Properties of poly(ethylene terephthalate)–poly(ethylene naphthalene 2,6‐dicarboxylate) blends with montmorillonite clay

The production and properties of blends of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) with three modified clays are reported. Octadecylammonium chloride and maleic anhydride (MAH) are used to modify the surface of the montmorillonite–Na⁺ clay particles (clay–Na⁺) to produce clay–C18 and clay–MAH, respectively, before they are mixed with the PET/PEN system. The transesterification degree, hydrophobicity and the effect of the clays on the mechanical, rheological and thermal properties are analysed. The PET–PEN/clay–C18 system does not show any improvements in the mechanical properties, which is attributed to poor exfoliation. On the other hand, in the PET–PEN/clay–MAH blends, the modified clay restricts crystallization of the matrix, as evidenced in the low value of the crystallization enthalpy. The process‐induced PET–PEN transesterification reaction is affected by the clay particles. Clay–C18 induces the largest proportion of naphthalate–ethylene–terephthalate (NET) blocks, as opposed to clay–Na⁺ which renders the lowest proportion. The clay readily incorporates in the bulk polymer, but receding contact‐angle measurements reveal a small influence of the particles on the surface properties of the sample. The clay–Na⁺ blend shows a predominant solid‐like behaviour, as evidenced by the magnitude of the storage modulus in the low‐frequency range, which reflects a high entanglement density and a substantial degree of polymer–particle interactions. Copyright © 2005 Society of Chemical Industry     

Wavelength-switchable fiber laser using acoustic waves

We report a wavelength-switchable fiber ring laser that includes a Bragg grating-based acoustooptic superlattice modulator. Wavelength switching of the laser emission is achieved by controlling the peak reflectivity of the different reflection bands that appear on both sides of the Bragg wavelength when a longitudinal acoustic wave propagates along the grating.     

Optimization of the properties obtained by quenching in martensitic stainless steels X30-40Cr13 and X40-60CrMoV14

An experimental study of the effects produced by different parameters of the heat-quenching cycle permitted the optimization of the properties typical of these martensitic stainless steels: hardness and corrosion resistance. The results obtained demonstrate that the heating temperatures currently used in industrial quenching treatment of these steels should be modified.     

Analysis of an interferometric optical fibre detection technique applied to silicon vibrating sensors

A simple and accurate analysis of a single-mode optical fibre interferometric displacement detection technique is resented. This analysis is in good agreement with experimental measurements, and shows that angular alignment between the fibre and the sensor is the most critical parameter.     

Land‐use dynamic discovery based on heterogeneous mobility sources

Nowadays, cities are the most relevant type of human settlement and their population has been endlessly growing for decades. At the same time, we are witnessing an explosion of digital data that capture many different aspects and details of city life. This allows detecting human mobility patterns in urban areas with more detail than ever before. In this context, based on the fusion of mobility data from different and heterogeneous sources, such as public transport, transport‐network connectivity and Online Social Networks, this study puts forward a novel approach to uncover the actual land use of a city. Unlike previous solutions, our work avoids a time‐invariant approach and it considers the temporal factor based on the assumption that urban areas are not used by citizens all the time in the same manner. We have tested our solution in two different cities showing high accuracy rates.     

Study of operating variables in the transformation of aqueous ethanol into hydrocarbons on an HZSM‐5 zeolite

With the aim of determining the possibilities of directly upgrading the liquid obtained from carbohydrate fermentation, the effect of operating conditions (temperature, space time, water content in the feed) has been studied in the catalytic transformation of aqueous ethanol into hydrocarbons on an HZSM‐5 zeolite in an isothermal fixed bed reactor. Special attention has been paid to the effect of water content on the yield, product distribution and catalyst deactivation. Although deactivation by coke decreases as the water content is increased, this content must be limited at 450 °C and higher temperatures in order to avoid irreversible deactivation of the catalyst by dealumination. © 2002 Society of Chemical Industry     

A study of the thermal expansion of isostructural organic radical cation salts κ-(BEDT-TTF)2Cu[N(CN)2]X (X = Br, Cl,I)

High resolution thermal expansion measurements on single crystals of κ-(BEDT-TTF)₂Cu[N(CN)₂]X, with X = Br, Cl, I were performed along the three principal directions in the temperature range from 2 to 300K. The temperature dependence of the linear thermal expansion of the two superconductors (X = Br, Cl) is found to be completely different from that of the non-superconducting I-salt. Cooling the I-crystal, we found an elongation of the c- axis, a larger contraction of the a-axis and a smaller contraction of the b-axis in comparison to the bromide- and the chloride- salt. Common to the three compounds are large anomalies in the linear thermal expansion coefficients _i at a temperature T_d = 84K, 80K, 73K for X = I, Br, Cl, respectively. The magnitude and the sign of these anomalies in _i strongly depend on the anion composition. At T_d the _i's show steplike changes, which lead to a lattice distortion of opposite sign for the superconductors and for the I-salt. These anomalies indicate a second order phase transition at T_d, which eventually may be related to a disorder-order transformation of the terminal ethylene groups of the donor molecules.     

On the origins of anticipation as an evolutionary framework: functional systems perspective

This paper discusses the problem of anticipation from an evolutionary and systems-theoretical perspective, developed in the context of Russian/Soviet evolutionary biological and neurophysiological schools in the early and mid-twentieth century. On this background, an outline is given of the epigenetic interpretation of anticipatory capacities formulated and substantiated by the eminent Russian neurophysiologist academician Peter K. Anokhin in the framework of functional systems theory. It is considered that several key positions of this theory are well confirmed by recent evidence on anticipation as an evolutionarily basic adaptive capacity, possibly inherent to the organization of life. In the field of neuroscience, the theory of functional systems may potentially facilitate future studies at the intersection of learning, development and evolution by representing an integrative approach to the problem of anticipation.