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Search Results: 1 - 10 of 192 matches for " Yoichiro Kamatani "
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Association of Common Variants in TNFRSF13B, TNFSF13, and ANXA3 with Serum Levels of Non-Albumin Protein and Immunoglobulin Isotypes in Japanese
Wael Osman, Yukinori Okada, Yoichiro Kamatani, Michiaki Kubo, Koichi Matsuda, Yusuke Nakamura
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0032683
Abstract: We performed a genome-wide association study (GWAS) on levels of serum total protein (TP), albumin (ALB), and non-albumin protein (NAP). We analyzed SNPs on autosomal chromosomes using data from 9,103 Japanese individuals, followed by a replication study of 1,600 additional individuals. We confirmed the previously- reported association of GCKR on chromosome 2p23.3 with serum ALB (rs1260326, Pmeta = 3.1×10?9), and additionally identified the significant genome-wide association of rs4985726 in TNFRSF13B on 17p11.2 with both TP and NAP (Pmeta = 1.2×10?14 and 7.1×10?24, respectively). For NAP, rs3803800 and rs11552708 in TNFSF13 on 17p13.1 (Pmeta = 7.2×10?15 and 7.5×10?10, respectively) as well as rs10007186 on 4q21.2 near ANXA3 (Pmeta = 1.3×10?9) also indicated significant associations. Interestingly, TNFRSF13B and TNFSF13 encode a tumor necrosis factor (TNF) receptor and its ligand, which together constitute an important receptor-ligand axis for B-cell homeostasis and immunoglobulin production. Furthermore, three SNPs, rs4985726, rs3803800, and rs11552708 in TNFRSF13B and TNFSF13, were indicated to be associated with serum levels of IgG (P<2.3×10?3) and IgM (P<0.018), while rs3803800 and rs11552708 were associated with IgA (P<0.013). Rs10007186 in 4q21.2 was associated with serum levels of IgA (P = 0.036), IgM (P = 0.019), and IgE (P = 4.9×10?4). Our results should add interesting knowledge about the regulation of major serum components.
Local Consistency of Markov Chain Monte Carlo Methods
Kengo Kamatani
Statistics , 2010, DOI: 10.1007/s10463-013-0403-3
Abstract: In this paper, we introduce the notion of efficiency (consistency) and examine some asymptotic properties of Markov chain Monte Carlo methods. We apply these results to the data augmentation (DA) procedure for independent and identically distributed observations. More precisely, we show that if both the sample size and the running time of the DA procedure tend to infinity the empirical distribution of the DA procedure tends to the posterior distribution. This is a local property of the DA procedure, which may be, in some cases, more helpful than the global properties to describe its behavior. The advantages of using the local properties are the simplicity and the generality of the results. The local properties provide useful insight into the problem of how to construct efficient algorithms.
Rate optimality of Random walk Metropolis algorithm in high-dimension with heavy-tailed target distribution
Kengo Kamatani
Statistics , 2014,
Abstract: High-dimensional asymptotics of the random walk Metropolis-Hastings (RWM) algorithm is well understood for a class of light-tailed target distributions. We develop a study for heavy-tailed target distributions, such as the Student $t$-distribution or the stable distribution. The performance of the RWM algorithms heavily depends on the tail property of the target distribution. The expected squared jumping distance (ESJD) is a common measure of efficiency for light-tail case but it does not work for heavy-tail case since the ESJD is unbounded. For this reason, we use the rate of weak consistency as a measure of efficiency. When the number of dimension is $d$, we show that the rate for the RWM algorithm is $d^2$ for the heavy-tail case where it is $d$ for the light-tail case. Also, we show that the Gaussian RWM algorithm attains the optimal rate among all RWM algorithms. Thus no heavy-tail proposal distribution can improve the rate.
Weak consistency of Markov chain Monte Carlo methods
Kengo Kamatani
Statistics , 2011,
Abstract: Markov chain Monte Calro methods (MCMC) are commonly used in Bayesian statistics. In the last twenty years, many results have been established for the calculation of the exact convergence rate of MCMC methods. We introduce another rate of convergence for MCMC methods by approximation techniques. This rate can be obtained by the convergence of the Markov chain to a diffusion process. We apply it to a simple mixture model and obtain its convergence rate. Numerical simulations are performed to illustrate the effect of the rate.
Local degeneracy of Markov chain Monte Carlo methods
Kengo Kamatani
Statistics , 2011, DOI: 10.1051/ps/2014004
Abstract: We study asymptotic behavior of Monte Carlo method. Local consistency is one of an ideal property of Monte Carlo method. However, it may fail to hold local consistency for several reason. In fact, in practice, it is more important to study such a non-ideal behavior. We call local degeneracy for one of a non-ideal behavior of Monte Carlo methods. We show some equivalent conditions for local degeneracy. As an application we study a Gibbs sampler (data augmentation) for cumulative logit model with or without marginal augmentation. It is well known that natural Gibbs sampler does not work well for this model. In a sense of local consistency and degeneracy, marginal augmentation is shown to improve the asymptotic property. However, when the number of categories is large, both methods are not locally consistent.
Efficient strategy for the Markov chain Monte Carlo in high-dimension with heavy-tailed target probability distribution
Kengo Kamatani
Statistics , 2014,
Abstract: The purpose of this paper is to introduce a new Markov chain Monte Carlo method and exhibit its efficiency by simulation and high-dimensional asymptotic theory. Key fact is that our algorithm has a reversible proposal transition kernel, which is designed to have a heavy-tailed invariant probability distribution. The high-dimensional asymptotic theory is studied for a class of heavy-tailed target probability distribution. As the number of dimension of the state space goes to infinity, we will show that our algorithm has a much better convergence rate than that of the preconditioned Crank Nicolson (pCN) algorithm and the random-walk Metropolis (RWM) algorithm. We also show that our algorithm is at least as good as the pCN algorithm and better than the RWM algorithm for light-tailed target probability distribution.
Interlimb Coordination of Ground Reaction Forces during Double Stance Phase at Fast Walking Speed  [PDF]
Yoichiro Sato, Norimasa Yamada
Advances in Physical Education (APE) , 2018, DOI: 10.4236/ape.2018.82024
Abstract: To better understand interlimb coordination during the double stance phase at fast walking speeds, we analyzed ground reaction forces generated by the leading and trailing limbs during the double stance phase at multiple speeds. Ground reaction forces were recorded during the double stance phase at slow, self-selected, and fast walking speeds in eleven healthy volunteers. We calculated the instantaneous phase of the ground reaction forces for the vertical and anterior-posterior components, and then calculated the relative phase between the leading and trailing limbs for each component. For the vertical component, the relative phase showed a significantly lower value in the fast condition than in the other two conditions in the early-double stance phase (fast vs. self-selected, p < 0.01; fast vs. slow, p < 0.001). For the anterior-posterior component, the relative phases in the early- and late-double stance phases in all speed conditions were significantly smaller than those in the mid-double stance phase. These findings suggest that interlimb coordination of the forces exerted by the leading and trailing limbs in the early-double stance phase would be an important factor for walking at fast speed.
Temporal Fossa Abscess Caused by Apical Periodontitis: A Case Report  [PDF]
Sayaka Yoshiba, Takaaki Kamatani, Tatsuo Shirota
Open Journal of Clinical Diagnostics (OJCD) , 2018, DOI: 10.4236/ojcd.2018.84005
Abstract:

According to the progress of the antibiotic medicine, the severe infection case is decreasing recently. We recently experienced a case of temporal fossa abscess caused by periapical periodontitis the upper left side of the second molar. A 79-year-old woman visited to Showa University Dental Hospital complaining of the painful swelling at the left side of the temporal and trismus. The routine blood test exhibited a severe inflammation. We performed drainage treatment at temporal skin and normal oral bacterial flora was detected by the bacteriological examination. Under treatment included the administration of antibiotics, the inflammation healed without serious complication and she recovered completely.

The Aharonov-Bohm Problem Revisited
Yoichiro Nambu
Physics , 1998, DOI: 10.1016/S0550-3213(00)00258-3
Abstract: The properties of a nonrelativistic charged particle in two dimensions in the presence of an arbitrary number of nonquantized magnetic fluxes are investigated in free space as well as in a uniform magnetic field. The fluxes are represented mathematically as branch points in one of the complex coordinates. It is found that in order to construct solutions, the fluxes have to be treated in general as dynamical objects dual to the charges. A medium made up of fluxes acts like an anti-magnetic field and tends to expel the charges.
From Three-Dimensional Electrophysiology to the Cable Model: an Asymptotic Study
Yoichiro Mori
Physics , 2009,
Abstract: Cellular electrophysiology is often modeled using the cable equations. The cable model can only be used when ionic concentration effects and three dimensional geometry effects are negligible. The Poisson model, in which the electrostatic potential satisfies the Poisson equation and the ionic concentrations satisfy the drift-diffusion equation, is a system of equations that can incorporate such effects. The Poisson model is unfortunately prohibitively expensive for numerical computation because of the presence of thin space charge layers at internal membrane boundaries. As a computationally efficient and biophysically natural alternative, we introduce the electroneutral model in which the Poisson equation is replaced by the electroneutrality condition and the presence of the space charge layer is incorporated in boundary conditions at the membrane interfaces. We use matched asymptotics and numerical computations to show that the electroneutral model provides an excellent approximation to the Poisson model. Further asymptotic calculations illuminate the relationship of the electroneutral or Poisson models with the cable model, and reveal the presence of a hierarchy of electrophysiology models.
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