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Journal Articles

Anomalous behavior of liquid molecules near solid nanoparticles; Novel interpretation on thermal conductivity enhancement in nanofluids

Hashimoto, Shunsuke*; Yamaguchi, Satoshi*; Harada, Masashi*; Nakajima, Kenji; Kikuchi, Tatsuya*; Oishi, Kazuki*

Journal of Colloid and Interface Science, 638, p.475 - 486, 2023/05

 Times Cited Count:1 Percentile:70.8(Chemistry, Physical)

Recently, it has been reported that anomalous improvement in the thermal conductivity of nanofluid composed of base liquids and dispersed solid nanoparticles, compared to the theoretically predicted value calculated from the particle fraction. Generally, the thermal conductivity values of gases and liquids are dominated by the mean free path of the molecules during translational motion. Herein, we present solid evidence showing the possible contribution of the vibrational behavior of liquid molecules around nanoparticles to increasing these thermal conductivities.

JAEA Reports

Theoretical study of the Cs isotope exchange reaction of CsI + Cs'$$rightarrow$$ Cs + ICs' (Contract research)

Kobayashi, Takanori; Hashimoto, Masashi; Yokoyama, Keiichi

JAEA-Research 2015-014, 7 Pages, 2015/12

JAEA-Research-2015-014.pdf:2.46MB

To discuss the exchange reaction of Cs isotope by CsI + Cs'$$rightarrow$$ Cs + ICs', the structure and chemical properties of Cs$$_2$$I intermediate and potential energy surface are calculated using M06/def2-TZVPPD density functional calculation. The calculation shows that the reaction to the intermediate has no barrier and the two Cs-I bonds of Cs$$_2$$I are chemically equivalent. Thus, the collision of CsI + Cs' results in Cs exchange with the high probability.

Journal Articles

Optics tuning for beam collimation in the J-PARC 3-50 beam transport line

Harada, Hiroyuki; Meigo, Shinichiro; Shirakata, Masashi*; Sato, Yoichi*; Tamura, Fumihiko; Tejima, Masaki*; Hashimoto, Yoshinori*; Igarashi, Susumu*; Koseki, Tadashi

JPS Conference Proceedings (Internet), 8, p.012010_1 - 012010_6, 2015/09

The J-PARC 3-50BT line is the beam transport line from 3-GeV rapid-cycling synchrotron (RCS) to 50-GeV main ring (MR). The RCS is the high-intensity proton accelerator, where designed beam power is 1 MW, and has the complex source of space charge effect, etc. Therefore, the uncontrolled emittance growth and beam halo increase nonlinearly with the increasing the beam power. Additionally, the physical aperture of MR with 81 $$pi$$ mm mrad is smaller than that of RCS with 486 $$pi$$ mm mrad. Therefore, the 3-50BT line has the collimators in order to remove the tail or halo of the extracted beam from the RCS. The designed collimator aperture is 54 $$pi$$ mm mrad. It is required to measure and optimize the optics parameters in the collimator area for taking full advantage of the beam collimation. Especially, it is very important to make the dispersion functions free in the collimator area and optimize the beta function. This paper will introduce the method of optics measurement and report the result of the measurement and optimization based on the simulation.

Journal Articles

Optics tuning at the J-PARC 3-50BT line

Harada, Hiroyuki; Meigo, Shinichiro; Shirakata, Masashi*; Sato, Yoichi*; Tamura, Fumihiko; Tejima, Masaki*; Hashimoto, Yoshinori*; Igarashi, Susumu*; Koseki, Tadashi

Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.39 - 43, 2014/06

The J-PARC 3-50 BT line is the beam transport line of extracted beam from 3-GeV rapid-cycling synchrotron (RCS) to 50-GeV main ring (MR). The RCS is the high-intensity proton accelerator, which designed beam power is 1 MW, and has the complex source of space charge effect, etc. Therefore, the uncontrolled emittance growth and beam halo increase nonlinearly with the increasing the beam power. Additionally, physical aperture of MR with 81 $$pi$$ mm mrad is smaller than that of RCS with 486 $$pi$$ mm mrad. Therefore, the 3-50 BT line has the collimators in order to scrape the tail/halo of extracted beam from the RCS. The designed collimator aperture is 54 $$pi$$ mm mrad. It is required to measure and optimize the optics parameter in the collimator area for taking full advantage of beam collimation. This paper will introduce the method of optics measurement and report the result of the measurement and optimization based on the simulation.

Journal Articles

Theoretical study for laser isotope separation of heavy-element molecules in a thermal distribution

Matsuoka, Leo; Ichihara, Akira; Hashimoto, Masashi; Yokoyama, Keiichi

Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 7 Pages, 2011/12

Journal Articles

Numerical study on quantum walks implemented on the cascade rotational transitions in a diatomic molecule

Matsuoka, Leo; Kasajima, Tatsuya; Hashimoto, Masashi; Yokoyama, Keiichi

Journal of the Korean Physical Society, 59(4), p.2897 - 2900, 2011/10

 Times Cited Count:12 Percentile:62.29(Physics, Multidisciplinary)

Journal Articles

Oxygen isotope separation utilizing two-frequency infrared multiphoton dissociation of 2,3-dihydropyran

Hashimoto, Masashi; Oba, Hironori; Yokoyama, Atsushi

Applied Physics B, 104(4), p.969 - 974, 2011/09

 Times Cited Count:1 Percentile:7.18(Optics)

Oxygen isotope separation has been examined by utilizing the two-frequency infrared multiphoton dissociation (IRMPD) of 2,3-dihydropyran (DHP). The two-frequency IRMPD reduces remarkably the required laser fluence. For example, dissociation probability of DHP containing $$^{18}$$O (D($$^{18}$$O)) and enrichment factor (S) were obtained to be 1.6$$times$$10$$^{-3}$$ /pulse and 316 respectively by the simultaneous irradiation with 1052.2 cm$$^{-1}$$ photons at 0.45 J/cm$$^{2}$$ and 1031.5 cm$$^{-1}$$ photons at 1.06 J/cm$$^{2}$$. These are comparable with D($$^{18}$$O) = 2.2$$times$$10$$^{-3}$$ /pulse and S = 391 obtained by the single-frequency irradiation of 1033.5 cm$$^{-1}$$ photons at 2.2 J/cm$$^{2}$$. Therefore, the production rate of an $$^{18}$$O enriched dissociation product has been increased to four times or more, compared with the single-frequency IRMPD, and this two-frequency method would promise a practical large scale separation.

Journal Articles

Isotope production for medical usage using fast neutron reactions

Hatsukawa, Yuichi; Nagai, Yasuki; Kin, Tadahiro; Segawa, Mariko; Harada, Hideo; Iwamoto, Osamu; Iwamoto, Nobuyuki; Ochiai, Kentaro; Takakura, Kosuke; Konno, Chikara; et al.

Proceedings in Radiochemistry, 1(1), p.327 - 329, 2011/09

Authors proposed a new route to produce $$^{99}$$Mo by the $$^{100}$$Mo($$n$$,2$$n$$)$$^{99}$$Mo reaction, which has some characteristic features. Such as the reaction cross section is large, about 1.5 barn at 12 $$<$$ $$E$$$$_{rm n}$$ $$<$$ 17 MeV, which is 10 times larger than the thermal-neutron capture cross section of $$^{98}$$Mo. Second, the cross sections of the ($$n$$,$$alpha$$), ($$n$$,$$np$$), and ($$n$$,$$p$$) reactions are less than a few mb at $$E$$$$_{rm n}$$ = 14 MeV. Third, a large amount of $$^{100}$$Mo target materials can be used, compared to that for proton beam irradiation on $$^{100}$$Mo. Fourth, intense neutrons with energy of 12-17 MeV are already available. In the present work we have measured all $$gamma$$-rays emitted from activities produced by bombarding a natural Mo target with neutrons from the D($$^3$$H,$$n$$)$$^4$$He reaction at Fusion Neutronics Source Facility (FNS) at Japan Atomic Energy Agency (JAEA) to study characteristic features mentioned above more in detail. The neutron flux was about 10$$^{12}$$n/cm$$^2$$s. The experimental results at FNS will be discussed in the conference.

Journal Articles

Narrow-band regenerative amplifier for momentum imaging spectroscopy of molecules

Matsuoka, Leo; Hashimoto, Masashi; Yokoyama, Keiichi

Proceedings of International Quantum Electronics Conference and the Pacific Rim Conference on Lasers and Electro-Optics (IQEC/CLEO Pacific Rim 2011) (CD-ROM), p.1363 - 1364, 2011/08

Journal Articles

Numerical study on quantum walks implemented on the cascade rotational transitions in a diatomic molecule

Matsuoka, Leo; Kasajima, Tatsuya; Hashimoto, Masashi; Yokoyama, Keiichi

arXiv.org (Internet), 5 Pages, 2011/04

Journal Articles

Beam injection tuning of the J-PARC main ring

Wei, G.; Koseki, Tadashi*; Igarashi, Susumu*; Tomizawa, Masahito*; Takano, Jumpei*; Ishii, Koji*; Shirakata, Masashi*; Fan, K.*; Hatakeyama, Shuichiro; Uota, Masahiko*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.3915 - 3917, 2010/05

Journal Articles

Performance of the main ring BPM during the beam commissioning at J-PARC

Toyama, Takeshi*; Arakawa, Dai*; Hiramatsu, Shigenori*; Igarashi, Susumu*; Lee, S.*; Matsumoto, Hiroshi*; Odagiri, Junichi*; Tejima, Masaki*; Tobiyama, Makoto*; Hashimoto, Yoshinori*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.981 - 983, 2010/05

Experiences of operating BPM's during beam commissioning at the J-PARC MR are reported. The subjects are: (1) bug report, statistics and especially the effect of a beam duct step, (2) position resolution estimation ($$<$$30 micrometers with 1 sec averaging), (3) beam based alignment.

JAEA Reports

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2008 - March 31, 2009)

Kanamori, Masashi; Hashimoto, Kazuichiro; Terunuma, Hiroshi; Ikeda, Takeshi; Omura, Akiko; Terakado, Naoya; Nagakura, Tomohiro; Fukumoto, Masahiro; Watanabe, Fumitaka; Yamamoto, Kazuya; et al.

JAEA-Review 2009-023, 61 Pages, 2009/09

JAEA-Review-2009-023.pdf:8.49MB

When a nuclear emergency occurs in Japan, the Japan Atomic Energy Agency (JAEA) provides technical support to the National government, local governments, police, fire station and license holder etc. They are Designated Public Organizations conforming to the Basic Law on Emergency Preparedness and the Basic Plan for Disaster Countermeasures. The Nuclear Emergency Assistance and Training Center (NEAT) of JAEA provides a comprehensive range of technical support activities to an Off-Site Center in case of a nuclear emergency. Specifically, NEAT gives technical advice and information, provides for the dispatch of specialist as required, supplies emergency equipments and materials to the Joint Council of Nuclear Disaster Countermeasures, which meets at the Off-Site Center. NEAT provide various lectures and training course concerning nuclear disaster prevention for those personnel taking an active part in emergency response organizations at normal time. And NEAT researches on nuclear disaster prevention and also cooperate with international organizations. This annual report summarized the activities of JAEA/NEAT in the fiscal year 2008.

Journal Articles

Practical method for producing a large amount of isotopically enriched silicon by infrared multi-photon dissociation of hexafluorodisilane

Oba, Hironori; Akagi, Hiroshi; Katsumata, Keiichi*; Hashimoto, Masashi; Yokoyama, Atsushi

Japanese Journal of Applied Physics, 47(11), p.8379 - 8381, 2008/11

 Times Cited Count:4 Percentile:18.82(Physics, Applied)

This paper presents a practical method for producing highly enriched silicon isotopes utilizing laser irradiation. One- or two-frequency CO$$_{2}$$ laser irradiation has been employed to separate the desired isotope of silicon by means of infrared multi-photon dissociation (IRMPD) of the hexafluorodisilane (Si$$_{2}$$F$$_{6}$$) molecules using a flow reaction system. The production of Si$$_{2}$$F$$_{6}$$ with $$^{28}$$Si fraction of 99.1% at a rate of 0.67 g($$^{28}$$Si)/h was successfully accomplished with a high yield by the two-frequency laser irradiation. The enriched SiF$$_{4}$$ gas with $$^{30}$$Si exceeding 31% was also continuously obtained at the production rate of 0.12 g/h by the one-frequency laser irradiation.

Journal Articles

Small-angle neutron scattering studies of chemical reaction and reaction-induced self-assembly

Tanaka, Hirokazu; Koizumi, Satoshi; Hashimoto, Takeji; Kurosaki, Kazuhiro*; Omae, Masashi*; Kobayashi, Shiro*

Physica B; Condensed Matter, 385-386(1), p.814 - 817, 2006/11

 Times Cited Count:3 Percentile:18.02(Physics, Condensed Matter)

We have investigated a self-assembling process of cellulose artificially synthesized via enzymatic polymerization by means of in-situ and time-resolved small-angle neutron scattering (SANS). The results elucidated the following: (1) cellulose molecules were synthesized at a special reaction site of the enzyme (cellulase) located on or near the smooth surface of the self-assembled enzymes formed in the reaction medium; (2) the synthesized molecules associated themselves via diffusion-limited aggregation (DLA) and crystallized into fibrils and (3) the fibrils formed the aggregates, which had the surface fractal dimension D$$_{s}$$ increasing from 2 to 2.3 with the reaction time, on the smooth surface of the enzyme aggregates.

Journal Articles

Chemical reaction at specific sites and reaction-induced self-assembly as observed by in situ and real time SANS; Enzymatic polymerization to synthetic cellulose

Hashimoto, Takeji; Tanaka, Hirokazu; Koizumi, Satoshi; Kurosaki, Kazuhiro*; Omae, Masashi*; Kobayashi, Shiro*

Biomacromolecules, 7(9), p.2479 - 2482, 2006/09

 Times Cited Count:13 Percentile:38.38(Biochemistry & Molecular Biology)

no abstracts in English

Journal Articles

Rhemium-186-monoaminemonoamidedithiol-conjugated bisphosphonate derivatives for bone pain palliation

Ogawa, Kazuma*; Mukai, Takahiro*; Arano, Yasushi*; Otaka, Akira*; Ueda, Masashi*; Uehara, Tomoya*; Magata, Yasuhiro*; Hashimoto, Kazuyuki; Saji, Hideo*

Nuclear Medicine and Biology, 33(4), p.513 - 520, 2006/05

 Times Cited Count:54 Percentile:80.22(Radiology, Nuclear Medicine & Medical Imaging)

To develop a radiopharmaceutical for the palliation of painful bone metastases based on the concept of bifunctional radiopharmaceuticals, we synthesized a bisphosphonate derivative labeled with rhenium-186 ($$^{186}$$Re) that contains a hydroxyl group at the central carbon of its bisphosphonate structure and attached a stable $$^{186}$$Re-MAMA chelate to the amino group of a 4-amino-butylidene-bisphosphonate derivative, $$^{186}$$Re-MAMA-HBP, and investigated the effect of a hydroxyl group at the central carbon of its bisphosphonate structure on the affinity for hydroxyapatite and biodistribution by conducting a comparative study with $$^{186}$$Re-MAMA-BP. $$^{186}$$Re-MAMA-HBP was prepared by a reaction with $$^{186}$$ReO$$_{4}$$$$^{-}$$ and SnCl$$_{2}$$ in citrate buffer after the deprotection of trityl groups of Tr-MAMA-HBP. After reversed phase HPLC, $$^{186}$$Re-MAMA-HBP had a radiochemical purity of over 95 %. Compared with $$^{186}$$Re-MAMA-BP, $$^{186}$$Re-MAMA-HBP showed a greater affinity for hydroxyapatite beads in vitro and accumulated a significantly higher level in the femur in vivo. Thus, the introduction of a hydroxyl group into $$^{186}$$Re complex-conjugated bisphosphonates would be effective in enhancing accumulation in bone. These findings provide useful information on the design of bone-seeking therapeutic radiopharmaceuticals.

Journal Articles

Silicon isotope separation utilizing infrared multiphoton dissociation of Si$$_{2}$$F$$_{6}$$ irradiated with two-frequency CO$$_{2}$$ laser lights

Yokoyama, Atsushi; Oba, Hironori; Hashimoto, Masashi; Katsumata, Keiichi; Akagi, Hiroshi; Ishii, Takeshi*; Oya, Akio*; Arai, Shigeyoshi*

Applied Physics B, 79(7), p.883 - 889, 2004/11

 Times Cited Count:9 Percentile:42.09(Optics)

Silicon isotope separation has been done utilizing the Infrared Multiphoton Dissociation of Si$$_{2}$$F$$_{6}$$ irradiated with two-frequency CO$$_{2}$$ laser lights. The two-frequency excitation method improved the separation efficiency with keeping the high enrichment factors. For example, Si$$_{2}$$F$$_{6}$$ with the $$^{28}$$Si fraction of 99.4 % was obtained at 40.0 % dissociation of Si$$_{2}$$F$$_{6}$$ after the simultaneous irradiation of 100 pulses with 966.23 cm$$^{-1}$$ photons (0.089 J/cm$$^{2}$$) and 954.55 cm$$^{-1}$$ photons (0.92 J/cm$$^{2}$$), while 1000 pulses were needed to obtain 99.0 % of $$^{28}$$Si at 27.2 % dissociation in the case of single frequency irradiation at 954.55 cm$$^{-1}$$ (0.92 J/cm$$^{2}$$). The single-step enrichment factors of $$^{29}$$Si and $$^{30}$$Si increased with increasing Si$$_{2}$$F$$_{6}$$ pressure. The reason for this enhancement has been discussed in terms of the rotational and vibrational relaxations by collisions with ambient gases.

Journal Articles

Validation of CAMP code for thermo-fluiddynamics of molten debris in lower Plenum

Maruyama, Yu; Moriyama, Kiyofumi; Nakamura, Hideo; Hashimoto, Kazuichiro; Hirano, Masashi; Nakajima, K.*

Proceedings of RASPLAV Seminar 2000 (CD-ROM), 8 Pages, 2000/11

no abstracts in English

Journal Articles

Production of hyperlithiated Li$$_{2}$$F by a laser albation of LiF-Li$$_{3}$$N mixture

Yokoyama, Keiichi; Haketa, Naoki*; Hashimoto, Masashi; Furukawa, Katsutoshi; Tanaka, Hiromasa*; Kudo, Hiroshi*

Chemical Physics Letters, 320(5-6), p.645 - 650, 2000/04

 Times Cited Count:35 Percentile:71.45(Chemistry, Physical)

no abstracts in English

49 (Records 1-20 displayed on this page)