A Bayes method for a monotone hazard rate via S-paths

A class of random hazard rates, which is defined as a mixture of an indicator kernel convolved with a completely random measure, is of interest. We provide an explicit characterization of the posterior distribution of this mixture hazard rate model via a finite mixture of S-paths. A closed and tractable Bayes estimator for the hazard rate is derived to be a finite sum over S-paths. The path characterization or the estimator is proved to be a Rao--Blackwellization of an existing partition characterization or partition-sum estimator. This accentuates the importance of S-paths in Bayesian modeling of monotone hazard rates. An efficient Markov chain Monte Carlo (MCMC) method is proposed to approximate this class of estimates. It is shown that S-path characterization also exists in modeling with covariates by a proportional hazard model, and the proposed algorithm again applies. Numerical results of the method are given to demonstrate its practicality and effectiveness.Comment: Published at http://dx.doi.org/10.1214/009053606000000047 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Deciphering the regulatory network of microRNAs in tuberculosis infected macrophages : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Genetics at Massey University, Albany, New Zealand

Tuberculosis is an infectious disease that is caused by Mycobacterium tuberculosis (Mtb), an intracellular pathogen that uses macrophages as a host for replication. The outcome of the disease depends highly on Mtb’s strategies to circumvent the immune responses of macrophages. MicroRNAs (miRNAs) are small regulatory RNAs that influence gene functions post-transcriptionally. Recent studies indicate that miRNAs have prominent roles in cellular host-pathogen interactions. The aim of this study is to advance our understanding of the regulatory mechanisms that control key miRNAs in mouse M1 macrophages during Mtb infection using network analysis. The study began with a construction of a mouse miRNA-centric regulatory network model by combining a network of miRNA-controlling transcription factors (TFs) with a miRNA target network. The final network places miRNAs at the center of a comprehensive regulatory network of TFs, miRNAs and their targets. This network represents a useful resource for investigating miRNA functions and their control. Subsequently, we populated the network with CAGE-derived expression data for either Mtb-infected mouse M1 macrophages or non-infected controls. We used network analysis to determine key regulatory elements during the infection process. As a result, we identified a core set of TFs and miRNAs, which are likely critical regulatory elements during M1 macrophage host and Mtb interactions. Our results also demonstrate that among the core set of regulatory elements three highly activated miRNAs, mmu-mir-149, mmu-mir-449a, and mmu-mir-449b, work in unison with mmu-mir-155, the top-ranked miRNA. They co-regulate a set of downstream tuberculosis immune response related genes. Four top-ranked TFs, Fosl1, Bhlhe40, Egr1, and Egr2, were identified that they transcriptionally control this group of miRNAs. The TFs and miRNAs, together with their targets constitute a mmu-mir-155 regulatory sub-network. Our results also imply that Bhlhe40 is likely an important TF that modulates the activities of the mmu-mir-155 regulatory sub-network. Bhlhe40 and the mmu-mir-155 regulatory sub-network may be exploited by Mtb to manipulate the host immune defense for advancing survival interests. The findings of this study provide new insights into the host immune regulatory mechanisms of activated macrophages that are essential to control tuberculosis

On the sustainability of currency boards : evidence from Argentina and Hong Kong : [Version: September 2008]

This paper examines the sustainability of the currency board arrangements in Argentina and Hong Kong. We employ a Markov switching model with two regimes to infer the exchange rate pressure due to economic fundamentals and market expectations. The empirical results suggest that economic fundamentals and expectations are key determinants of a currency board’s sustainability. We also show that the government’s credibility played a more important role in Argentina than in Hong Kong. The trade surplus, real exchange rate and inflation rate were more important drivers of the sustainability of the Hong Kong currency board

Train schedule coordination at an interchange station through agent negotiation

In open railway markets, coordinating train schedules at an interchange station requires negotiation between two independent train operating companies to resolve their operational conflicts. This paper models the stakeholders as software agents and proposes an agent negotiation model to study their interaction. Three negotiation strategies have been devised to represent the possible objectives of the stakeholders, and they determine the behavior in proposing offers to the proponent. Empirical simulation results confirm that the use of the proposed negotiation strategies lead to outcomes that are consistent with the objectives of the stakeholders

Capital Income Taxation Revisited: The Role of Information Asymmetry in the Credit Market

This paper reexamines the issue of optimal capital income taxation in an endogenous growth model with overlapping generations. By assuming costly state verification for capital producing projects, we show that the presence of the information asymmetry creates inefficiency in the credit market by driving a wedge between the rate of interest and the rate of transformation. In this context, we further show that capital income taxation worsens the credit market distortions and, subsequently, induces greater adverse effects on growth and welfare. Taken together, our analysis suggests that the presence of informational frictions in the credit market introduces a rationale for more conservative taxation on capital income from both growth and welfare perspectives.Capital income taxation; Asymmetric information; Economic growth