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Search Results: 1 - 10 of 2772 matches for " Yuichi Ito "
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Starspots - Transit Depth Relation of the Evaporating Planet Candidate KIC 12557548b
Hajime Kawahara,Teruyuki Hirano,Kenji Kurosaki,Yuichi Ito,Masahiro Ikoma
Physics , 2013, DOI: 10.1088/2041-8205/776/1/L6
Abstract: Violent variation of transit depths and an ingress-egress asymmetry of the transit light curve discovered in KIC 12557548 have been interpreted as evidences of a catastrophic evaporation of atmosphere with dust (M_p gtrsim 1 M_oplus/Gyr) from a close-in small planet. To explore what drives the anomalous atmospheric escape, we perform time-series analysis of the transit depth variation of Kepler archival data for ~ 3.5 yr. We find a ~ 30% periodic variation of the transit depth with P1 = 22.83 pm 0.21 days, which is within the error of the rotation period of the host star estimated using the light curve modulation, Prot = 22.91 pm 0.24 days. We interpret the results as evidence that the atmospheric escape of KIC 12557548b correlates with stellar activity. We consider possible scenarios that account for both the mass loss rate and the correlation with stellar activity. X-ray and ultraviolet (XUV)-driven evaporation is possible if one accepts a relatively high XUV flux and a high efficiency for converting the input energy to the kinetic energy of the atmosphere. Star-planet magnetic interaction is another possible scenario though huge uncertainty remains for the mass loss rate.
Constant-Time Algorithms for Sparsity Matroids
Hiro Ito,Shin-ichi Tanigawa,Yuichi Yoshida
Computer Science , 2011,
Abstract: A graph $G=(V,E)$ is called $(k,\ell)$-full if $G$ contains a subgraph $H=(V,F)$ of $k|V|-\ell$ edges such that, for any non-empty $F' \subseteq F$, $|F'| \leq k|V(F')| - \ell$ holds. Here, $V(F')$ denotes the set of vertices incident to $F'$. It is known that the family of edge sets of $(k,\ell)$-full graphs forms a family of matroid, known as the sparsity matroid of $G$. In this paper, we give a constant-time approximation algorithm for the rank of the sparsity matroid of a degree-bounded undirected graph. This leads to a constant-time tester for $(k,\ell)$-fullness in the bounded-degree model, (i.e., we can decide with high probability whether an input graph satisfies a property $P$ or far from $P$). Depending on the values of $k$ and $\ell$, it can test various properties of a graph such as connectivity, rigidity, and how many spanning trees can be packed. Based on this result, we also propose a constant-time tester for $(k,\ell)$-edge-connected-orientability in the bounded-degree model, where an undirected graph $G$ is called $(k,\ell)$-edge-connected-orientable if there exists an orientation $\vec{G}$ of $G$ with a vertex $r \in V$ such that $\vec{G}$ contains $k$ arc-disjoint dipaths from $r$ to each vertex $v \in V$ and $\ell$ arc-disjoint dipaths from each vertex $v \in V$ to $r$. A tester is called a one-sided error tester for $P$ if it always accepts a graph satisfying $P$. We show, for $k \geq 2$ and (proper) $\ell \geq 0$, any one-sided error tester for $(k,\ell)$-fullness and $(k,\ell)$-edge-connected-orientability requires $\Omega(n)$ queries.
Clinical Characteristics of Japanese Type 2 Diabetic Patients Responsive to Sitagliptin  [PDF]
Kouichi Inukai, Takumi Hirata, Takashi Sumita, Masaki Watanabe, Yuichi Ikegami, Daisuke Ito, Susumu Kurihara, Nobuyuki Yasukawa, Jiro Morimoto, Nobuki Takata, Kenta Kanazawa, Tamotsu Neda, Yoshikazu Sumitani, Kiyoaki Inoue, Yuichi Noguchi, Toshio Hosaka, Hitoshi Ishida, Shigehiro Katayama
Journal of Diabetes Mellitus (JDM) , 2014, DOI: 10.4236/jdm.2014.43025

Japanese type 2 diabetic patients were treated with sitagliptin to evaluate the efficacy of this agent, and also to investigate the clinical characteristics of those who responded to sitagliptin. In total, 1001 diabetic patients, inadequately controlled (HbA1c ≥ 6.5%) with oral hypoglycemic agents (OHA) other than DPP-4 inhibitors or with diet and exercise only, were enrolled. We added 50mg of sitagliptin to the therapeutic regimens of 410 patients including 68 OHA naive patients, while the other 591 patients were switched from a single OHA to 50 mg of sitagliptin. After 6 months, glycemic control was significantly improved due to both reduced insulin resistance, as demonstrated by a significant HOMA-R reduction, and recovery of pancreatic β cell function, as assessed by HOMA-β and the proinsulin/insulin (PI/I) ratio. In the bivariable analysis, a good response, defined as an HbA1c reduction during the 6 months of at least 0.9%, was associated with high HbA1c and PI/I at baseline and combination treatments with sulfonylurea, biguanide and α-glucosidase inhibitors, but not with obesity. On the other hand, in the multivariable regression analysis, only high baseline HbA1c and combination treatment with anα-glucosidase inhibitor were significantly associated with a good response to sitagliptin. In patients with type 2 diabetes, the addition of sitagliptin or switching from another OHA to this agent achieved an HbA1c reduction without overloading

Recent Advances in X-Ray Structures of Metal-Phenoxyl Radical Complexes  [PDF]
Yuichi Shimazaki
Advances in Materials Physics and Chemistry (AMPC) , 2013, DOI: 10.4236/ampc.2013.31A009

An “experimental” valence state of metal complexes is sometime different from the “formal” oxidation state, especially in the species having redox active ligands. This difference can be seen in biological system, such as iron(IV)-porphyrin π-cation radical in some heme proteins and copper(II)-phenoxyl radical in galactose oxidase (GO). Although structural characterizations of these species by X-ray diffraction methods have been rare due to their stability, some artificial metal-phenoxyl radical complexes have been synthesized and successfully characterized by X-ray crystal structure. In this review, syntheses and X-ray crystal structures of the one-electron oxidized metal-phenolate complexes, metal- phenoxyl radical, and high-valent metal phenolate species are discussed.

Relationships among Risk Assessment, Risk Perception and Acceptance Model of the Residents near Nuclear Power Plants in Japan  [PDF]
Yuichi Otsuka
Open Journal of Safety Science and Technology (OJSST) , 2015, DOI: 10.4236/ojsst.2015.52005
Abstract: This study aims at revealing the relationships among risk assessment result, risk perception model and risk acceptance model of the residents near nuclear power plants in Japan. Risk acceptance model is based on the trust of resident to nuclear power plants (NPPs) companies. The risk perception of the residents is very fragile and is not always based on objective technical knowledge. In addition, there are two models of risk acceptance: traditional trust model and salient value similarity model. In order to discuss the risk communication framework between NPPs with residents, applicability of two modes on the perception of the residents should be investigated. The author collected questionnaire from local resident near Kashiwazaki-Kariwa NPP in Niigata, Japan. Severity of risk is significantly affected by the extents of risks, not by amount of knowledge. Radiation relating hazard is normally evaluated higher risk. Risk acceptance level is significantly related to the factors of social benefits and trust to the NPPs company, not by regional interest nor amount of knowledge. Furthermore, value similarity model was not significant in this study. The results demonstrated that risk acceptance model of local residents near NPPs could be arranged by traditional trust model. In order to establish mutual trustworthy relationships between local residents and NPPs engineer, expert knowledge in nuclear power, communication skills, and expertise in safety are necessary to the engineers.
New Computer-Aided Diagnosis of Dementia Using Positron Emission Tomography: Brain Regional Sensitivity-Mapping Method
Akihiro Kakimoto, Yuichi Kamekawa, Shigeru Ito, Etsuji Yoshikawa, Hiroyuki Okada, Sadahiko Nishizawa, Satoshi Minoshima, Yasuomi Ouchi
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0025033
Abstract: Purpose We devised a new computer-aided diagnosis method to segregate dementia using one estimated index (Total Z score) derived from the Brodmann area (BA) sensitivity map on the stereotaxic brain atlas. The purpose of this study is to investigate its accuracy to differentiate patients with Alzheimer's disease (AD) or mild cognitive impairment (MCI) from normal adults (NL). Methods We studied 101 adults (NL: 40, AD: 37, MCI: 24) who underwent 18FDG positron emission tomography (PET) measurement. We divided NL and AD groups into two categories: a training group with (Category A) and a test group without (Category B) clinical information. In Category A, we estimated sensitivity by comparing the standard uptake value per BA (SUVR) between NL and AD groups. Then, we calculated a summated index (Total Z score) by utilizing the sensitivity-distribution maps and each BA z-score to segregate AD patterns. To confirm the validity of this method, we examined the accuracy in Category B. Finally, we applied this method to MCI patients. Results In Category A, we found that the sensitivity and specificity of differentiation between NL and AD were all 100%. In Category B, those were 100% and 95%, respectively. Furthermore, we found this method attained 88% to differentiate AD-converters from non-converters in MCI group. Conclusions The present automated computer-aided evaluation method based on a single estimated index provided good accuracy for differential diagnosis of AD and MCI. This good differentiation power suggests its usefulness not only for dementia diagnosis but also in a longitudinal study.
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.
Prognostic factors after palliative resection for colorectal cancer with incurable synchronous liver metastasis  [PDF]
Kiichi Sugimoto, Kazuhiro Sakamoto, Yuichi Tomiki, Michitoshi Goto, Yutaka Kojima, Hiromitsu Komiyama, Makoto Takahashi, Yukihiro Yaginuma, Shun Ishiyama, Koichiro Niwa, Kiichi Nagayasu, Shingo Ito, Masaya Kawai, Kazuhiro Takehara, Yoshihiko Tashiro, Shinya Munakata
Open Journal of Gastroenterology (OJGas) , 2013, DOI: 10.4236/ojgas.2013.35044
Abstract: Purpose: With the improvements in newer chemotherapeutic agents, there is currently no consensus regarding the validity of palliative resection of the primary tumor for colorectal cancer with incurable distant metastasis. We retrospectively analyzed prognostic factor in patients with colorectal cancer accompanied by incurable synchronous liver metastasis. Methods: 82 patients with incurable synchronous liver metastases, who underwent primary tumor resection alone, were enrolled. Results: The multivariate analysis revealed that the presence of ascites (P = 0.001, Hazard ratio = 2.96) and differentiation (P = 0.003, Hazard ratio = 3.68) were found to be significant independent prognostic factors. The median survival time among the patients with ascites was 4.8 months and that among the patients with poorly-differentiated or mucinous adenocarcinoma, or signet ring cell carcinoma (high grade differentiation) was 1.4 months, respectively. Conclusion: The presence of ascites and differentiation were prognostic factors in the patients with incurable liver metastases. Therefore, because prognosis is generally poor after primary tumor resection in the patients with ascites or high grade differentiation, the introduction of systemic chemotherapy with alleviation of symptoms related to the primary tumor should be taken into account as one of the therapeutic strategies.
Azelnidipine Inhibits Cultured Rat Aortic Smooth Muscle Cell Death Induced by Cyclic Mechanical Stretch
Jing Zhao, Kentaro Ozawa, Yoji Kyotani, Kosuke Nagayama, Satoyasu Ito, Akira T. Komatsubara, Yuichi Tsuji, Masanori Yoshizumi
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0102813
Abstract: Acute aortic dissection is the most common life-threatening vascular disease, with sudden onset of severe pain and a high fatality rate. Clarifying the detailed mechanism for aortic dissection is of great significance for establishing effective pharmacotherapy for this high mortality disease. In the present study, we evaluated the influence of biomechanical stretch, which mimics an acute rise in blood pressure using an experimental apparatus of stretching loads in vitro, on rat aortic smooth muscle cell (RASMC) death. Then, we examined the effects of azelnidipine and mitogen-activated protein kinase inhibitors on mechanical stretch-induced RASMC death. The major findings of the present study are as follows: (1) cyclic mechanical stretch on RASMC caused cell death in a time-dependent manner up to 4 h; (2) cyclic mechanical stretch on RASMC induced c-Jun N-terminal kinase (JNK) and p38 activation with peaks at 10 min; (3) azelnidipine inhibited RASMC death in a concentration-dependent manner as well as inhibited JNK and p38 activation by mechanical stretch; and (4) SP600125 (a JNK inhibitor) and SB203580 (a p38 inhibitor) protected against stretch-induced RASMC death; (5) Antioxidants, diphenylene iodonium and tempol failed to inhibit stretch-induced RASMC death. On the basis of the above findings, we propose a possible mechanism where an acute rise in blood pressure increases biomechanical stress on the arterial walls, which induces RASMC death, and thus, may lead to aortic dissection. Azelnidipine may be used as a pharmacotherapeutic agent for prevention of aortic dissection independent of its blood pressure lowering effect.
A Theoretical Study on Van Der Pauw Measurement Values of Inhomogeneous Compound Semiconductor Thin Films  [PDF]
Toru Matsumura, Yuichi Sato
Journal of Modern Physics (JMP) , 2010, DOI: 10.4236/jmp.2010.15048
Abstract: The influence of intermixing heterogeneous regions that have different electrical properties from the base materials on van der Pauw measurement values was theoretically studied by computer simulation using the finite-element method. The measurement samples selected were thin films of inhomogeneous semiconductors. Calculated electrical properties, such as resistivity, carrier density, and mobility of the thin films, varied in predictable ways when heterogeneous regions were dispersed in wide ranges over the samples. On the other hand, the mobility of the thin films showed a different change when heterogeneous regions were locally concentrated in the measurement samples.
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