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  • 1
    Electronic Resource
    Electronic Resource
    Effect of Zr on the microstructure and magnetic properties of Sm(CobalFe0.1Cu0.088Zrx)8.5 magnets (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 399-403 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of Zr content on the microstructure and magnetic properties of Sm(CobalFe0.1Cu0.088Zrx)8.5 magnets with x varying from 0 to 0.1 was systematically studied using magnetic, x-ray diffraction, and transmission electron microscopy measurements. The results have revealed that addition of Zr greatly affects the microstructure and magnetic properties. X-ray diffraction, electron diffraction, and thermomagnetic data showed that the normal microstructure consists of 2:17 cells surrounded by 1:5 cell boundaries and intersected by lamella phase perpendicular to the c axis. The lamella phase appears to have the SmCo3 structure and its amount increases with increasing Zr content. When the Zr content is above 0.08, the microstructure becomes inhomogeneous, showing regions with a considerable amount of mixtures of 1:3 and 2:7 phases. The formation of the cellular microstructure mainly depends on the Cu content, and the existence of the lamellar phase can stabilize a uniform cellular microstructure with larger cells and help the redistribution of Cu at the cell boundaries, improving the coercivity greatly. A room temperature intrinsic coercivity of around 40 kOe has been obtained in magnets with a wide range of Zr contents from x=0.02–0.06. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371874
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  • 2
    Electronic Resource
    Electronic Resource
    Drift mode calculations for the Large Helical Device (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 4942-4947 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A fully kinetic assessment of the stability properties of toroidal drift modes has been obtained for a case for the Large Helical Device [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)]. This calculation retains the important effects in the linearized gyrokinetic equation, using the lowest-order "ballooning representation" for high toroidal mode number instabilities in the electrostatic limit. Results for toroidal drift waves destabilized by trapped particle dynamics and ion temperature gradients are presented, using three-dimensional magnetohydrodynamic equilibria reconstructed from experimental measurements. The effects of helically trapped particles and helical curvature are investigated. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1317521
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  • 3
    Electronic Resource
    Electronic Resource
    Gyrokinetic simulations in general geometry and applications to collisional damping of zonal flows : The 41st annual meeting of the division of plasma physics of the american physical society (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 1857-1862 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A fully three-dimensional gyrokinetic particle code using magnetic coordinates for general geometry has been developed and applied to the investigation of zonal flows dynamics in toroidal ion-temperature-gradient turbulence. Full torus simulation results support the important conclusion that turbulence-driven zonal flows significantly reduce the turbulent transport. Linear collisionless simulations for damping of an initial poloidal flow perturbation exhibit an asymptotic residual flow. The collisional damping of this residual causes the dependence of ion thermal transport on the ion–ion collision frequency, even in regimes where the instabilities are collisionless. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874008
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  • 4
    Electronic Resource
    Electronic Resource
    On the gyrokinetic equilibrium (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 991-1000 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent developments in gyrokinetic-magnetohydrodynamics (MHD) theory and in electromagnetic gyrokinetic particle simulations raise the question of consistency between the gyrokinetic model and the fluid model. Due to the special characteristics of the guiding center coordinates, it is a nontrivial exercise to show this consistency. In this paper it is shown, in a very general setting, that the gyrokinetic theory and the fluid equations do give an equivalent description of plasma equilibrium (∂/∂t=0). The fluid continuity equation and momentum equation for equilibrium plasmas are recovered entirely from the gyrokinetic theory. However, it was Spitzer who first realized the importance of consistency between guiding-center motion and fluid equations. In particular, he studied the "apparent paradoxical result" regarding the difference between perpendicular particle flow and guiding-center flow, which will be referred to as the Spitzer paradox in this paper. By recovering the fluid equations from the gyrokinetic theory, we automatically resolve the Spitzer paradox, whose essence is how the perpendicular current and flow are microscopically generated from particles' guiding-center motion. The mathematical construction in the gyrokinetic theory which relates observable quantities in the laboratory frame to the distribution function in the guiding-center coordinates is consistent with Spitzer's original physical picture, while today's gyrokinetic-MHD theory covers a much wider range of problems in a much more general and quantitative way. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873898
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  • 5
    Electronic Resource
    Electronic Resource
    Gyrocenter-gauge kinetic theory (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 4433-4445 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gyrocenter-gauge kinetic theory is developed as an extension of the existing gyrokinetic theories. In essence, the formalism introduced here is a kinetic description of magnetized plasmas in the gyrocenter coordinates which is fully equivalent to the Vlasov–Maxwell system in the particle coordinates. In particular, provided the gyroradius is smaller than the scale-length of the magnetic field, it can treat high-frequency range as well as the usual low-frequency range normally associated with gyrokinetic approaches. A significant advantage of this formalism is that it enables the direct particle-in-cell simulations of compressional Alfvén waves for magnetohydrodynamic (MHD) applications and of rf (radio frequency) waves relevant to plasma heating in space and laboratory plasmas. The gyrocenter-gauge kinetic susceptibility for arbitrary wavelength and arbitrary frequency electromagnetic perturbations in a homogeneous magnetized plasma is shown to recover exactly the classical result obtained by integrating the Vlasov–Maxwell system in the particle coordinates. This demonstrates that all the waves supported by the Vlasov–Maxwell system can be studied using the gyrocenter-gauge kinetic model in the gyrocenter coordinates. This theoretical approach is so named to distinguish it from the existing gyrokinetic theory, which has been successfully developed and applied to many important low-frequency and long parallel wavelength problems, where the conventional meaning of "gyrokinetic" has been standardized. Besides the usual gyrokinetic distribution function, the gyrocenter-gauge kinetic theory emphasizes as well the gyrocenter-gauge distribution function, which sometimes contains all the physics of the problems being studied, and whose importance has not been realized previously. The gyrocenter-gauge distribution function enters Maxwell's equations through the pull-back transformation of the gyrocenter transformation, which depends on the perturbed fields. The efficacy of the gyrocenter-gauge kinetic approach is largely due to the fact that it directly decouples particle's gyromotion from its gyrocenter motion in the gyrocenter coordinates. As in the case of kinetic theories using guiding center coordinates, obtaining solutions for this kinetic system involves only following particles along their gyrocenter orbits. However, an added advantage here is that unlike the guiding center formalism, the gyrocenter coordinates used in this theory involves both the equilibrium and the perturbed components of the electromagnetic field. In terms of solving the kinetic system using particle simulation methods, the gyrocenter-gauge kinetic approach enables the reduction of computational complexity without the loss of important physical content. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1309031
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of Zr and Cu content on the microstructure and coercivity in Sm(CobalFe0.1CuyZrx)8.5 magnets (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5308-5310 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of Cu and Zr on the microstructure and coercivity of Sm(CobalFe0.1CuyZrx)8.5 magnets has been studied using magnetometry and transmission electron microscopy. For Zr-free samples, when y=0.088, a cellular microstructure is not formed. Instead a rod-like 1:5 phase is observed, distributed in the 2:17 matrix phase. For a sample with y=0.168, the cellular microstructure develops after a short aging. However, the cellular microstructure coarsens and becomes highly nonuniform and finally, breaks down with further aging. This leads to a reduction in coercivity from an optimal value of 5.6–2 kOe. After adding Zr(x=0.04), the cellular microstructure along with a lamellar phase can be formed even with a Cu content as low as 0.048 and the coercivity increases dramatically. Coercivities of up to 8.9 and 38.4 kOe are obtained for the y=0.048 and 0.168 samples, respectively. These results show that the formation of cellular structure strongly depends on the Cu content. But the formation of the lamellar phase can stabilize a uniform cellular microstructure over a wide range of cell size and help the redistribution of Cu at the cell boundaries, which is a key to obtain appropriate microstructures with high coercivity. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373330
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  • 7
    Electronic Resource
    Electronic Resource
    Sm(Co, Fe, Cu, Zr)z magnets fabricated by simple processing (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 421-422 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optimization studies in Sm(Co, Cu, Fe, Zr)z magnets for high-temperature applications led to some compositions which develop their high coercivity with simple processing. Homogenized magnets with higher Cu and Zr content acquire a coercivity of above 20 kOe after a short aging (3 h) at 850 °C without the traditional slow cooling to 400 °C which is required for the commercial magnets. Microstructure studies showed that the homogenized magnets consist of a mixture of Sm(Co, Cu)5 precipitates in a disordered 2:17 matrix as compared to a uniform and featureless microstructure of the traditional homogenized magnets. Because of this, the time required for the full development of uniform cellular and lamellar structures with the right microchemistry is much shorter in the magnets. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126996
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  • 8
    Electronic Resource
    Electronic Resource
    High-frequency plant regeneration via somatic embryogenesis and organogenesis and in vitro flowering of regenerated plantlets in Panax ginseng (2000)
    Springer
    Plant cell reports 19 (2000), S. 727-732 
    Details
    ISSN: 1432-203X
    Keywords: Key words Panax ginseng ; C.A. Meyer ; Somatic embryogenesis ; Organogenesis ; In vitro flowering of regenerated plantlets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The morphogenesis ability of light yellowish globular callus derived from cotyledons of mature zygotic embryos of Panax ginseng was investigated. The optimal media for somatic embryogenesis and shoot organogenesis were MS medium containing 0.5 mg l–1 2,4-dichlorophenoxyacetic acid, 0.1 mg l–1 6-benzyladenine (BA), and 500 mg l–1 lactoalbumin hydrolysate, and SH medium supplemented with 0.5 mg l–1 α-naphthaleneacetic acid, 0.1 mg l–1 BA, and 500 mg l–1casein hydrolysate. The influences of glucose, mannose, fructose, and sorbose in the media on somatic embryogenesis and shoot organogenesis were revealed as differences in the numbers of somatic embryos and adventitious shoots per gram of morphogenic callus. The best regeneration of somatic embryos was obtained on medium containing glucose, with a mean of 8.7 somatic embryos per gram of callus. The best regeneration of shoots was observed on medium containing fructose, with an average of 12.2 adventitious shoots per gram of callus. Of the somatic embryos 95% were converted into regenerated plantlets, and 100% of adventitious shoots rooted to form regenerated plantlets. Regenerated plants were successfully established in soil. Flowering was observed in 5.7% of the regenerated plants derived from shoot organogenesis and in 1.4% of the regenerated plants derived from somatic embryogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002999900170
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  • 9
    Electronic Resource
    Electronic Resource
    Preparation of a new type of manganese oxide by selective lithium extraction from monoclinic Li2MnO3 for lithium rechargeable batteries (2000)
    Springer
    Journal of materials science 19 (2000), S. 1361-1363 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006753216616
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  • 10
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    Secreted and membrane attractin result from alternative splicing of the human ATRN gene (2000)
    National Academy of Sciences
    Details
    Publication Date: 2000-05-16
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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