Vinylogous Mannich reactions. Additions of trimethylsilyloxyfuran to fluorinated aldimines

Trifluoromethyl aldimines reacted with trimethylsilyloxyfuran in presence of Lewis acids to provide butenolides in high yields with total diastereoselectivity (>98%). The configuration of these products is anti. The butyrolactone 4a, substituted with a 2-trifluoromethyl ethyl amine, could be converted into a trans α-trifluoromethyl piperidine derivative.     

Magnetic semiconducting anatase TiO2−δ grown on (1 0 0) LaAlO3 having magnetic order up to 880 K

We demonstrate a semiconducting material, TiO_2−δ, with magnetism up to 880 K, without the introduction of magnetic ions. The magnetism in these films stems from the controlled introduction of anion defects from both the film–substrate interface as well as processing under a deficient oxygen atmosphere. First-principle band structure calculations indicate that the exchange between Ti cations mediated by an oxygen anion is positive, i.e., ferromagnetic, whereas the exchange between cations via a vacancy is negative, i.e., ferrimagnetic. It is likely that both the mechanisms are active in this system. This represents a new and promising approach in the search for room-temperature magnetic semiconductors.     

Shear characterization of CaCO3-filled linear low density polyethylene

Shear properties of CaCO₃-filled linear low density polyethylene have been determined over a wide range of filler loading. The viscosity rises with the filler loading especially at low shear rates and a yield value appears for CaCO₃-contents larger than 5%. The decrease of the die-swell ratios of the filled samples indicates a reduction of the melt elasticity.     

Invasion threshold in heterogeneous metapopulation networks

We study the dynamics of epidemic and reaction-diffusion processes in metapopulation models with heterogeneous connectivity patterns. In susceptible-infected-removed-like processes, along with the standard local epidemic threshold, the system exhibits a global invasion threshold. We provide an explicit expression of the threshold that sets a critical value of the diffusion/mobility rate below, which the epidemic is not able to spread to a macroscopic fraction of subpopulations. The invasion threshold is found to be affected by the topological fluctuations of the metapopulation network. The results presented provide a general framework for the understanding of the effect of travel restrictions in epidemic containment.     

Ellipsoidal core-shell cylindrical microphases in PS-b-PB-b-PCL triblock copolymers with a crystallizable matrix

Polystyrene-block-polybutadiene-block-poly(ϵ-caprolactone) SBC triblock copolymers with a PCL matrix exhibit microphase separation into three different phases within the spherulitic superstructures. Mixing of the PS-block can occur upon melting of the PCL-block if the molecular weight is low enough. Even though the crystallization takes place well below the PS-glass transition, a deformation of the amorphous microphases into ellipsoidal core-shell cylindrical microdomains is observed by TEM. These copolymers have mechanical properties which are dominated by the PCL (poly(ϵ-caprolactone)) matrix with an influence of the amorphous blocks.     

FTIR analysis of cysteic acid and cysteine-S-thiosulphate on untreated and bleached human hair

Human hair was analysed by FTIR spectroscopy and single fibre analysis was achieved using an IR microscope, an ATR diamond cell was also found very useful in determining the cysteic acid content of hair tress samples. Several different data manipulations were also assessed.     

Polymorphism and Thermal Behaviour of Syndiotactic Poly(propylene)/Carbon Nanotube Composites

Summary: Nanocomposite materials were obtained by blending multi‐wall carbon nanotubes (CN), obtained by acetylene catalytic chemical vapour deposition (CVD) on Co/Fe‐modified NaY zeolite, with syndiotactic poly(propylene) (sPP). The nanotubes, well dispersed in the polymer matrix, favour the crystallization of the sPP helical chains and significantly improve the sPP thermal stability either in nitrogen or in air. The morphology of the sPP affects the behaviour of the sPP degradation in air.

Thermogravimetric analysis in air of pure sPP and the nanocomposite material.     

Transport properties of poly(ethylene terephthalate) crystallized from the glassy state

Poly(ethylene terephthalate) was crystallized from the glassy state at 120 and 200°C. The structural organization of samples, after the primary and secondary crystallizations, was analyzed by density, X-rays, infrared and transport properties of dichloromethane vapor. The values of crystallinity derived with different methods do not agree, indicating that the crystallized samples cannot be considered simply biphasic. Since the fraction of the impermeable phase is much higher than the fraction of the crystalline phase, it suggested that the presence of mesomorphic form, impermeable to the vapors at low activity. With this hypothesis, the complete composition of the crystalline samples, in terms of fraction of crystalline, amorphous and mesomorphic form was derived. A value of density of the mesomorphic form of 1.39 g/cm³ was also derived.