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Takeshi Kataoka

Publications and source records attributed to Takeshi Kataoka.

6 recordsLinked to original sources
PubMed2004

Instability of solitary wave solutions to long-wavelength transverse perturbationsin the generalized Kadomtsev-Petviashvili equation with negative dispersion.

The present paper is a more detailed article of the previously published Letter [Phys. Rev. Lett. 84, 3065 (2000)]], which discovered the transversely unstable solitary wave solutions of the generalized Kadomtsev-Petviashvili (GKP) equation with negative dispersion. In addition to detailed explanation of stability analysis to long-wavelength transverse perturbations, numerical calculation of the GKP equation is carried out here to study the transverse stability to perturbations of finite wavelength. The numerical results show that there is a short-wavelength cutoff to the transverse instability. Moreover, we reveal the existence of transversely unstable solitons.

Journal Article↗
PubMed2004

Lattice Boltzmann method for the compressible Euler equations.

The lattice Boltzmann model for the compressible Euler equations is proposed together with its rigorous theoretical background. The proposed model has completely overcome the defects of the previous model that the specific-heat ratio cannot be chosen freely. The macroscopic variables obtained from the solution are shown to satisfy, in the limit of the small Knudsen number, the compressible Euler equations if the variation of the solution is moderate. This is the case where no shock waves or contact discontinuities appear. In contrast, when the solution makes steep variation at several localized regions due to the appearance of shock waves and contact discontinuities, the corresponding macroscopic variables satisfy the weak form of the Euler equations. Their derivation is carried out rigorously by taking into account the scale of variation of the solution correctly. This is the first study that has laid the theoretical foundation of the lattice Boltzmann model for the simulation of flows with shock waves and contact discontinuities. Numerical examples and the error estimates are also given, which are consistent with the above theoretical arguments.

Journal Article↗
PubMed2004

Lattice Boltzmann model for the compressible Navier-Stokes equations with flexible specific-heat ratio.

We have developed a lattice Boltzmann model for the compressible Navier-Stokes equations with a flexible specific-heat ratio. Several numerical results are presented, and they agree well with the corresponding solutions of the Navier-Stokes equations. In addition, an explicit finite-difference scheme is proposed for the numerical calculation that can make a stable calculation with a large Courant number.

Journal Article↗
PubMed2004

The effect of surgical treatment of obstructive sleep apnea syndrome on the plasma TNF-alpha levels.

Obstructive sleep apnea syndrome (OSAS) is defined as intermittent complete or partial upper airway obstruction during sleep, causing mental and physical effects. Both the local and systemic inflammation observed in OSAS induce certain potent pro-inflammatory mediators, which may contribute to the development of cardiovascular consequences. The present study was designed to evaluate the plasma levels of TNF-alpha, which is one of the known pro-inflammatory cytokines, in patients with OSAS and to assess the effect of surgical treatment on the levels of TNF-alpha levels. Twenty seven patients diagnosed to have OSAS, 7 non-apneic patients with chronic tonsillitis (non-OSAS patients), and 4 healthy subjects were enrolled in this study. Blood samples were collected one week preoperatively and postoperatively, and the plasma TNF-alpha levels were measured using high-sensitivity ELISA. The plasma TNF-alpha levels in patients with OSAS were significantly elevated in comparison to normal healthy subjects. In contrast, there was no difference between the patients with non-OSAS and healthy subjects. Moreover, the surgical treatment to enlarge the upper airway in patients with OSAS significantly decreased the levels of TNF-alpha levels. Surgical treatment of patients with OSAS reduces the plasma TNF-alpha levels, thereby ameliorating the systemic inflammation and preventing the development of cardiovascular consequences.

Adolescent↗
PubMed2003

Modulation of neutrophil adhesion to vascular endothelial cells in rat experimental otitis media treated with a macrolide.

OBJECT: We previously reported that erythromycin (EM) affected the adhesion molecules that interact with neutrophils and inhibited neutrophil infiltration in a rat experimental otitis media model. PURPOSE: The purpose of the present study was to examine whether EM affects the adhesion of rat neutrophils to endothelial cells. METHODS: The adhesion of neutrophils to WK-5 endothelial cells was evaluated. One group of rats was given EM for 2 weeks, while the other group received no treatment. The adhesion of peripheral-blood neutrophils and neutrophils accumulated in the middle ear from these two groups were compared. RESULTS: Two-week EM pretreatment inhibited adhesion of neutrophils to WK-5 cells. The adhesion of neutrophils accumulated in the middle ear cavity to WK-5 cells was significantly higher than that of peripheral-blood neutrophils from control rats. CONCLUSION: The results suggest that EM affects the adhesion of neutrophils to endothelial cells.

Animals↗