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Search Results: 1 - 10 of 2847 matches for " Shunsuke Saito "
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Fano-Ricci limit spaces and spectral convergence
Akito Futaki,Shouhei Honda,Shunsuke Saito
Mathematics , 2015,
Abstract: We study the behavior under Gromov-Hausdorff convergence of the spectrum of weighted $\overline{\partial}$-Laplacian on compact K\"ahler manifolds. This situation typically occurs for a sequence of Fano manifolds with anticanonical K\"ahler class. We apply it to show that, if an almost smooth Fano-Ricci limit space admits a K\"ahler-Ricci limit soliton and the space of all $L^2$ holomorphic vector fields is a Lie algebra with respect to the Lie bracket, then the Lie algebra has the same structure as smooth K\"ahler-Ricci solitons. In particular if a $\mathbb{Q}$-Fano variety admits a K\"ahler-Ricci limit soliton and all holomorphic vector fields are $L^2$ then the Lie algebra has the same structure as smooth K\"ahler-Ricci solitons. If the sequence consists of K\"ahler-Ricci solitons then the Ricci limit space is a weak K\"ahler-Ricci soliton on a $\mathbb{Q}$-Fano variety and the space of limits of $1$-eigenfunctions for the weighted $\overline{\partial}$-Laplacian forms a Lie algebra with respect to the Poisson bracket and admits a similar decomposition as smooth K\"ahler-Ricci solitons.
Should We Overlook All Altruistic Behavior by Politicians?  [PDF]
Shunsuke Sekiguchi
Theoretical Economics Letters (TEL) , 2013, DOI: 10.4236/tel.2013.33023
Abstract:

Not all policies benefit their intended targets even though they are motivated by political altruism. This paper analyzes how the frequency of altruistic behavior changes depending on whether consumers (i.e., the electorate) or producers (i.e., politicians) bear the responsibility. It compares the strict liability rule, which means the altruist must bear all damages, with the no liability rule, which means the recipient must bear all damages. It finds that under the no liability rule, if politicians are altruist, the frequency of altruistic behavior is less than under the strict liability rule. Therefore, the paper shows that if politicians were altruists, they would prefer the strict liability rule.

Recent Clinical and Experimental Advances in Atrial Fibrillation
Shigeru Miyagawa,Taichi Sakaguchi,Hiroyuki Nishi,Yasushi Yoshikawa,Satsuki Fukushima,Shunsuke Saito,Yoshiki Sawa
ISRN Cardiology , 2011, DOI: 10.5402/2011/958189
Abstract: Atrial fibrillation (AF) is the most common arrhythmia in clinical settings (Fuster et al., 2001), and it is often associated with congestive heart diseases (Issac et al., 2007). Many studies in both laboratory and clinical settings have sought to analyze the mechanisms of AF, develop treatments based on these mechanisms, and examine atrial remodeling in chronic AF. The aim of this paper is to analyze recent findings regarding the atrial remodeling that occurs in AF. In particular, we will describe the electrical and structural changes that involve atrial myocytes and the extracellular matrix. We will also describe the general classification and basic pathophysiology of AF and its surgical treatments. 1. Classification of AF The joint American College of Cardiology/American Heart Association/European Society of Cardiology proposed a classification system for AF to simplify its heterogeneous clinical aspects and clarify its clinical states [1]. Patients are initially classified as having a “first detected episode of AF,” when AF is confirmed by clinicians. If a patient has two or more episodes, the AF is classified as recurrent. Recurrent AF is designated as paroxysmal or persistent. Paroxysmal AF is an episode that generally continues for 7 or fewer days and terminates on its own. Persistent AF usually continues for more than 7 days without self-terminating and requires clinicians to terminate it using pharmacological treatment or electrical cardioversion to restore the sinus rhythm. Permanent AF is a situation in which the sinus rhythm cannot be sustained after cardioversion, and further medical efforts are required to restore it. 2. Pathophysiology of AF 2.1. The Basic Mechanisms of AF Many researchers agree that inflammation [2], neurohormonal disorders [3], cardiovascular diseases such as valvular diseases [4], diabetes, hypertension, congestive heart failure, myocardial infarction [5], and genetic factors [6] are “modulating factors” that can induce AF. Classically, AF mechanisms are described by the concept of atrial ectopic foci [7], which fire spontaneously in the atrium, a single reentry circuit, or multiple reentry circuits [8, 9]. The surgical maze procedure is designed to block the multiple reentry circuits and create an isolated electrical lesion in the atrium [10]. Haissaguerre et al. reported that triggers located in the pulmonary veins initiate most cases of paroxysmal AF [7], while in some cases the trigger, such as a venous remnant in the left atrium (LA) and superior vena cavae, occurs outside the pulmonary vein. This finding supports
Impact of microRNA Expression in Human Atrial Tissue in Patients with Atrial Fibrillation Undergoing Cardiac Surgery
Hiroyuki Nishi, Taichi Sakaguchi, Shigeru Miyagawa, Yasushi Yoshikawa, Satsuki Fukushima, Shunsuke Saito, Takayoshi Ueno, Toru Kuratani, Yoshiki Sawa
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0073397
Abstract: Background Although microRNA (miRNA) regulates initiation and/or progression of atrial fibrillation (AF) in canine AF models, the underlying mechanism in humans remains unclear. We speculated that certain miRNAs in atrial tissue are related to AF, and evaluated the relationship of miRNA expression in human atrial tissue in cardiac surgery patients. Methods Right atrial tissues from 29 patients undergoing cardiovascular surgery were divided into 3 groups [A: chronic AF or unsuccessful maze, n=6; B: successful maze, n=10; C: sinus rhythm (SR) n=13]. miRNA expression was determined using high density microarrays and with Reverse transcriptase-polymerase chain reaction (RT-PCR). Fibrosis was examined using Masson trichrome staining. Results miRNA microarray analysis showed elevated miRNA-21, miRNA-23b, miRNA-199b, and miRNA-208b in AF as compared to SR groups. RT-PCR showed elevated miRNA-21 (1.9-fold) and miRNA-208b (4.2-fold) in AF as compared to the SR groups. miRNA-21 expression increased from Group C to A (A: 2.1-fold, B: 1.8-fold, C: 1.0-fold). Fibrosis increased from C to A (A: 43.0±12.9%, B: 21.3±6.1%, C: 11.9±3.1%). Percent fibrosis and miRNA-21 expression were correlated (r=0.508, p<0.05). The plasma levels of miRNA-21 in AF patients was significantly decreased as compared to the healthy volunteers (p<0.05). Conclusion The expression of miRNA-21 in human atrial tissue was found to be related to atrial fibrosis and might affect AF occurrence, indicating its usefulness as a biomarker for cardiac surgery management.
Rationality and Stability of Equilibrium in a Search-Theoretic Model of Money  [PDF]
Tetsuya Saito
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.23052
Abstract: In this short note, I examine the rationality of money-search equilibrium in a basic second-generation money search model, which is a perfectly divisible goods and indivisible money model. I then show that only an inflationary economy can generate a socially and individually rational stable equilibrium. On the basis of this finding, I demonstrate that there is no loss of generality in an analysis that assumes dictatorial buyers in an inflationary economy, since the properties of a dictatorial buyers model are identical to those of a general inflationary economy model. The result of this paper is especially useful for empirical applications since we are generally incapable of finding data showing bargaining power. This result also alerts us against employing the second-generation model to analyze a deflationary economy and commodity money.
Impacts to the Micronesian islands by environmental change of globalization and climate change
Shunsuke Nagashima
Journal of Ecology and Field Biology , 2010,
Abstract: This article focused on the environmental changes on atolls in Micronesia. First, we considered the problem. Second,we designed research that focused on the impacts of environmental changes especially in relation to globalization andglobal warming in the Federated States of Micronesia (FSM). The results were in accordance to the hypotheses that globalizationhad impacted prominently in communities on main islands and impact was lessened with increased distancefrom the centre. The fact that the islands are remotely situated and thus, in theory, do not have much outside influence,has not alleviated them from having societal concerns. The earth’s environmental change is causing an impact on themain islands as well. This has been governed by distinctive characteristics in their geographical, regional, and contents.Moreover, they showed stronger concerns about impacts on the environment than globalization. A set of questionnaireswas used as the principal assessment method to quantify the concerns relating to the environmental changes.
Organization of Neural Systems for Aversive Information Processing: Pain, Error, and Punishment
Shunsuke Kobayashi
Frontiers in Neuroscience , 2012, DOI: 10.3389/fnins.2012.00136
Abstract: The avoidance of aversive events is critically important for the survival of organisms. It has been proposed that the medial pain system, including the amygdala, periaqueductal gray (PAG), and anterior cingulate cortex (ACC), contains the neural circuitry that signals pain affect and negative value. This system appears to have multiple defense mechanisms, such as rapid stereotyped escape, aversive association learning, and cognitive adaptation. These defense mechanisms vary in speed and flexibility, reflecting different strategies of self-protection. Over the course of evolution, the medial pain system appears to have developed primitive, associative, and cognitive solutions for aversive avoidance. There may be a functional grading along the caudal-rostral axis, such that the amygdala-PAG system underlies automatic and autonomic responses, the amygdala-orbitofrontal system contributes to associative learning, and the ACC controls cognitive processes in cooperation with the lateral prefrontal cortex. A review of behavioral and physiological studies on the aversive system is presented, and a conceptual framework for understanding the neural organization of the aversive avoidance system is proposed.
Destructible Bars in Disk Galaxies under the Dynamical Influence of a Massive Central Black Hole
Shunsuke Hozumi
Physics , 2011, DOI: 10.1093/pasj/64.1.5
Abstract: The characteristics of the galactic bars that are prone to suffer a damaging impact from a massive central black hole are examined using flat stellar disks. We construct three disk model groups that consist of exponential disks with one type of velocity distribution and Kuzmin-Toomre disks with two different types of exact equilibrium distribution function. For each disk model group, three disks that have different typical Toomre's Q values are evolved to form bars through dynamical instability. Once a bar is fully developed, a black hole (BH), whose mass is 1% of the disk mass, is adiabatically added at the center of the disk. Our results show that lower-amplitude bars, that is, weaker bars are dissolved more easily by that BH. We have found that this destructibility is rooted in the characteristic feature that the bar formed spontaneously becomes shorter in length and rounder in shape with decreasing bar amplitude. Since such weaker bars are found to originate from colder disks in each disk model group, it follows that for a given form of velocity structure, the coldness of an initial disk determines whether the bar produced in that disk is favorable to dissolution induced by a massive central BH. In addition, the existence of bar-dissolved galaxies of the kind studied here is also discussed.
A Phase-Space Approach to Collisionless Stellar Systems Using a Particle Method
Shunsuke Hozumi
Physics , 1997, DOI: 10.1086/304623
Abstract: A particle method for reproducing the phase space of collisionless stellar systems is described. The key idea originates in Liouville's theorem which states that the distribution function (DF) at time t can be derived from tracing necessary orbits back to t=0. To make this procedure feasible, a self-consistent field (SCF) method for solving Poisson's equation is adopted to compute the orbits of arbitrary stars. As an example, for the violent relaxation of a uniform-density sphere, the phase-space evolution which the current method generates is compared to that obtained with a phase-space method for integrating the collisionless Boltzmann equation, on the assumption of spherical symmetry. Then, excellent agreement is found between the two methods if an optimal basis set for the SCF technique is chosen. Since this reproduction method requires only the functional form of initial DFs but needs no assumptions about symmetry of the system, the success in reproducing the phase-space evolution implies that there would be no need of directly solving the collisionless Boltzmann equation in order to access phase space even for systems without any special symmetries. The effects of basis sets used in SCF simulations on the reproduced phase space are also discussed.
A characteristic p analogue of plt singularities and adjoint ideals
Shunsuke Takagi
Mathematics , 2006,
Abstract: We introduce a new variant of tight closure and give an interpretation of adjoint ideals via this tight closure. As a corollary, we prove that a log pair $(X,\Delta)$ is plt if and only if the modulo $p$ reduction of $(X,\Delta)$ is divisorially F-regular for all large $p \gg 0$. Here, divisorially F-regular pairs are a class of singularities in positive characteristic introduced by Hara and Watanabe in terms of Frobenius splitting.
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