Preliminary study on analysis and removal of wax from a Carrara marble statue

Abstract

This preliminary study has mainly focused on the wax identification by nuclear magnetic resonance (NMR) and removal. Wax is used for many purposes in the field of art as protective coatings on wooden, stone or metal objects. From the comparison of the spectra H NMR and in particular with the correspondence of the resonance peaks of the samples taken from the statue and beeswax and paraffin, we can conclude that the wax applied on the statue surface is beeswax. From our data, it can be concluded that, to remove the beeswax, from any stone support, the more effective solvent is the mixture of cyclohexane/ethyl acetate. The removal percentages ranged from 19 to 99%. Lower percentages of removal have been observed in the case of yellow marble, probably because of its high porosity. We can affirm that, this solvent mixture can be employed in real art objects using cotton swabs to remove protective wax.     

Neuroprotective effect of peroxiredoxin 6 against hypoxia-induced retinal ganglion cell damage

Background  

The ability to respond to changes in the extra-intracellular environment is prerequisite for cell survival. Cellular responses to the environment include elevating defense systems, such as the antioxidant defense system. Hypoxia-evoked reactive oxygen species (ROS)-driven oxidative stress is an underlying mechanism of retinal ganglion cell (RGC) death that leads to blinding disorders. The protein peroxiredoxin 6 (PRDX6) plays a pleiotropic role in negatively regulating death signaling in response to stressors, and thereby stabilizes cellular homeostasis.     

Nickel(0)-mediated [2+2+1] cyclization reaction of chromium carbene complexes and internal alkynes

Alkyl, aryl, and heteroaryl chromium Fischer carbene complexes undergo Ni(0)-mediated [2+2+1] cyclization reaction with internal unactivated and electron-poor internal alkynes to yield highly substituted cyclopentadienes with complete regioselectivity in most cases. The intramolecular version of this cyclization has been accomplished with 1,8-diphenyl-1,7-octadiyne to produce indene derivatives. This three-component [2+2+1] cyclization represents a very uncommon process in the chemistry of Fischer carbene complexes.     

Nachweis und Bestimmung des Bleis

Ohne Zusammenfassung     

Nickel-Catalyzed Csp2−OMe Functionalization for Chemoselective Aromatic Homologation En Route to Nanographenes

A Ni-catalyzed C_sp2−OMe ortho-functionalization methodology to form chemoselectively alkyne monoannulation or aromatic homologation products is reported as a novel protocol towards the valorisation of substrates containing C_sp2−OMe units. Double activation of C_sp2−OMe and C_sp2−F bonds is also demonstrated. Further use of aromatic homologation products towards the synthesis of nanographene-like compounds is described.