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  • 1
    Electronic Resource
    Electronic Resource
    Nanostructure and magnetic properties of composite CoPt:C films for extremely high-density recording (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6959-6961 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nanostructure and magnetic properties of composite CoPt:C films at room temperature were investigated as a function of annealing temperature, carbon concentration, and film thickness. CoPt:C films with a variety of carbon concentrations were fabricated by cosputtering Co, Pt, and C onto water-cooled Si(100) substrates followed by annealing. X-ray diffraction and transmission electron microscopy analyses indicate that nanocrystallites of face-centered-tetragonal (fct) CoPt phase, which has a uniaxial magnetocrystalline anisotropy constant of about 5×107 erg/cm3, can be formed in carbon matrix when the annealing temperature is higher than 600 °C. The grain sizes of the fct CoPt crystallites are about 10 nm and the coercivities can be as high as 12 kOe. Higher annealing temperature and lower carbon concentration generally lead to larger grain sizes and perhaps more complete formation of the fct CoPt phase, and therefore higher coercivities. The coercivity is insensitive to the film thickness until the thickness is smaller than the CoPt grain size, when the coercivity starts to decrease with film thickness. The magnetic activation volumes are typically around 1×10−18 cm3. The nanostructure and the associated magnetic properties of these composite CoPt:C films are promising as potential media for extremely high-density recording. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372899
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  • 2
    Electronic Resource
    Electronic Resource
    Feedback stabilization of nonaxisymmetric resistive wall modes in tokamaks. I. Electromagnetic model (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3681-3690 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Active feedback stabilization of pressure-driven modes in tokamaks is studied computationally in toroidal geometry. The stability problem is formulated in terms of open-loop transfer functions for fluxes in sensor coils resulting from currents in feedback coils. The transfer functions are computed by an extended version of the MARS stability code [A. Bondeson et al., Phys. Fluids B 4, 1889 (1992)] and can be accurately modeled by low order rational functions. In the present paper stability is analyzed for a system with an ideal amplifier (current control). It is shown that feedback with modest gain, and a single coil array poloidally, gives substantial stabilization for a range of coil shapes. Optimum design uses sensors for the poloidal field, located inside the resistive wall, in combination with rather wide feedback coils outside the wall. Typically, the feedback does not strongly modify the plasma-generated magnetic field perturbation. A future companion paper [C. M. Fransson et al., Phys. Plasmas (accepted for publication)] will apply control theory to study the limitations arising for finite time-constant of the amplifier-feedback coil circuit. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287744
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetic theory of interaction of high frequency waves with a rotating plasma (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 596-608 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The equations of motion of charged particles of a strongly magnetized flowing plasma under the influence of high frequency waves are derived in the guiding center approximation. A quasilinear theory of the interactions of waves with rotating plasmas is formulated. This is applied to investigate the effect of radio frequency waves on a rotating tokamak plasma with a heated minority species. The angular momentum drive is mainly due to the rf-induced radial minority current. The return current by the bulk plasma gives an equal and opposite rotation drive on the bulk. Using moment equations and a small banana width approximation, the J×B drive was evaluated for the bulk plasma. Quite remarkably, although collisions are included, the net rotation drive is due to a term which can be obtained by neglecting collisions. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873846
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  • 4
    Electronic Resource
    Electronic Resource
    Gyrokinetic theory in the White–Chance–Boozer coordinates (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 4609-4615 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The noncanonical Lagrangian theory of guiding center orbits is applied to the coordinate system of White–Chance–Boozer. The result is a generalized set of equations of motion which eliminates certain approximations of the static field and includes the effects of large rotations and high frequency waves. A quasilinear gyrokinetic theory is shown to readily follow from these equations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287740
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  • 5
    Electronic Resource
    Electronic Resource
    Continuous, dense, highly collimated sodium beam (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 3668-3676 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a slow, highly collimated, and bright sodium atom beam suitable for orientation and alignment studies in cold collisions. A combination of transverse-optical collimation, longitudinal cooling, rapid decoupling from the longitudinal cooling cycle, and a final "optical-force extrusion" stage produces an atom density of 1×1010 cm−3 within a beam-divergence solid angle of 2×10−6 sr. Rapid Zeeman-cooler decoupling results in a narrow laboratory velocity distribution of 5 m/s full width at half maximum and a cold binary intrabeam collision temperature of 4 mK. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289683
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  • 6
    Electronic Resource
    Electronic Resource
    Evidence for ferroelectric border traps near the SrBi2Ta2O9/Si interface through capacitance–voltage measurement (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 564-566 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A metal–ferroelectric–semiconductor (MFS) structure has been developed by depositing SrBi2Ta2O9 (SBT) films directly on n-type (100) Si by pulsed laser deposition. In the MFS structure, evidence for ferroelectric border traps in the SBT film has been obtained by high-frequency capacitance–voltage (C–V) measurement. When the ramp rate of voltage is higher than 200 mV/s, typical ferroelectric C–V hysteresis loops with the counterclockwise direction are obtained in C–V plots. When the ramp rate is lower than 80 mV/s, the ferroelectric hysteresis loops are replaced by the trap-induced ones with the clockwise direction. This pronounced change results from the fact that more and more border traps in SBT can communicate with the underlying Si. The border-trap density at the ramp rate of 10 mV/s is as high as 1.8×1012 cm−2. Moreover, the width of the hysteresis loops changes linearly with the logarithmic decrease in ramp rate, which is consistent with the ferroelectric border traps communicating with Si by tunneling or a thermally activated process. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.127045
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  • 7
    Electronic Resource
    Electronic Resource
    Simple and high-yield method for synthesizing single-crystal GaN nanowires (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1961-1963 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple and high-yield method involving vapor-liquid-solid wire-like growth mechanism was developed for the synthesis of GaN nanowires. In this process, the mixture of Ga and SiO2 reacted with ammonia in the presence of the Fe2O3 catalyst supported by Al2O3. The x-ray powder diffraction measurement and transmission electron microscopy observations confirmed that the synthesized GaN nanowires are single-crystal hexagonal wurtzite structure with diameters ranged from 10 to 50 nm and lengths up to several micrometers. Based on the fact that a small Fe dominant particle attached to one end of some nanowires, a growth model of the GaN nanowires was proposed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1312853
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Process Conditions on the Physical and Sensory Properties of Extruded Oat-Corn Puff (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 65 (2000), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: : The effect of processing variables, including screw speed (200,300, and 400 rpm), moisture content (18, 19.5, and 21%), and four different percentages (55,70,85, and 100%) of oat flour, on the extrudate physical properties (expansion, bulk density, and texture profiles) and sensory properties were studied. Increasing the percentage of oat flour resulted in extrudates with a lower specific length, higher bulk density, lower lightness, higher redness, lower yellowness, higher hardness, and lower springiness, gumminess, and chewiness. Higher moisture content reduced expansion, except for the 100% oat flour puffs. Screw speed had no significant effect on the bulk density, specific length, and expansion ratio. Principal Component Analysis showed that decreasing moisture content and increasing screw speed resulted in increased product temperature, which was highly correlated with attributes of a more expanded product such as lightness, crispness, shininess, and an open cell structure. With a higher screw speed and a higher product temperature, corn-related flavors were more likely to develop. High correlations between physical and sensory properties were observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2000.tb10274.x
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  • 9
    Electronic Resource
    Electronic Resource
    Hypothalamic Vasopressin Gene Expression Increases in Both Males and Females Postpartum in a Biparental Rodent (2000)
    Oxford, UK : Blackwell Science Ltd
    Journal of neuroendocrinology 12 (2000), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In previous studies, the closely related neuropeptide hormones oxytocin and vasopressin have been implicated in the central mediation of parental behaviour. Several studies in rats and sheep have demonstrated a role for oxytocin in the initiation of maternal behaviour. Recently, a few studies in a biparental species, the prairie vole (Microxytocinus ochrogaster) have suggested that vasopressin is important for paternal care. The present study investigated this latter possibility by measuring changes in vasopressin and oxytocin hypothalamic gene expression 1 day and 6 days following parturition in prairie voles which show paternal care and in montane voles (M. montanus) which lack paternal care. In prairie voles, vasopressin gene expression increased in both males and females postpartum, relative to sexually naive controls. In the non-paternal montane vole, no change in vasopressin gene expression was observed in either sex. In contrast to this species difference in vasopressin gene expression, hypothalamic oxytocin gene expression increased in both prairie and montane vole females, but not in males of either species. To augment measures of gene expression, we assessed vasopressin (V1a) and oxytocin receptor binding in both species. Although forebrain vasopressin V1a receptor binding was not altered following parturition in either species, oxytocin receptor binding increased in the ventromedial nucleus of the hypothalamus in females, but not males, in both prairie and montane voles. In summary, vasopressin gene expression increases in both males and females postpartum in a biparental species and oxytocin gene expression and receptor binding increase selectively in females. These results are consistent with earlier reports of a role for vasopressin in paternal care and for oxytocin in maternal behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2826.2000.00435.x
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  • 10
    Electronic Resource
    Electronic Resource
    Solving crystal structures from two-wavelength X-ray powder diffraction data – breaking the phase ambiguity in the noncentrosymmetric case (2000)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 592-595 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Direct methods of breaking phase ambiguities in protein crystallography have been introduced in powder diffraction analysis. This is aiming at ab initio solution of noncentrosymmetric structures using two-wavelength anomalous powder diffraction data. The known structure of the hydrogen bromide salt of leotidine (C14H20O2N2·HBr) in space group P212121 was used for simulating two-wavelength anomalous powder diffraction with the Br atom as anomalous scatterer. X-ray wavelengths are selected at \lambda_1 = 0.920 and \lambda_2 = 1.500 Å. Unique reflections from the diffraction pattern of \lambda_2 were able to locate the Br atom accurately. All overlapping diffraction peaks were uniformly partitioned to decompose into single reflections. Structure-factor amplitudes were then extracted. With these and the substructure of Br atoms, unique phases for centric reflections (hk0, h0l and 0kl) and phase doublets for noncentric reflections were obtained. The direct method was used to break the phase ambiguity leading to an interpretable electron-density map, from which five cycles of Fourier iteration yielded the complete structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767300011417
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