We compare the performance of two database selection algorithms reported in the literature. Their performance is compared using a common testbed designed specifically for database selection techniques. The testbed is a decomposition of the TREC TIPSTER data into 236 subcollections. The databases from our testbed were ranked using both the gGlOSS and CORI techniques and compared to a baseline derived from TREC relevance judgements. We examined the degree to which CORI and gGlOSS approximate this baseline. Our results con rm our earlier observation that the gGlOSS Ideall ranks do not estimate relevancebased ranks well. We also nd that CORI is a uniformly better estimator of relevance-based ranks than gGlOSS for the test environment used in this study. Part of the advantage of the CORI algorithm can be explained by a strong correlation between gGlOSS and a size-based baseline SBR. We also nd that CORI produces consistently accurate rankings on testbeds ranging from 100 921 sites. However for a given level of recall, search e ort appears to scale linearly with the number of databases.

The molecular mechanism of apatite formation on bioactive glass surface is studied using the techniques of XRD, EDX, SEM, FT-IR, and solid-state 31 P NMR. Using the sol-gel method a bioactive glass system containing glass beads of 2 to 3 microns in size is prepared with the composition containing 30% CaO -70% SiO 2 . Our experimental data support the apatite formation mechanism proposed by Hench concerning the precipitation and crystallization of calcium phosphate. The phosphate ions initially deposited on the glass surface are largely in amorphous phase and have substantial amount of water molecules in the surrounding. As the soaking time in simulated body fluid increases, some of the water molecules diffuse out of the phosphate lattice, leading to the formation of a crystalline phase. Our data show that the structure of the crystalline phase is different from type B carbonate apatite but similar to hydroxyapatite.

Biomolecular self-assemblies are of great interest to nanotechnologists because of their functional versatility and their biocompatibility. Over the past decade, sophisticated single-component nanostructures composed exclusively of nucleic acids, peptides and proteins have been reported, and these nanostructures have been used in a wide range of applications, from drug delivery to molecular computing. Despite these successes, the development of hybrid co-assemblies of nucleic acids and proteins has remained elusive. Here we use computational protein design to create a protein-DNA co-assembling nanomaterial whose assembly is driven via non-covalent interactions. To achieve this, a homodimerization interface is engineered onto the Drosophila Engrailed homeodomain (ENH), allowing the dimerized protein complex to bind to two double-stranded DNA (dsDNA) molecules. By varying the arrangement of protein-binding sites on the dsDNA, an irregular bulk nanoparticle or a nanowire with single-molecule width can be spontaneously formed by mixing the protein and dsDNA building blocks. We characterize the protein-DNA nanowire using fluorescence microscopy, atomic force microscopy and X-ray crystallography, confirming that the nanowire is formed via the proposed mechanism. This work lays the foundation for the development of new classes of protein-DNA hybrid materials. Further applications can be explored by incorporating DNA origami, DNA aptamers and/or peptide epitopes into the protein-DNA framework presented here.

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