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Dry Etching of InGaN/GaN Multiple Quantum-Well LED Structures in Inductively Coupled Cl2/Ar Plasmas
H.J.Park,R.J.Choi,한윤봉,Y.H.Im,A.Yoshikawa 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.3
A parametric study of the etch characteristics of InGaN/GaN multiple quantum-well (MQW) light-emitting diode (LED) structures has been carried out with Cl2/Ar in an inductively coupled plasma (ICP) discharge. The etch rate increased with Cl2 concentration up to 60 % and remained relatively constant at higher Cl2 percentages. It also increased monotonically with the ICP source and the rf chuck powers. The attainable etch rate for the InGaN/GaN MQW structures was about 4,500 A/min under moderate ICP conditions: 700 W ICP source power, 100 W chuck power, 10 mTorr, and 50 % Cl2. The experimental results overall showed that the dominant etch mechanism of the ICP etching of the InGaN/GaN MQW LED structures was an energetic ion-enhanced chemical etching.
Conditional PTEN-deficient Mice as a Prostate Cancer Chemoprevention Model
Koike, Hiroyuki,Nozawa, Masahiro,De Velasco, Marco A,Kura, Yurie,Ando, Naomi,Fukushima, Emiko,Yamamoto, Yutaka,Hatanaka, Yuji,Yoshikawa, Kazuhiro,Nishio, Kazuto,Uemura, Hirotsugu Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.5
Background: We generated a mouse model of prostate cancer based on the adult-prostate-specific inactivation of phosphatase and tensin homolog (PTEN) using the Cre-loxP system. The potential of our mice as a useful animal model was examined by evaluating the chemopreventive efficacy of the anti-androgen, chlormadinone acetate (CMA). Materials and Methods: Six-week-old mice were treated subcutaneously with $50{\mu}g/g$ of CMA three times a week for 9 or 14 weeks and sacrificed at weeks 15 and 20. Macroscopic change of the entire genitourinary tract (GUT) and histologically evident prostate gland tumor development were evaluated. Proliferation and apoptosis status in the prostate were examined by immunohistochemistry. Results: CMA triggered significant shrinkage of not only the GUT but also prostate glands at 15 weeks compared to the control (p=0.017 and p=0.010, respectively), and the trend became more marked after a further five-weeks of treatment. The onset of prostate adenocarcinoma was not prevented but the proliferation of cancer cells was inhibited by CMA, which suggested the androgen axis is critical for cancer growth in these mice. Conclusions: Conditional PTEN-deficient mice are useful as a preclinical model for chemoprevention studies and serve as a valuable tool for the future screening of potential chemopreventive agents.
Namioka, T.,Saito, A.,Inoue, Y.,Park, Y.,Min, T.j.,Roh, S.a.,Yoshikawa, K. Applied Science Publishers 2011 APPLIED ENERGY Vol.88 No.6
Operating conditions for low-temperature pyrolysis and steam reforming of plastics over a ruthenium catalyst were investigated. In the range studied, the highest gas and lowest coke fractions for polystyrene (PS) with a 60gh<SUP>-1</SUP> scale, continuous-feed, two-stage gasifier were obtained with a pyrolyzer temperature of 673K, steam reforming temperature of 903K, and weight hourly space velocity (WHSV) of 0.10g-sample g-catalyst<SUP>-1</SUP>h<SUP>-1</SUP>. These operating conditions are consistent with optimum conditions reported previously for polypropylene. Our results indicate that at around 903K, the activity of the ruthenium catalyst was high enough to minimize the difference between the rates of the steam reforming reactions of the pyrolysates from polystyrene and polypropylene. The proposed system thus has the flexibility to compensate for differences in chemical structures of municipal waste plastics. In addition, the steam reforming temperature was about 200K lower than the temperature used in a conventional Ni-catalyzed process for the production of hydrogen. Low-temperature steam reforming allows for lower thermal input to the steam reformer, which results in an increase in thermal efficiency in the proposed process employing a Ru catalyst. Because low-temperature steam reforming can be also expected to reduce thermal degradation rates of the catalyst, the pyrolysis-steam reforming process with a Ru catalyst has the potential for use in small-scale production of hydrogen-rich gas from waste plastics that can be used for power generation.
A high‐frequency study of the Sunyaev–Zel’dovich effect morphology in galaxy clusters
Prokhorov, D. A.,Colafrancesco, S.,Akahori, T.,Million, E. T.,Nagataki, S.,Yoshikawa, K. Blackwell Publishing Ltd 2011 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.416 No.1
<P><B>ABSTRACT</B></P><P>High‐frequency, high‐resolution imaging of the Sunyaev–Zel’dovich (SZ) effect is an important technique to study the complex structures of the atmospheres of merging galaxy clusters. Such observations are sensitive to the details of the electron spectrum. We show that the morphology of the SZ intensity maps in simulated galaxy clusters observed at 345, 600 and 857 GHz are significantly different because of SZ relativistic corrections. These differences can be revealed by high‐resolution imaging instruments.</P><P>We calculate relativistically corrected SZ intensity maps of a simulated, massive, merging galaxy cluster and of the massive, merging clusters 1E0657−558 (the Bullet cluster) and Abell 2219. The morphologies of the SZ intensity maps are remarkably different between 345 and 857 GHz for each merging cluster. We show that high‐resolution imaging observations of the SZ intensity maps at these frequencies, obtainable with the LABOCA and HERSCHEL‐SPIRE instruments, allow to fully exploit the astrophysical relevance of the predicted SZ morphological effect.</P>
Digital silicon photomultiplier readout of a new fast and bright scintillation crystal (Ce:GFAG)
Lee, Y.S.,Leem, H.T.,Yamamoto, S.,Choi, Y.,Kamada, K.,Yoshikawa, A.,Park, S.G.,Yeom, J.Y. North-Holland 2016 Nuclear Instruments & Methods in Physics Research. Vol.832 No.-
A new Gadolinium Fine Aluminum Gallate (Ce:GFAG) scintillation crystal with both high energy resolution and fast timing properties has successfully been grown. Compared to Gd<SUB>3</SUB>Al<SUB>2</SUB>Ga<SUB>3</SUB>O<SUB>12</SUB> (Ce:GAGG), this new inorganic scintillation crystal has a high luminosity similar to and a faster decay time. In this paper, we report on the timing and energy performance results of the new GFAG scintillation crystal read out with digital silicon photomultipliers (dSiPM) for positron emission tomography (PET) application. The best coincidence resolving time (FWHM) of polished 3x3x5mm<SUP>3</SUP> crystals was 223+/-6ps for GFAG crystals compared to 396+/-28ps for GAGG crystals and 131+/-3ps for LYSO crystals respectively. An energy resolution (511keV peak of Na-22) of 10.9+/-0.2% was attained with GFAG coupled to dSiPM after correcting for saturation effect, compared to 9.5+/-0.3% for Ce:GAGG crystals and 11.9+/-0.4% for LYSO crystals respectively. It is expected that this new scintillator may be competitive in terms of overall properties such as energy resolution, timing resolution and growing (raw material) cost, compared to existing scintillators for positron emission tomography (PET).
Density fluctuation measurements in the tandem mirror GAMMA 10
masayuki Yoshikawa,A. Nakahara,A. Itakura,H. Hojo,H. Higaki,N. Yanagi,T. Kobayashi,T. Cho,Y. Shima 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
Fluctuation in the plasma needs to be measured for studying the improvement of the plasma confinement by the formation of the plasma confinement potential. A newly constructed multichannel microwave interferometer and ultrashort-pulse reflectometry were used for measuring the line integrated plasma density profile and density fluctuation profile in a few plasma shots. The first results of density and density fluctuation measurements in the central cell of the tandem mirror GAMMA 10 are described by using the multi-channel interferometer and ultrashort-pulse reflectometry.
High-Power ECRH Experiments in the GAMMA 10 Tandem Mirror
yoshinori Tatematsu,A. Itakura,D. Nagai,H. Higaki,H. Hojo,I. Katanuma,J. Kohagura,K. Nozaki,K. Sakamotoa,K. Ishii,M. Ichimura,M. Yoshikawa,M. Hirata,M. K. Islam,N. Machida,O. Watanabe,T. Imai,T. Numak 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
Power-up of gyrotrons was carried out and corresponding launcher systems were designed for plug and central-cell ECRH systems in the GAMMA 10 tandem mirror. Then, a high-power ECRH experiment was started. For the plug ECRH, new 500-kW gyrotrons produced a new record value of the confining potential. For the central-cell ECRH, development of a new antenna system has increased the transmission rate of incident microwave power and focused it onto the machine axis in the resonance surface. As a result, a clear increase of the diamagnetism was observed during the pulse of ECRH.
atsushi Kojima,A. Itakura,H. Kakiuchi,H. Higaki,K. Ishii,M. Ichimura,M. Yoshikawa,N. Kaidou,S. Fujimoto,T. Cho,T. Yamaguchi,Y. Miyata 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
The radial particle flux induced by drift-type fluctuations is observed by use of a gold neutral beam probe in the tandem mirror GAMMA 10. When the drift waves are excited in the plasma, the measured phase difference between the density and potential fluctuations is not zero; the radial profile of the phase difference is not constant. This showed that the radial particle flux had some profile and then the density profile would be varied due to the radial particle transport induced by the fluctuations through the radial particle flux. Experimental results showed the density reduction due to the transport induced by the drift-type fluctuations. The phase difference is an important parameter to decide the radial particle flux. The profiles of the phase difference are measured to understand the decision mechanism of the phase difference. The radial profile of the phase difference is varied by the ion heating power, the density and the potential profiles. As a result, the phase difference had a correlation with the difference between the local drift frequency (the electron diamagnetic drift frequency and the E×B drift frequency) and the observed frequency.
Prokhorov, D. A.,Dubois, Y.,Nagataki, S.,Akahori, T.,Yoshikawa, K. Blackwell Publishing Ltd 2011 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.415 No.3
<P><B>ABSTRACT</B></P><P>The Sunyaev–Zel’dovich (hereinafter SZ) effect is a promising tool to derive the gas temperature of galaxy clusters. Approximation of a spherically symmetric gas distribution is usually used to determine the temperature structure of galaxy clusters, but this approximation cannot properly describe merging galaxy clusters. The methods used so far, which do not assume the spherically symmetric distribution, permit us to derive 2D temperature maps of merging galaxy clusters. In this paper, we propose a method to derive the standard temperature deviation and temperature variance along the line of sight, which permits us to analyse the 3D temperature structure of galaxy clusters by means of the thermal SZ effect. We also propose a method to reveal merger shock waves in galaxy clusters by analysing the presence of temperature inhomogeneities along the line of sight.</P>
J. H. Mun,A. Jouini,A. Yoshikawa,Lyon1 University,T. Fukuda,J. S. Lee 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.5
Undoped and (0, 0.5, 5 mol%) Lu2O3 single crystals were grown by the micro-pulling-down method. Crystals were transparent with yellowish color with 4.2 mm in diameter and 6-9 mm in length. Yb-doped Lu2O3 single crystals have a good compositional homogeneity along the growth axis. Both, thermal diffusivity and heat capacity decrease when the Yb concentration increase. As a result, the calculated thermal conductivity for 5 mol% Yb3+-doped Lu2O3 decreases from 14.32 to 12.42 Wm−1 K−1 . We have also investigated the absorption, fluorescence spectra and measured fluorescence lifetimes as a function of the Yb content.