Architecture and Building Technology Department

Es bien conocido el empleo de trazados a tamaño natural, denominados monteas, como paso previo a la ejecución de construcciones pétreas. Los autores argumentan que estas monteas aportan datos acerca de las técnicas de cantería que no facilitan ni las propias piezas, ni los tratados y manuscritos, incluso los más cercanos a la práctica constructiva. En concreto, examinan dos monteas renacentistas en la catedral de Murcia: una de ellas hallada en 1999 bajo el altar de la recapilla de Junterón y otra recientemente aparecida en los muros de la sacristía catedralicia al desmontar la cajonería quinientista. Tras comparar ambas monteas con las piezas de cantería correspondientes, los autores analizan en qué medida ambas monteas se separan de los métodos estereotómicos propuestos por la literatura hispánica de la cantería.

Full-scale tracings, drawn in plaster surfaces or engraved in stone walls and floors, were used frequently in Renaissance construction to control the execution of ashlar masonry.  In many occasions, these tracings furnished the shape of the templates used in the dressing process, either in true size or orthogonal projection. A large example of these tracings appeared in 2009 in the vestry of Murcia Cathedral, when the sacristy drawers were disassembled to execute a conservation treatment against woodworm. At first sight, the tracing seemed to be related to the vault over the vestry, built in 1525 by Jacopo Torni l’Indaco, one of the first examples of ashlar sail vaults in Europe; a number of surveys confirmed that the tracing corresponds with the vault quite precisely. In this study, after an introductory section dealing with tracings and dressing techniques, the authors explain the measuring methods used in the surveys, describe the tracing, compare the tracing with the built vault, and discuss the relevance of the tracing, in order to advance knowledge of the evolution of European stonecutting.

A first time report on the reactive sensing capabilities of polyaniline (PANI) is presented. Microfibrous silkfibroin mats were coated with polyaniline (PANI) through in situ chemical polymerization. The mat givesclosed coulovoltammetric responses in acidic aqueous solution, indicating that only reversible PANI oxi-dation/reduction reactions occur. Inside the reversible range the chronopotentiometric responses changewith (sense) the reaction variables: electrolyte concentration, pH, temperature and driving current. Thepotential of the materials, or the consumed electrical energy, for a constant reaction time follow the linearor semilogarithmic relationships with each of the experimental variables predicted by the electrochem-ical kinetics. The reversible charge from the closed coulovoltammetric loop also senses the chemical orthermal energetic conditions of the reaction acting on the conformational movements getting deeperoxidation states for rising energetic working conditions.

The reactivity of conducting polymers can be exploited to generate new sensors of their working conditions.
Here, we verified that the reactive (redox) nature of a chemically generated polypyrrole (PPy) on a
polyurethane (PU) microfibrous mat senses the surrounding (physical and chemical) conditions. The (PU/
PPy) microfibrous mat was obtained by in situ chemical polymerization of pyrrole from aqueous medium
using tetra fluoromethane sulfonate as dopant and a polyurethane microfibrous mat, produced by electrospinning
of a PU solution, as template. SEM images showed the homogenous growth of nanostructured
PPy on each fiber of the PU microfibrous mat. The cyclic voltammogram (CV) revealed an oxidation peak
at 0.22 V and a reduction peak at 0.08 V vs Ag/AgCl, indicating that the electrochemical activity of the
material is imparted by PPy component. Sensing abilities with regard to the surrounding conditions were
monitored through chronopotentiometric (CP) responses between two defined oxidation states. The consumed
electrical energy during the electrochemical reactions was a linear function of the applied currents
or of the working temperature (the reaction material is a current sensor and a temperature sensor) and a
semi-logarithmic dependence of the electrolyte concentration (concentration sensor). These sensing abilities
are explained on the basis of recently developed theories on the reactivity of conducting polymers.

Conducting polymers are soft, wet and reactive gels capable of mimicking biological functions. They are the
electrochemomechanical actuators having the ability to sense the surrounding variables simultaneously. The
sensing and actuating signals are sent/received back through the same two connecting wires in these materials. The
sensing ability is a general property of all conducting polymers arises from the unique electrochemical reaction
taking place in them. This sensing ability is verified for two different conducting polymers here – for an
electrochemically generated polypyrrole triple layer bending actuator exchanging cations and for a chemically
generated polytoluidine linear actuator exchanging anions. The configuration of the polypyrrole actuator device
corresponds to polypyrrole-dodecyl benzene sulfonate (pPy-DBS) film/tape/ pPy-DBS film in which the film on
one side of the triple layer is acted as anode and the film on the other side acted as cathode simultaneously, and the
films interchanged their role when move in the opposite direction. The polytoluidine linear actuator was
fabricated using a hydrgel microfiber through in situ chemical polymerization. The sensing characteristics of these
two actuators were studied as a function of their working conditions: applied current, electrolyte concentration and
temperature in aqueous electrolytes. The chronopotentiometric responses were studied by applying square electrical
currents for a specified time. For the pPy actuator it was set to produce angular movement of ± 45º by the free end
of the actuator, consuming constant charges of 60 mC. In both the actuators the evolution of the muscle potential
along the electrical current cycle was found to be a function of chemical and physical variables acting on the
polymer reaction rates: electrolyte concentration, temperature or driving electrical current. The muscle potential
evolved decreases with increasing electrolyte concentrations, increasing temperatures or decreasing driving
electrical currents. The electrical energy consumed during reaction was a linear function of the working
temperature or of the driving electrical current and a double logarithmic function of the electrolyte concentration.
Thus, the conducting polymer based actuators exchanging cations or anions during electrical current flow is a
sensor of the working physical and chemical conditions which is a general property of all conducting polymers.