Defining Degradability

The accessibility of the fullerenes [1] in macroscopic quantities [2] opened up the unprecedented opportunity to develop a rich three-dimensional chemistry of spherical and polyfunctional all carbon molecules. [3-8] A large multitude of fullerene derivatives like exohedral covalent addition products, salts, cluster opened and defined degradation products, heterofullerenes and endohedral derivatives can be imagined and numerous examples, especially of covalent adducts have been synthesized and characterized. [3-8] Within a few years the fullerenes became essential building blocks in organic chemistry. Most of the chemistry of fullerenes has so far been carried out with Ceo (1) with little work on C70 and few experiments with C76 and Cg4. This is simply due to the fact that Ceo... 

Addition and redox reactions lead to covalent exohedral adducts and salts, respectively. Subsequent transformations of specifically activated adducts pave the way to other classes of fullerene derivatives (Fig. 1). These are heterofuller-enes, defined degradation products or partial structures, open cage species and endohedral fullerenes. 

The combination of several factors defines degradation as thermo-oxidative, photo-oxidative or even thermo-photo-oxidative. 

Since the thermogravimetric curve of PVC (Figure 5.11) shows two well-defined degradation steps (maxima at 320°C and 450°C), it can be argued that the first weight loss step corresponds to the HCl evolution (theoretical content of HCl in PVC 58%, by weight), whereas the second degradation step would be due to the evolution of aromatic hydrocarbons. 

Corrosion is defined as the spontaneous degradation of a reactive material by an aggressive environment and, at least in the case of metals in condensed media, it occurs by the simultaneous occurrence of at least one anodic (metal oxidation) and one cathodic (e.g. reduction of dissolved oxygen) reaction. Because these partial reactions are charge-transfer processes, corrosion phenomena are essentially electrochemical in nature. Accordingly, it is not surprising that electrochanical techniques have been used extensively in the study of corrosion phenomena, both to determine the corrosion rate and to define degradation mechanisms. 

Haanappel, V.A.C., Rowekamp, B., Tropartz, C., Wesemeyer, H., Smith, M.J., and de Haart, L.G.J. (2008) Long-term endurance tests of single cells and defining degradation. In... 

In this formula, and are the correction factors for the individual change factors. Once we correct for all these factors, we can monitor the degradation of the corrected power or heat rate at base load conditions. We can define degradation factors as we did for the axial compressor efficiency and flow as ... 

Dicarboxylic acids Polyanhydrides are biocompatible and have well defined degradation characteristics. Degrades by hydrolysis of the anhydride linkage (surface degradation) (Leong et al. 1985 Uhrichetal. 1997)... 

Methanolysis of sodium or lithium clavulanate provides a high yield of the pyrrole (79) 52,53,54). Since the enamine (78) has also been isolated a fairly well defined degradative pathway for the formation of (79) can be postulated further verifying the fused p-lactam-oxazolidine structure of clavulanic acid. Rupture of the P-lactam followed by fragmentation of the oxazolidine (76) would lead to the keto acid (77) decarboxylation provides... 

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