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The photoisomerization of disperse red 1 (DR1) in polymethylmethacrylate thin films is demonstrated by monitoring the refractive index variations by the attenuated total reflection method. Absorption spectrum measurements give a confirmation of this phenomenon. The kinetics of photoisomerization and of thermal relaxation are nonexponential. Some other molecules are studied. As in solution, azobenzene derivatives (N—N) produce reversible isomerization while dimethylaminonitrostilbene, a stilbene derivative (C—C), exhibits no thermal cis→trans relaxation.

We review the 'skill-biased technological change (SBTC) versus North-South trade (NST)' debate in order to explain widening wage inequality between skilled and unskilled workers. The traditional explanations based on exogenous SBTC and on the North-South Heckscher-Ohlin-Samuelson approach, as well as the early estimates that diagnosed a clear prevalence of the former, are firstly exposed and discussed. A presentation is then made of the recent theoretical literature that endogenizes SBTC, introduces new channels of impacts from NST, and combines both explanations. Finally, the current estimates show that (i) both explanations are relevant, (ii) their impacts differ according to industries and countries, (iii) outsourcing is the main vector of impact from NST and (iv) SBTC and NST interact.

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