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Hokkaido University Collection of Scholarly and Academic Papers (130.505 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 3.618

  1. Emergent odd-parity multipoles and magnetoelectric effects on a diamond structure : Implication for the 5d transition metal oxides AOsO(4) (A = K, Rb, and Cs)

    Hayami, Satoru; Kusunose, Hiroaki; Motome, Yukitoshi
    We report our theoretical predictions on the linear magnetoelectric (ME) effects originating from odd-parity multipoles associated with spontaneous spin and orbital ordering on a diamond structure. We derive a two-orbital model for d electrons in e(g) orbitals by including the effective spin-orbit coupling which arises from the mixing between e(g) and t(2g) orbitals. We show that the model acquires a net antisymmetric spin-orbit coupling once staggered spin and orbital orders occur spontaneously. The staggered orders are accompanied by odd-parity multipoles: magnetic monopole, quadrupoles, and toroidal dipoles. We classify the types of the odd-parity multipoles according to the symmetry of the...

  2. Diatom records in the Quaternary marine sequences around the Japanese Islands

    Koizumi, Itaru; Yamamoto, Hirofumi
    Understanding the Quaternary is a key to estimating what the Earth's climate will be like in the future. Such studies demand high-resolution analyses based on paleoclimatic proxy records of changing Earth's orbital forcing and solar insolation that affect the climate system. Quaternary diatom biostratigraphy and paleoceanography have been well established based on the Quaternary marine sequences obtained by piston coring and deep-sea drilling around the Japanese Islands. This paper firstly reviews the Quaternary diatom datum levels that are directly tied to magnetic polarity, and then the late Pleistocene and Holocene rhythmic fluctuations in Td'-derived SSTs (degrees C) which correlate with...

  3. Phylogenetic Position of Arctotanais in the Suborder Tanaidomorpha (Peracarida : Tanaidacea)

    Kakui, Keiichi; Kajihara, Hiroshi; Kobayashi, Norio
    Lack of an ischium on pereiopods 1–6 was previously considered a synapomorphy for the tanaidacean superfamily Tanaoidea, although descriptions of Arctotanais alascensis (Richardson, 1899), the sole species in Arctotanais, indicated presence or absence of the ischium. To resolve this ambiguity, we examined newly collected specimens of A. alascensis (including males, which had not previously been described) from Hokkaido, Japan, using light and scanning electron microscopy. We also conducted molecular phylogenetic analyses based on partial sequences of the 18S rRNA gene to examine the phylogenetic position of A. alascensis. Here we describe in detail the morphology of the male of A....

  4. Cosmopolitan or Cryptic Species? A Case Study ofCapitella teleta(Annelida: Capitellidae)

    Tomioka, Shinri; Kondoh, Tomohiko; Sato-Okoshi, Waka; Ito, Katsutoshi; Kakui, Keiichi; Kajihara, Hiroshi
    Capitella teleta Blake et al., 2009 is an opportunistic capitellid originally described from Massachusetts (USA), but also reported from the Mediterranean, NW Atlantic, and North Pacific, including Japan. This putatively wide distribution had not been tested with DNA sequence data; intraspecific variation in morphological characters diagnostic for the species had not been assessed with specimens from non-type localities, and the species status of the Japanese population(s) was uncertain. We examined the morphology and mitochondrial COI (cytochrome c oxidase subunit I) gene sequences of Capitella specimens from two localities (Ainan and Gamo) in Japan. Specimens from Ainan and Gamo differed from...

  5. A quantitative method for analyzing species-specific vocal sequence pattern and its developmental dynamics

    Imai, Raimu; Sawai, Azusa; Hayase, Shin; Furukawa, Hiroyuki; Asogwa, Chinweike Norman; Sanchez, Miguel; Wang, Hongdi; Mori, Chihiro; Wada, Kazuhiro
    Background: Songbirds are a preeminent animal model for understanding the neural basis underlying the development and evolution of a complex learned behavior, bird song. However, only a few quantitative methods exist to analyze these species-specific sequential behaviors in multiple species using the same calculation method. New method: We report a method of analysis that focuses on calculating the frequency of characteristic syllable transitions in songs. This method comprises two steps: The first step involves forming correlation matrices of syllable similarity scores, named syllable similarity matrices (SSMs); these are obtained by calculating the round-robin comparison of all the syllables in two...

  6. Variety and sustainability of volcanic lakes : Response to subaqueous thermal activity predicted by a numerical model

    Terada, Akihiko; Hashimoto, Takeshi
    We use a numerical model to investigate the factors that control the presence or absence of a hot crater lake at an active volcano. We find that given a suitable pair of parameters (e.g., the enthalpy of subaqueous fumaroles and the ratio of mass flux of the fluid input at the lake bottom to lake surface area), hot crater lakes can be sustained on relatively long timescales. Neither a high rate of precipitation nor an impermeable layer beneath the lake bottom are always necessary for long-term sustainability. The two controlling parameters affect various hydrological properties of crater lakes, including temperature,...

  7. Dual role of the active-center cysteine in human peroxiredoxin 1 : Peroxidase activity and heme binding

    Watanabe, Yuta; Ishimori, Koichiro; Uchida, Takeshi
    HBP23, a 23-kDa heme-binding protein identified in rats, is a member of the peroxiredoxin (Prx) family, the primary peroxidases involved in hydrogen peroxide catabolism. Although HBP23 has a characteristic Cys-Pro heme-binding motif, the significance of heme binding to Prx family proteins remains to be elucidated. Here, we examined the effect of heme binding to human peroxiredoxin-1 (PRX1), which has 97% amino acid identity to HBP23. PRX1 was expressed in Escherichia coli and purified to homogeneity. Spectroscopic titration demonstrated that PRX1 binds heme with a 1:1 stoichiometry and a dissociation constant of 0.17 mu M. UV-vis spectra of heme-PRX1 suggested that...


    Giga, Yoshikazu; Gries, Mathis; Hieber, Matthias; Hussein, Amru; Kashiwabara, Takahito
    Consider the 3-d primitive equations in a layer domain Ω = G×(−h,0), G = (0,1)2, subject to mixed Dirichlet and Neumann boundary conditions at z = −h and z = 0, respectively, and the periodic lateral boundary condition. It is shown that this equation is globally, strongly well-posed for arbitrary large data of the form a = a1 + a2, where a1 ∈ C(G;Lp(−h,0)), a2 ∈ L∞(G;Lp(−h,0)) for p > 3, and where a1 is periodic in the horizontal variables and a2 is sufficiently small. In particular, no differentiability condition on the data is assumed. The approach relies on L∞...

  9. Recent fragmentation of the endangered Blakiston’s fish owl (Bubo blakistoni) population on Hokkaido Island, Northern Japan, Revealed by Mitochondrial DNA and Microsatellite Analyses

    Omote, Keita; Nishida, Chizuko; Takenaka, Takeshi; Saito, Keisuke; Shimura, Ryohji; Fujimoto, Satoshi; Sato, Takao; Masuda, Ryuichi
    Introduction Blakiston’s fish owl (Bubo blakistoni) was previously widespread on Hokkaido Island, Japan, but is now distributed only in limited forest areas. The population size on Hokkaido decreased during the 20th century due to reduction and fragmentation of the owl’s habitat. To elucidate temporal and spatial changes in population structure and genetic diversity, we analyzed 439 individuals collected over the last 100 years. Results We detected a population bottleneck and fragmentation event indicated by mitochondrial DNA (mtDNA) haplotype and microsatellite analyses. The lowest value for effective population size, which was estimated by moment and temporal methods from microsatellite data, occurred in the 1980s....

  10. Spatial and temporal variation at major histocompatibility complex class IIB genes in the endangered Blakiston’s fish owl

    Kohyama, Tetsuo I; Omote, Keita; Nishida, Chizuko; Takenaka, Takeshi; Saito, Keisuke; Fujimoto, Satoshi; Masuda, Ryuichi
    Introduction Quantifying intraspecific genetic variation in functionally important genes, such as those of the major histocompatibility complex (MHC), is important in the establishment of conservation plans for endangered species. The MHC genes play a crucial role in the vertebrate immune system and generally show high levels of diversity, which is likely due to pathogen-driven balancing selection. The endangered Blakiston’s fish owl (Bubo blakistoni) has suffered marked population declines on Hokkaido Island, Japan, during the past several decades due to human-induced habitat loss and fragmentation. We investigated the spatial and temporal patterns of genetic diversity in MHC class IIβ genes in Blakiston’s...

  11. Midlatitude sporadic-E episodes viewed by L-band split-spectrum InSAR

    Suzuki, Takato; Maeda, Jun; Heki, Kosuke; Furuya, Masato
    Sporadic-E (Es) is a layer of ionization that irregularly appears within the E region of the ionosphere and is known to generate an unusual propagation of very high frequency waves over long distances. The detailed spatial structure of Es remains unclear due to the limited spatial resolution in the conventional ionosonde observations. We detect midlatitude Es by interferometric synthetic aperture radar (InSAR), which can clarify the spatial structure of Es with unprecedented resolution. Moreover, we use the range split-spectrum method (SSM) to separate dispersive and nondispersive components in the InSAR image. While InSAR SSM largely succeeds in decomposing into dispersive...

  12. 9,10-Dihydrophenanthrene with Two Spiro(dibenzocycloheptatriene) Units : A Highly Strained Caged Hydrocarbon Exhibiting Reversible Electrochromic Behavior

    Ishigaki, Yusuke; Hayashi, Yuki; Sugawara, Kazuma; Shimajiri, Takuya; Nojo, Wataru; Katoono, Ryo; Suzuki, Takanori
    The title dispiro hydrocarbon 1 was designed as a new electrochromic material. This multiply clamped hexaphenylethane-type electron donor was prepared from 2,2'-diiodobiphenyl via biphenyl-2,2'-diylbis(dibenzotropylium) 2(2+) salt. X-ray analysis of 1 revealed a highly strained structure as reflected by an elongated ethane bond [bond length: 1.6665(17) angstrom] and nearly eclipsed conformation. The weakened bond was cleaved upon two-electron oxidation to regenerate the deeply colored dication 2(2+). The reversible interconversion between 1 and 2(2+) is accompanied not only by a drastic color change but also by C-C bond formation/cleavage. Thus, the voltammogram showed a pair of well-separated redox waves, which is characteristic...

  13. Paternal phylogeographic structure of the brown bear (Ursus arctos) in northeastern Asia and the effect of male-mediated gene flow to insular populations

    Hirata, Daisuke; Mano, Tsutomu; Abramov, Alexei V.; Baryshnikov, Gennady F.; Kosintsev, Pavel A.; Murata, Koichi; Masuda, Ryuichi
    Background: Sex-biased dispersal is widespread among mammals, including the brown bear (Ursus arctos). Previous phylogeographic studies of the brown bear based on maternally inherited mitochondrial DNA have shown intraspecific genetic structuring around the northern hemisphere. The brown bears on Hokkaido Island, northern Japan, comprise three distinct maternal lineages that presumably immigrated to the island from the continent in three different periods. Here, we investigate the paternal genetic structure across northeastern Asia and assess the connectivity among and within intraspecific populations in terms of male-mediated gene flow. Results: We analyzed paternally inherited Y-chromosomal DNA sequence data and Y-linked microsatellite data of...

  14. A long source area of the 1906 Colombia-Ecuador earthquake estimated from observed tsunami waveforms

    Yamanaka, Yusuke; Tanioka, Yuichiro; Shiina, Takahiro
    The 1906 Colombia-Ecuador earthquake induced both strong seismic motions and a tsunami, the most destructive earthquake in the history of the Colombia-Ecuador subduction zone. The tsunami propagated across the Pacific Ocean, and its waveforms were observed at tide gauge stations in countries including Panama, Japan, and the USA. This study conducted slip inverse analysis for the 1906 earthquake using these waveforms. A digital dataset of observed tsunami waveforms at the Naos Island (Panama) and Honolulu (USA) tide gauge stations, where the tsunami was clearly observed, was first produced by consulting documents. Next, the two waveforms were applied in an inverse...

  15. Tube construction by a tanaidacean crustacean using a novel mucus secretion system involving the anal opening

    Kakui, Keiichi; Hiruta, Chizue
    Background: Animals in diverse aquatic groups construct tubes using mucus and filaments, and the acquisition of this capability has likely played an important role in the evolution and diversification of small benthic animals. Tanaidacea is a crustacean order that includes tube-constructing species, most of which belong to Tanaidoidea and Paratanaoidea, with a few in Kalliapseudidae (Apseudoidea). Two previously reported systems used in tube construction are the thoracic-gland system, with secretory glands in thoracic segments (pereonites), and the pereopodal-gland system, with glands in pereopods. Results: Parapseudidae (Apseudoidea) also includes a tube-constructing species, Parapseudes algicola (Shiino, 1952), which lacks large secretory glands...

  16. Neutron diffraction study on single-crystalline UAu2Si2

    Tabata, Chihiro; Klicpera, Milan; Ouladdiaf, Bachir; Saito, Hiraku; Valiska, Michal; Uhlirova, Klara; Miura, Naoyuki; Sechovsky, Vladimir; Amitsuka, Hiroshi
    The magnetic structure of tetragonal UAu2Si2 was investigated by single-crystal neutron-diffraction experiments. Below T-N= 20 K it orders antiferromagnetically with a propagation vector of k = (2/3,0,0) and magnetic moments of uranium ions pointing along the tetragonal c axis. Weak signs of the presence of a ferromagnetic component of magnetic moment were traced out. Taking into account a group theory calculation and experimental results of magnetization and Si-29 nuclear magnetic resonance, the magnetic structure is determined to be a squared-up antiferromagnetic structure, with a stacking sequence (+ + -) of the ferromagnetic ac-plane sheets along the a axis. This result...

  17. Stepwise cyclopropanation on the polycyclopropanated polyketide formation in jawsamycin biosynthesis

    Hiratsuka, Tomoshige; Suzuki, Hideaki; Minami, Atsushi; Oikawa, Hideaki
    Jawsamycin is a polyketide-nucleoside hybrid with a unique poly-cyclopropane moiety on a single polyketide chain. The unexpected isolation of cyclopropane deficient jawsamycin analogs allowed us to propose a stepwise cyclopropanation mechanism for the enzymatic synthesis of this polyketide. The concise timing of the cyclopropanation could be regulated by a delicate balance between reaction rates of the condensation and cyclopropanation reactions.

  18. Selective contribution of the telencephalic arcopallium to the social facilitation of foraging efforts in the domestic chick

    Xin, Qiuhong; Ogura, Yukiko; Uno, Leo; Matsushima, Toshiya
    To investigate the neural basis of socio-economic behaviors in birds, we examined the effects of bilateral electrolytic lesions of arcopallium (Arco, the major descending pallial area of the avian telencephalon) and the surrounding nuclei in domestic chicks. We tested foraging effort (running distance) in an I-shaped maze with two food patches that delivered food in a biased manner according to a variable interval schedule. Normally, chicks run back and forth between the patches, and the patch use time matches the respective food delivery rate. In the paired phase, even without actual interference of food, chicks showed social facilitation of running...

  19. The potential of GRACE gravimetry to detect the heavy rainfall-induced impoundment of a small reservoir in the upper Yellow River

    Yi, Shuang; Song, Chunqiao; Wang, Qiuyu; Wang, Linsong; Heki, Kosuke; Sun, Wenke
    Artificial reservoirs are important indicators of anthropogenic impacts on environments, and their cumulative influences on the local water storage will change the gravity signal. However, because of their small signal size, such gravity changes are seldom studied using satellite gravimetry from the Gravity Recovery and Climate Experiment (GRACE). Here we investigate the ability of GRACE to detect water storage changes in the Longyangxia Reservoir (LR), which is situated in the upper main stem of the Yellow River. Three different GRACE solutions from the CSR, GFZ, and JPL with three different processing filters are com- pared here. We find that heavy precipitation in the summer of 2005...

  20. Ionospheric anomalies immediately before M(w)7.0-8.0 earthquakes

    He, Liming; Heki, Kosuke
    Recent observations suggested that ionospheric anomalies appear immediately before large earthquakes with moment magnitudes (M-w) of 8.2 or more. Do similar phenomena precede smaller earthquakes? Here we answer this question by analyzing vertical total electron contents (VTEC) observed near the epicenters before and after 32 earthquakes with M(w)7.0-8.0 using data from nearby Global Navigation Satellite Systems stations. To detect anomalies, we defined the reference curves to fit the observed VTEC and considered the departure from the curves as anomalies. In estimating the reference curves, we excluded time windows, prescribed for individual earthquakes considering M-w, possibly affected by earthquakes. We validated...

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