Yutaka Yamamoto

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This paper studies matrix fractional representation for impulse responses of a certain class of infinite-dimensional linear systems which contains, in particular, delay-differential systems. Such impulse responses are called pseudo-rational in this paper. This fractional representation is effectively used to derive concrete function space models from the(More)
This paper proposes a min-max design of noise-shaping delta-sigma modulators. We first characterize the all stabilizing loop-filters for a linearized modulator model. By this characterization, we formulate the design problem of lowpass, bandpass, and multi-band modulators as minimization of the maximum magnitude of the noise transfer function (NTF) in fixed(More)
This paper studies the relationships among various stability notions for a class of infinite-dimensional systems, which contains a class of systems not covered by the existing method, e.g., those having infinitely many unstable poles. It is proved thai i) internal L2-stability and exponential stability are equivalent; ii) internal stability implies(More)
Estrogen receptor (ER) alpha plays a crucial role in normal breast development and has also been linked to mammary carcinogenesis and clinical outcome in breast cancer patients. However, the molecular mechanisms controlling the expression of ERalpha are as yet not fully understood. Gene amplification is one of the important factors regulating protein(More)
This paper proves that the frequency response gains of fast-sample/fasthold approximations of a sampled-data system converge to that of the original system as the sampling rate gets faster. While this may appear to hold trivially, there is a serious technical difficulty, and the proof is indeed nontrivial. It is also guaranteed that this convergence is(More)
Purpose: Anaplastic thyroid cancer (ATC) is one of the most aggressive malignancies. Although multidisciplinary treatments have been introduced, patients with this disease rarely survive longer than 1 year. These findings prompted us to investigate the antitumor activity of molecular targeting agents in thyroid cancer cells. Methods: Two tyrosine kinase(More)