A representation theorem on a filtering model with first-passage-type stopping time

We present a representation theorem for a filtering model with first-passage-type stopping time. The model is constructed from two unobservable processes and one observable process that is under the influence of two unobservable processes.A filter is constructed using Brownian motion in the observable process and a first-passage-type stopping time in an unobservable process.Though our theorems are similar to those of Nakagawa\cite{Nakagawa}, we do not use pinned Brownian motion measure, which is difficult to deal with. In addition, we describe a representation theorem for another filtration that was not discussed by Nakagaw

Selective Sampling for Example-based Word Sense Disambiguation

This paper proposes an efficient example sampling method for example-based word sense disambiguation systems. To construct a database of practical size, a considerable overhead for manual sense disambiguation (overhead for supervision) is required. In addition, the time complexity of searching a large-sized database poses a considerable problem (overhead for search). To counter these problems, our method selectively samples a smaller-sized effective subset from a given example set for use in word sense disambiguation. Our method is characterized by the reliance on the notion of training utility: the degree to which each example is informative for future example sampling when used for the training of the system. The system progressively collects examples by selecting those with greatest utility. The paper reports the effectiveness of our method through experiments on about one thousand sentences. Compared to experiments with other example sampling methods, our method reduced both the overhead for supervision and the overhead for search, without the degeneration of the performance of the system.Comment: 25 pages, 14 Postscript figure

Recent topics in fibrodysplasia ossificans progressiva

AbstractFibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant disorder characterized by progressive heterotopic bone formation in skeletal muscle tissue. Patients with FOP show malformed digits, osteochondroma, and other skeletal abnormalities due to abnormal patterning during development. Heterozygous mutations in the Activin A receptor type I (ACVR1) gene, which encodes the bone morphogenetic protein (BMP) type I receptor ALK2, have been identified in not only typical FOP patients but also patients with unusually mild or severe clinical features. The serine/threonine kinase activity of ALK2 may be constitutively activated by mutations in the GS domain or the kinase domain. Based on these findings, selective small chemical inhibitors and allele-specific RNAi approaches for mutant ALK2 have been developed for preventing heterotopic bone formation in FOP. Other novel treatments have also been reported to block heterotopic bone formation in patients with FOP. These findings open the door to the next step in FOP treatment and related research

A fluctuation-response relation of many Brownian particles under non-equilibrium conditions

We study many interacting Brownian particles under a tilted periodic potential. We numerically measure the linear response coefficient of the density field by applying a slowly varying potential transversal to the tilted direction. In equilibrium cases, the linear response coefficient is related to the intensity of density fluctuations in a universal manner, which is called a fluctuation-response relation. We then report numerical evidence that this relation holds even in non-equilibrium cases. This result suggests that Einstein's formula on density fluctuations can be extended to driven diffusive systems when the slowly varying potential is applied in a direction transversal to the driving force.Comment: 5 pages, 5 figure