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450 results on '"Muramatsu, M."'

1. Design of a compact superconducting accelerator for advanced heavy-ion therapy

Author

Iwata, Y., Shirai, T., Mizushima, K., Matsuba, S., Yang, Y., Noda, E., Urata, M., Muramatsu, M., Katagiri, K., Yonai, S., Inaniwa, T., Sato, S., Abe, Y., Fujimoto, T., Sasano, T., Shiraishi, T., Suzuki, T., Takahashi, K., Kondo, Ki., Sakaki, H., Nishiuchi, M., Orikasa, T., Takayama, S., Amano, S., Nakanishi, K., Tachibana, M., Touchi, Y., Tsubomatsu, S., and Nomura, S.

Published
2023
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23. Particle-image velocimetry study of a pediatric ventricular assist device

Author

Ferrara, E., Muramatsu, M., Christensen, K.T., and Cestari, I.A.

Subjects
Biomechanics -- Research, Engineering and manufacturing industries, Science and technology
Abstract

Particle-image velocimetry (PIV) was used to visualize the flow within an optically transparent pediatric ventricular assist device (PVAD) under development in our laboratory. The device studied is a diaphragm type pulsatile pump with an ejection volume of 30 ml per beating cycle intended for temporary cardiac assistance as a bridge to transplantation or recovery in children. Of particular interest was the identification of flow patterns, including regions of stagnation and/or strong turbulence that often promote thrombus formation and hemolysis, which can degrade the usefulness of such devices. For this purpose, phase-locked PIV measurements were performed in planes parallel to the diaphram that drives the flow in the device. The test fluid was seeded with 10 [micro]m polystyrene spheres, and the motion of these particles was used to determine the instantaneous flow velocity distribution in the illumination plane. These measurements revealed that flow velocities up to 1.0 m/s can occur within the PVAD. Phase-averaged velocity fields revealed the fixed vortices that drive the bulk flow within the device, though significant cycle-to-cycle variability was also quite apparent in the instantaneous velocity distributions, most notably during the filling phase. This cycle-to-cycle variability can generate strong turbulence that may contribute to greater hemolysis. Stagnation regions have also been observed between the input and output branches of the prototype, which can increase the likelihood of thrombus formation. [DOI: 10.1115/1.4001252]

Published
2010

25. Experiments with fundamental aspects performed in a small ECR ion source for a new carbon therapy facility

Author

Drentje, A.G., Kitagawa, A., and Muramatsu, M.

Subjects
Ion sources -- Research, Heavy ions -- Properties, Carbon -- Isotopes, Carbon -- Properties, Business, Chemistry, Electronics, Electronics and electrical industries
Abstract

A small permanent magnet electron cyclotron resonance ion source (ECRIS) has been developed for the production of [C.sup.4+] ions for the third carbon-therapy facility in Japan. The emphasis of the design is on stability, easy operation and prevention of maintenance, where high charge state production is not a requirement. Tests with different feed-gases have shown that carbon-hydrogen compounds are favorable, in particular with carbon to hydrogen ratio of 1:1. A parallel study of (highly charged) [C.sup.5+] production revealed that the various compounds of feed-gas are behaving as if feeding the two components separately. This includes the behavior of replacing hydrogen by deuterium. From these a plausible reason was found for the observed failure of hydrogen as a mixing gas. Other experiments with the small source were performed to study the effect of inserting an aluminum (-oxide) cylinder inside the electron cyclotron resonance plasma-chamber. Earlier research found an increase in production of high charge states, but a good explanation was still missing. By adapting an insulated cylinder that can be biased positively, it was shown that ion diffusion to the side walls can be reduced, in particular when the cylinder is made of strips covering the pole pieces of the hexapole magnet. The new tool can be used to study the mechanism in more detail and also has possibilities of further improving a source for higher charge state production. Index Terms--Carbon ions, electron cyclotron resonance ion sources (ECRISs), gas-mixing, heavy ion therapy.

Published
2008

28. Vacancy-impurity complexes in polycrystalline Si used as gate electrodes of HfSiON-based metal-oxide-semiconductors probed using monoenergetic positron beams

Author

Uedono, A., Ikeuchi, K., Otsuka, T., Yamabe, K., Eguchi, K., Takayanagi, M., Ishibashi, S., Ohdaira, T., Muramatsu, M., and Suzuki, R.

Subjects
Positrons -- Research, Metal oxide semiconductor field effect transistors -- Research, Silicon compounds -- Electric properties, Physics
Abstract

Vacancy-impurity complexes in polycrystalline Si (poly-Si) used as gate electrodes of HfSiON-based metal-oxide-semiconductor field-effect transistor (MOSFET) are detected by using monoenergetic positron beams. The results have suggested that suppression of the oxygen diffusion from high-k gate dielectrics into gate electrodes are necessary for MOSFETs and the positron annihilation parameter is sensitive to change in the vacancy-type defects in poly-Si used as gate electrodes.

Published
2006

29. Annealing properties of open volumes in HfSiO(sub x) and HfAlO(sub x) gate dielectrics studied using monoenergetic positron beams

Author

Uedono, A., Ikeuchi, K., Yamabe, K., Ohdaira, T., Muramatsu, M., Suzuki, R., Hamid, A.S., Chikyow, T., Torii, K., and Yamada, K.

Subjects
Hafnium -- Electric properties, Hafnium -- Chemical properties, Annihilation reactions -- Research, Physics
Abstract

The thin Hf(sub 0.6)Si(sub 0.4)O(sub x) and Hf(sub 0.3)Al(sub 0.7)O(sub x) films, which are fabricated by metal-organic chemical-vapor deposition and atomic-layer-deposition techniques, are characterized using monoenergetic positron beams. The results show that positron annihilation parameter is sensitive to change in the matrix structure of amorphous high-k materials and can be used to determine process parameters for the fabrication of high-k gate dielectrics.

Published
2005

31. Spontaneous haemorrhage into metastatic brain tumours after stereotactic radiosurgery using a linear accelerator. (Paper)

Author

Suzuki, H., Toyoda, S., Muramatsu, M., Shimizu, T., Kojima, T., and Taki, W.

Subjects
Hemorrhage -- Diagnosis -- Risk factors -- Complications and side effects -- Care and treatment, Brain tumors -- Care and treatment -- Complications and side effects -- Diagnosis -- Risk factors, Radiosurgery -- Evaluation, Health, Psychology and mental health, Diagnosis, Care and treatment, Evaluation, Complications and side effects, Risk factors
Abstract

Objective: To determine the incidence and clinical characteristics of spontaneous haemorrhage into metastatic brain tumours after radiosurgery. Methods: Intratumour haemorrhage rate, clinical features, and treatment were evaluated in 54 patients [...]

Published
2003

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