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Hokkaido University Collection of Scholarly and Academic Papers (135.711 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.

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Mostrando recursos 1 - 20 de 252

  1. Plasticity in extended phenotype increases offspring defence despite individual variation in web structure and behaviour

    DiRienzo, Nicholas; Aonuma, Hitoshi
    Many animals actively defend their offspring using a range of behaviours from calling and mobbing in birds, to physical grappling in crustaceans, and the expression of these behaviours positively scale with offspring value. While this role of behaviour in defence is well studied, very little is known about how other traits, specifically the structure of architectural constructions such as webs and nests, contribute to offspring defence. Additionally, although some taxa show consistent individual differences in offspring defence behaviour, it is completely unknown whether individuals also differ in defensive structures. We addressed these questions in the redback spider, Latrodectus hasselti, by...

  2. Super-resolution structural analysis of dendritic spines using three-dimensional structured illumination microscopy in cleared mouse brain slices

    Sawada, Kazuaki; Kawakami, Ryosuke; Shigemoto, Ryuichi; Nemoto, Tomomi
    Three-dimensional (3D) super-resolution microscopy technique structured illumination microscopy (SIM) imaging of dendritic spines along the dendrite has not been previously performed in fixed tissues, mainly due to deterioration of the stripe pattern of the excitation laser induced by light scattering and optical aberrations. To address this issue and solve these optical problems, we applied a novel clearing reagent, LUCID, to fixed brains. In SIM imaging, the penetration depth and the spatial resolution were improved in LUCID-treated slices, and 160-nm spatial resolution was obtained in a large portion of the imaging volume on a single apical dendrite. Furthermore, in a morphological...

  3. A Single Spherical Assembly of Protein Amyloid Fibrils Formed by Laser Trapping

    Yuyama, Ken-ichi; Ueda, Mariko; Nagao, Satoshi; Hirota, Shun; Sugiyama, Teruki; Masuhara, Hiroshi
    Protein amyloids have received much attention owing to their correlation with serious diseases and to their promising mechanical and optical properties as future materials. Amyloid formation has been conducted by tuning temperature and chemical conditions, so that its nucleation and the following growth are analyzed as ensemble dynamics. A single spherical assembly of amyloid fibrils of cytochrome c domain-swapped dimer was successfully generated upon laser trapping. The amyloid fibrillar structure was confirmed by fluorescence characterization and electron microscopy. The prepared spheres were further manipulated individually in solution to fabricate a three-dimensional microstructure and a line pattern. Amyloid formation dynamics and...

  4. White light induced photo-thermal switching in a graphene-flake-mixed ZnO nanoparticle random laser

    Fujiwara, Hideki; Niyuki, Ryo; Sasaki, Keiji

  5. Current reinforcement model reproduces center-in-center vein trajectory of Physarum polycephalum

    Akita, Dai; Schenz, Daniel; Kuroda, Shigeru; Sato, Katsuhiko; Ueda, Kei-ichi; Nakagaki, Toshiyuki
    Vein networks span the whole body of the amoeboid organism in the plasmodial slime mould Physarum polycephalum, and the network topology is rearranged within an hour in response to spatio-temporal variations of the environment. It has been reported that this tube morphogenesis is capable of solving mazes, and a mathematical model, named the current reinforcement rule', was proposed based on the adaptability of the veins. Although it is known that this model works well for reproducing some key characters of the organism's maze-solving behaviour, one important issue is still open: In the real organism, the thick veins tend to trace...

  6. Thermoelectric phase diagram of the SrTiO3-SrNbO3 solid solution system

    Zhang, Yuqiao; Feng, Bin; Hayashi, Hiroyuki; Tohei, Tetsuya; Tanaka, Isao; Ikuhara, Yuichi; Ohta, Hiromichi
    Here, we present a thermoelectric phase diagram for the SrTi1-xNbxO3 (0.05 <= x <= 1) solid solution system, which we derived from the characterization of epitaxial films. We observed two thermoelectric phase boundaries in the system, which originate from the step-like decrease in carrier effective mass at x similar to 0.3 and from a local minimum in carrier relaxation time at x similar to 0.5. The origins of these phase boundaries are considered to be related to isovalent/heterovalent B-site substitution: parabolic Ti 3d orbitals dominate electron conduction for compositions with x < 0.3, whereas the Nb 4 d orbital dominates...

  7. High Thermoelectric Power Factor of High-Mobility 2D Electron Gas

    Ohta, Hiromichi; Kim, Sung Wng; Kaneki, Shota; Yamamoto, Atsushi; Hashizume, Tamotsu
    Thermoelectric conversion is an energy harvesting technology that directly converts waste heat from various sources into electricity by the Seebeck effect of thermoelectric materials with a large thermopower (S), high electrical conductivity (σ), and low thermal conductivity (κ). State-of-the-art nanostructuring techniques that significantly reduce κ have realized high-performance thermoelectric materials with a figure of merit (ZT = S2∙σ∙T∙κ−1) between 1.5 and 2. Although the power factor (PF = S2∙σ) must also be enhanced to further improve ZT, the maximum PF remains near 1.5–4 mW m−1 K−2 due to the well-known trade-off relationship between S and σ. At a maximized PF,...

  8. Thermopower modulation clarification of the intrinsic effective mass in transparent oxide semiconductor BaSnO3

    Sanchela, Anup V.; Onozato, Takaki; Feng, Bin; Ikuhara, Yuichi; Ohta, Hiromichi
    The exact intrinsic carrier effective mass m* of a well-studied transparent oxide semiconductor BaSnO3 is unknown because the reported m* values are scattered from 0.06m(0) to 3.7m(0). This paper identifies the intrinsic m* of BaSnO3, m* = 0.40 +/- 0.01m(0), by the thermopower modulation clarification method and determines the threshold of the degenerate/nondegenerate semiconductor. At the threshold, the thermopower values of both the La-doped BaSnO3 and BaSnO3 thin-film transistor structures are 240 mu V K-1, the bulk carrier concentration is 1.4 x 10(19) cm(-3), and the two-dimensional sheet carrier concentration is 1.8 x 10(12) cm(-2). When the Fermi energy E-F...

  9. Experimental models for Murray's law

    Akita, Dai; Kunita, Itsuki; Fricker, Mark D.; Kuroda, Shigeru; Sato, Katsuhiko; Nakagaki, Toshiyuki
    Transport networks are ubiquitous in multicellular organisms and include leaf veins, fungal mycelia and blood vessels. While transport of materials and signals through the network plays a crucial role in maintaining the living system, the transport capacity of the network can best be understood in terms of hydrodynamics. We report here that plasmodium from the large, single-celled amoeboid Physarum was able to construct a hydrodynamically optimized veinnetwork when evacuating biomass from confined arenas of various shapes through a narrow exit. Increasingly thick veins developed towards the exit, and the network spanned the arena via repetitive bifurcations to give a branching...

  10. Channeling Exciton Migration into Electron Transfer in Formamidinium Lead Bromide Perovskite Nanocrystal/Fullerene Composites

    Nair, Vijayakumar C.; Muthu, Chinnadurai; Rogach, Andrey L.; Kohara, Reiko; Biju, Vasudevanpillai
    Hydrophobically capped nanocrystals of formamidinium lead bromide (FAPbBr(3)) perovskite (PNC) show bright and stable fluorescence in solution and thin-film states. When compared with isolated PNCs in a solution, closepacked PNCs in a thin film show extended fluorescence lifetime (ca. 4.2 mu s), which is due to hopping or migration of photogenerated excitons among PNCs. Both fluorescence quantum efficiency and lifetime decrease in a PNC thin film doped with fullerene (C-60), which is attributed to channeling of exciton migration into electron transfer to C-60. On the other hand, quenching of fluorescence intensity of a PNC solution is not accompanied by any...

  11. Channeling Exciton Migration into Electron Transfer in Formamidinium Lead Bromide Perovskite Nanocrystal/Fullerene Composites

    Nair, Vijayakumar C.; Muthu, Chinnadurai; Rogach, Andrey L.; Kohara, Reiko; Biju, Vasudevanpillai
    Hydrophobically capped nanocrystals of formamidinium lead bromide (FAPbBr(3)) perovskite (PNC) show bright and stable fluorescence in solution and thin-film states. When compared with isolated PNCs in a solution, closepacked PNCs in a thin film show extended fluorescence lifetime (ca. 4.2 mu s), which is due to hopping or migration of photogenerated excitons among PNCs. Both fluorescence quantum efficiency and lifetime decrease in a PNC thin film doped with fullerene (C-60), which is attributed to channeling of exciton migration into electron transfer to C-60. On the other hand, quenching of fluorescence intensity of a PNC solution is not accompanied by any...

  12. Microtubule array observed in the posterior-vegetal cortex during cytoplasmic and cortical reorganization of the ascidian egg

    Ishii, Hirokazu; Goto, Toshiyuki; Nishikata, Takahito
    Body axis formation during embryogenesis results from asymmetric localization of maternal factors in the egg. Shortly before the first cleavage in ascidian eggs, cell polarity along the anteroposterior (A-P) axis is established and the cytoplasmic domain (myoplasm) relocates from the vegetal to the posterior region in a microtubule-dependent manner. Through immunostaining, tubulin accumulation during this reorganization is observable on the myoplasm cortex. However, more detailed morphological features of microtubules remain relatively unknown. In this study, we invented a new reagent that improves the immunostaining of cortical microtubules and successfully visualized a parallel array of thick microtubules. During reorganization, they covered...

  13. Microtubule array observed in the posterior-vegetal cortex during cytoplasmic and cortical reorganization of the ascidian egg

    Ishii, Hirokazu; Goto, Toshiyuki; Nishikata, Takahito
    Body axis formation during embryogenesis results from asymmetric localization of maternal factors in the egg. Shortly before the first cleavage in ascidian eggs, cell polarity along the anteroposterior (A-P) axis is established and the cytoplasmic domain (myoplasm) relocates from the vegetal to the posterior region in a microtubule-dependent manner. Through immunostaining, tubulin accumulation during this reorganization is observable on the myoplasm cortex. However, more detailed morphological features of microtubules remain relatively unknown. In this study, we invented a new reagent that improves the immunostaining of cortical microtubules and successfully visualized a parallel array of thick microtubules. During reorganization, they covered...

  14. Chordotonal organs in hemipteran insects: unique peripheral structures but conserved central organization revealed by comparative neuroanatomy

    Nishino, Hiroshi; Mukai, Hiromi; Takanashi, Takuma
    Hemipteran insects use sophisticated vibrational communications by striking body appendages on the substrate or by oscillating the abdominal tymbal. There has been, however, little investigation of sensory channels for processing vibrational signals. Using sensory nerve stainings and low invasive confocal analyses, we demonstrate the comprehensive neuronal mapping of putative vibration-responsive chordotonal organs (COs) in stink bugs (Pentatomidae and Cydinidae) and cicadas (Cicadidae). The femoral CO (FCO) in stink bugs consists of ventral and dorsal scoloparia, homologous to distal and proximal scoloparia in locusts, which are implicated in joint movement detection and vibration detection, respectively. The ligament of the dorsal scoloparium...

  15. Mechanoresponsive luminescence and liquid-crystalline behaviour of a cyclophane featuring two 1,6-bis(phenylethynyl)pyrene groups

    Sagara, Yoshimitsu; Tamaoki, Nobuyuki
    Cyclophanes have been attractive targets over recent decades because of their fascinating molecular structures and inherent ability to act as supramolecular hosts. However, cyclophanes that exhibit stimuli-responsive luminescence in their condensed states are still very rare, although luminescent cyclophanes could be suitable platforms for sophisticated photofunctional molecular assembled materials. We here report that a pyrenophane featuring two p-extended pyrene groups exhibits mechanoresponsive luminescence in the solid states and shows a nematic liquid-crystalline phase at elevated temperature. Two 1,6-bis(phenylethynyl)pyrene moieties form intramolecular excimers in a diluted chloroform solution, whereas no clear intra-and/or intermolecular excimer formation was observed for the solid state...

  16. Mechanoresponsive luminescence and liquid-crystalline behaviour of a cyclophane featuring two 1,6-bis(phenylethynyl)pyrene groups

    Sagara, Yoshimitsu; Tamaoki, Nobuyuki
    Cyclophanes have been attractive targets over recent decades because of their fascinating molecular structures and inherent ability to act as supramolecular hosts. However, cyclophanes that exhibit stimuli-responsive luminescence in their condensed states are still very rare, although luminescent cyclophanes could be suitable platforms for sophisticated photofunctional molecular assembled materials. We here report that a pyrenophane featuring two p-extended pyrene groups exhibits mechanoresponsive luminescence in the solid states and shows a nematic liquid-crystalline phase at elevated temperature. Two 1,6-bis(phenylethynyl)pyrene moieties form intramolecular excimers in a diluted chloroform solution, whereas no clear intra-and/or intermolecular excimer formation was observed for the solid state...

  17. Sustained dynamics of a weakly excitable system with nonlocal interactions

    Kobayashi, Yasuaki; Kitahata, Hiroyuki; Nagayama, Masaharu
    We investigate a two-dimensional spatially extended system that has a weak sense of excitability, where an excitation wave has a uniform profile and propagates only within a finite range. Using a cellular automaton model of such a weakly excitable system, we show that three kinds of sustained dynamics emerge when nonlocal spatial interactions are provided, where a chain of local wave propagation and nonlocal activation forms an elementary oscillatory cycle. Transition between different oscillation regimes can be understood as different ways of interactions among these cycles. Analytical expressions are given for the oscillation probability near the onset of oscillations.

  18. Inverse Tunnel Magnetocapacitance in Fe/Al-oxide/Fe3O4

    Kaiju, Hideo; Nagahama, Taro; Sasaki, Shun; Shimada, Toshihiro; Kitakami, Osamu; Misawa, Takahiro; Fujioka, Masaya; Nishii, Junji; Xiao, Gang
    Magnetocapacitance (MC) effect, observed in a wide range of materials and devices, such as multiferroic materials and spintronic devices, has received considerable attention due to its interesting physical properties and practical applications. A normal MC effect exhibits a higher capacitance when spins in the electrodes are parallel to each other and a lower capacitance when spins are antiparallel. Here we report an inverse tunnel magnetocapacitance (TMC) effect for the first time in Fe/AlOx/Fe3O4 magnetic tunnel junctions (MTJs). The inverse TMC reaches up to 11.4% at room temperature and the robustness of spin polarization is revealed in the bias dependence of...

  19. Infrared-transmittance tunable metal-insulator conversion device with thin-film-transistor-type structure on a glass substrate

    Katase, Takayoshi; Endo, Kenji; Ohta, Hiromichi
    Infrared (IR) transmittance tunable metal-insulator conversion was demonstrated on a glass substrate by using thermochromic vanadium dioxide (VO2) as the active layer in a three-terminal thin-film-transistor-type device withwater-infiltrated glass as the gate insulator. Alternative positive/negative gate-voltage applications induce the reversible protonation/deprotonation of a VO2 channel, and two-orders of magnitude modulation of sheet-resistance and 49% modulation of IR-transmittance were simultaneously demonstrated at room temperature by the metal-insulator phase conversion of VO2 in a non-volatile manner. The present device is operable by the room-temperature protonation in an all-solid-state structure, and thus it will provide a new gateway to future energy-saving technology as...

  20. The role of noise in self-organized decision making by the true slime mold Physarum polycephalum

    Meyer, Bernd; Ansorge, Cedrick; Nakagaki, Toshiyuki
    Self-organized mechanisms are frequently encountered in nature and known to achieve flexible, adaptive control and decision-making. Noise plays a crucial role in such systems: It can enable a self-organized system to reliably adapt to short-term changes in the environment while maintaining a generally stable behavior. This is fundamental in biological systems because they must strike a delicate balance between stable and flexible behavior. In the present paper we analyse the role of noise in the decision-making of the true slime mold Physarum polycephalum, an important model species for the investigation of computational abilities in simple organisms. We propose a simple...

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