxylate arm then gives isomeric pyran-2-ones 6. The calculated free energies reproduce the observed kinetics semi-quantitatively.status: publishe