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Journal Articles

Method to reduce long-lived fission products by nuclear transmutations with fast spectrum reactors

Chiba, Satoshi*; Wakabayashi, Toshio*; Tachi, Yoshiaki; Takaki, Naoyuki*; Terashima, Atsunori*; Okumura, Shin*; Yoshida, Tadashi*

Scientific Reports (Internet), 7(1), p.13961_1 - 13961_10, 2017/10

 Times Cited Count:18 Percentile:94.32(Multidisciplinary Sciences)

Transmutation of long-lived fission products (LLFPs: $$^{79}$$Se, $$^{93}$$Zr, $$^{99}$$Tc, $$^{107}$$Pd, $$^{129}$$I, and $$^{135}$$Cs) into short-lived or non-radioactive nuclides by fast neutron spectrum reactors without isotope separation has been proposed as a solution to the problem of radioactive wastes disposal. Despite investigation of many methods, such transmutation remains technologically difficult. To establish an effective and efficient transmutation system, we propose a novel neutron moderator material, yttrium deuteride (YD$$_{2}$$), to soften the neutron spectrum leaking from the reactor core. Neutron energy spectra and effective half-lives of LLFPs, transmutation rates, and support ratios were evaluated with the continuous-energy Monte Carlo code MVP-II/MVP-BURN and the JENDL-4.0 cross section library. With the YD$$_{2}$$ moderator in the radial blanket and shield regions, effective half-lives drastically decreased from 10$$^{6}$$ to 10$$^{2}$$ years and the support ratios reached 1.0 for all six LLFPs. This successful development and implementation of a transmutation system for LLFPs without isotope separation contribute to developing a self-consuming cycle of LLFPs using fast spectrum reactors to reduce radioactive waste.

Journal Articles

Laser therapy for twin-to-twin transfusion syndrome; Today and near-future

Yamashita, Hiromasa*; Oka, Kiyoshi; Yamanaka, Noriaki*; Seki, Takeshi; Kim, K.*; Kuwana, Kenta*; Masamune, Ken*; Naganawa, Akihiro*; Dohi, Takeyoshi*; Chiba, Toshio*

Nihon Reza Igakkai-Shi, 33(2), p.122 - 130, 2012/08

no abstracts in English

Journal Articles

Nucleosynthesis in supernovae and neutrino oscillation

Suzuki, Toshio*; Yoshida, Takashi*; Chiba, Satoshi; Kajino, Toshitaka*

Nihon Butsuri Gakkai-Shi, 67(1), p.49 - 54, 2012/01

Neutrino processes play important roles in synthesis of $$^7$$Li, $$^{11}$$B, $$^{138}$$La, $$^{180}$$Ta and other elements in explosive environments realized in supernovae. In order to understand better the neutrino processes, we constructed new shell model Hamiltonians based on recent progress of physics in unstable nuclei near the neutron drip-line. We then applied these Hamiltonians to calculate the neutrino-nucleus reaction cross sections through detailed and careful comparison of nuclear properties with those of relevant experimental data. We can thus carry out precise and reliable theoretical estimate of supernova nucleosynthesis of $$^{7}$$Li, $$^{11}$$B, etc including the neutrino processes. Finally we propose a new method to determine unknown neutrino oscillation parameters, namely the mixing angle $$theta_{13}$$ and the mass hierarchy, by making use of strong dependence of the yields of $$^{7}$$Li, $$^{11}$$B on these parameters.

Journal Articles

Nucleosynthesis in supernovae and neutrino oscillation

Suzuki, Toshio*; Yoshida, Takashi*; Chiba, Satoshi; Kajino, Toshitaka*

Nihon Butsuri Gakkai-Shi, 67(1), p.49 - 54, 2012/01

Neutrino-nucleus reaction processes play important roles in synthesis of $$^7$$Li, $$^{11}$$B, $$^{138}$$La, $$^{180}$$Ta and other elements in explosive environments realized in supernovae. We have constructed new shell model Hamiltonians based on recent progress of physics in unstable nuclei near the neutron drip-line. The spin responses of nuclei are found to be remarkably improved by the new Hamiltonians. We then applied these Hamiltonians to calculate the neutrino-nucleus reaction cross sections, and obtained more precise and reliable theoretical estimate of supernova nucleosynthesis of $$^7$$Li, $$^{11}$$B, etc including the neutrino processes. Finally we propose a new method to determine unknown neutrino oscillation parameters, namely the mixing angle $$theta_{13}$$ and the mass hierarchy, by making use of strong dependence of the yields of $$^7$$Li and $$^{11}$$B on these parameters.

Journal Articles

A Novel ultrasmall composite optical fiberscope

Oka, Kiyoshi; Seki, Takeshi; Naganawa, Akihiro*; Kim, K.*; Chiba, Toshio*

Surgical Endoscopy, 25(7), p.2368 - 2371, 2011/07

 Times Cited Count:4 Percentile:25.4(Surgery)

We developed an ultrasmall composite-type optical fiberscope (1.1-mm diameter) with a central cauterizing laser fiber surrounded by imaging and illumination fibers as a tool for various surgical applications. Porcine mesenteric blood vessels were laser irradiated in vivo and the procedure was filmed using ultrahigh-speed (max 1,000,000 frames per second) and thermographic cameras. Blood flow was decreased by 81.7% after laser irradiation and the diameter of the vessels at the irradiated point was approximately 46-48% smaller than that of the unirradiated vessels. Medical doctors also confirmed that the blood vessel was blocked after the experiments. From these results, it was shown that this device is applicable to all medical regions.

Journal Articles

Laser irradiation control of fetal endoscopic surgery for twin-twin transfusion syndrome; Verification of blood-flow interception by in vivo experiment

Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi; Chiba, Toshio*

Keisoku Jido Seigyo Gakkai Sangyo Rombunshu, 9(10), p.70 - 75, 2010/04

The fetoscopic laser photocoagulation of chorionic plate anastomosing vessels is main treatment for the twin-twin transfusion syndrome. However, in this treatment, it is required highly endoscopic technologies, for example, blood flow measurement, estimation of distance between placental vessels and irradiation fiber tip and so on. We research and develop a composite-type optical fiberscope (2.2 mm in diameter), which has centrally-located cautery laser fiber and surrounding located fiberglasses for viewing. The laser transmitting efficiency of our fiberscope was very high (84.7%), and certain degree of cauterization was performed with from 20 to 40W laser power, when the distance between irradiated area and fiber tip was 10 mm. In addition, we emitted the laser to porcine liver for laser power control using a thermocouple as a basic research for intercepting placental blood flow, and we controlled the temperature of irradiation spot within $$pm$$0.3$$^{circ}$$C error in previous paper. In this study, we emitted the laser to in vivo porcine mesenteric vessel with blood flow for laser power control under temperature measurement. From the experimental result, the target temperature of 60 and 70$$^{circ}$$C with feedback control system using thermocouple was controlled low power of about 17W maintain target temperature within $$pm$$2.0$$^{circ}$$C error. Moreover, we measured the blood flow before and after laser irradiation by a laser Doppler blood-flow meter, and confirmed quantitatively the blood flow blocking.

Journal Articles

The Development of a composite-type optical fiberscope system for fetoscopic laser photocoagulation of chorionic plate anastomosing vessels (FLPC)

Oka, Kiyoshi; Seki, Takeshi; Naganawa, Akihiro*; Yamashita, Hiromasa*; Kim, K.*; Chiba, Toshio*

Minimally Invasive Therapy and Allied Technologies, 19(2), p.94 - 99, 2010/04

 Times Cited Count:6 Percentile:33.02(Surgery)

We developed a new laser device using a composite-type optical fiberscope for laser surgery to treat twin-twin transfusion syndrome. The composite-type optical fiberscope (2.2 mm in external diameter) consists of a centrally located single fiber for laser treatment (0.1mm in diameter) and its surrounding fibers for diagnosis. This fiberscope enables transmission of 40-W Yb fiber laser. The Yb fiber laser can be focused to 10 mm focal length using two lenses on the tip of the fiberscope. In this research, we emitted the laser to in vivo porcine mesenteric vessel with blood flow both with an established laser fiber of 0.6-mm diameter (0.6-mm normal fiber) and with our composite-type optical fiberscope to compare the cautery performance of those devices.

Journal Articles

Blood flow measurement system for fetoscopic laser photocoagulation of chorionic plate anastomosing vessels (FLPC)

Seki, Takeshi*; Oka, Kiyoshi; Naganawa, Akihiro*; Yamashita, Hiromasa*; Kim, K.*; Chiba, Toshio*

Minimally Invasive Therapy and Allied Technologies, 18(6), p.350 - 355, 2009/12

 Times Cited Count:3 Percentile:17.42(Surgery)

Fetoscopic laser photocoagulation of chorionic plate anastomosing vessels (FLPC) applies to the treatment of previable fetuses with severe twin-twin transfusion syndrome (TTTS). However, there has not been an established method to confirm that the blood flow is blocked. For this issue, we have developed a composite-type optical fiberscope (2.2 mm in diameter). This fiberscope enables transmission of 50 W Yb fiber laser which can be focused to 10 mm focal length using two lenses on the fiberscope tip. In this study, we combined the fiberscope and a laser blood-flow meter, and irradiated cautery laser to porcine mesenteric vein with measuring blood flow at the same time. From the experimental results, we could quantitatively measure the blood flow before and after laser irradiation, and confirm the blood flow blocking with our system.

Journal Articles

Neutrino-nucleus reaction cross sections for light element synthesis in supernova explosions

Yoshida, Takashi*; Suzuki, Toshio*; Chiba, Satoshi; Kajino, Toshitaka*; Yokomakura, Hidekazu*; Kimura, Keiichi*; Takamura, Akira*; Hartmann, D.*

Astrophysical Journal, 686(1), p.448 - 466, 2008/10

The neutrino-nucleus reaction cross sections of $$^4$$He and $$^{12}$$C are evaluated using new shell model Hamiltonians. Branching ratios of various decay channels are calculated to evaluate the yields of Li, Be, and B produced through the $$nu$$-process in supernova explosions. The new cross sections enhance the yields of $$^{7}$$Li and $$^{11}$$B produced during the supernova explosion of a 16.2 M$$_odot$$ star model compared to our previous study by factors of 1.3 and 1.2, respectively. On the other hand, the yield of $$^{10}$$B decreases by a factor of three. The yields of $$^{6}$$Li, $$^{9}$$Be, and the radioactive nucleus $$^{10}$$Be are found at a level of 10 to 11 M$$_odot$$. The temperature of $$nu mu, tau$$- and $$bar{nu} mu, tau$$-neutrinos inferred from the supernova contribution of $$^{11}$$B in Galactic chemical evolution models is constrained to be in the range 4.5 MeV to 6.4 MeV. The increase in the $$^{7}$$Li and $$^{11}$$B yields due to neutrino oscillations is demonstrated with the new cross sections.

Journal Articles

Neutrino-nucleus reaction cross sections for light element synthesis in supernova explosions

Yoshida, Takashi*; Suzuki, Toshio*; Chiba, Satoshi; Kajino, Toshitaka*; Yokomakura, Hidekazu*; Kimura, Keiichi*; Takamura, Akira*; Hartmann, D. H.*

Astrophysical Journal, 686(1), p.448 - 466, 2008/10

 Times Cited Count:85 Percentile:90.15(Astronomy & Astrophysics)

The neutrino-nucleus reaction cross sections of $$^4$$He and $$^{12}$$C are evaluated using new shell model Hamiltonians. The new cross sections enhance the yields of $$^7$$Li and $$^{11}$$B produced during the supernova explosion of a 16.2 $$M_odot$$ star model compared to the case using the conventional cross sections by about 10%. On the other hand, the yield of $$^{10}$$B decreases by a factor of two. The yields of $$^6$$Li, $$^9$$Be, and the radioactive nucleus $$^{10}$$Be are found at a level of $$sim 10^{-11} M_odot$$. The temperature of $$nu_{mu,tau}$$- and $$bar{nu}_{mu,tau}$$-neutrinos inferred from the supernova contribution of $$^{11}$$B in Galactic chemical evolution models is constrained to be in the range 4.3 MeV to 6.5 MeV. The increase in the $$^7$$Li and $$^{11}$$B yields due to neutrino oscillations is demonstrated with the new cross sections.

Journal Articles

Laser irradiation control of fetal endoscopic surgery for twin-twin transfusion syndrome; Performance verification using temperature sensor

Naganawa, Akihiro*; Oka, Kiyoshi; Suzuki, Katsumasa*; Seki, Takeshi*; Chiba, Toshio*

Keisoku Jido Seigyo Gakkai Sangyo Rombunshu, 7(8), p.53 - 59, 2008/07

no abstracts in English

Journal Articles

Neutrino-nucleus reactions based on recent advances in shell-model calculations

Suzuki, Toshio*; Chiba, Satoshi; Yoshida, Takashi*; Higashijima, Koji*; Homma, Michio*; Kajino, Toshitaka*; Otsuka, Takaharu*

Nuclear Physics A, 805(2), p.579 - 581, 2008/02

Neutrino-nucleus reactions on $$^{12}$$C and $$^4$$He are studied based on new shell model Hamiltonians. The cross sections are found to be enhanced compared with those obtained by conventional Hamiltonians. The production yield of $$^7$$Li and $$^{11}$$B during supernova explosions are pointed out to be enhanced, and a possibility of determining the neutrino mixing angle $$theta_{13}$$ is discussed in case of neutrino oscillations. Neutrino induced reactions on Fe and Ni isotopes are also studied based on recent advances in shell model calculations in the $$fp$$-shell. The reaction crowds sections are found to be enhanced compared with those obtained by a modified KB3 Hamiltonian.

Journal Articles

Composite-type optical fiberscope for laser surgery for twin-to-twin transfusion syndrome

Oka, Kiyoshi; Naganawa, Akihiro*; Yamashita, Hiromasa*; Nakamura, Tetsuya*; Chiba, Toshio*

Lecture Notes in Computer Science 5128, p.251 - 259, 2008/00

We present our new laser device for prospective human fetoplacental surgery including that of twin-twin transfusion syndrome. We developed acomposite-type optical fiberscope (2.2-mm in diameter) that enables transmission of 40-W Yb fiber laser light alongside of coaxial fetoscopic images. Using a laser condensing lens on the fiberscope tip, Yb fiber laser light can be focused 10-mm off. Using porcine liver tissue, despite changes in delivered laser energy, the diameter and depth of cauterized areas remained constant when the liver position agreed with the laser focal point, although the laser output altered the extent of tissue ablation. In conclusion, the performance of the fiberscope can be well controlled with accurate and efficient ablation of the target tissue. This Yb fiber laser fiberscope is expected to work much better if mounted on a miniature bending manipulator and if provided with additional functions (realtime distance and blood flow measurements).

Journal Articles

Neutrino-nucleus reactions based on new shell model hamiltonians

Suzuki, Toshio*; Chiba, Satoshi; Yoshida, Takashi*; Kajino, Toshitaka*; Otsuka, Takaharu*

Physical Review C, 74(3), p.034307_1 - 034307_9, 2006/09

 Times Cited Count:93 Percentile:97.16(Physics, Nuclear)

no abstracts in English

Journal Articles

Neutrino-nucleus reactions induced by supernova neutrinos

Suzuki, Toshio*; Chiba, Satoshi; Iwamoto, Osamu; Kajino, Toshitaka*

AIP Conference Proceedings 847, p.479 - 481, 2006/07

no abstracts in English

Oral presentation

A Tissue cauterization test with new laser endoscope for FLPC in TTTS

Oka, Kiyoshi; Nakamura, Tetsuya*; Ueda, Hirohisa*; Chiba, Toshio*

no journal, , 

no abstracts in English

Oral presentation

Composite-type optical fiberscope for laser surgery for Twin-to-twin Transfusion Syndrome (TTTS)

Oka, Kiyoshi; Yamashita, Hiromasa*; Nakamura, Tetsuya*; Ueda, Hirohisa*; Chiba, Toshio*

no journal, , 

In fetoscopic laser photocoagulation of placental communicating vessels (FLPC) for twin-to-twin transfusion syndrome (TTTS), there are several technical issues. These include; (1) laser light diffusion that reduces the energy density over the placental surface, (2) unknown distances between the placental surface and laser fiber tip, (3) difficulties in assessing actual flow of the targeted blood vessels, and (4) difficulties in controlling laser light direction for perpendicular irradiation. To settle these problems, we successfully developed a new small composite-type optical fiberscope. In this report, we present our experimental outcomes to assess its clinical availability/feasibility for clinical TTTS laser surgery.

Oral presentation

Advanced development of a laser endoscopy for FLPC of TTTS

Oka, Kiyoshi; Nakamura, Tetsuya*; Ueda, Hirohisa*; Toriya, Tomoaki*; Tsumanuma, Koji*; Naganawa, Akihiro*; Watanabe, Shinsuke*; Ishiyama, Akihiko*; Yamashita, Hiromasa*; Chiba, Toshio*

no journal, , 

no abstracts in English

Oral presentation

Quantitative evaluation of blood flow interception of fetoscopic laser irradiation control

Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi; Yamashita, Hiromasa*; Chiba, Toshio*

no journal, , 

We developed a new laser device using the composite-type optical fiberscope for laser surgery for twin-twin transfusion syndrome. A composite-type optical fiberscope (2.2 mm in diameter) consists of a centrally located single fiber for laser treatment and its surrounding fibers for diagnosis. This fiberscope enables transmission of 50-W Yb fiber laser. The Yb fiber laser can focus laser to 10 mm focal length using two lenses on tip of the fiberscope. In this paper, we describe the experimental results of temperature control during blood-flow interception of porcine mesenteric venous flow and measure blood flow before and after laser irradiation for evaluation blood flow interception.

Oral presentation

Development of minimally invasive laser device using composite-type optical fiberscope of 1.1 mm in diameter

Seki, Takeshi*; Oka, Kiyoshi; Naganawa, Akihiro*; Chiba, Toshio*

no journal, , 

During conventional endoscopic laser treatments, it is difficult to keep distance between target tissue and fiberscope tip for effective laser irradiation. Moreover, the choice of laser power and diagnosis of a successful procedure depend on the operator's skill or instincts. Therefore, we developed a new minimally invasive laser device using a 1.1 mm in diameter composite-type optical fiberscope (COF) to overcome the above problems. This device enables transmission of 50 W Yb fiber laser and an image in parallel. In addition, this COF enables the measurement of the blood-flow of target tissue and estimates of the distance between irradiation area and the fiber tip in real time by means of an embedded laser Doppler blood-flow meter. In this paper, we present a configuration of the minimally invasive laser device using the 1.1 mm COF and the results of the basic performance experiments.

Oral presentation

Development and usefulness of the optical fiberscope with a laser irradiation function of 1.1 mm of outer diameters

Oka, Kiyoshi; Seki, Takeshi*; Naganawa, Akihiro*; Chiba, Toshio*

no journal, , 

no abstracts in English

21 (Records 1-20 displayed on this page)