Analytical study of polychromy on exterior sculpted stone

A complete study on the remnants of the polychromy in the main entrance portal of Saint Paul's church (16th century, Úbeda, Spain) has been carried out using Raman microspectroscopy in combination with optical microscopy and scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM‐EDX). The polychromy in red areas showed the superposition of two well‐defined pictorial layers. The first one (probably original) was composed of cinnabar, red lead and hematite over a preparation coating containing calcite, gypsum and lead white. The second red pictorial layer was mainly constituted by cinnabar and was over a thicker preparation coating. Green samples showed a single pictorial layer over the weathered stone. The high fluorescence background made the examination of the latter samples extremely difficult by means of Raman microspectroscopy. SEM‐EDX detected abundance of copper and chlorine, and a detailed inspection of Raman spectra revealed the presence of a copper hydroxychloride, analogous to the naturally occurring mineral atacamite. Azurite remnants of the original polychromy were only found in the cracks of mortar joints. Alteration products like calcium and copper oxalates were also widely distributed in this layer. Copyright © 2009 John Wiley & Sons, Ltd.     

Separating families of locale maps and localic embeddings

We establish the notion of a separating family of locale maps, which is the localic analogue of the topological concept of separating points from closed sets by continuous maps. We then present a localic version of the topological embedding (or diagonal) theorem. Applications to arbitrary locales, zero-dimensional locales, and completely regular locales are given. Using the axiom of choice, we are able to control the number of factors of the target localic products so that it does not exceed the weight of the embeddable locale. Apart from the proofs of results involving the weights of locales, the remaining proofs are valid in topos logic.     

Formation of polymer vesicles by liquid crystal amphiphilic block copolymers

We report the formation of polymer vesicles (or polymersomes) by a new class of amphiphilic block copolymers in which the hydrophobic block is a side-on nematic liquid crystal polymer. Two series of these block copolymers, named PEG-b-PA444 and PEG-b-PMAazo444, with different hydrophilic/hydrophobic ratios were synthesized and characterized in detail. Polymersomes and nanotubes were formed by adding water into a solution of copolymers in dioxane. Polymersomes in water were finally obtained by dialyzing the resulting mixture against water. These self-assemblies have been studied by classical TEM and cryo-TEM. For the PEG-b-PA444 series, polymersomes were observed for hydrophilic/hydrophobic ratios ranging from 40/60 to 19/81. For PEG-b-PMAazo444 series, polymersomes were observed for hydrophilic/hydrophobic ratios ranging from 26/74 to 18/82. For a PEG-b-PA444 sample with hydrophilic/hydrophobic ratio equal to 25/75, a tubular morphology with tube diameter of typically 100 nm and tube length of up to 10 mum was also observed together with polymersomes during addition of water into the polymer solution in dioxane.     

Structural,magnetic and thermal characterization of Fe50Se50 powders obtained by mechanical alloying

Journal of Thermal Analysis and Calorimetry - In this paper, Fe50Se50 alloy powders were synthesized from pure elemental powder by mechanical allowing. The structure, microstructure, morphology,...     

Thermal behavior of several Fe-Ni alloys prepared by mechanical alloying and rapid solidification

Several Fe-Ni-P-Si alloys were produced in an amorphous state by mechanical alloying and rapid solidification. Thermal behavior of the as prepared alloys was analyzed and compared with identical alloys stored during 1 and 2 years. During annealing time, several exothermic processes related to the structural relaxation were detected at low temperature and with further crystallization at high temperature. As increasing the storage time, the powdered samples were relaxed at lower temperatures. The activation energy, E, of the main crystallization process varies between 2.7 and 4.7 eV at.^-1. The E values obtained remains similar with the storage time. Small contamination from the milling tools was found. Furthermore, powdered alloys are more sensible to oxidation processes than as quenched ribbons.     

Structure-activity studies of ferroelectric and antiferroelectric imine ligands and their square-planar complexes

The synthesis and characterization of the mesomorphic and dielectric properties of a series of new imine-based liquid crystalline compounds that exhibit tilted SmC* phases is reported. The presence of an imino linkage within the mesogenic nucleus of these compounds is significant due to the ability of salicylaldimines to coordinate to metals. Structure-activity studies have also been carried out by varying the structural elements in the ligands. The structural variations include changing the length of the chiral chain and incorporating fluorocarbon segments in the achiral terminal chain.     

Fluorene‐based liquid crystalline networks with linearly polarized blue emission

A series of fluorene‐based luminophores containing methacrylic end groups have been prepared and incorporated into uniaxially oriented liquid crystalline films by in situ photopolymerization. Various structural modifications on the 2‐(4‐cyanophenyl)fluorene core, which include alkyl chains at the 9‐position and elongation of the rigid core with one additional phenyl ring, have been investigated to generate emitters with adjusted liquid crystal compatibility, improved luminescence and dichroic properties. Polarized blue‐emitting films were produced that had an acceptable photostability, and it was found that the polarization emission was better for samples with low (5%) cross‐linker contents. Polarization of the luminescence was favored by the liquid crystalline properties of the luminophore. In addition, the detrimental effect of the alkyl substituent at the fluorene core on the mesomorphism and on the emission polarization can be overcome by lengthening the π‐system. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4804–4817, 2007     

Generalized analytical expressions for the burning velocity in a combustion model with non-constant transport coefficients and several specific heats

We derive new expressions to estimate the burning velocity of a laminar gas flame in a simplified combustion model based on a one-step single reaction with transport coefficients (mass and heat) depending on temperature, and species with different specific heats. These new expressions generalize the bounds and approximations previously derived by Williams, von Karman, Zeldovich and Frank-Kamenetskii, Benguria and Depassier, and the matching asymptotic expansion method in a two zone model. The comparison of the flame speed predicted by these new analytical expressions with that numerically simulated by the full combustion model for a large variety of cases allows us to determine their range of validity. The upper bound based on the Benguria and Depassier method provides very good approximations for the actual propagation speed of combustion flames, being substantially better than the asymptotic method used in the recent papers.     

Stability in a population model without random deaths by the Verhulst factor

A large amount of population models use the concept of a carrying capacity. Simulated populations are bounded by invoking finite resources through a survival probability, commonly referred to as the Verhulst factor. The fact, however, that resources are not easily accounted for in actual biological systems makes the carrying capacity parameter ill-defined. Henceforth, we deem it essential to consider cases for which the parameter is unnecessary. This work demonstrates the possibility of Verhulst-free steady states using the Penna aging model, with one semelparous birth per adult. Stable populations are obtained by setting a mutation threshold that is higher than the reproduction age.     

Gibbs–Jaynes Entropy Versus Relative Entropy

The maximum entropy formalism developed by Jaynes determines the relevant ensemble in nonequilibrium statistical mechanics by maximising the entropy functional subject to the constraints imposed by the available information. We present an alternative derivation of the relevant ensemble based on the Kullback–Leibler divergence from equilibrium. If the equilibrium ensemble is already known, then calculation of the relevant ensemble is considerably simplified. The constraints must be chosen with care in order to avoid contradictions between the two alternative derivations. The relative entropy functional measures how much a distribution departs from equilibrium. Therefore, it provides a distinct approach to the calculation of statistical ensembles that might be applicable to situations in which the formalism presented by Jaynes performs poorly (such as non-ergodic dynamical systems).