Thermodynamic properties of polyolefin solutions at high temperature: 2. Lower critical solubility temperatures for polybutene-1, polypentene-1 and poly(4-methylpentene-1) in hydrocarbon solvents and determination of the polymer-solvent interaction parameter for PB1 and one ethylene-propylene copolymer

Lower critical solubility temperature (LCST) for 3 polyolefins, polybutene-1 (PB1), polypentene-1 (PP1) and poly(4-methylpentene-1) (P4MP1), and the x interaction parameter in concentrated solutions for PB1 and the 33% ethylene ethylene-propylene copolymer have been measured in linear, branched, cyclic alkanes and some other solvents. Effects on x of the equation of state term, of correlations of molecular orientations (CMO) and of the solvent steric hindrance were investigated. The solvent density d_s is found to be a good empirical parameter to characterize the equation of state term and to correlate the LCST. The parameter $\text{d}{}_{\mathrm{s}}\text{d}{}_{\mathrm{p}}$ (where d_p is the polymer density) affords an excellent correlation for the LCST of all polyolefins in normal and branched alkanes (polyethylene (PE) excepted). In dilute solution (at the LCST) the effect of CMO and solvent steric hindrance could not be distinguished from equation of state effects. However, values of x, found to be higher in branched than in linear alkanes in solutions of the linear polymer (PE) but not with the branched PB1 and the copolymer, are indicative of the importance in concentrated solutions of CMO even at high temperatures (100°–135°C). Furthermore, the lowering of x from linear PE to the branched PE and to the ethylene-propylene copolymers, following the expected diminution of CMO in the corresponding melts, is another indication of the persistance of CMO at high temperature. Solvent steric hindrance is seen to lower x (measured here by gas-liquid chromatography).     

Effect of macerating enzyme treatment on the polyphenol and polysaccharide composition of red wines

Effect of macerating enzymes on the polyphenol and polysaccharide composition of Merlot wines after 20 months of ageing was studied over three vintages (2004, 2005, 2006). Pectinase rich enzyme preparations, by degrading grape berry cell walls, led to a modification of the molecular weight distribution of polysaccharides released into the wines. Enzyme-treated wines contained more Rhamnogalacturonan II (RG-II) and less polysaccharides rich in arabinose and galactose (PRAGs) over the three vintages. The enzyme treatment also modified wine polyphenol composition. An increase of colour intensity, of derived pigments resistant to sulphite bleaching and of proanthocyanidins (condensed tannins) was observed, modulated by vintage effect. Principal Component Analysis of all the data indicated both vintage and enzyme effects. Beside the vintage effect separating the wine samples, the impact of enzyme treatment on wines was established for each year.     

Sequence determinants governing the topology and biological activity of a lasso peptide, microcin J25

Microcin J25 is a potent antibacterial peptide produced by Escherichia coli AY25. It displays a lasso structure, which consists of a knot involving an N-terminal macrolactam ring through which the C-terminal tail is threaded and sterically trapped. In this study, we rationally designed and performed site-specific mutations in order to pinpoint the sequence determinants of the lasso topology. Structures of the resulting variants were analysed by a combination of methods (mass spectrometry, NMR spectroscopy, enzymatic digestion), and correlated to the antibacterial activity. The selected mutations resulted in the production of branched-cyclic or lasso variants. The C-terminal residues below the ring (Tyr20, Gly21) and the size of the macrolactam ring were revealed to be critical for both the lasso scaffold and bioactivity, while shortening the loop region (Tyr9-Ser18) or extending the C-terminal tail below the ring did not alter the lasso structure, but differentially affected the antibacterial activity. These results provide new insights for the bioengineering of antibacterial agents using a lasso peptide as template.     

Traits at work: The design of a new trait-based stream library

Recent years saw the development of a composition mechanism called traits. Traits are pure units of behavior that can be composed to form classes or other traits. The trait composition mechanism is an alternative to multiple or mixin inheritance in which the composer has full control over the trait composition.To evaluate the expressiveness of traits, some hierarchies were refactored, showing code reuse. However, such large refactorings, while valuable, may not exhibit all possible composition problems, since the hierarchies were previously expressed using single inheritance and following certain patterns.This paper presents our work on designing and implementing a new trait-based stream library named Nile. It evaluates how far traits enable reuse, what problems can be encountered when building a library using traits from scratch and compares the traits solution to alternative composition mechanisms. Nile's core allows the definition of compact collection and file streaming libraries as well as the implementation of a backward-compatible new stream library. Nile method size shows a reduction of 40% compared to the Squeak equivalent. The possibility to reuse the same set of traits to implement two distinct libraries is a concrete illustration of trait reuse capability.     

Pressure and temperature dependence of the structural properties of the molecular semiconducting salt: α′-(BEDT-TTF)2Ag(CN)2

The temperature and pressure dependence of the electrical conductivity of the α′-(BEDT-TTF)₂Ag(CN)₂ salt shows a transition between two semiconducting phases at a critical temperature depending on pressure. This transition is crystallographically characterized by the appearance of a superstructure corresponding to the doubling of the b parameter. We present and discuss here the parameters evolution at decreasing temperature and increasing pressure and the structural evolution under constraints.     

Magnetic properties of BEDT-TTF radical ion salts with Keggin type polyoxometalates

ESR measurements of the series of radical salts formed by ET and inorganic polyoxometalates are presented and compared with the susceptibility data. Both experiments show that the organic radicals are antiferromagnetically coupled whereas no sizable magnetic coupling is found between the two magnetic sublattices.     

Injection locking of CW ring dye lasers

An analytical treatment of the injection locking of CW dye lasers, taking into account the Fabry-Perot enhancement of the laser cavity is presented. The analysis, restricted to the case where the injected radiation is resonant within the injected resonator, is based on a set of rate equations for the population densities and photon flux. Analytical solutions are found which allow the injection threshold conditions to be easily determined, and which describe the different intracavity intensities characterizing the system. The dependence of these quantities on various parameters such as input coupler transparency, pump intensity, injected intensity, and wavelength is analyzed. These results correct, in the case of steady-state laser operation, the theoretical predictions obtained by Ganiel et al. from a model where only the field intensities were considered instead of the field amplitudes. The experimental feasibility of CW ring dye laser injection locking is discussed and the conditions for an optimum system, in terms of intracavity power are determined.