The Potential of On-Chip Multiprocessing for QCD Machines

We explore the opportunities offered by current and forthcoming VLSI technologies to on-chip multiprocessing for Quantum Chromo Dynamics (QCD), a computational grand challenge for which over half a dozen specialized machines have been developed over the last two decades. Based on a careful study of the information exchange requirements of QCD both across the network and within the memory system, we derive the optimal partition of die area between storage and functional units. We show that a scalable chip organization holds the promise to deliver from hundreds to thousands flop per cycle as VLSI feature size scales down from 90 nm to 20 nm, over the next dozen years

Modulation of exon skipping by high-affinity hnRNP A1-binding sites and by intron elements that repress splice site utilization.

The RNA-binding protein hnRNP A1 is a splicing regulator produced by exclusion of alternative exon 7B from the A1 pre-mRNA. Each intron flanking exon 7B contains a high-affinity A1-binding site. The A1-binding elements promote exon skipping in vivo, activate distal 5' splice site selection in vitro and improve the responsiveness of pre-mRNAs to increases in the concentration of A1. Whereas the glycine-rich C-terminal domain of A1 is not required for binding, it is essential to activate the distal 5' splice site. Because A1 complexes can interact simultaneously with two A1-binding sites, we propose that an interaction between bound A1 proteins facilitates the pairing of distant splice sites. Based on the distribution of putative A1-binding sites in various pre-mRNAs, an A1-mediated change in pre-mRNA conformation may help define the borders of mammalian introns. We also identify an intron element which represses the 3' splice site of exon 7B. The activity of this element is mediated by a factor distinct from A1. Our results suggest that exon 7B skipping results from the concerted action of several intron elements that modulate splice site recognition and pairing