Fragile states

The concretions arising from the two sources mentioned above, may be up to 15 cm thick and must be removed prior to any conservation method being carried out. This has to be done carefully as it is very easy to cause severe damage to the artefact particularly if it is in a very fragile state. 

Mass spectrometry requires that the material being studied be converted into a vapor. Great strides have been taken in recent years to address this problem, especially in enticing large, thermally fragile (bio)molecules into the vapor state. Matrix assisted laser ionization-desorption (MALDI) and electrospray ionization (ESI) are two current forefront methods that accomplish this task. Even components of bacteria and intact viruses are being examined with these approaches. John B. Fenn and Koichi Tanaka shared in the award of a Nobel Prize in 2002 for their respective contributions to development of electrospray ionization and soft laser desorption. 

Whereas 3c/4e hypervalent interactions (4.77) tend to be relatively uncommon and fragile in main-group compounds (often leading to transition states for nucleophilic displacement reactions, rather than stable equilibrium species), the corresponding interactions in transition-metal coordination compounds are ubiquitous and robust. The far higher prevalence of hypervalent co-bonding in transition-metal chemistry may be attributed to three major factors. 

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