Mechanisms of thermal decomposition of organic monolayers grafted on (111) silicon.

The thermal stability of different organic layers on silicon has been investigated by in situ infrared spectroscopy, using a specially designed variable-temperature cell. The monolayers were covalently grafted onto atomically flat (111) hydrogenated silicon surfaces through the (photochemical or catalytic) hydrosilylation of 1-decene, heptadecafluoro-1-decene or undecylenic acid. In contrast to alkyl monolayers, which desorb as alkene chains around 300 degrees C by the breaking of the Si-C bond through a beta-hydride elimination mechanism, the alkyl layers functionalized with a carboxylic acid terminal group undergo successive chemical transformations. At 200-250 degrees C, the carboxyl end groups couple forming anhydrides, which subsequently decompose at 250-300 degrees C by loss of the functional group. In the case of fluorinated alkyl chains, the C-C bond located between CH2 and CF2 units is first broken at 250-300 degrees C. In either case, the remaining alkyl layer is stable up to 350 degrees C, which is accounted for by a kinetic model involving chain pairing on the surface.

Effective interventions for reading disability.

A simple, readily accessible, and inexpensive intervention which produces immediate improvements in the reading comprehension abilities of reading-disabled children has been found. The intervention consists of colored overlays, or overlays which reduce the contrast of printed materials. This intervention produces reading comprehension gains in approximately 80 percent of the reading-disabled children tested.