1,481 research outputs found
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
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