Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 73, Issue 4
Displaying 1-50 of 50 articles from this issue
  • Yoshichika Onuki, Rikio Settai, Kiyohiro Sugiyama, Tetsuya Takeuchi, T ...
    2004 Volume 73 Issue 4 Pages 769-787
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We present recent advances in the magnetism and superconductivity of rare earth and uranium compounds. Heavy fermions are formed on the basis of the competition between the RKKY interaction and the Kondo effect in these compounds. The application of pressure to these compounds is useful to control the electronic states in the antiferromagnets CeRh2Si2 and CeRhIn5, and the ferromagnet UGe2. The quadrupole interaction or the quadrupole Kondo effect is found to be responsible for heavy fermions in PrFe4P12. A rich variety of superconducting properties are demonstrated: superconductivity of CeCoIn5 and CeRhIn5 in the vicinity of a quantum critical point, coexistence of ferromagnetism and superconductivity in UGe2, and superconductivity based on the quadrupole fluctuations in PrOs4Sb12, together with the relation between the superconducting transition temperature and the quasi-two dimensionality of the electronic states.
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  • Akihiro Kasahara, Hiizu Nakanishi
    2004 Volume 73 Issue 4 Pages 789-791
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We study the static structure of piles made of polydisperse disks in the rigid limit with and without friction using molecular dynamic simulations for various disk elasticities and pile preparation procedures. The coordination numbers are calculated to examine the isostaticity of the pile structure. For the frictionless pile, it is demonstrated that the coordination number converges to 4 in the rigid limit, which implies that the structure of the rigid disk pile is isostatic. On the other hand, for the frictional case with the infinite friction constant, the coordination number depends on the preparation procedure of the pile, but we find that, in the rigid limit, the structure becomes very close to an isostatic one with the coordination number 3 when the pile is formed through the process that tends to make a pile of random configuration.
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  • Shunji Nojima
    2004 Volume 73 Issue 4 Pages 792-795
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    Theoretical investigations are carried out for optical modes in a mechanically perturbed (rotating) microstructure (microdisk). Whispering gallery modes with twofold degeneracy in the microdisk at rest split off due to the onset of rotation (the Sagnac effect). This rotation also excites a number of extra modes that appear to have developed from vacuum states in the microdisk at rest. These modes exhibit anticrossing and merging-regeneration phenomena as the rotation speed increases and consequently form a photonic band structure. The above phenomena can be explained in terms of optical mode mixing caused by coupling between different optical states through the angular momentum of rotation.
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  • Takashi Kambe, Yoshio Nogami, Kokichi Oshima, Wataru Fujita, Kunio Awa ...
    2004 Volume 73 Issue 4 Pages 796-799
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We found for the first time a structural phase transition in two-dimensional kagomé antiferromagnet m-N-methylpyridinium α-nitronyl nitroxide (m-MPYNN)·BF4·\\frac13 (acetone). As, below Ts=128.7 K, the intense satellite reflections are clearly observed at the modulation wave vector of qs=(\\frac13,\\frac13,0), the unit cell of the low-temperature phase is enlarged to \\sqrt3a×\\sqrt3a×c. In the low-temperature phase, the space group is determined to be P31c. The orientation of acetone molecules orders below Ts, leading to the lack of the three-fold axis. To confirm whether the low-temperature phase maintains a kagomé-like network structure or not, we estimate the overlap integrals between the singly occupied molecular orbital wave functions of the MPYNN molecules by the extended Hückel method. The result is that all the overlap integrals are modified below Ts, suggesting that the system below Ts cannot be regarded as the uniform S=1 kagomé antiferromagnet.
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  • Norio Shimizu, Satoshi Sasaki, Takayasu Hanashima, Kouji Yamawaki, Hir ...
    2004 Volume 73 Issue 4 Pages 800-803
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We have succeeded in measuring fluorescence X-ray magnetic circular dichroism (XMCD) and absorption spectra at the Co K absorption edge for a small amount of doped Co ions in a CoxTi1−xO2 anatase film (x=0.07; 700-Å-thickness) on a LaAlO3 (001) substrate. X-ray fluorescence intensity was accumulated for 3 d at the pseudo-total-reflection geometry in a synchrotron undulator beamline, BL-39XU at SPring-8. Negative-to-positive dispersion-type XMCD spectra were clearly observed at E=7.725 keV, suggesting the ferromagnetism at room temperature and unlikelihood on the existence of Co-metal clusters. XANES spectra support the Co2+ oxidation state and participation of a partial structure of ilmenite-type CoTiO3. We have proposed a crystal structure of Co-doped anatase films and the ferromagnetic order scheme by Co–Ti–O polysynthetic twin lamellae. A (012) CoTiO3 layer interstitially distributes parallel to the (001) plane of anatase and replaces a quarter of the anatase cell at intervals of three and half times of the cell along the c axis.
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  • Masahisa Tsuchiizu, Yoshikazu Suzumura
    2004 Volume 73 Issue 4 Pages 804-807
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We investigate the electronic properties of a doped two-leg Hubbard ladder with both the onsite and nearest-neighbor Coulomb repulsions by using the weak-coupling renormalization-group method. It is shown that, for strong nearest-neighbor repulsions, the charge-density-wave state coexisting with the p-density-wave state becomes a dominant fluctuation where spins form intrachain singlets. By increasing doping rate, we have also shown that the effects of the nearest-neighbor repulsions are reduced and the system exhibits a quantum phase transition into the d-wave-like (or rung-singlet) superconducting state. We derive the effective fermion theory which describes the critical properties of the transition point with the gapless excitation of magnon. The phase diagram of the two-leg ladder compound, Sr14−xCaxCu24O41, is discussed.
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  • Mitsuhiro Arikawa, Takashi Yamamoto, Yasuhiro Saiga, Yoshio Kuramoto
    2004 Volume 73 Issue 4 Pages 808-811
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    The dynamical spin structure factor S(q,ω) is obtained analytically for the one-dimensional supersymmetric tJ model with 1⁄r2 interaction. In contrast with the conventional view on the spin–charge separation, interpretation of S(q,ω) requires both fractionalized and non-fractionalized electrons depending on the energy–momentum region. At low energies, the spectrum is naturally explained in terms of spinons, holons, and antiholons, all of which obey fractional exclusion statistics.
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  • Hisashi Kondo, Tôru Moriya
    2004 Volume 73 Issue 4 Pages 812-814
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We study spin fluctuation (SF) mediated superconductivity (SC) in a half-filled square lattice Hubbard model with the transfer matrices −t between nearest neighbor sites and −t′ between a half of next nearest neighbor sites neighboring along only one of the ⟨1,1⟩ directions, considering application of this model to organic κ-(BEDT-TTF)2X compounds. Varying the t′⁄t value from 0 to 1, one can interpolate between a square and an equilateral triangular lattice, the latter giving frustration to antiferromagnetically (AF) coupled spin systems. Within the fluctuation exchange (FLEX) approximation, we calculate χ(q,ω), Tc and the SC order parameter for various model parameter values and find that both AF and SC are suppressed as one approaches the frustration geometry or |(t′⁄t)−1|→0. The SC phase, however, extends beyond the AF phase boundary fairly close to t′⁄t=1 for realistic Ut values. The order parameter is of x2y2-type for t′⁄t<1 and of xy-type for t′⁄t>1.
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  • Sotaro Sasaki, Hiroaki Ikeda, Kosaku Yamada
    2004 Volume 73 Issue 4 Pages 815-818
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We investigate pairing symmetry and transition temperature in a quasi-one-dimensional repulsive Hubbard model. We solve the Eliashberg equation using the third-order perturbation expansion with respect to the on-site repulsion U. We find that when the electron number density is shifted from the half-filled state, a transition into unconventional superconductivity is expected. When one-dimensionality is weak, a spin-singlet state is favorable. In contrast, when one-dimensionality is strong and electron number density is far from the half-filled state, a spin-triplet state is stabilized. Finally, we discuss the possibility of unconventional superconductivity caused by the on-site Coulomb repulsion in β-Na0.33V2O5.
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  • Shigeki Yonezawa, Yuji Muraoka, Yoshitaka Matsushita, Zenji Hiroi
    2004 Volume 73 Issue 4 Pages 819-821
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We report the discovery of a new pyrochlore oxide superconductor RbOs2O6. The compound crystallizes in the same β-pyrochlore structure as the recently discovered superconductor KOs2O6, where Os atoms form a corner-sharing tetrahedral network called the pyrochlore lattice with Rb or K atoms in the cage. Resistivity, magnetic susceptibility and specific heat measurements on polycrystalline samples evidence a bulk superconductivity with Tc=6.3 K.
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  • Shoji Yamamoto, Hiromitsu Hori
    2004 Volume 73 Issue 4 Pages 822-825
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    A new theory is proposed to interpret nuclear spin–lattice relaxation-time (T1) measurements on the spin-1 quasi-one-dimensional Heisenberg antiferromagnet Ni(C2H8N2)2NO2(ClO4) (NENP). While Sagi and Affleck [Phys. Rev. B 53 (1996) 9188] pioneeringly discussed this subject in terms of field-theoretical languages, there is no theoretical attempt yet to explicitly simulate the novel observations of T1−1 reported by Fujiwara et al. [Phys. Rev. B 47 (1993) 11860]. By means of modified spin waves, we interpret the minimum of T1−1 as a function of an applied field, pending for the past decade.
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  • Kohji Kamada, Isao Yoshizawa
    2004 Volume 73 Issue 4 Pages 826-829
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    Heating by less than 10°C of heavy water was observed at room temperature upon the propagation of acoustic waves of 6 MHz with intensity of about 2 W/cm2 during the scanning of a magnetic field from 800 to 1000 mT. A control experiment with light water did not show the heating. As a quantitative explanation of this heating, the “spin-flip phonon maser” action of deuterons due to the thermal Raman process of spin-phonon coupling is considered. Good agreement with the experimental result was obtained. The 6 MHz acoustic waves induce the pumping transitions of the nuclear spin system.
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  • Ken-ichi Maruno, Wen-Xiu Ma, Masayuki Oikawa
    2004 Volume 73 Issue 4 Pages 831-837
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    A set of conditions is presented for Casorati determinants to give solutions to the Toda lattice equation. It is used to establish a relation between the Casorati determinant solutions and the generalized Casorati determinant solutions. Positons, negatons and their interaction solutions of the Toda lattice equation are constructed through the generalized Casorati determinant technique. A careful analysis is also made for general positons and negatons, the resulting positons and negatons of order one being explicitly computed. The generalized Casorati determinant formulation for the two dimensional Toda lattice (2dTL) equation is presented. It is shown that positon, negaton and complexiton type solutions in the 2dTL equation exist and these solutions reduce to positon, negaton and complexiton type solutions in the Toda lattice equation by the standard reduction procedure.
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  • Akira Nakamura
    2004 Volume 73 Issue 4 Pages 838-842
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We consider the generalized ladder operators of the special functions. This scheme can be applied to the problem of obtaining the N-soliton solutions of the 2+1 dimensional finite Toda equation. Analytically the N-soliton solutions can be expressed by the use of Hyper Geometric Functions with two variables.
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  • Toru Nakamura, Hiroshi Ezawa, Keiji Watanabe, Frederik W. Wiegel
    2004 Volume 73 Issue 4 Pages 843-854
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    For the d=3-dimensional Brownian motion ω(t) starting from x∈\\mathbbR3 and for a given function V(r), r∈\\mathbbR3, we show that XT[ω]=∫0TV(ω(t))dt converges in law as T→∞ if VL1(\\mathbbR3)∩Lκ(\\mathbbR3) for some κ>3⁄2 and determine its limit probability density. In distinction with the cases of d=1 and 2 as studied in our previous papers, it is found that: (i) XT converges without the division by ν(T), which are T1⁄2 and log[DT⁄γ] for d=1 and 2, respectively, and (ii) the probability density pV(X,x) of X=limT→∞XT depends on the starting point x as well as on the shape of V. In particular, when x is outside the support of V, the density has a term p0δ(X) with some probability p0. We find pV(X,x) for the cases of V of the square-well and the exponential types. The case of the Coulomb-potential type ∉Lκ(\\mathbbR3) (for any κ) requires a renormalization. This study has an application to modeling the process of chemoreception in the immune system of living bodies, in which a number of cells, called B-cells, perform Brownian motions in a distribution V(r) of antigens, and the number X of antigens each B-cell captures in a long time is counted by a lymphatic system, which in this way is capable of determining the density distibution of the antigens from the statistics of X.
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  • Tomoko Yonemura, Sachiko Kitajima, Fumiaki Shibata
    2004 Volume 73 Issue 4 Pages 855-861
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    Theory of quantum mechanical communication channel under the influence of environmental fluctuations is formulated on the basis of non-equilibrium statistical mechanics. The formalism is explicitly applied to the quantum dense coding process where a qubit signal is sent into the channel in which the temperature and/or quantum fluctuations disturb an initial coherency of the signal. A quantum channel matrix, the Shannon’s mutual information and quantum mechanical mutual information are analytically obtained and numerically evaluated. It is shown that the temperature effect is quite large in the signal transmission processes.
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  • Ryuji Ishizaki, Masayoshi Inoue
    2004 Volume 73 Issue 4 Pages 862-866
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We study random walks of a decimal point of a two-sided infinite sequence (…at(−2)at(−1).at(0)at(1)…) where the point is driven by a generalized shift (GS) map, and find the super-diffusion whose distribution does not obey a Lévy distribution. The diffusion depends on the rule of GS map, and we calculate the mean square displacement σ2(n)∝nζ for diffusive dynamics rules and a fluctuated drift rule where a parameter P is introduced which represents the probability of a(i+1)0 whose value is the same with a(i)0. We find that ζ depends on P for the diffusive rules, whereas ζ is independent of P for the fluctuated drift rule.
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  • Tatsuya Uezu, Aya Hirano, Masato Okada
    2004 Volume 73 Issue 4 Pages 867-874
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We examine a previouly introduced attractor neural network model that explains the persistent activities of neurons in the anterior ventral temporal cortex of the brain. In this model, the coexistence of several attractors including correlated attractors was reported in the cases of finite and infinite loading. In this paper, by means of a statistical mechanical method, we study the statics and dynamics of the model in both finite and extensive loading, mainly focusing on the retrieval properties of the Hopfield and correlated attractors. In the extensive loading case, we derive the evolution equations by the dynamical replica theory. We found several characteristic temporal behaviours, both in the finite and extensive loading cases. The theoretical results were confirmed by numerical simulations.
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  • Hiroaki Ueno, Hiroshi Taneichi, Yoshio Takahashi, Tomokazu Suzuki, Kat ...
    2004 Volume 73 Issue 4 Pages 875-881
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    The cross sections and angular distributions of (γ,p) and (γ,d) reactions on 10B have been measured in the giant resonance region by the (e,p) and (e,d) reactions applying the virtual photon theory. The E2 cross section of the (γ,p0) reaction derived by a model dependent analysis of the angular distributions shows contributions of 26.5±4.5% to the E2 energy weighted sum rule. The (γ,p0,2) integrated cross section up to 27 MeV is 6.1±0.2% of the E1 sum rule value which is smaller than 30% for 10B(γ,n). This suggests that the (γ,p) reaction leaves high-lying residual states as the prediction of the shell model calculation. The E2 strength deduced from the 10B(γ,d0) reaction is 0.14±0.05% of the E2 energy weighted sum rule, which is one order of magnitude smaller than the case of neighboring odd–odd nuclei; 6Li and 14N. This may be suppressed by a competition with (γ,d1).
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  • Keiji Kosaka
    2004 Volume 73 Issue 4 Pages 882-884
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    A local-scaling density functional theory (LS-DFT) [J. Phys. Soc. Jpn. 72 (2003) 1926] is reformulated excluding an artificial expression. In the formulation, two kinds of local-scaling transformations are proposed. The basic equation of the LS-DFT is derived. It is shown that the equation is equivalent to the differential virial theorem proposed by Holas and March [Phys. Rev. A 51 (1995) 2040].
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  • Takeshi Kai, Toshihiro Kubo, Rajesh Srivastava, Shinobu Nakazaki
    2004 Volume 73 Issue 4 Pages 885-891
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We calculate differential cross sections and Stokes parameters using the R-matrix method with 24, 32 and 38 target states for the transition from the 3s2 1S state to the 3s3d 1D state in magnesium by electron impact. Results at incident electron energies of 10 and 20 eV are obtained and compared with available experimental and theoretical results. Except at near forward-scattering angles at 10 eV, overall good agreement is found with measurements for the differential cross sections.
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  • Tamayo Ono, Etsuko Shimaki, Yasuhiko Kojima, Yoshitaka Kiyama, Tosiyas ...
    2004 Volume 73 Issue 4 Pages 892-897
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    Differential cross sections have been measured for vibrationally elastic scattering of electrons from ozone molecules at incident electron energies from 2 eV to 10 eV in the angular range from 20° to 120°. Absolute values of the differential cross sections have been obtained by means of the relative flow method. Integral and momentum transfer cross sections have been derived from the measured data by extrapolating to 0° and 180° scattering angles. Comparison was made between the present measurements and those from other experiments and theoretical calculations.
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  • J. L. V. Lewandowski
    2004 Volume 73 Issue 4 Pages 898-906
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    A computational study of resistive drift waves in the edge plasma of a bumpy torus is presented. The magnetohydrodynamic equilibrium is obtained from a three-dimensional local equilibrium model. The use of a local magnetohydrodynamic equilibrium model allows for a computationally-efficient systematic study of the impact of the magnetic field structure on drift wave stability.
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  • Kiyoyuki Yambe, Sadao Masamune, Shinsuke Maki, Nobuyuki Watarai, Hidek ...
    2004 Volume 73 Issue 4 Pages 907-913
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    The analysis of particle and energy fluxes was made by using electrostatic probes in the edge region of STP-3(M) reversed field pinch plasma. One of the new findings is that the plasma potential profile in the case of high current plasma indicates an increase in radial electric field Er (=−∇Vs) in the region where 0.92<ra<1.00, which implies the generation of Er×Bp velocity shear. The electrostatic part of the particle flux was observed to decrease in the shear region, while the electron density and temperature profiles remained unchanged. Thus, spontaneous generation of velocity shear suppresses the electrostatic particle flux locally, but transition to global confinement improvement is not realized. The contribution of electrostatic fluctuations to energy flux in the edge is estimated as about 50%, and of stochastic diffusion is estimated as about 50%.
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  • Jun-Ichi Yamaura, Touru Yamauchi, Masahiko Isobe, Hiroyuki Yamada, Yut ...
    2004 Volume 73 Issue 4 Pages 914-920
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We performed the X-ray diffraction measurements at low temperature under ambient pressure for the pressure-induced superconductor β′-Cu0.65V2O5. Satellite reflections were observed with an incommensurate modulation and a successive commensurate state depending on the cooling rate. The X-ray structure analysis in the commensurate state indicates the structural deformation on the vanadium ladder. We suggest the occurrence of the charge disproportionation for the origin of the structural transition. Additionally, we reveal the structural and electronic character for β (β′)-vanadium bronzes.
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  • Masashi Watanabe, Yukio Noda, Yoshio Nogami, Hatsumi Mori
    2004 Volume 73 Issue 4 Pages 921-925
    Published: April 15, 2004
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    θ-(BEDT-TTF)2RbZn(SCN)4 is known as a two-dimensional organic conductor exhibiting a metal–insulator phase transition associated with a charge ordering phenomena at TMI=200 K under ambient pressure. The transition temperature increases with applied pressure and reaches room temperature at 1.1 GPa. The structural change by pressure induced phase transition was investigated by X-ray diffraction using synchrotron radiation. A superlattice formation of 2c was found above 1.1 GPa. A single crystal structural analysis taking account of the superlattice was carried out at 1.2 GPa. Displacements of BEDT-TTF molecules were found to be similar to the displacements in the low temperature phase at the ambient pressure. However, the shrinkage of the c-axis under pressure was four times as large as that under cooling at the transition point. Decreases in the intermolecular distances between BEDT-TTF molecules resulted in increases of the intersite Coulomb energies V and an increase of the electric bandwidth W. UW (U: on-site Coulomb energy) decreased as a result of an increase of W. Such a change of UW is obstructive to the enhancement of the charge ordered phase. This indicates that an effect of V is indispensable to the charge-ordered phase in this material.
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  • Shio Inagaki, James T. Jenkins
    2004 Volume 73 Issue 4 Pages 926-931
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We have created a flat piling of disks in a numerical experiment, using the Distinct Element Method (DEM), by depositing them under gravity. In the resulting pile, we then measured increments in stress and strain that were associated with a small decrease in gravity. We first describe the stress in terms of the strain using isotropic elasticity theory. Then, from a micro-mechanical view point, we calculate the relation between the stress and strain using the mean strain assumption. We compare the predicted values of Young’s modulus and Poisson’s ratio with those that were measured in the numerical experiment.
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  • Yunmin Yang, Naoto Sekimura, Hiroaki Abe
    2004 Volume 73 Issue 4 Pages 932-942
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    The deformation behavior of glissile interstitial clusters containing 7, 37, 187 and 517 interstitials were investigated for FCC copper in this paper by molecular dynamics simulation. The results show that: The interaction between small interstitial clusters (containing less than 37 SIAs) and dislocation can generate many possible configurations depend on the cluster’s size and their relative position to dislocation. The classical dislocation theory cannot be used to describe such reactions. Clusters containing 7-SIAs can be incorporated into dislocation easily and then travel quickly along the dislocation to free surface. Clusters containing 37-SIAs can be incorporated into and then slip with dislocations under stress. Clusters containing 187-SIAs cannot be incorporated into dislocation. Atomistic resolution slipping process of perfect loop was firstly reported in this study. Perfect loops containing 517-SIAs were elongated due to the difference in mobility of every segments and one pair of screw dislocation were generated between prismatic planes.
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  • Ling Wang, Xi-Jing Ning
    2004 Volume 73 Issue 4 Pages 943-949
    Published: April 15, 2004
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    Molecular dynamics simulations are performed to investigate the behavior of helium atoms generated from tritium decay in copper crystals at 300 K. At the early stage just after a He atom generation, the lattice structure is badly deformed and the local temperature rises considerably above 300 K. In perfect crystals, single He atom diffuses by interstitial paths whereas two He atoms attract each other and can form a stable dimmer, which pushes a Cu atom off its original lattice site and occupies the vacancy. This dimmer can catch another He atom to form a trimmer. In a Cu crystal with a prepared vacancy, single He atom rapidly occupies the vacancy with little lattice deformation.
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  • Katsuhiko Hasebe, Takanao Asahi, Takashi Yoshida, Yukihiko Kawamura, H ...
    2004 Volume 73 Issue 4 Pages 950-955
    Published: April 15, 2004
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    The I–II phase transition of betaine phosphate crystal associated with the ordering of PO4 groups has been studied by X-ray scattering: The observations are concerned on (1) the temperature dependence of lattice constants, (2) the temperature dependence of the order parameter of PO4 which followed the relation η∝(TcT)β, β=0.42(1), and (3) the anisotropic distribution of critical diffuse scattering in the reciprocal space above Tc; elongated along the c-direction, shortened along the b*-direction. The critical X-ray diffuse scattering has been analyzed. The correlation lengths along three principal directions of anisotropic scattering distribution were estimated. The temperature dependence of the correlation length and staggered susceptibility were discussed.
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  • Ryuichi Goto, Fuyuki Shimojo, Kozo Hoshino
    2004 Volume 73 Issue 4 Pages 956-963
    Published: April 15, 2004
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    The temperature dependence of the electronic states of the liquid In2Te3 mixtures is studied by ab initio molecular-dynamics simulations. To clarify the microscopic mechanism of the semiconductor–metal transition in the liquid In2Te3, we calculated the total and the partial densities of states, the gross charges, the overlap populations and the maximally localized Wannier functions. We showed from these results that In atoms have fourfold coordination at lower temperatures, while, at higher temperatures, fourfold-coordinated In atoms decrease and that accompanying with this structural change, partially-filled non-bonding states are generated around the twofold-coordinated In and Te atoms, which cause the metallic state of the liquid In2Te3.
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  • Ashok Chatterjee, Yasutami Takada
    2004 Volume 73 Issue 4 Pages 964-969
    Published: April 15, 2004
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    Effects of cubic and quartic anharmonic phonons on the polaronic properties are investigated in the one-dimensional Hubbard–Holstein model at half filling, using the variable-displacement Lang–Firsov canonical transformation and the exact solution of Lieb and Wu. Although the quartic anharmonicity always reduces the effect of the Coulomb repulsion U, the cubic one mainly responsible for the thermal expansion of lattice brings about the effect of strong asymmetric nature in the sign of the electron–phonon coupling constant g; it enhances the effect of U for positive g, while it suppresses for negative g. As a result, the overall features of the anharmonic system are basically similar to those in the harmonic one for positive g, but even in the range of the realistic magnitudes for those anharmonicities, they may become qualitatively so different for negative g as to provide a first-order phase transition.
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  • Yunori Nisikawa, Manabu Usuda, Jun-ichi Igarashi, Hironobu Shoji, Tosh ...
    2004 Volume 73 Issue 4 Pages 970-975
    Published: April 15, 2004
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    We study the resonant inelastic x-ray scattering (RIXS) at the K edge of Ge. We measure RIXS spectra with systematically varying momenta in the final state. The spectra are a measure of exciting an electron–hole pair. We find a single-peak structure (except the elastic peak) as a function of photon energy, which is nearly independent of final-state momenta. We analyze the experimental data by means of the band structure calculation. The calculation reproduces well the experimental shape, clarifying the implication of the spectral shape.
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  • Jun-Ichi Yamaura, Akiko Nakao, Reizo Kato
    2004 Volume 73 Issue 4 Pages 976-982
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    The two-dimensional molecular conductor β′-Et2Me2P[Pd(dmit)2]2 is a Mott insulator under ambient pressure and exhibits a metallic state accompanied by the superconductivity with applying pressure. And, in the higher pressure region, another non-metallic behavior appears. X-ray single-crystal structure analyses under high pressures were performed at room and low temperatures to reveal the mechanism of the pressure effect. Tight-binding band calculations based on the resultant structural data indicate that the insulator-to-metal transition is a Mott transition due to an increase of the band width of the HOMO-based band and the HOMO–LUMO band overlap mechanism proposed in the previous report does not apply to this case. The high-pressure non-metallic state is relevant to the structural transition with a symmetry breaking.
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  • Hiroki Nakano, Yoshinori Takahashi
    2004 Volume 73 Issue 4 Pages 983-990
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    Metal–insulator transition in the ground state of the Hubbard chain with the next-nearest-neighbor hopping is studied by exact diagonalization method. This model shows the partially ferromagnetic metal near the Mott insulator for large Coulomb repulsion while the model reveals the non-magnetic metal for small but finite Coulomb repulsion. We find the transition between the partially ferromagnetic metal and the Mott insulator without phase separation. A new critical exponent of the diverging charge compressibility with respect to the hole density is observed when the system approaches the metal–Mott-insulator transition point from the side of the partially ferromagnetic metal. We also find the occurrence of the phase separation between partially ferromagnetic metal and the Mott insulator for even larger Coulomb repulsion. The model proposed here is interesting in view of the magnetism as well as the metal–insulator transition.
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  • Masafumi Ito, Yukio Yasui, Satoshi Iikubo, Minoru Soda, Akito Kobayash ...
    2004 Volume 73 Issue 4 Pages 991-999
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    Magnetic excitation spectra χ″(q,ω) of YBa2Cu3Oy, La2−xSrxCuO4, La2−yxNdySrxCuO4 and Nd2−xCexCuO4 are compared with those of model calculations, where q and ω are the wave vector and the energy of the excitations. In the model, the dynamical spin susceptibility is calculated by the expression χ(q,ω)=χ0(q,ω)⁄{1+J(q0(q,ω)}, where χ0(q,ω) is obtained by adopting the effective energy dispersion of the quasi particles which can reproduce the shapes of the Fermi surface, and J(q) is the exchange coupling between the Cu–Cu electrons. It is important to consider the experimentally observed quasi particle broadening (Γ) to reproduce the observed spectra of YBa2Cu3Oy, while to reproduce the data of La2−xSrxCuO4 and La2−yxNdySrxCuO4, very small Γ values have to be used, even in the phases without the static “stripe” order. This may be caused by the existence of the “stripe” correlations or “stripe” fluctuations.
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  • Youichi Yanase
    2004 Volume 73 Issue 4 Pages 1000-1017
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    The pseudogap phenomena induced by the SC fluctuation are investigated in details. We perform a calculation beyond the 1-loop approximation. The SC fluctuation is microscopically derived on the basis of the repulsive Hubbard model. The vertex corrections are collected in the infinite order with use of the quasi-static approximation. The single-particle excitations, NMR 1⁄T1T, spin susceptibility and superconducting transition temperature are discussed. The important role of the vertex correction is pointed out for the single particle spectral function. On the other hand, the validity of the 1-loop order theory is confirmed for other quantities. We shed light on the essential nature of SC fluctuation leading to the pseudogap from the comparison with spin and charge fluctuations.
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  • Takanori Kida, Mikio Koyano, Koichi Higashimine
    2004 Volume 73 Issue 4 Pages 1018-1022
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We have grown a new composite of [MnO]x[MoO2+δ]1−x (0≤x≤1) co-sputtered films. The film structures exhibit strong dependence of Mn contents. The films, with x≤0.1, 0.2≤x≤0.4, and 0.5≤x≤0.8, have MoO2 polycrystalline structures, MoO2+δ and MnO amorphous structures, and MnO nanocrystallites with about 10 nm in diameter, respectively. The magnetic phase diagram (spin-glass-like and mixed-magnetic phases) of the composite is consistent with the corresponding film structure. Results of magnetic measurements indicate that the uncompensated magnetic moments at grain boundaries of MnO nanocrystalline surface play an important role in their magnetic properties.
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  • Satoshi Iikubo, Youhei Ohno, Yoshiaki Kobayashi, Yukio Yasui, Masafumi ...
    2004 Volume 73 Issue 4 Pages 1023-1030
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    Ferromagnetic spinel system Cu1−xZnxCr2Se4 has been studied by neutron diffraction, NMR and magnetization measurements on both polycrystalline and single crystal samples. The magnetic state are discussed mainly for x=0.7: At low temperature, the system is essentially in the conically ordered state, and the uniform magnetization M and the modulation vector Qm are along ⟨100⟩ in zero magnetic field but not necessarily parallel to each other. All Cr moments within a plane perpendicular to Qm are parallel, where the conical angle θc of the Cr moment is ∼50° and the pitch δφ of the azimuthal angles φ is estimated to be ∼38°. The width of the random distribution of δφ around the average value increases rather significantly with increasing temperature T, while the correlation length of the ferromagnetic component does not exhibit significant change up to room temperature. When the external magnetic field is applied, the conical axis of each domain rotates toward the field direction without changing the modulation vector Qm. Brief discussion on the relationship between the non-trivial magnetic structure and the behavior of the anomalous Hall resistivity is also given.
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  • Satoru Kobayashi, Toshihiro Osawa, Hiroyuki Kimura, Yukio Noda, Isao K ...
    2004 Volume 73 Issue 4 Pages 1031-1035
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We report results of dielectric and neutron diffraction measurements in zero field on magnetic ordering of weakly ferroelectric ErMn2O5. Around the ferroelectric transition temperature of TC1∼38 K below TN1=44 K, we observed successive magnetic phase transitions from a two-dimensionally-modulated (2D) incommensurate magnetic (ICM) phase with the propagation vector q=(qx,0,qz) to another 1D-ICM one with q=(qx,0,\\frac14) at T=39.1 K, and then to a commensurate magnetic (CM) phase with q=(\\frac12,0,\\frac14) at T=37.7 K. These two magnetic phase transitions (39.1 K and 37.7 K) were found to be associated with an anomaly in the dielectric constant along the b axis. In addition, we found that in the case of a rapid-cooling procedure a low-temperature ICM state characterized by q=(\\frac12,0,0.265) shows up and coexists with the CM phase below TN2=11.5 K where evolution of magnetic order of the Er ions is inferred from measurements of the magnetoelectric effect. These observations indicate the strong coupling between ferroelectricity and magnetic ordering in this system.
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  • M. Ishiwata, M. Yoshikawa Murata, T. Yoshida
    2004 Volume 73 Issue 4 Pages 1036-1044
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    For H and F nuclei in CHClF2 adsorbed on a NaY zeolite, dependences of T1 on temperature, an observation frequency and a pore filling factor are observed. All of these T1 data are sucessfully analyzed on the basis of both the nucleus–electron dipolar interaction with a Fe3+ ion substituting Al3+ in the zeolite framework, and the translational diffusion model for adsorbate motion of capture on and release from an adsorption site Na+ which compensates charge of Al3+ in the aluminosilicate. From these relaxation analyses under the assumption of isotropic random jump of the absorbate molecule, temperature and loading rate dependences of an adsorption lifetime, a mean squared jump distance and a diffusion coefficient are determined. Then, microdynamics of the CHClF2 molecule are discussed by use of these variables in physical adsorption.
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  • Takahiro Iijima, Kenjiro Hashi, Atsushi Goto, Tadashi Shimizu, Shinobu ...
    2004 Volume 73 Issue 4 Pages 1045-1049
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    The 31P NMR spectra were measured using 31P, 113In and 115In triple-resonance and magic-angle spinning (MAS) to investigate an indirect spin–spin interaction in undoped and Fe-doped InP semiconductors. The linewidth of the static NMR spectrum obtained by cross polarization (CP) of 115In→31P with 115In decoupling was explained by the lattice sum of 31P–31P dipolar couplings. On the other hand, the linewidth of the MAS NMR spectrum obtained by CP of 115In→31P without 115In decoupling was interpreted by the isotropic indirect interaction of neighboring 115In–31P spins. We obtained 10 equally spaced lines corresponding to 113In spin state from the MAS NMR spectrum measured with CP from rare 113In to 31P under 115In decoupling. From these experiments, the isotropic contributions of the electron-mediated nuclear coupling between the nearest neighboring 113,115In–31P spins was obtained as |1Jiso(I,S)|=224±5 Hz for undoped and Fe-doped InP samples. The 1Jiso(I,S) value was found to be unaffected by the carrier with the density in the range of 107–1015 cm−3.
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  • Yasuhiro Yoneda, Yoshiki Kohmura, Yoshio Suzuki, Shin-ichi Hamazaki, M ...
    2004 Volume 73 Issue 4 Pages 1050-1053
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We have observed 90° domain walls in a bulk BaTiO3 crystal by synchrotron radiation topography, coupled with a CCD detector. The BaTiO3 multi-domain crystal was revealed to be strained at the 90° domain boundary. The polar direction of the BaTiO3 crystal was tilted by this strain, and this strain also causes the irregular angle of the surface bending mode. The synchrotron X-ray topography can be performed on a sample with electrodes. The topographic image of the ferroelectric domain with an electric field clarified that the well-known stripe domain configuration can not be observed without a weak electric field due to the lattice strain at the domain boundary.
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  • Chieko Totsuji
    2004 Volume 73 Issue 4 Pages 1054-1058
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    The properties of hydrogen-bonded materials such as isotope effect and pressure effect in phase transition and thermodynamical behavior have been investigated by quantum mechanical analysis of our model for an isolated hydrogen bond. It is found that the pressure derivative of transition temperature is positive for the materials with hydrogen bonds which do not largely shrink under applied pressure, while it is negative when hydrogen-bond length is reduced by the pressure. The analysis of the model extended to include interactions between electrons suggests that the difference in phase transition properties between Me-HPLN and Br-HPLN originates in the difference of the electronic distributions on hydrogen bonds between these materials.
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  • Keiji Fukui, Akio Kotani
    2004 Volume 73 Issue 4 Pages 1059-1064
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We give a theoretical prediction for the angle dependence of the magnetic circular dichroism in resonant X-ray emission spectroscopy (MCD-RXES) by the electric quadrupole excitation. After general analytic calculations with an atomic model, we perform numerical calculations of L2,3M4,5 MCD-RXES for Sm3+, where the 2p–4f electric quadrupole excitation, as well as the 2p–5d electric dipole excitation, is followed by the 3d–2p X-ray emission by the electric dipole transition. Tuning the incident X-ray energy in the pre-edge region of the L3 X-ray absorption, the change of the spectral shape of MCD-RXES is studied in detail with the change of the incident and emitted X-ray angles. We also discuss the possibility of detecting the signal of the electric quadrupole excitation in the MCD-RXES spectra, separately from that of the electric dipole excitation, by changing the incident and emission angles.
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  • Makoto Kuwata-Gonokami, Motoyoshi Kubouchi, Ryo Shimano, Andre Mysyrow ...
    2004 Volume 73 Issue 4 Pages 1065-1069
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    Using ultrafast time-resolved IR spectroscopy, we measure the transition from the populated 1s state to the 2p state of the yellow excitonic series of Cu2O. We show that this technique can provide information on the populations of n=1 ortho- and paraexcitons, their distribution in momentum space, their inter-conversion rate, as well as their expansion through the crystal.
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  • Akihiko Matsuyama
    2004 Volume 73 Issue 4 Pages 1070-1076
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We theoretically study volume phase transitions of a nematic gel immersed in mixed solvents, consisting of a low molecular weight liquid crystalline molecule (nematogen) and an isotropic solvent. Combining Flory model for an elastic free energy of the nematic gel with Maier–Saupe model for nematic ordering, we calculate the equilibrium swelling of the gel, orientational order parameters, and elongation of the gel as a function of the concentration of nematogens in the mixed solvents. We find an isotropic gel is discontinuously condensed into a nematic state with increasing the concentration of the nematogen. We also discuss swelling behaviors of the gel accompanying a nematic–isotropic phase separation in a bulk phase outside the gel.
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  • Jeong Won Kang, Ho Jung Hwang
    2004 Volume 73 Issue 4 Pages 1077-1081
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    We investigated the internal dynamics of a bulky shuttle memory system, consisting of a C36+ or C60+ encapsulated in a C640 nanocapsule. Energetics and operating response of a C36+@C640 and a C60+@C640 bucky shuttle memory device, such as transitions between the two states of the C640 end caps, were examined by using classical molecular dynamics simulations of the C36+ or C60+ shuttle in the C640 nanocapsule under the external force fields. For the stable operations of the shuttle memory device, the periods and the magnitudes of the operating force fields were investigated.
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  • Hirotoshi Shimada, Takemasa Ikeda, Jun-ichi Wakita, Hiroto Itoh, Sayur ...
    2004 Volume 73 Issue 4 Pages 1082-1089
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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    The formation of concentric ring-like colonies by bacterial species Bacillus subtilis has been investigated, focusing our attention on the effect of local cell density upon the bacterial motility: (i) Neither any chemicals nor a pacemaker at the center of the ring takes part in the concentric ring formation. (ii) Phase entrainment between two colonies having different phase of concentric ring does not occur. (iii) From the measurement of lag-phase time when varying the initial cell density, the start of the first migration phase is found to depend on the cell density. (iv) When cutting the part of a colony which is behind a migration phase just after the start of migration, the migration phase becomes shorter. On the other hand, the following consolidation phase becomes longer. (v) By the replica-printing method, active bacteria move collectively from inside to outside of the outermost consolidation terrace. Our present experimental results are qualitatively consistent with the results of the other bacterial species P. mirabilis, although the individual cell motility is quite different from each other. The present results suggest that the essential factor of the change of the bacterial motility of B. subtilis during concetric ring formation is the local cell density.
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  • Bijun Fang, Yuejin Shan, Hideo Imoto, Haiqing Xu, Haosu Luo, Zhiwen Yi ...
    2004 Volume 73 Issue 4 Pages 1090-1091
    Published: April 15, 2004
    Released on J-STAGE: July 25, 2007
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