Jie Zhang

Poly(ADP‐ribose) polymerase‐1 (PARP‐1) safeguards genomic integrity by limiting sister chromatid exchanges. Overstimulation of PARP‐1 by extensive DNA damage, however, can result in cell death, as prolonged PARP‐1 activation depletes NAD+, a substrate, and elevates nicotinamide, a product. The decline of NAD+ and the rise of nicotinamide may downregulate the activity of Sir2, the NAD+‐dependent deacetylases, because deacetylation by Sir2 is dependent on high concentration of NAD+ and inhibited by physiologic level of nicotinamide. The Sir2 deacetylase family has been implicated in mediating gene silencing, longevity and genome stability. It is conceivable that poly(ADP‐ribosyl)ation by PARP‐1, which is induced by DNA damage, could modulate protein deacetylation by Sir2 via the NAD+/nicotinamide connection. The possible linkage of the two ancient pathways that mediate broad biological activities may spell profound evolutionary roles for the conserved PARP‐1 and Sir2 gene families in multicellular eukaryotes. BioEssays 25:808–814, 2003. © 2003 Wiley Periodicals, Inc.

Bakhtin’s social semiotics, Lotman’s structural literary semiotics, and Uspenskij’s linguistic cultural semiotics are the three important theoretical cornerstones of the mansion of semiotics in the former Soviet Union, whose influences have long gone beyond the territory of the former Soviet Union, and have attracted widespread attention of the literary and semiotic circle from China and the rest of the world as well. However, researches so far have been mainly separate studies of their distinct theories, while a comparative study of the characteristics of Bakhtin, Lotman, and Uspenskij’s theories and methodologies has not been initiated. This paper attempts to compare the Russian troika’s conceptions and research methodologies of semiotics, and explores how they reach the same goal of the study of social-cultural system from different approaches — linguistics and trans-linguistics. This paper further reveals how they break the thinking mode of dualism and construct a pluralistic critical mode, and finally points out the contribution they have made to semiotics and the overall studies of humanities and social sciences.

Given the rapid growth of participatory media content such as blogs, there is a need to design personalized recommender systems to recommend only useful content to users. We be- lieve that in addition to producing useful recommendations, certain insights from media research such as simplification and opinion diversity in recommendations should form the foundations of such recommender systems, so that the be- havior of the systems can be understood more closely, and modified if necessary. We propose and evaluate such a sys- tem based on a Bayesian user-model. We use the underlying social network of blog authors and readers to model the pref- erence features for individual users. The initial results of our proposed solution are encouraging, and set the agenda for fu- ture research. Introduction