ABSTRACT
In cultural heritage, several initiatives are promoted to transfer the green chemistry in replacing traditional and toxic methods and products, and in ensuring safety of both artworks and restorers during cleaning operations. This study is aimed to establish the validity of new green solvents to replace toxic solvents, commonly used, to remove old paint varnishes. In particular, the research is focused on the use of acetals to remove old varnishes paintings. The acetals are common functional groups in natural products which are generated by reactions between alcohols and aldehydes. The tests were performed on four different resins (DAMAR, RETOUCHER, PVA and PMMA). Several samples were prepared to reproduce the common stratigraphy succession of the oil painting. The performances of the solvents were monitored by visible light/UV light, photography and optical microscopy, spectro-colorimetric analysis. Then, FTIR spectra of the cleaned surface have been acquired to detect the residues after cleaning.
Subject(s)
Paint/analysis , Paintings , Colorimetry , Solvents/chemistry , Spectrophotometry, InfraredABSTRACT
The cardiac responses of Oreochromis niloticus acclimated to 25 degrees C were assessed using ventricle strips mounted for isometric force recording (Fc) and in vivo heart rate (f(H)). f(H) increased progressively from 25 to 40 degrees C. At extracellular Ca(2+) concentrations of 1.25 and 9.25 mM, a transition from 25 to 40 degrees C resulted in a decreased Fc. At both 25 and 40 degrees C, Fc rose when [Ca(2+)] was increased from 1.25 to 9.25 mM. Fc remained constant at 72 and 120 contractions.min(-1) at 25 and 40 degrees C, respectively, and declined thereafter. The post-rest potentiation was not influenced by ryanodine, indicating that the sarcoplasmic reticulum is not important to the excitation-contraction coupling.
