limitations of our cognitive system? Or are errors indispensable parts of every intelligent system? From the first perspective, all errors are at best unnecessary and at worst harmful. Consider an error commonly made by children. When asked to find the sum of 1/2 and 1/3. the answer is often 2/5. This is called the freshman error of adding numerators and adding denominators {Silver. 1986). But ...

A symbol is a pattern (of physical marks, electromagnetic energy, etc.) which denotes, designates, or otherwise has meaning. The notion that intelligence requires the use and manipulation of symbols, and that humans are therefore symbol systems, has been extremely in uential in arti cial intelligence. keywords: symbol, reasoning, intelligence, representation, logic This article has two parts. W...

Alpha-2-macroglobulin (alpha 2M) may function as a proteinase inhibitor in vivo. Levels of this protein are decreased in sepsis, but the reason these levels are low is unknown. Therefore, we analyzed the behavior of alpha 2M in a baboon model for sepsis. Upon challenge with a lethal (4 baboons) or a sublethal (10 baboons) dose of Escherichia coli, levels of inactivated alpha 2M (i alpha 2M) ste...

lanthanide(iii) chloro complexes of 4[n-(4’-hydroxy-3’-methoxybenzalidene) amino] antipyrine semicarbazone (hmbaaps) (i) and 4[n-(3’,4’,5’-trimethoxybenzalidene) amino] antipyrine semicarbazone (tmbaaps) (ii) with the general composition lncl3.2l (ln = la, pr, nd, sm, gd, tb, dy or ho; l = hmbaaps or tmbaaps) are reported. all the complexes were synthesized in ethanolic medium and refluxed the ...

The complexation of an arene to a chromium tricarbonyl unit changes its chemical behavior, giving rise to unprecedented transformations. The electron-withdrawing effect of the unit allows efficient nucleophilic attack (S(N)Ar and dearomatization reactions), stabilizes negative charges in benzylic positions and activates C(Ar)-halogen bonds for cross-coupling reactions. In addition, the Cr(CO)(3...