Tissue biocompatibility of cellulose and its derivatives was examined in two in vivo tests, one for absorbance by living tissue and one for foreign body reaction. The samples examined were regenerated celluloses and cellulose derivatives: methyl cellulose, ethyl cellulose, aminoethyl cellulose, hydroxyethyl cellulose, and cellulosic polyion complexes. The in vivo absorbance by living tissue was found to depend on the degree of crystallinity and the chemical structure of the sample. The foreign body reaction was relatively mild for all the samples examined, showing that cellulose can be converted to biocompatible materials by physical and/or chemical transformation.

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This paper assesses the impact of the September 11 terrorist attacks and its after-effects on U.S. airline demand. Using monthly time-series data from 1986 to 2003, we find that September 11 resulted in both a negative transitory shock of over 30% and an ongoing negative demand shock amounting to roughly 7.4% of pre-September 11 demand. This ongoing demand shock has yet to dissipate (as of November 2003) and cannot be explained by economic, seasonal, or other factors.