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Search Results: 1 - 10 of 1034 matches for " Takuya Yamagishi "
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A case of infective endocarditis after transurethral prostatic resection
Kawahara Takashi,Taguchi Hiroki,Yamagishi Takuya,Udagawa Koichi
Urology Annals , 2010,
Abstract: We report a case of infective endocarditis (IE) after transurethral prostatic resection (TUR-P). A 63-year-old man who had underwent TUR-P for benign prostatic hyperplasia. After 40 days of surgery, he developed a fever. A diagnosis of IE was established by cardiography which detected large vegetation at mitral valve. After intravenous antibiotics therapy, he underwent mitral valve replacement surgery.
Ureteral Stent Retrieval Using the Crochet Hook Technique in Females
Takashi Kawahara, Hiroki Ito, Hideyuki Terao, Takuya Yamagishi, Takehiko Ogawa, Hiroji Uemura, Yoshinobu Kubota, Junichi Matsuzaki
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0029292
Abstract: Introduction We developed a method for ureteral stent removal in female patients that requires no cystoscopy or fluoroscopic guidance using a crochet hook. In addition, we also investigated the success rate, complications and pain associated with this procedure. Methods A total of 40 female patients (56 stents) underwent the removal of ureteral stents. All procedures were carried out with the patients either under anesthesia, conscious sedation, or analgesic suppositories as deemed appropriate for each procedure including Shock Wave Lithotripsy (SWL), Ureteroscopy (URS), Percutaneous Nephrolithotomy (PCNL), and ureteral stent removal. At the time of these procedures, fluoroscopy and/or cystoscopy were prepared, but they were not used unless we failed to successfully remove the ureteral stent using the crochet hook. In addition, matched controls (comprising 50 stents) which were removed by standard ureteral stent removal using cystoscopy were used for comparison purposes. Results A total of 47 of the 56 stents (83.9%) were successfully removed. In addition, 47 of 52 (90.4%) were successfully removed except for two migrated stents and two heavily encrusted stents which could not be removed using cystoscopy. Ureteral stent removal using the crochet hook technique was unsuccessful in nine patients, including two encrustations and two migrations. Concerning pain, ureteral stent removal using the crochet hook technique showed a lower visual analogue pain scale (VAPS) score than for the standard technique using cystoscopy. Conclusions Ureteral stent removal using a crochet hook is considered to be easy, safe, and cost effective. This technique is also easy to learn and is therefore considered to be suitable for use on an outpatient basis.
Phase-Field Modeling for the Three-Dimensional Space-Filling Structure of Metal Foam Materials  [PDF]
Takuya Uehara
Open Journal of Modelling and Simulation (OJMSi) , 2015, DOI: 10.4236/ojmsi.2015.33013
Abstract: Phase-field modeling for three-dimensional foam structures is presented. The foam structure, which is generally applicable for porous material design, is geometrically approximated with a space-filling structure, and hence, the analysis of the space-filling structure was performed using the phase field model. An additional term was introduced to the conventional multi-phase field model to satisfy the volume constraint condition. Then, the equations were numerically solved using the finite difference method, and simulations were carried out for several nuclei settings. First, the nuclei were set on complete lattice points for a bcc or fcc arrangement, with a truncated hexagonal structure, which is known as a Kelvin cell, or a rhombic dodecahedron being obtained, respectively. Then, an irregularity was introduced in the initial nuclei arrangement. The results revealed that the truncated hexagonal structure was stable against a slight irregularity, whereas the rhombic polyhedral was destroyed by the instability. Finally, the nuclei were placed randomly, and the relaxation process of a certain cell was traced with the result that every cell leads to a convex polyhedron shape.
Numerical Simulation of a Domain-Tessellation Pattern on a Spherical Surface Using a Phase Field Model  [PDF]
Takuya Uehara
Open Journal of Modelling and Simulation (OJMSi) , 2016, DOI: 10.4236/ojmsi.2016.42003
Abstract: A numerical simulation scheme is proposed to analyze domain tessellation and pattern formation on a spherical surface using the phase-field method. A multi-phase-field model is adopted to represent domain growth, and the finite-difference method (FDM) is used for numerical integration. The lattice points for the FDM are distributed regularly on a spherical surface so that a mostly regular triangular domain division is realized. First, a conventional diffusion process is simulated using this lattice to confirm its validity. The multi-phase-field equation is then applied, and pattern formation processes under various initial conditions are simulated. Unlike pattern formation on a flat plane, where the regular hexagonal domains are always stable, certain different patterns are generated. Specifically, characteristic stable patterns are obtained when the number of domains, n, is 6, 8, or 12; for instance, a regular pentagonal domain division pattern is generated for n = 12, which corresponds to a regular dodecahedron.
Molecular Dynamics Simulation of Grain Refinement in a Polycrystalline Material under Severe Compressive Deformation  [PDF]
Takuya Uehara
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.812067
Abstract: Grain refinement in a polycrystalline material resulting from severe compressive deformation was simulated using molecular dynamics. A simplified model with four square grains surrounded by periodic boundaries was prepared, and compressive deformation was imposed by shortening the length in the y direction. The model first deformed elastically, and the compressive stress increased monotonically. Inelastic deformation was then initiated, and the stress decreased drastically. At that moment, dislocation or slip was initiated at the grain boundaries or triple junction and then spread within the grains. New grain boundaries were then generated in some of the grains, and sub-grains appeared. Finally, a microstructure with refined grains was obtained. This process was simulated using two types of grain arrangements and three different combinations of crystal orientations. Grain refinement generally proceeded in a similar fashion in each scenario, whereas the detailed inelastic deformation and grain refinement behavior depended on the initial microstructure.
Modeling and Simulation of Particle-Packing Structures and Their Stability Using the Distinct Element Method  [PDF]
Takuya Uehara
Open Journal of Modelling and Simulation (OJMSi) , 2018, DOI: 10.4236/ojmsi.2018.64005
Abstract: A numerical method for simulating the stability of particle-packing structures is presented. The packing structures were modeled on the basis of face-centered cubic (fcc) and body-centered cubic (bcc) structures, and the stability of these structures was investigated using the distinct element method. The interaction between the particles was simplified by considering repulsive, adhesive, and damping forces, and the stability against the gravitational force was simulated. The results under a certain set of parameters showed characteristic deformation when the particles were arranged in an fcc array. Focusing on the local structure, the resulting model was divided into several domains: The bottom base, four top corners, and intermediate domains. The bottom base notably became a body-centered tetragonal (bct) structure, which corresponds to a uniaxially compressed bcc structure. Conversely, the models based on the bcc arrangement were structurally stable, as no specific deformation was observed, and a monotonously compressed bct structure was obtained. Consequently, the bcc arrangement is concluded to be more stable against uniaxial compression, such as the gravitational force, in a particle-packing system.
A Note on modified Veselov-Novikov Hierarchy
Kengo Yamagishi
Physics , 1999, DOI: 10.1016/S0370-2693(99)00342-1
Abstract: Because of its relevance to lower-dimensional conformal geometry, known as a generalized Weierstrass inducing, the modified Veselov-Novikov (mVN) hierarchy attracts renewed interest recently. It has been shown explicitly in the literature that an extrinsic string action \`a la Polyakov (Willmore functional) is invariant under deformations associated to the first member of the mVN hierarchy. In this note we go one step further and show the explicit invariance of the functional under deformations associated to all higher members of the hierarchy.
Spontaneous symmetry breaking and the formation of columnar structures in the primary visual cortex II --- Local organization of orientation modules
Kengo Yamagishi
Physics , 1996,
Abstract: Self-organization of orientation-wheels observed in the visual cortex is discussed from the view point of topology. We argue in a generalized model of Kohonen's feature mappings that the existence of the orientation-wheels is a consequence of Riemann-Hurwitz formula from topology. In the same line, we estimate partition function of the model, and show that regardless of the total number N of the orientation-modules per hypercolumn the modules are self-organized, without fine-tuning of parameters, into definite number of orientation-wheels per hypercolumn if N is large.
Crepant resolutions of Slodowy slice in nilpotent orbit closure in sl_N(C)
Ryo Yamagishi
Mathematics , 2014,
Abstract: One of our results of this article is that every (projective) crepant resolution of a Slodowy slice in a nilpotent orbit closure in $\mathfrak{sl}_N(\mathbf{C})$ can be obtained as the restriction of some crepant resolution of the nilpotent orbit closure. We also show that there is a decomposition of the Slodowy slice into other Slodowy slices with good properties. From this decomposition, one can count the number of crepant resolutions.
Diophantine approximation of polynomials over $\mathbb{F}_q[t]$ satisfying a divisibility condition
Shuntaro Yamagishi
Mathematics , 2015,
Abstract: Let $\mathbb{F}_q[t]$ denote the ring of polynomials over $\mathbb{F}_q$, the finite field of $q$ elements. We prove an estimate for fractional parts of polynomials over $\mathbb{F}_q[t]$ satisfying a certain divisibility condition analogous to that of intersective polynomials in the case of integers. We then extend our result to consider linear combinations of such polynomials as well.
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