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  • American Institute of Physics (AIP)  (18)
  • American Association for the Advancement of Science (AAAS)  (7)
  • American Chemical Society  (1)
  • 2015-2019  (8)
  • 2010-2014  (2)
  • 2000-2004  (4)
  • 1990-1994  (12)
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  • 1
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    Instability and associated roll structure of Marangoni convection in high Prandtl number liquid bridge with large aspect ratio (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-02-19
    Description: This paper reports the experimental results on the instability and associated roll structures (RSs) of Marangoni convection in liquid bridges formed under the microgravity environment on the International Space Station. The geometry of interest is high aspect ratio ( AR = height/diameter ≥ 1.0) liquid bridges of high Prandtl number fluids ( Pr = 67 and 207) suspended between coaxial disks heated differentially. The unsteady flow field and associated RSs were revealed with the three-dimensional particle tracking velocimetry. It is found that the flow field after the onset of instability exhibits oscillations with azimuthal mode number m = 1 and associated RSs traveling in the axial direction. The RSs travel in the same direction as the surface flow (co-flow direction) for 1.00 ≤ AR ≤ 1.25 while they travel in the opposite direction (counter-flow direction) for AR ≥ 1.50, thus showing the change of traveling directions with AR . This traveling direction for AR ≥ 1.50 is reversed to the co-flow direction when the temperature difference between the disks is increased to the condition far beyond the critical one. This change of traveling directions is accompanied by the increase of the oscillation frequency. The characteristics of the RSs for AR ≥ 1.50, such as the azimuthal mode of oscillation, the dimensionless oscillation frequency, and the traveling direction, are in reasonable agreement with those of the previous sounding rocket experiment for AR = 2.50 and those of the linear stability analysis of an infinite liquid bridge.
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Carbon nanotube dispersed conductive network for microbial fuel cells (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-08-27
    Description: Microbial fuel cells (MFCs) are promising devices for capturing biomass energy. Although they have recently attracted considerable attention, their power densities are too low for practical use. Increasing their electrode surface area is a key factor for improving the performance of MFC. Carbon nanotubes (CNTs), which have excellent electrical conductivity and extremely high specific surface area, are promising materials for electrodes. However, CNTs are insoluble in aqueous solution because of their strong intertube van der Waals interactions, which make practical use of CNTs difficult. In this study, we revealed that CNTs have a strong interaction with Saccharomyces cerevisiae cells. CNTs attach to the cells and are dispersed in a mixture of water and S. cerevisiae , forming a three-dimensional CNT conductive network. Compared with a conventional two-dimensional electrode, such as carbon paper, the three-dimensional conductive network has a much larger surface area. By applying this conductive network to MFCs as an anode electrode, power density is increased to 176  μ W/cm 2 , which is approximately 25-fold higher than that in the case without CNTs addition. Maximum current density is also increased to approximately 8-fold higher. These results suggest that three-dimensional CNT conductive network contributes to improve the performance of MFC by increasing surface area.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 3
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    Symbiotic bacterium modifies aphid body color (2010)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2010-11-26
    Description: Color variation within populations of the pea aphid influences relative susceptibility to predators and parasites. We have discovered that infection with a facultative endosymbiont of the genus Rickettsiella changes the insects' body color from red to green in natural populations. Approximately 8% of pea aphids collected in Western Europe carried the Rickettsiella infection. The infection increased amounts of blue-green polycyclic quinones, whereas it had less of an effect on yellow-red carotenoid pigments. The effect of the endosymbiont on body color is expected to influence prey-predator interactions, as well as interactions with other endosymbionts.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tsuchida, Tsutomu -- Koga, Ryuichi -- Horikawa, Mitsuyo -- Tsunoda, Tetsuto -- Maoka, Takashi -- Matsumoto, Shogo -- Simon, Jean-Christophe -- Fukatsu, Takema -- New York, N.Y. -- Science. 2010 Nov 19;330(6007):1102-4. doi: 10.1126/science.1195463.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Molecular Entomology Laboratory, RIKEN Advanced Science Institute, Wako 351-0198, Japan. t-tsuchida@riken.jp〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21097935" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Aphids/*microbiology/physiology ; Carotenoids/metabolism ; Color ; Coxiellaceae/classification/*physiology ; Phylogeny ; *Symbiosis
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Bioactive polyamine production by a novel hybrid system comprising multiple indigenous gut bacterial strategies (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018-06-28
    Description: Metabolites of the intestinal microbiota are thought to be generated through metabolic pathways spanning multiple taxa of intestinal bacteria. We have previously shown that the level of putrescine, a polyamine found abundantly in the human intestinal lumen, is increased in the colonic lumen following administration of arginine and the probiotic Bifidobacterium sp.; however, the underlying mechanism remained poorly understood. We report a novel pathway for putrescine production from arginine through agmatine involving the collaboration of two bacterial groups, and triggered by environmental acidification (drop in pH to below 6.5 from neutral). This pathway comprises the acid tolerance system of Escherichia coli , representing bacteria that have an arginine-dependent acid resistance system; the energy production system of Enterococcus faecalis , representing bacteria that have an agmatine deiminase system; and the acid production system of the acid-producing bacteria, represented by Bifidobacterium spp. This pathway is unique in that it represents a relationship between the independent survival strategies of multiple bacteria.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Effect of the hexagonal phase interlayer on rectification properties of boron nitride heterojunctions to silicon (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-02-07
    Description: Rectification properties of boron nitride/silicon p-n heterojunction diodes fabricated under low-energy ion impact by plasma-enhanced chemical vapor deposition are studied in terms of the resistive sp 2 -bonded boron nitride (sp 2 BN) interlayer. A two-step biasing technique is developed to control the fraction of cubic boron nitride (cBN) phase and, hence, the thickness of the sp 2 BN interlayer in the films. The rectification ratio at room temperature is increased up to the order of 10 4 at ±10 V of biasing with increasing the sp 2 BN thickness up to around 130 nm due to suppression of the reverse leakage current. The variation of the ideality factor in the low bias region is related to the interface disorders and defects, not to the sp 2 BN thickness. The forward current follows the Frenkel-Poole emission model in the sp 2 BN interlayer at relatively high fields when the anomalous effect is assumed. The transport of the minority carriers for reverse current is strongly limited by the high bulk resistance of the thick sp 2 BN interlayer, while that of the major carriers for forward current is much less affected.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 6
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    Novel excitations near quantum criticality in geometrically frustrated antiferromagnet CsFeCl3 (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉The investigation of materials that exhibit quantum phase transition provides valuable insights into fundamental problems in physics. We present neutron scattering under pressure in a triangular-lattice antiferromagnet that has a quantum disorder in the low-pressure phase and a noncollinear structure in the high-pressure phase. The neutron spectrum continuously evolves through critical pressure; a single mode in the disordered state becomes soft with the pressure and it splits into gapless and gapped modes in the ordered phase. Extended spin-wave theory reveals that the longitudinal and transverse fluctuations of spins are hybridized in the modes because of noncollinearity, and previously unidentified magnetic excitations are formed. We report a new hybridization of the phase and amplitude fluctuations of the order parameter near a quantum critical point in a spontaneously symmetry-broken state.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
    Electronic Resource
    Electronic Resource
    Monoenergetic positron beam study of Si-doped GaAs epilayers grown by low-pressure metalorganic chemical vapor deposition using tertiarybutylarsine (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3880-3885 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si-doped GaAs epilayers grown by low-pressure metalorganic chemical vapor deposition (MOCVD) using tertiarybutylarsine (tBAs) were investigated using a slow positron beam. The concentration of Ga vacancies, VGa, generated in GaAs epilayers was increased drastically by heavy Si doping of more than 1019 cm−3, where the deactivation of Si occurred. This result suggests that the deactivation of Si in GaAs is mainly caused by a VGa-related defect, such as a VGa-SiGa complex. The VGa concentration in the samples grown using tBAs was found to be almost the same as that grown using arsine (AsH3). On the other hand, the VGa concentration in MOCVD-grown Si-doped GaAs is lower than that in molecular-beam-epitaxy-grown material for the same Si concentrations. The generation mechanisms of VGa were found to be greatly dependent on the growth and/or doping methods, in addition to the Si doping concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352900
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal conversion of semi-insulating GaAs in high-temperature annealing (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 615-618 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-temperature annealing of semi-insulating GaAs has been studied. Thermal conversion induced by annealing at 1060–1200 °C can be explained by the causes of both the reduction of EL2 concentration and the generation of deep acceptors during high-temperature annealing. Both of them can be rationalized by the supposition that the antisite defect, AsGa, breaks into AsI and VGa, and the latter is a deep acceptor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353371
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  • 9
    Electronic Resource
    Electronic Resource
    Electrical and optical properties of CuAlSe2 grown by iodine chemical vapor transport (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1648-1655 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Resistivities, carrier concentrations, optical absorption, and photoluminescences of undoped and Cd,Zn-doped CuAlSe2 single crystals grown by chemical vapor transport were studied. The electrical and optical properties were almost unchanged after annealing under Se pressure. However, the resistivity increased about seven orders of magnitude after annealing in vacuum. The resistivity also increased by Cd or Zn doping. The samples showed p-type conduction even when Cd or Zn was doped. An acceptor ionization energy of about 65 meV was obtained. The mobility showed the dominance of lattice scattering for temperatures between 80 and 200 K. Two independent, broad, red luminescences having their own excitation energies were observed at relatively low temperature. We have proposed the configuration coordinate model for this characteristic emission. The emission can be interpreted as radiative transitions from a deep center to the respective A or C valence bands, accompanied by a lattice relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349531
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  • 10
    Electronic Resource
    Electronic Resource
    11B and 10B magic-angle spinning nuclear magnetic resonance studies of cubic boron nitride films prepared by plasma chemical vapor deposition (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1734-1737 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 11B and 10B magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy was conducted to characterize cubic boron nitride films prepared by plasma chemical vapor deposition. Similarities and differences between cubic boron nitride films and polycrystals synthesized at high pressure and high temperature were clarified by chemical shift and linewidth. The same local structure and tetrahedral symmetry of boron atoms in both forms was demonstrated, and a higher defective density appeared to exist in the film form, agreeing well with results from Raman measurements. Noncubic-phase impurities, i.e., amorphous, turbostratic, and hexagonal phases, in films were also detected in 11B MAS NMR spectra, and the possibility of removing these impurities by chemical etching was demonstrated. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1338516
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