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Hokkaido University Collection of Scholarly and Academic Papers (135.521 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 1.792

  1. Synthesis ofN,N′-Disubstituted Urea from Ethylene Carbonate and Amine Using CaO

    Fujita, Shin-ichiro; Bhanage, Bhalchandra M.; Arai, Masahiko
    Calcium oxide has been proved to be an excellent solid catalyst for the synthesis of N,N′-disubstituted ureas from ethylene carbonate and primary amines under mild conditions.

  2. Asymmetric hydrogenation of ketones : Tactics to achieve high reactivity, enantioselectivity, and wide scope

    OHKUMA, Takeshi
    Ru complexes with chiral diphosphines and amine-based ligands achieve high catalytic activity and enantioselectivity for the hydrogenation of ketones under neutral to slightly basic conditions. The chiral environment is controllable by changing the combination of these two ligands. A concerted six-membered transition state is proposed to be the origin of the high reactivity. The η6-arene/TsDPEN–Ru and MsDPEN–Cp*Ir catalysts effect the asymmetric reaction under slightly acidic conditions. A variety of chiral secondary alcohols are obtained in high enantiomeric excess.

  3. Chemical Fixation of Carbon Dioxide : Synthesis of Cyclic Carbonate, Dimethyl Carbonate, Cyclic Urea and Cyclic Urethane

    Fujita, Shin-ichiro; Arai, Masahiko
    Chemical fixation of carbon dioxide (CO2) may be very important in the future as a solution for the problem of increased atmospheric CO2 levels. Recent developments for chemical fixation of CO2 to cyclic carbonate, dimethyl carbonate (DMC), cyclic urea and cyclic urethane are reviewed. Synthesis of cyclic carbonate via CO2 addition to epoxide has been already applied on the industrial scale, but catalyst development continues. Direct oxidative carboxylation of olefin is preferable for the synthesis of cyclic carbonate, but requires the development of catalysis for the epoxidation step in the presence of CO2. Direct synthesis of DMC is not in...

  4. Selective Hydrogenation of Phenylacetylene with Graphite Intercalated Platinum Nanosheets

    Shirai, Masayuki; Bhanage, Bhalchandra M.; Senboku, Hisanori; Fujita, Shin-ichiro; Arai, Masahiko
    Platinum nanosheets between graphite layers were active for hydrogenation of ethynyl group of phenylacetylene but less active for that of aromatic rings of phenylacetylene and benzene due to its structural characteristics.

  5. Triboluminescence of Lanthanide Coordination Polymers with Face-to-Face Arranged Substituents

    Hirai, Yuichi; Nakanishi, Takayuki; Kitagawa, Yuichi; Fushimi, Koji; Seki, Tomohiro; Ito, Hajime; Hasegawa, Yasuchika
    Luminescence upon the grinding of solid materials (triboluminescence, TL) has long been a puzzling phenomenon in natural science and has also attracted attention because of its broad application in optics. It has been generally considered that the TL spectra exhibit similar profiles as those of photoluminescence (PL), although they occur from distinct stimuli. Herein, we describe for the first time a large spectral difference between these two physical phenomena using lanthanide(III) coordination polymers with efficient TL and PL properties. They are composed of emission centers (Tb-III and Eu-III ions), antenna (hexafluoroacetylacetonate=hfa), and bridging ligands (2,5-bis(diphenylphosphoryl)furan=dpf). The emission color upon grinding...

  6. Prevention of Catastrophic Volcanic Eruptions, Large Earthquakes underneath Big Cities, and Giant Earthquakes at Subduction Zones

    Fujii, Yoshiaki; Sheshpari, Morteza; Kodama, Jun-ichi; Fukuda, Daisuke; Dassanayake, Anjula BN
    Catastrophic volcanic eruptions, large earthquakes beneath big cities, or giant earthquakes at subduction zones are apparently the biggest problems facing the sustainability of human society. However, imminent prediction methods for these events have never been established, except that volcanic eruptions can only be predicted by exceptional efforts by dedicated researchers. Even if a prediction method has been established, the method cannot significantly reduce infrastructure damage, although it could slightly reduce the number of fatalities. On the other hand, prevention of eruptions or earthquakes could significantly reduce, not only the number of fatalities, but also infrastructure damage. Therefore, the authors propose...

  7. Synoptic climatology of winter daily temperature extremes in Sapporo, northern Japan

    Farukh, M. A.; Yamada, Tomohito J.
    Extreme winter daily temperature is an important parameter for determining winter precipitation. This study used a principal component analysis and k-means clustering to characterize the circulation patterns of extreme daily temperatures for 19 winter seasons in Sapporo, Hokkaido, Japan. Climatological anomaly maps were constructed for sea level pressure (SLP) and the 500-hPa geopotential height for the identified minimum (Tmin(10); 239days) and maximum (Tmax(90); 236days) daily temperature extremes. The Tmax(90) SLP anomaly pattern was the opposite (west-east orientation) of the Tmin(10) pattern. The circulation patterns that predominantly contributed to winter rainfall were derived from cyclones over the Sea of Japan via...

  8. Controlling Rashba spin-orbit interaction in quantum wells by adding symmetric potential

    Egami, Yoshiyuki; Akera, Hiroshi
    The incorporation of a symmetric electrostatic potential into quantum wells (QWs) is proposed as a method for modifying the coefficient a of the Rashba spin-orbit interaction. In a symmetric QW for which a = a(so)E(z), where E-z is the perpendicular electric field, the constant a(so) can be controlled by the symmetric potential. The sign reversal of a(so) with the increasing strength of the symmetric potential is demonstrated in (001)-oriented GaAs/AlGaAs QWs via a tight-binding model. The present findings can be used to realize structures with vanishing a in nonzero E-z.

  9. Genetic Analysis of Norovirus Strains that Caused Gastroenteritis Outbreaks Among River Rafters in the Grand Canyon, Arizona

    Kitajima, Masaaki; Iker, Brandon C.; Magill-Collins, Anne; Gaither, Marlene; Stoehr, James D.; Gerba, Charles P.
    Toilet solid waste samples collected from five outbreaks among rafters in the Grand Canyon were subjected to sequencing analysis of norovirus partial capsid gene. The results revealed that a GI.3 strain was associated with one outbreak, whereas the other outbreaks were caused by GII.5 whose sequences shared > 98.9% homology.

  10. Excitation of cavitation bubbles in low-temperature liquid nitrogen

    Sasaki, Koichi; Harada, Shingo
    We excited a cavitation bubble by irradiating a Nd: YAG laser pulse onto a titanium target that was installed in liquid nitrogen at a temperature below the boiling point. To our knowledge, this is the first experiment in which a cavitation bubble has been successfully excited in liquid nitrogen. We compared the cavitation bubble in liquid nitrogen with that in water on the basis of an equation reported by Florschuetz and Chao [J. Heat Transfer 87, 209 (1965)].

  11. Mechanisms of photo-induced degradation of polythiophene derivatives: re-examination of the role of singlet oxygen

    Ohta, Hiroki; Koizumi, Hitoshi
    Roles of singlet oxygen (1O2) in photo-induced degradation of poly(3-hexylthiophene) (P3HT) and poly(3-hexyloxythiophene) (P3HOT) were examined. The results indicate that 1O2 has a considerable role in the degradation of P3HT and P3HOT. Photo-irradiation of P3HT in air resulted in the reduction of the pi-conjugation. The photo-induced reduction also occurred for P3HOT, and it was much faster than that of P3HT. Manceau et al. have reported that 1O2 was generated by photo-irradiation of P3HT in the presence of oxygen and, nevertheless, 1O2 is not the principal photo-oxidative degradation intermediate of P3HT (Manceau et al., Macromol Rapid Commun 29:1823-1827, 2008). However, exposures...

  12. Reaction kinetics for the production of methylene urea from synthetic human urine

    Kabore, Steve; Ito, Ryusei; Funamizu, Naoyuki
    The production of methylene urea from human urine is an important contribution to the world demand of nitrogen fertilizer. In this study, a simplified reaction model was proposed. The kinetics parameters at room temperature were assessed and the reaction constants k(1), k(2), k(3), k(4) were evaluated and determined for the different parts of the proposed reaction model. The relationship between the Formaldehyde/Urea (F/U ratio) and the recovery of nitrogen was also evaluated based on the contribution of the by-products from the reaction. The optimum F/U condition to maximize the recovery of nitrogen was determined.

  13. Solid-phase partitioning of mercury in artisanal gold mine tailings from selected key areas in Mindanao, Philippines, and its implications for mercury detoxification

    Opiso, Einstine M.; Aseneiro, John Paul J.; Banda, Marybeth Hope T.; Tabelin, Carlito B.
    The solid-phase partitioning of mercury could provide necessary data in the identification of remediation techniques in contaminated artisanal gold mine tailings. This study was conducted to determine the total mercury content of mine wastes and identify its solid-phase partitioning through selective sequential extraction coupled with cold vapour atomic absorption spectroscopy. Samples from mine tailings and the carbon-in-pulp (CIP) process were obtained from selected key areas in Mindanao, Philippines. The results showed that mercury use is still prevalent among small-scale gold miners in the Philippines. Tailings after ball mill-gravity concentration (W-BM and Li-BM samples) from Mt Diwata and Libona contained high...

  14. Dirty two-band superconductivity with interband pairing order

    Asano, Yasuhiro; Sasaki, Akihiro; Golubov, Alexander A.
    We study theoretically the effects of random nonmagnetic impurities on the superconducting transition temperature T-c in a two-band superconductor characterized by an equal-time s-wave interband pairing order parameter. Because of the two-band degree of freedom, it is possible to define a spin-triplet s-wave pairing order parameter as well as a spin-singlet s-wave order parameter. The former belongs to odd-band-parity symmetry class, whereas the latter belongs to even-band-parity symmetry class. In a spin-singlet superconductor, Tc is insensitive to the impurity concentration when we estimate the self-energy due to the random impurity potential within the Born approximation. On the other hand in...

  15. Extreme air pollution events in Hokkaido, Japan, traced back to early snowmelt and large-scale wildfires over East Eurasia: Case studies

    Yasunari, Teppei J.; Kim, Kyu-Myong; da Silva, Arlindo M.; Hayasaki, Masamitsu; Akiyama, Masayuki; Murao, Naoto
    To identify the unusual climate conditions and their connections to air pollutions in a remote area due to wildfires, we examine three anomalous large-scale wildfires in May 2003, April 2008, and July 2014 over East Eurasia, as well as how products of those wildfires reached an urban city, Sapporo, in the northern part of Japan (Hokkaido), significantly affecting the air quality. NASA's MERRA-2 (the Modern-Era Retrospective analysis for Research and Applications, Version 2) aerosol re-analysis data closely reproduced the PM2.5 variations in Sapporo for the case of smoke arrival in July 2014. Results show that all three cases featured unusually...

  16. The magnetic properties of Fe3O4/nonmagnetic metal/Fe hybrid systems

    Omori, K.; Kawai, T.; Takahashi, N.; Yanase, T.; Shimada, T.; Nagahama, T.
    Fe3O4 possesses unique properties such as high Curie temperature and half-metallic nature and therefore can function as a high-spin-polarized electrode in spintronic devices. In order to use this compound in such devices, the magnetic characteristics of multilayers used in these devices, which include Fe3O4, should be highly controllable. In this study, we fabricated Fe3O4/Pt or Cr (0-10 nm)/Fe systems through epitaxial growth on MgO(110) substrates in order to investigate the magnetic coupling in Fe3O4 and metallic hybrid systems. We found that these two systems show a marked difference in the dependence of the coercive field (H-c) of the Fe layer...

  17. Bacterial histo-blood group antigens contributing to genotype-dependent removal of human noroviruses with a microfiltration membrane

    Amarasiri, Mohan; Hashiba, Satoshi; Miura, Takayuki; Nakagomi, Toyoko; Nakagomi, Osamu; Ishii, Satoshi; Okabe, Satoshi; Sano, Daisuke
    We demonstrated the genotype-dependent removal of human norovirus particles with a microfiltration (MF) membrane in the presence of bacteria bearing histo-blood group antigens (HBGAs). Three genotypes (GII.3, GII.4, and GII.6) of norovirus-like particles (NoVLPs) were mixed with three bacterial strains (Enterobacter sp. SENG-6, Escherichia coli 086:K61:B7, and Staphylococcus epidermidis), respectively, and the mixture was filtered with an MF membrane having a nominal pore size of 0.45 mu m. All NoVLP genotypes were rejected by the MF membrane in the presence of Enterobacter sp. SENG-6, which excreted HBGAs as extracellular polymeric substances (EPS). This MF membrane removal of NoVLPs was not...

  18. Key Factors Affecting Strength Development of Steel Slag-Dredged Soil Mixtures

    Toda, Kanako; Sato, Haruna; Weerakoon, Nilan; Otake, Tsubasa; Nishimura, Satoshi; Sato, Tsutomu
    Some of the steel slag from ironworks and dredged soils from marine and waterfront engineering work are partially treated as waste. However, a mixture of these two kinds of waste has the potential to be used as construction materials when mixed, due to chemical reactions forming secondary phases. Utilizing waste of such kind as a resource will help to improve sustainability in society by reducing waste and replacing virgin resources such as cement. Recently, it was reported that mixtures of steel slag and dredged soil hardens under specific conditions. The phase compositions of dredged soils and steel slags vary depending...

  19. Formation of Fe- and Mg-Rich Smectite under Hyperalkaline Conditions at Narra in Palawan, the Philippines

    Shimbashi, Misato; Sato, Tsutomu; Yamakawa, Minoru; Fujii, Naoki; Otake, Tsubasa
    The formation of Fe- and Mg-rich smectite and zeolite under alkaline conditions, as secondary minerals after the alkaline alteration of bentonite in repositories for radioactive waste, is of major concern. It is crucial for safety assessments to know whether smectite is formed as a secondary mineral after the alkaline alteration of bentonite. In the present paper, Fe- and Mg-rich smectite, which interacted with the hyperalkaline groundwater at Narra in Palawan, Philippines, was used. Mineralogical and geochemical investigation was conducted to understand the formation process of the smectite and the factors determining the formation of secondary mineral species. The results suggest...

  20. Dissolved Silica Effects on Adsorption and Co-Precipitation of Sb(III) and Sb(V) with Ferrihydrite

    Zhou, Shuang; Sato, Tsutomu; Otake, Tsubasa
    Elevated antimony concentrations in aqueous environments from anthropogenic sources are becoming of global concern. In this respect iron oxides are known to strongly adsorb aqueous antimony species with different oxidation states, but the effect of silica on the removal characteristics is not well understood despite being a common component in the environment. In this study, ferrihydrite was synthesized at various Si/Fe molar ratios to investigate its adsorption and co-precipitation behaviors with aqueous antimony anionic species, Sb(III) and Sb(V). The X-ray diffraction analyses of the precipitates showed two broad diffraction features at approximately 35° and 62° 2θ, which are characteristics of...

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