On recursive Bayesian predictive distributions

A Bayesian framework is attractive in the context of prediction, but a fast recursive update of the predictive distribution has apparently been out of reach, in part because Monte Carlo methods are generally used to compute the predictive. This paper shows that online Bayesian prediction is possible by characterizing the Bayesian predictive update in terms of a bivariate copula, making it unnecessary to pass through the posterior to update the predictive. In standard models, the Bayesian predictive update corresponds to familiar choices of copula but, in nonparametric problems, the appropriate copula may not have a closed-form expression. In such cases, our new perspective suggests a fast recursive approximation to the predictive density, in the spirit of Newton's predictive recursion algorithm, but without requiring evaluation of normalizing constants. Consistency of the new algorithm is shown, and numerical examples demonstrate its quality performance in finite-samples compared to fully Bayesian and kernel methods.Comment: 22 pages, 3 figures, 3 table

Mapping of RNA- temperature-sensitive mutants of Sindbis virus: assignment of complementation groups A, B, and G to nonstructural proteins

Four complementation groups of temperature-sensitive (ts) mutants of Sindbis virus that fail to make RNA at the nonpermissive temperature are known, and we have previously shown that group F mutants have defects in nsP4. Here we map representatives of groups A, B, and G. Restriction fragments from a full-length clone of Sindbis virus, Toto1101, were replaced with the corresponding fragments from the various mutants. These hybrid plasmids were transcribed in vitro by SP6 RNA polymerase to produce infectious RNA transcripts, and the virus recovered was tested for temperature sensitivity. After each lesion was mapped to a specific region, cDNA clones of both mutants and revertants were sequenced in order to determine the precise nucleotide change responsible for each mutation. Synthesis of viral RNA and complementation by rescued mutants were also examined in order to study the phenotype of each mutation in a uniform genetic background. The single mutant of group B, ts11, had a defect in nsP1 (Ala-348 to Thr). All of the group A and group G mutants examined had lesions in nsP2 (Ala-517 to Thr in ts17, Cys-304 to Tyr in ts21, and Gly-736 to Ser in ts24 for three group A mutants, and Phe-509 to Leu in ts18 and Asp-522 to Asn in ts7 for two group G mutants). In addition, ts7 had a change in nsP3 (Phe-312 to Ser) which also rendered the virus temperature sensitive and RNA-. Thus, changes in any of the four nonstructural proteins can lead to failure to synthesize RNA at a nonpermissive temperature, indicating that all four are involved in RNA synthesis. From the results presented here and from previous results, several of the activities of the nonstructural proteins can be deduced. It appears that nsP1 may be involved in the initiation of minus-strand RNA synthesis. nsP2 appears to be involved in the initiation of 26S RNA synthesis, and in addition it appears to be a protease that cleaves the nonstructural polyprotein precursors. It may also be involved in shutoff of minus-strand RNA synthesis. nsP4 appears to function as the viral polymerase or elongation factor. The functions of nsP3 are as yet unresolved

The Impact of Domestic and Import Prices on U.S. Lamb Imports: A Production System Approach

As U.S. lamb imports increased relative to domestic production, and the relative share of chilled to frozen lamb imports increased, importers of chilled lamb have become less responsive to domestic and import prices, while the direct opposite is the case for frozen lamb imports. From 1990 to 2003, chilled lamb imports from Australia and New Zealand became less and less responsive to U.S. prices, and frozen imports became more responsive. Unconditional own-price elasticities also show that, over time, imports of chilled lamb became less responsive to import prices while frozen imports became more responsive to import prices.lamb, demand, imports, trade, import demand, production, International Relations/Trade,

Real-time, step-wise, electrical detection of protein molecules using dielectrophoretically aligned SWNT-film FET aptasensors

Aptamer functionalized addressable SWNT-film arrays between cantilever electrodes were successfully developed for biosensor applications. Dielectrophoretically aligned SWNT suspended films made possible highly specific and rapid detection of target proteins with a large binding surface area. Thrombin aptamer immobilized SWNT-film FET biosensor resulted in a real-time, label-free, and electrical detection of thrombin molecules down to a concentration of ca. 7 pM with a step-wise rapid response time of several seconds.X113338sciescopu