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Hamidian, M. H.,Edkins, S. D.,Joo, Sang Hyun,Kostin, A.,Eisaki, H.,Uchida, S.,Lawler, M. J.,Kim, E.-A.,Mackenzie, A. P.,Fujita, K.,Lee, Jinho,Davis, J. C. Sé,amus Nature Publishing Group, a division of Macmillan P 2016 Nature Vol.532 No.7599
<P>The quantum condensate of Cooper pairs forming a superconductor was originally conceived as being translationally invariant. In theory, however, pairs can exist with finite momentum Q, thus generating a state with a spatially modulated Cooper-pair density(1,2). Such a state has been created in ultracold Li-6 gas(3) but never observed directly in any superconductor. It is now widely hypothesized that the pseudogap phase(4) of the copper oxide superconductors contains such a 'pair density wave' state(5-21). Here we report the use of nanometre-resolution scanned Josephson tunnelling microscopy(22-24) to image Cooper pair tunnelling from a d-wave superconducting microscope tip to the condensate of the superconductor Bi2Sr2CaCu2O8+x. We demonstrate condensate visualization capabilities directly by using the Cooper-pair density variations surrounding zinc impurity atoms(25) and at the Bi2Sr2CaCu2O8+x crystal supermodulation(26). Then, by using Fourier analysis of scanned Josephson tunnelling images, we discover the direct signature of a Cooper-pair density modulation at wavevectors Q(P) approximate to (0.25, 0)2 pi/a(0) and (0, 0.25)2 pi/a(0) in Bi2Sr2CaCu2O8+x. The amplitude of these modulations is about five per cent of the background condensate density and their form factor exhibits primarily s or s' symmetry. This phenomenology is consistent with Ginzburg-Landau theory(5,13,14) when a charge density wave(5,27) with d-symmetry form factor(28-30) and wavevector Q(C) = Q(P) coexists with a d-symmetry superconductor; it is also predicted by several contemporary microscopic theories for the pseudogap phase(18-21).</P>
Simultaneous Transitions in Cuprate Momentum-Space Topology and Electronic Symmetry Breaking
Fujita, K.,Kim, Chung Koo,Lee, Inhee,Lee, Jinho,Hamidian, M. H.,Firmo, I. A.,Mukhopadhyay, S.,Eisaki, H.,Uchida, S.,Lawler, M. J.,Kim, E.-A.,Davis, J. C. American Association for the Advancement of Scienc 2014 Science Vol.344 No.6184
<P><B>Under the Dome</B></P><P>The superconducting transition temperature <I>T<SUB>c</SUB></I> of copper oxides has a dome-shaped dependence on chemical doping. Whether there is a quantum critical point (QCP) beneath the dome, and whether it is related to the enigmatic pseudogap, has been heavily debated. Two papers address this question in two different families of Bi-based cuprates. In (Bi,Pb)<SUB>2</SUB>(Sr,La)<SUB>2</SUB>CuO<SUB>6+δ</SUB>, <B>He <I>et al.</I></B> (p. 608) found that the Fermi surface (FS) undergoes a topological change as doping is increased, which points to the existence of a QCP at a doping close to the maximum in <I>T<SUB>c</SUB></I>, seemingly uncorrelated with the pseudogap. <B>Fujita <I>et al.</I></B> (p. 612) studied a range of dopings in Bi<SUB>2</SUB>Sr<SUB>2</SUB>CaCu<SUB>2</SUB>O<SUB>8+δ</SUB> to find an FS reconstruction simultaneous with the disappearance of both rotational and translational symmetry breaking, the latter of which has been associated with the pseudogap. These findings point to a concealed QCP.</P>
S. Fujieda,A. Fujita,K. Fukamichi,S. Suzuki 한국자기학회 2013 Journal of Magnetics Vol.18 No.2
La1-zNdz(Fe0.88Si0.12)13 and their hydrides were investigated to obtain large magnetocaloric effects (MCEs) in a wide temperature range, including room temperature, for applications in magnetic refrigents. Since the magnetization change due to the itinerant-electron metamagentic (IEM) transition for La1-zNdz(Fe0.88Si0.12)13 becomes larger with increasing z, the isothermal magnetic entropy change ΔSm and the relative cooling power (RCP) are enhanced. In addition, the Curie temperatrue TC of La0.8Nd0.2(Fe0.88Si0.12)13 is increased from 193 to 319 K by hydrogen absorption, with the IEM transition. The maximum value of -ΔSm, -ΔSm<SUP>max</SUP>, in a magnetic field change of 2 T for La0.8Nd0.2(Fe0.88Si0.12)13H1.1 is about 23 J/kg K at TC = 288 K, which is larger than that of 19 J/kg K at TC = 276 K for La(Fe0.88Si0.12)13H1.0. The value of RCP = 179 J/kg of the former is also larger than 160 J/kg of the latter. It is concluded that the partial substitution of Nd improves MCEs in a wide temperautre range, including room temperature.
일반 및 무중력에서 부상 화염의 진동 특성에 관한 연구
원상희(S. H. Won),김준홍(J. Kim),신무경(M. K. Shin),정석호(S. H. Chung),O. Fujita,T. Mori,J. H. Choi,K. Ito 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Characteristics of oscillating lifted flames in coflow have been investigated experimentally with highly<br/> diluted propane in normal and micro gravities to elucidate the stabilization mechanism. In normal gravity,<br/> oscillating lifted flames with the frequency of 2-5 Hz were observed in a certain range of fuel mole fraction<br/> and jet velocity. The oscillation frequency correlated well with jet velocity in terms of Strouhal number,<br/> defined with the stoichiometric laminar burning velocity. This demonstrated the importance of the<br/> propagation characteristics of tribrachial flames at the base of lifted flames in the flame oscillation.<br/> Microgravity experiments have been conducted after the oscillating lifted flames are stabilized in normal<br/> gravity. During the change in gravitational acceleration, the flames rapidly stabilized as nozzle attached<br/> flame mode and became stationary. This behavior confirmed that the lifted flame oscillation in normal<br/> gravity is due to the buoyancy driven instability. Numerical simulation has also been performed<br/> accounting the change in gravitational acceleration. The results successfully predicted the transition<br/> behavior from oscillating lifted flame in normal gravity to stationary attached flame in microgravity and the<br/> variation of flame shapes during the transition.
Propofol decreases in vivo binding of 11C-PBR28 to translocator protein (18 kDa) in the human brain.
Hines, Christina S,Fujita, Masahiro,Zoghbi, Sami S,Kim, Jin Su,Quezado, Zenaide,Herscovitch, Peter,Miao, Ning,Ferraris Araneta, Maria D,Morse, Cheryl,Pike, Victor W,Labovsky, Julia,Innis, Robert B Society of Nuclear Medicine 2013 The Journal of nuclear medicine Vol.54 No.1
<P>The PET radioligand (11)C-PBR28 targets translocator protein (18 kDa) (TSPO) and is a potential marker of neuroimmune activation in vivo. Although several patient populations have been studied using (11)C-PBR28, no investigators have studied cognitively impaired patients who would require anesthesia for the PET procedure, nor have any reports investigated the effects that anesthesia may have on radioligand uptake. The purpose of this study was to determine whether the anesthetic propofol alters brain uptake of (11)C-PBR28 in healthy subjects.</P>
Linear Polarization Measurement of Gamma Rays in 155Gd by Using a Segmented Compton Polarimeter
J.H.Lee,S.Tanaka,T.Shinozuka,M.Fujita,A.Yamazaki,T.Sonoda,Y.K.Kim,J.S.Chai,C.S.Lee,J.Y.Huh,J.Y.Moon,Y.K.Kwon,Y.Gono,T.Fukuchi 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.40 No.5
A linear polarization measurement for gamma rays has been performed to directly determine the parities for the levels in 155Gd. High-spin states in 155Gd were populated in the 154Sm(,3n )155Gd reaction by using 35-MeV alphas. Linearly polarized gamma rays emitted from oriented states were measured by using a Compton polarimeter which is made of a planar-type germanium crystal and is segmented into 25 cathodes. The linear polarization of the gamma rays was measured by selecting Compton-scattered events red in coincidence between two adjacent cathodes. The sign of the measured linear polarization enabled us to distinguish between electric and magnetic types of gamma-ray transitions. Accordingly, the parities of the high-spin states in 155Gd were directly determined. Our parity assignment is in excellent agreement with a previous one. A linear polarization measurement for gamma rays has been performed to directly determine the parities for the levels in 155Gd. High-spin states in 155Gd were populated in the 154Sm(,3n )155Gd reaction by using 35-MeV alphas. Linearly polarized gamma rays emitted from oriented states were measured by using a Compton polarimeter which is made of a planar-type germanium crystal and is segmented into 25 cathodes. The linear polarization of the gamma rays was measured by selecting Compton-scattered events red in coincidence between two adjacent cathodes. The sign of the measured linear polarization enabled us to distinguish between electric and magnetic types of gamma-ray transitions. Accordingly, the parities of the high-spin states in 155Gd were directly determined. Our parity assignment is in excellent agreement with a previous one.