Hokkaido University Collection of Scholarly and Academic Papers
(65.351 recursos)
HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.
Mostrando recursos 1 - 20 de 121
1.
Contribution of cellular contractility to spatial and temporal variations in cellular stiffness - Nagayama, Masafumi; Haga, Hisashi; Takahashi, Masayuki; Saitoh, Takayuki; Kawabata, Kazushige
Scanning probe microscopy and immunofluorescence observations indicated that cellular stiffness was attributed to a contractile network structure consisting of stress fibers. We measured temporal variations in cellular stiffness when cellular contractility was regulated by dosing with lysophosphatidic acid or Y-27632. This experiment reveals a clear relation between cellular stiffness and contractility: Increases in contractility cause cells to stiffen. On the other hand, decreases in contractility reduce cellular stiffness. In both cases, not only the stiffness of the stress fibers but also that of the whole of the cell varies. Immunofluorescence observations of myosin II and vinculin indicated that the stiffness...
2.
Decomposition of methane hydrates in sand, sandstone, clays and glass beads - Uchida, Tsutomu; Takeya, Satoshi; Chuvilin, Evgene M.; Ohmura, Ryo; Nagao, Jiro; Yakushev, Vladimir S.; Istomin, Vladimir A.; Minagawa, Hideki; Ebinuma, Takao; Narita, Hideo
An edited version of this paper was published by AGU. Copyright 2004 American Geophysical Union.
3.
Scanning ultrafast Sagnac interferometry for imaging two-dimensional surface wave propagation - Tachizaki, Takehiro; Muroya, Toshihiro; Matsuda, Osamu; Sugawara, Yoshihiro; Hurley, David H.; Wright, Oliver B.
We describe an improved two-dimensional optical scanning technique combined with an ultrafast Sagnac interferometer for delayed-probe imaging of surface wave propagation. We demonstrate the operation of this system, which involves the use of a single focusing objective, by monitoring surface acoustic wave propagation on opaque substrates with picosecond temporal and micron lateral resolutions. An improvement in the lateral resolution by a factor of 3 is achieved in comparison with previous setups for similar samples.
4.
Quenching of phase coherence in quasi-one-dimensional ring crystals - Shimatake, K.; Toda, Y.; Tanda, S.
A comparison of the single-particle (SP) dynamics of whisker and ring NbSe3 crystals provides new insight into the phase transition properties of quasi-one-dimensional charge density wave (CDW) systems. In the incommensurate CDW phase, SP relaxation triggered by an ultrafast laser pulse reflects the formation of collective states, and reveals the divergence of the relaxation time when approaching a transition temperature. The degree of divergence is less pronounced in rings than in whiskers, suggesting a loss of phase coherence in ring crystals characterized by a closed-loop topology.
5.
Photo-induced phenomena in chalcogenide glass : Comparison with those in oxide glass and polymer - Tanaka, Keiji
Two topics, the both being related with localized states in non-crystalline solids, are studied. One is a comparison of photo-induced phenomena in oxide, chalcogenide, and organic materials. Despite of different inorganic and organic structures, there exist many similarities in photo-induced phenomena, which can be ascribed to excitation of localized electronic states. The other topic concerns photo-induced phenomena induced by linear and non-linear excitation. A result on As2S3 demonstrates that band-gap excitation by one- and two-photon processes provides different changes. It is suggested that the two-photon process occurs resonantly at around localized states in amorphous materials, and the process plays important...
6.
Imaging Ripples on Phononic Crystals Reveals Acoustic Band Structure and Bloch Harmonics - Profunser, Dieter M.; Wright, Oliver B.; Matsuda, Osamu
Broadband surface phonon wave packets on a phononic crystal made up of a microstructured line pattern are tracked in two dimensions and in real time with an ultrafast optical technique. The eigenmode distribution and the 2D acoustic band structure are obtained from spatiotemporal Fourier transforms of the data up to 1 GHz. We find stop bands at the zone boundaries for both leaky-longitudinal and Rayleigh waves, and show how the structure of individual acoustic eigenmodes in k space depends on Bloch harmonics and on mode coupling.
7.
Acoustic phonon generation and detection in GaAs/Al_{0.3}Ga_{0.7}As quantum wells with picosecond laser pulses - Matsuda, O.; Tachizaki, T.; Fukui, T.; Baumberg, J. J.; Wright, O. B.
Picosecond acoustic-phonon pulse generation and detection is investigated in a sample containing three GaAs/Al0.3Ga0.7As quantum wells of different thickness with an interferometric optical pump and probe technique. The pump photon energy is tuned through the hh1-e1 transitions of each well and the probe photon energy is chosen to allow the detection of the phonon pulses at the sample surface. The phonon pulse shapes are explained with a model that relates the carrier wave functions to the acoustic strain, and the acoustic strain to the detected optical reflectance and phase changes.
8.
Coherent Shear Phonon Generation and Detection with Ultrashort Optical Pulses - Matsuda, O.; Wright, O. B.; Hurley, D. H.; Gusev, V. E.; Shimizu, K.
Using an optical technique we generate and detect picosecond shear and quasishear coherent acoustic phonon pulses in the time domain. Thermoelastic and piezoelectric generation are directly achieved by breaking the sample lateral symmetry using crystalline anisotropy. We demonstrate efficient detection in isotropic and anisotropic media with various optical incidence geometries.
9.
Laser picosecond acoustics with oblique probe light incidence - Matsuda, O.; Wright, O. B.
Laser picosecond acoustics involves the excitation and detection of picosecond acoustic strain pulses in thin films with ultrashort light pulses. The use of oblique probe light incidence permits a greater degree of freedom in choosing the optical probing conditions and thereby should allow the extraction of more information about the profile of the propagating acoustic strain pulses. Here, we present a theory for the modulation of light reflected at oblique incidence from a solid containing an acoustic strain distribution. The theory can account for the real and imaginary parts of the reflectance variation, and involves both the effect of the...
10.
Quasi-automatic phase-control technique for chirp compensation of pulses with over-one-octave bandwidth-generation of few- to mono-cycle optical pulses - Yamashita, Mikio; Yamane, Keisaku; Morita, Ryuji
This paper introduces our self-recognition type of the computer-controlled spectral phase compensator (SRCSC), which consists of a greatly accurate phase manipulator with a spatial light modulator (SLM), a highly sensitive phase characterizer using a modified spectral phase interferometry for direct electric field reconstruction (M-SPIDER), and a computer for phase analysis and SLM control operating in the immediate feedback (FB) mode. The application of the SRCSC to adaptive compensation of various kinds of complicated spectral phases such as nonlinear chirped pulses with a weak intensity, induced-phase modulated pulses, photonic-crystal-fiber (PCF) output pulses, and nonlinear chirped pulses exceeding a 500-rad phase variation...
11.
Application of self-deconvolution method to shift-and-add solar imaging - Sudo, Y; Baba, N; Miura, N; Ueno, S; Kitai, R
A shift-and-add (SAA) operation is conducted to reconstruct a high-spatial-resolution image from atmospherically degraded solar images. The self-deconvolving data reconstruction algorithm is used to augment high-spatial-frequency components in solar speckle images and rectify the background component that results from the SAA operation. Self-deconvolved solar speckle images are shift and added and the resulting image shows high-spatial-resolution features.
12.
Correlation effects of quantum rotors in Ge crystals - Shima, Hiroyuki; Nakayama, Tsuneyoshi
We address the accurate treatment of dipolar interaction effects between oxygen defects in Ge crystals on the low-temperature properties of bulk systems. On the basis of a quantum rotor model, we reveal that the interaction between adjacent oxygen defects generates nontrivial low-lying excitations that result in power-law specific heats below 0.1 K. In addition, a peculiar hump is observed for the dielectric susceptibilities at approximately I K. Further, we contend that the predicted power-law specific heats are well described by the two-level tunneling theory, which is based on the random distribution of interacting oxygen defects in Ge samples.
13.
Nonlinear propagation analysis of few-optical-cycle pulses for subfemtosecond compression and carrier envelope phase effect - Mizuta, Yo; Nagasawa, Minoru; Ohtani, Morimasa; Yamashita, Mikio
A numerical approach called Fourier direct method (FDM) is applied to nonlinear propagation of optical pulses with the central wavelength 800 nm, the width 2.67–12.00 fs, and the peak power 25–6870 kW in a fused-silica fiber. Bidirectional propagation, delayed Raman response, nonlinear dispersion (self-steepening, core dispersion), as well as correct linear dispersion are incorporated into "bidirectional propagation equations" which are derived directly from Maxwell's equations. These equations are solved for forward and backward waves, instead of the electric-field envelope as in the nonlinear Schrödinger equation (NLSE). They are integrated as multidimensional simultaneous evolution equations evolved in space. We investigate, both...
14.
Geometric effects on critical behaviours of the Ising model - Shima, Hiroyuki; Sakaniwa, Yasunori
We investigate the critical behaviour of the two-dimensional Ising model defined on a curved surface with a constant negative curvature. Finite-size scaling analysis reveals that the critical exponents for the zero-field magnetic susceptibility and the correlation length deviate from those for the Ising lattice model on a flat plane. Furthermore, when reducing the effects of boundary spins, the values of the critical exponents tend to those derived from the mean field theory. These findings evidence that the underlying geometric character is responsible for the critical properties of the Ising model when the lattice is embedded on negatively curved surfaces.
15.
Electronic structure and spontaneous internal field around nonmagnetic impurities in spin-triplet chiral p-wave superconductors - Takigawa, Mitsuaki; Ichioka, Masanori; Kuroki, Kazuhiko; Tanaka, Yukio
The electronic structure around an impurity in spin-triplet p-wave superconductors is studied by the
Bogoliubov–de Gennes theory on a tight-binding model, where we have chosen sin px+i sin py-wave or
sin(px+py)+i sin(−px+py)-wave states, which are considered to be candidates for the pairing state in Sr2RuO4.
We calculate the spontaneous current and the local density of states around the impurity and discuss the
difference between the two types of pairing. We propose that it is possible to discriminate the two pairing states
by studying the spatial dependence of the magnetic field around a pair of impurities.
16.
Layer Formation and Annihilation in an Immiscible Polymer Blend under Electric and Shear Flow Fields - Na, Yang-Ho; Yoshino, Ayaka; Tominaga, Shinsuke; Orihara, Hiroshi; Ujie, Seiji; Nagaya, Tomoyuki
Simultaneous observation of morphological change and measurement of shear stress in an
immiscible polymer blend of a liquid crystalline polymer (LCP) and a methyl phenyl silicone
oil (MPS) were carried out in electric and shear flow fields by using a system combining a
rheometer and a confocal scanning laser microscope (CSLM). Under shear flow and no
electric field a thin MPS layer with low viscosity was formed between two parallel plates of
the rheometer, which reduced the apparent viscosity. When subjected to an electric field the
layer was broken, resulting in the viscosity increase. The relationship between the
morphology and the rheology was studied in detail.
17.
Photo-induced phenomena in GeO2 glass - Terakado, Nobuaki; Tanaka, Keiji
Photo-induced changes in GeO2 glass have been studied in terms of its optical and structural properties. Band-gap excitation gives rise to modifications in mid-gap optical absorption and photo-luminescence spectra. It also produces electron-spin signals at g 1.995 and 2.008. Raman-scattering spectrum becomes sharper, X-ray diffraction patterns show a disappearance of a crystalline peak, and the illuminated surfaces expand. These observations can be accounted for by assuming bond transformations from rutile-like to defective quartz-like structures and/or from small to large rings. These photo-induced changes in GeO2 are discussed in comparison with those in SiO2 and GeS2.
18.
Generalized phase retrieval algorithm based on information measures - Shioya, Hiroyuki; Gohara, Kazutoshi
An iterative phase retrieval algorithm based on the maximum entropy method (MEM) is presented. Introducing a new generalized information measure, we derive a novel class of algorithms which includes the conventionally used error reduction algorithm and a MEM-type iterative algorithm which is presented for the first time. These different phase retrieval methods are unified on the basis of the framework of information measures used in information theory.
19.
Josephson current through superconductor/diffusive-normal-metal/superconductor junctions: Interference effects governed by pairing symmetry - Asano, Yasuhiro; Tanaka, Yukio; Yokoyama, Takehito; Kashiwaya, Satoshi
The Josephson effect in superconductor/diffusive-normal-metal/superconductor junctions is studied numerically by using the recursive Green function method. In superconductors, we consider spin-singlet s- and d-wave and spin-triplet p-wave pairing symmetries. The pairing symmetry governs two interference effects in junctions: the formation of a midgap Andreev resonant state at junction interfaces and the proximity effect in diffusive normal metals. A cooperative effect between the two interference effects causes anomalous Josephson current in a p-wave symmetry.
20.
Direct observation of Gouy phase shift in a propagating optical vortex - Hamazaki, Junichi; Mineta, Yuriya; Oka, Kazuhiro; Morita, Ryuji
Direct observation of Gouy phase shift on an optical vortex was presented through investigating the intensity profiles of a modified LG_p^m beam with an asymmetric defect, around at the focal point. It was quantitatively found that the rotation profile of a modified LG_p^m beam manifests the Gouy phase effect where the rotation direction depends on only the sign of topological charge m. This profile measurement method by introducing an asymmetric defect is a simple and useful technique for obtaining the information of the Gouy phase shift, without need of a conventional interference method. In addition, the 3-dimernsional trajectory of the...
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