Phase transitions in one dimension: are they all driven by domain walls?

Two known distinct examples of one-dimensional systems which are known to exhibit a phase transition are critically examined: (A) a lattice model with harmonic nearest-neighbor elastic interactions and an on-site Morse potential, and (B) the ferromagnetic, spin 1/2 Ising model with long-range pair interactions varying as the inverse square of the distance between pairs. In both cases it can be shown that the domain wall configurations become entropically stable at, or very near, the critical temperature. This might provide a "positive" criterion for the occurrence of a phase transition in one-dimensional systems.Comment: 9 pages, 3 figures. To appear in a special volume of Physica D (Serge Aubry 60th birthday symposium

Cleaning of water-gilded surfaces using hydro- and solvent-gels

This paper describes the implementation of three customized gels on a 19th century panel painting for the removal of its degraded natural resin varnish from a water-gilded surface and a complex solvent-sensitive stratigraphic construction over the gilded substrate. At first, the varnish was unsoiled with a typical hydrogel that was composed of an aqueous phase buffered at pH 5.5 with sodium acetate, poly(ethylene glycol) p-(1,1,3,3-tetramethylbutyl)-phenyl ether surfactant and hydroxy-prorylmethyl cellulose. The removal of the entire aged varnish was facilitated with a microemulsion of an aqueous phase buffered at pH 8.5 with triethanolaminate, a fatty phase of a mineral spirit - benzyl alcohol solution and a polyoxy-ethylene(23)lauryl ether surfactant, altogether incorporated in a viscous gel generated from the dissolution of a polyacrylic acid in poly(oxy-1,2-ethanediyl) cocoalkylamine surfactant. The third gel, which was based on a polyacrylic acid of higher viscosity and incorporating a microemulsion of the same aqueous phase (pH 8.5) as in the second gel, and a fatty phase made of benzyl alcohol and a polyoxyethylene(23)lauryl ether surfactant, enabled the selective removal of the degraded varnish over the elaborate gilded area with a composite stratigraphy over the golden leaf. Fourier transform infrared spectroscopy and UV fluorescence imaging were employed for the analysis of the aged varnish and the monitoring of the cleaning procedure, respectively. The conservation procedure determined the effectiveness of the customized gels employed for this special implementation. The fine preservation of the water-gildings and of the complex solvent-sensitive stratigraphic construction of the painted surface was a satisfactory outcome

Nonlinear structures and thermodynamic instabilities in a one-dimensional lattice system

The equilibrium states of the discrete Peyrard-Bishop Hamiltonian with one end fixed are computed exactly from the two-dimensional nonlinear Morse map. These exact nonlinear structures are interpreted as domain walls (DW), interpolating between bound and unbound segments of the chain. The free energy of the DWs is calculated to leading order beyond the Gaussian approximation. Thermodynamic instabilities (e.g. DNA unzipping and/or thermal denaturation) can be understood in terms of DW formation.Comment: 4 pages, 5 figures, to appear in Phys. Rev. Let

Laser Cleaning Applications for Religious Objects

Laser clearing is nowadays employed successfully for the removal of unwanted layers of diverse chemical and physical nature from historical and religious monuments and objects. Significant research evolution has been made via close collaboration between scientists, conservators and curators. Several studies have shown that the maximum efficiency of the laser-induced divestment can be obtained in parallel with the safety of the preservable artefact. The examples discussed herein and the numerous case studies presented in the biennial international LACONA conferences demonstrate that in the future laser cleaning may be the leading technique for the preservation of churches, historical monuments and religious objects with great cultural heritage significance

A design model for punching shear of FRP-reinforced slab-column connections

The overall aim of this paper is to develop a unified design method for the punching shear resistance of slab-column connections irrespective of the type of internal reinforcement. In the first part of the paper a design model for the punching shear resistance of concrete slab-column connections reinforced with fibre-reinforced polymers (FRP) is proposed. This design model is based on the authors’ theoretical analysis for such slabs, which considers the physical behavior of the connections under load. The effects of the inherent linear brittle response, the lower elastic modulus and the different bond features, as compared to steel, of the FRP reinforcement are all accounted for in the present study. The proposed model does not incorporate any fitting factors to match the theory to the trend of the available FRP slab test results. The excellent agreement between the predicted and published test results should give confidence to engineers and designers in using FRP as a sound structural reinforcement for slab-column connections. It is then shown that the proposed design model for FRP slabs and the previous model of the authors for steel reinforced slabs are both identical in nature and structure, thus constituting a unified approach to design for punching shear in slabs. On the basis of the unified model comparison and correlation between an FRP slab and a reference steel reinforced slab, confirmed by the available test results, are presented. The unified model also enables the development of a more rational and reliable equivalent steel reinforcement ratio which can be applied to existing code equations for steel reinforced slabs to estimate the punching resistance of FRP-reinforced slabs

Studies on Woolen Threads from Historical Tapestries

Fourier transform (FTIR) attenuated total reflectance (ATR)and second derivative spectroscopy has been used for the first time to evaluate the state of degradation in historical woollen threads from the collections of Flemish tapestries (15th-17th centuries) in the Royal Palace, Madrid, Hampton Court Palace, and museums in Brussels. The work was performed as part of the EC-funded project ‘Monitoring of Damage in Historic Tapestries’, also known as the MODHT project. The overall aim was to develop procedures for recognising tapestries at risk and provide analysis for informing collection care. Prior to the testing of the historical threads, model tapestries were prepared according to traditional techniques of weaving and dyeing. They were then subjected to accelerated light ageing. This paper reports on the part of the MODHT project in which ATR-FTIR was used. It was selected since it is a non-destructive method, and also because it has previously been used to study the oxidation products of cystine in wool and to provide a semi-quantitative assessment of change. Evaluation was conducted on the model tapestries, and the cysteic acid peak was selected as the marker for change, as it showed a systematic change with light ageing. The same marker was usedto assess the change in historical threads

Transferring intermediate technologies to rural enterprises in developing economies: a conceptual framework

This paper integrates the contributions from different branches of the technology transfer literature to identify enablers driving the transfer of intermediate or appropriate technologies to recipients in rural areas of developing economies. An in-depth analysis of the literature shows that many enablers identified in the literature focus on high technology transfers and are of limited relevance in the context of rural enterprises. Other important enablers in this specific setting are ignored or insufficiently considered. This paper proposes a framework comprising a specific set of enablers that facilitates technology transfer in rural enterprises in developing regional economies