Bulking treatments reactive

In reactive bulking treatments, a chemical is covalently bonded to the cell wall. Cross-linking of the cell wall material may also occur. Such treatments sometimes swell the wood and sometimes cause it to shrink. Examples of reactive bulking treatments include alkylene oxides and impregnation with thermosetting resins. These treatments are essentially nonreversible, but they often improve the stiffness of the cell walls. As a result of their nonreversibility, the conservation community is very cautious about adopting such treatments. It is, however, likely that these methods will find some utility with very deteriorated objects that cannot be satisfactorily stabilized by more traditional techniques. 

Different mechanisms to explain the disinfection ability of photocatalysts have been proposed [136]. One of the first studies of Escherichia coli inactivation by photocatalytic Ti02 action suggested the lipid peroxidation reaction as the mechanism of bacterial death [137]. A recent study indicated that both degradation of formaldehyde and inactivation of E. coli depended on the amount of reactive oxygen species formed under irradiation [138]. The action with which viruses and bacteria are inactivated by Ti02 photocatalysts seems to involve various species, namely free hydroxyl radicals in the bulk solution for the former and free and surface-bound hydroxyl radicals and other oxygen reactive species for the latter [139]. Different factors were taken into account in a study of E. coli inactivation in addition to the presence of the photocatalyst treatment with H202, which enhanced the inactivation... 

The dual treatment in the Buhler botde-to-bottle process is an important aspect in food safety considerations. The bulk of the contaminants are removed in the extruder. However, the SSP process provides a back-up to remove any residual contaminants, which are now homogeneously distributed in the PET pellets. The cleaning becomes a well-defined and predictable diffusion controlled process, which is defined by pellet diameter, treatment temperature and time. The same parameters also regulate the SSP process. For products with similar reactivity, a known increase in molecular weight during the solid-state process will also provide a known cleaning efficiency. 

Not unexpectedly, predictions on reactivity and regiochemistry based on a FMO treatment can be overruled by steric effects (13). The change in reactivity may be illustrated by the following example 2-Phenylsulfonyl-norbomadiene reacts with 2-diazopropane at the electron-deficient C=C bond, as expected. However, 2-phenylsulfonyl-3-trimethylsilyl-norbomadiene reacts with the same dipole at the unsubstituted double bond, probably as a result of the steric bulk of the trimethylsilyl group (27). 

The continual evolution of the discipline of chemistry is reflected in our treatment of the elements. The careful reader will note that we have included articles for the first 104 elements the remainder of the elements are recently discovered or exist only as short-lived species and, accordingly, are not readily available for the usual chemical studies that reveal, for example, their bulk properties or reactivity and much of the standard chemistry that is of interest. Much of what little we know about the elements beyond 104 permits us to place these elements in their appropriate places in the periodic table, which nevertheless still turns out to be quite insightful from a chemical point of view. 

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