The empirical Kestin model and the second order transport properties of binary mixtures of Ne,Ar, Kr and Xe

It is showed from the experimental α_T data for the dilute binary mixtures of Ne, Ar, Kr and Xe at 340 K that the law of corresponding states proposed by Kestin, Ro and Wakeham is able to predict the mentioned second order kinetic property altogether with the first order transport and thermodynamic properties of the examined mixtures.     

Shrinkage effect on polyethylene based blends

An experimental study of the shrinkage effect in low density-high density polyethylene blends, high density-high density polyethylene blends and low density polyethylene-ethylene vinyl acetate copolymer blends is presented. Viscosity measurements are also included.The strain recovery is analysed as the addition of the interfacial tension effect and the elastic recoverable strain. The results are compared with those obtained for other polyolefin blends observing that in the case of compatible systems as low density-high density polyethylene and high density-high density polyethylene blends the strain recovery and the viscosity follow approximately the additive rule. In the case of more incompatible systems like polyethylene-ethylene vinyl acetate copolymer, polyethylene-polypropylene and others very large recoveries were observed. The formation of minifibres of the dispersed phase during the preparation of the samples is suggested as responsible for the obtained results.     

Conformational Plasticity in Glycomimetics: Fluorocarbamethyl‐L‐idopyranosides Mimic the Intrinsic Dynamic Behaviour of Natural Idose Rings

Sugar function, structure and dynamics are intricately correlated. Ring flexibility is intrinsically related to biological activity; actually plasticity in L ‐iduronic rings modulates their interactions with biological receptors. However, the access to the experimental values of the energy barriers and free‐energy difference for conformer interconversion in water solution has been elusive. Here, a new generation of fluorine‐containing glycomimetics is presented. We have applied a combination of organic synthesis, NMR spectroscopy and computational methods to investigate the conformational behaviour of idose‐ and glucose‐like rings. We have used low‐temperature NMR spectroscopic experiments to slow down the conformational exchange of the idose‐like rings. Under these conditions, the exchange rate becomes slow in the ¹⁹F NMR spectroscopic chemical shift timescale and allows shedding light on the thermodynamic and kinetic features of the equilibrium. Despite the minimal structural differences between these compounds, a remarkable difference in their dynamic behaviour indeed occurs. The importance of introducing fluorine atoms in these sugars mimics is also highlighted. Only the use of ¹⁹F NMR spectroscopic experiments has permitted the unveiling of key features of the conformational equilibrium that would have otherwise remained unobserved.     

Mechanical and barrier properties of ternary nanocomposite films based on polycarbonate/amorphous polyamide blends modified with a nanoclay

Ternary polycarbonate (PC)/amorphous polyamide–nanoclay (naPA) nanocomposite (PC/naPA) films were obtained by melt mixing and drawing, and the effects of the naPA content and the draw ratio (DR) on the structure, morphology and mechanical and barrier properties were studied. Despite the presence of nanoclay, the films exhibited a negligible roughness and the excellent optical properties of PC and amorphous polyamide (aPA). The dispersed naPA phase was pure and small, indicating compatibility. The naPA did not hinder the drawing ability of PC. At low DRs the dispersed phase was elongated and oriented along the machine direction (extrusion flow direction), but at high DRs, it fibrillated due to the higher non‐isothermal elongational flow induced by drawing. The laminar structure of the nanoclay allowed the films to be reinforced both in the machine and the transverse directions. The oxygen permeability of PC was reduced by 42% in the nanocomposite with 25% of naPA, and dropped further with the DR, which is attributed to the increased tortuosity of the oxygen path induced by fibrillation. Copyright © 2015 John Wiley & Sons, Ltd.     

Complexing capacity profiles of naturally occurring ligands in Tempranillo wines for Cu and Zn: an electroanalytical approach for cupric casse

Complexing capacity of naturally occurring ligands in Vitis vinifera (Tempranillo variety) wines has been studied with respect to two target metals (Cu and Zn) by differential pulse anodic stripping voltammetry (DPASV). Eight commercial wines of two certified brands of origin (CBO) and a young wine along its vinification process were monitored. Conditional stability constants and total complexing ligand(s) concentration(s) have been calculated for both metals. Discussion of the particular electrochemical responses for Cu and Zn for all samples is presented. A follow-up of the Cu stripping response allowed differentiating a commercial wine from one under processing related to the cupric casse phenomenon. Interaction of Cu with two molecular forms of cyanidin has been theoretically modeled at natural wine pH.     

Ionic complexes of biosynthetic poly(malic acid) and poly(glutamic acid) as prospective drug-delivery systems

The hydrolytic degradability and erythromycin release from stoichiometric ionic complexes of biotechnological poly(beta,L-malic acid)s and poly(gamma,D-glutamic acid)s with alkyltrimethylammonium surfactants were investigated. The influence of pH, temperature and antibiotic load on hydrolysis rate was examined. It was found that poly(malic acid) complexes degraded by a surface erosion mechanism at a higher rate than poly(glutamic acid) complexes, which eroded in bulk. Erythromycin was lodged in the paraffinic subphase of the complexes and upon aging it was delivered according to a sigmoidal profile that appeared to be independent on the antibiotic load.     

Role of the polymer microstructure in the thermoreversible gelation of poly(vinyl chloride)

Gels of polyvinylchloride (PVC) and PVC copolymers of different microstructure and molar composition, were prepared in a series of diester-like solvents. The viscoelastic properties of these gels were evaluated as a function of temperature and the molecular structure was studied by small-angle neutron scattering. The degrees of proton association in the polymer solutions were determined by ¹H NMR spectroscopy by measuring the intensity of proton bands of CH₂ monomeric units. The body of experimental data shows clearly that there is a straight relation between molecular structure, viscoelastic properties of the gel, degree of polymer-solvent interaction and polymer microstructure.     

Mimicking Chitin: Chemical Synthesis,Conformational Analysis,and Molecular Recognition of the β(1→3) N‐Acetylchitopentaose Analogue

Mimicking Nature by using synthetic molecules that resemble natural products may open avenues to key knowledge that is difficult to access by using substances from natural sources. In this context, a novel N‐acetylchitooligosaccharide analogue, β‐1,3‐N‐acetamido‐gluco‐pentasaccharide, has been designed and synthesized by using aminoglucose as the starting material. A phthalic group has been employed as the protecting group of the amine moiety, whereas a thioalkyl was used as the leaving group on the reducing end. The conformational properties of this new molecule have been explored and compared to those of the its chito analogue, with the β‐1,3 linkages, by a combined NMR spectroscopic/molecular modeling approach. Furthermore, the study of its molecular recognition properties towards two proteins, a lectin (wheat germ agglutinin) and one enzyme (a chitinase) have also been performed by using NMR spectroscopy and docking protocols. There are subtle differences in the conformational behavior of the mimetic versus the natural chitooligosaccharide, whereas this mimetic is still recognized by these two proteins and can act as a moderate inhibitor of chitin hydrolysis.     

Statistical Mechanical Theory of a Closed Oscillating Universe

Based on Newton’s laws reformulated in the Hamiltonian dynamics combined with statistical mechanics, we formulate a statistical mechanical theory supporting the hypothesis of a closed universe oscillating in phase-space. We find that the behavior of this universe as a whole can be represented by a free entropic oscillator whose lifespan is nonhomogeneous, thus implying that time is shorter or longer according to the state of this universe given through its entropy. We conclude that time reduces to the entropy production of this universe and that a nonzero entropy production means that local fluctuations could exist giving rise to the appearance of masses and to the curvature of the space.     

Ionic Complexes of Polyacids and Cationic Surfactants

Comb-like ionic complexes were prepared from polyuronic acids (pectinic and alginic acids) and alkyltrimethylammonium surfactants bearing linear alkyl chains with 18, 20 and 22 carbon atoms. In the condensed state, these complexes were able to self-assemble in ordered structures which were thermally stable up to ∼200 °C. The complexes were analysed by DSC and WAXS/SAXS and compared to their analogous made from poly(γ-glutamic acid). They all adopt a biphasic layered structure in which the main chain and the alkyl side chain alternate with a nanometric periodicity. Alkyl side chains were partially crystallized in these complexes and they show reversible melting at temperatures within the 60-80 °C range depending on the length of the polymethylene segment.