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Search Results: 1 - 10 of 569 matches for " Hiroko Nagahara "
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Theoretical Emission Spectra of Atmospheres of Hot Rocky Super-Earths
Yuichi Ito,Masahiro Ikoma,Hajime Kawahara,Hiroko Nagahara,Yui Kawashima,Taishi Nakamoto
Physics , 2015, DOI: 10.1088/0004-637X/801/2/144
Abstract: Motivated by recent detection of transiting high-density super-Earths, we explore the detectability of hot rocky super-Earths orbiting very close to their host stars. In the environment hot enough for their rocky surfaces to be molten, they would have the atmosphere composed of gas species from the magma oceans. In this study, we investigate the radiative properties of the atmosphere that is in the gas/melt equilibrium with the underlying magma ocean. Our equilibrium calculations yield Na, K, Fe, Si, SiO, O, and O$_2$ as the major atmospheric species. We compile the radiative-absorption line data of those species available in literature, and calculate their absorption opacities in the wavelength region of 0.1--100~$\mathrm{\mu m}$. Using them, we integrate the thermal structure of the atmosphere. Then, we find that thermal inversion occurs in the atmosphere because of the UV absorption by SiO. In addition, we calculate the ratio of the planetary to stellar emission fluxes during secondary eclipse, and find prominent emission features induced by SiO at 4~$\mathrm{\mu m}$ detectable by Spitzer, and those at 10 and 100~$\mathrm{\mu m}$ detectable by near-future space telescopes.
Catalytic Site Cysteines of Thiol Enzyme: Sulfurtransferases
Noriyuki Nagahara
Journal of Amino Acids , 2011, DOI: 10.4061/2011/709404
Abstract: Thiol enzymes have single- or double-catalytic site cysteine residues and are redox active. Oxidoreductases and isomerases contain double-catalytic site cysteine residues, which are oxidized to a disulfide via a sulfenyl intermediate and reduced to a thiol or a thiolate. The redox changes of these enzymes are involved in their catalytic processes. On the other hand, transferases, and also some phosphatases and hydrolases, have a single-catalytic site cysteine residue. The cysteines are redox active, but their sulfenyl forms, which are inactive, are not well explained biologically. In particular, oxidized forms of sulfurtransferases, such as mercaptopyruvate sulfurtransferase and thiosulfate sulfurtransferase, are not reduced by reduced glutathione but by reduced thioredoxin. This paper focuses on why the catalytic site cysteine of sulfurtransferase is redox active. 1. Introduction Cysteine residues in proteins maintain the protein conformation, coordinate metal(s), and regulate protein function [1–3]. Enzymes with catalytic site cysteines (Table 1) [4–42] have critical roles in biologic processes such as cell cycle regulation, apoptosis, and signal transduction [43]. Table 1: Typical thiol enzymes. A cysteine residue that easily accepts and donates (an) electron(s) is referred to as a redox-active cysteine, and has a lower pKa value than an unperturbed cysteine residue. Clairborne and colleagues extensively and successfully studied redox changes of cysteine residues and reviewed the biologic importance of redox-active cysteine [44, 45]; a redox-active cysteine is generally a thiolate at physiologic pH and is easily oxidized to a sulfenic acid. Cysteine-related enzymes are generally inhibited by mild oxidation and are reversibly reduced by thioredoxin or glutathione. The sulfenyl form is a reaction intermediate for peroxiredoxin to form disulfide [46] or protein tyrosine phosphatase 1B to form sulfenyl amide [47, 48]. The sulfenyl form is further oxidized to the sulfinyl form and/or sulfonyl form. It is noteworthy that cysteine sulfinate desulfinase catalyzes the desulfination of cysteine sulfinic acid [49, 50], which is not a reversible reaction. On the other hand, cysteine sulfinic acid reductase (sulfiredoxin) catalyzes the reduction of cysteine sulfinic acid [51, 52], although neither thioredoxin nor glutathione can reduce sulfinic acid. Thus, sulfination of cysteine residues is a reversible oxidative process under the conditions that cysteine sulfinic acid reductase can access the catalytic site cysteine of an enzyme. When the reductase cannot
Min-Max Design of FIR Digital Filters by Semidefinite Programming
Masaaki Nagahara
Mathematics , 2013,
Abstract: In this article we consider two problems: FIR (Finite Impulse Response) approximation of IIR (Infinite Impulse Response) filters and inverse FIR filtering of FIR or IIR filters. By means of Kalman-Yakubovich-Popov (KYP) lemma and its generalization (GKYP), the problems are reduced to semidefinite programming described in linear matrix inequalities (LMIs). MATLAB codes for these design methods are given. An design example shows the effectiveness of these methods.
YY Filter - A Paradigm of Digital Signal Processing
Masaaki Nagahara
Mathematics , 2013,
Abstract: YY filter, named after the founder Prof. Yutaka Yamamoto, is a digital filter designed by sampled-data control theory, which can optimize the analog performance of the signal processing system with AD/DA converters. This article discusses problems in conventional signal processing and introduces advantages of the YY filter.
Multirate Digital Signal Processing via Sampled-Data H-infinity Optimization
Masaaki Nagahara
Mathematics , 2013,
Abstract: In this thesis, we present a new method for designing multirate signal processing and digital communication systems via sampled-data H-infinity control theory. The difference between our method and conventional ones is in the signal spaces. Conventional designs are executed in the discrete-time domain, while our design takes account of both the discrete-time and the continuous-time signals. Namely, our method can take account of the characteristic of the original analog signal and the influence of the A/D and D/A conversion. While the conventional method often indicates that an ideal digital low-pass filter is preferred, we show that the optimal solution need not be an ideal low-pass when the original analog signal is not completely band-limited. This fact can not be recognized only in the discrete-time domain. Moreover, we consider quantization effects. We discuss the stability and the performance of quantized sampled-data control systems. We justify H-infinity control to reduce distortion caused by the quantizer. Then we apply it to differential pulse code modulation. While the conventional Delta modulator is not optimal and besides not stable, our modulator is stable and optimal with respect to the H-infinity-norm. We also give an LMI (Linear Matrix Inequality) solution to the optimal H-infinity approximation of IIR (Infinite Impulse Response) filters via FIR (Finite Impulse Response) filters. A comparison with the Nehari shuffle is made with a numerical example, and it is observed that the LMI solution generally performs better. Another numerical study also indicates that there is a trade-off between the pass-band and stop-band approximation characteristics.
Sparsity Methods for Networked Control
Masaaki Nagahara
Mathematics , 2014,
Abstract: In this presentation, we introduce sparsity methods for networked control systems and show the effectiveness of sparse control. In networked control, efficient data transmission is important since transmission delay and error can critically deteriorate the stability and performance. We will show that this problem is solved by sparse control designed by recent sparse optimization methods.
Discrete Signal Reconstruction by Sum of Absolute Values
Masaaki Nagahara
Mathematics , 2015, DOI: 10.1109/LSP.2015.2414932
Abstract: In this letter, we consider a problem of reconstructing an unknown discrete signal taking values in a finite alphabet from incomplete linear measurements. The difficulty of this problem is that the computational complexity of the reconstruction is exponential as it is. To overcome this difficulty, we extend the idea of compressed sensing, and propose to solve the problem by minimizing the sum of weighted absolute values. We assume that the probability distribution defined on an alphabet is known, and formulate the reconstruction problem as linear programming. Examples are shown to illustrate that the proposed method is effective.
Gemtuzumab ozogamicin in the treatment of adult acute myeloid leukemia  [PDF]
Hiroko Tsunemine, Takayuki Takahashi
Health (Health) , 2013, DOI: 10.4236/health.2013.55A002

Gemtuzumab ozogamicin (GO) is a humanized anti-CD33 monoclonal antibody conjugated to a derivative of an antitumor antibiotic, calicheamicin. GO was approved for the treatment of relapsed acute myeloid leukemia (AML) in the United States (US) in 2000. However, GO was withdrawn from the US market in June 2010, because a large-scale clinical trial failed to show additive or synergistic effects with conventional chemotherapy for newly diagnosed AML. GO is currently available only in Japan. However, several large clinical studies have demonstrated beneficial effects of GO when added to chemotherapy for AML in recent years; therefore, reconsideration of GO availability is gaining attention. Therefore, the role and efficacy of GO as monotherapy or in combination therapy for de novo or relapsed AML should be positively investigated.

Initial Academic Literacies/EAP/Genre Practices: Towards Horizontal and Participatory Online-Offline Learning in a Changing World  [PDF]
Nara Hiroko Takaki
Open Journal of Social Sciences (JSS) , 2014, DOI: 10.4236/jss.2014.210005
Abstract: This article argues in favor of extended possibilities for under-graduate students’ initial development of academic literacies/EAP/genre practices. The description of a particular learner’s initiative and its consequences constitutes the focus of the paper, which is the result of a research project in a specific context of higher education in Brazil. Qualitative and interpretive aspects characterize the methodology adopted for this investigation for the researcher and the participants’ perspectives are considered. It also assumes academic literacy/EAP/genre as situated social practices. The learning theories support the use of Facebook in English language instruction. Portability and multitasking, opportunity to structure learning on personal time and schedule, space for critical authorship and multimodal tasks in collaborative fashion suggest the inseparability between non-dominant forma of literacies and conventional academic literacy/EAP/genre studies.
FIR Digital Filter Design by Sampled-Data H-infinity Discretization
Masaaki Nagahara,Yutaka Yamamoto
Mathematics , 2014,
Abstract: FIR (finite impulse response) digital filter design is a fundamental problem in signal processing. In particular, FIR approximation of analog filters (or systems) is ubiquitous not only in signal processing but also in digital implementation of controllers. In this article, we propose a new design method of an FIR digital filter that optimally approximates a given analog filter in the sense of minimizing the H-infinity norm of the sampled-data error system. By using the lifting technique and the KYP (Kalman-Yakubovich-Popov) lemma, we reduce the H-infinity optimization to a convex optimization described by an LMI (linear matrix inequality). We also extend the method to multi-rate and multi-delay systems. A design example is shown to illustrate the effectiveness of the proposed method.
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