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  • Springer  (15)
  • American Institute of Physics (AIP)  (7)
  • Blackwell Science Ltd  (5)
  • 2000-2004  (27)
  • 1965-1969
  • 1955-1959
  • 2001  (27)
  • 1
    Electronic Resource
    Electronic Resource
    Particle transport in DIII-D discharges with internal regions of enhanced confinement and counter injected neutral beams (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 1565-1572 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An analysis of experimentally measured particle transport in tokamak plasmas with negative central magnetic shear is presented. The analysis is presented in terms of a simple model for turbulent transport which allows the separation of diagonal and off diagonal terms and allows the direct comparison of particle and energy transport. Comparing the measured fluxes to the fluxes predicted by a simple quasi analytical model which specifies a relation between the diagonal and off diagonal terms allows an understanding of the reason for the difference between energy and particle fluxes. In the center of discharges with a region of enhanced confinement (or internal transport barrier), the ion thermal diffusivity becomes small and comparable to neoclassical values and the particle diffusivity also becomes small and approaches the neoclassical values. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1358311
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  • 2
    Electronic Resource
    Electronic Resource
    Comparison of particle confinement in the high confinement mode plasmas with the edge localized mode of the Japan Atomic Energy Research Institute Tokamak-60 Upgrade and the DIII-D tokamak (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 1607-1611 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Particle confinement was compared for the high confinement mode plasmas with the edge localized mode in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [S. Ishida, JT-60 Team, Nucl. Fusion 39, 1211 (1999)] and the DIII-D tokamak [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159] considering separate confinement times for particles supplied by neutral beam injection (NBI) (center fueling) and by recycling and gas-puffing (edge fueling). Similar dependence on the NBI power was obtained in JT-60U and DIII-D. The particle confinement time for center fueling in DIII-D was smaller by a factor of 4 in the low density discharges and by a factor of 1.8 in the high density discharges than JT-60U scaling, respectively, suggesting the stronger dependence on the density in DIII-D. The particle confinement time for edge fueling in DIII-D was comparable with JT-60U scaling in the low density discharges. However, it decreased to a much smaller value in the high density discharges. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1362295
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  • 3
    Electronic Resource
    Electronic Resource
    Progress toward long-pulse high-performance Advanced Tokamak discharges on the DIII-D tokamak : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2208-2216 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Significant progress has been made in obtaining high-performance discharges for many energy confinement times in the DIII-D tokamak [J. L. Luxon et al., Plasma Physics and Controlled Fusion Research (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159]. Normalized performance (measured by the product of βNH89 and indicative of the proximity to both conventional β limits and energy confinement quality, respectively) ∼10 has been sustained for 〉5 τE with qmin〉1.5. These edge localized modes (ELMing) H-mode discharges have β∼5%, which is limited by the onset of resistive wall modes slightly above the ideal no-wall n=1 limit, with approximately 75% of the current driven noninductively. The remaining Ohmic current is localized near the half-radius. The DIII-D electron cyclotron heating system is being upgraded to replace this inductively driven current with localized electron cyclotron current drive (ECCD). Density control, which is required for effective ECCD, has been successfully demonstrated in long-pulse high-performance ELMing H-mode discharges with βNH89∼7 for up to 6.3 s. In plasma shapes compatible with good density control in the present divertor configuration, the achieved βN is somewhat less than that in the high βNH89=10 discharges. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1355980
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal diffusivities in DIII-D show evidence of critical gradients (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 4128-4137 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ion thermal diffusivities (χi) in DIII-D [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)] discharges exhibit a strong nonlinear dependence on the measured temperature gradients. In low confinement mode (L-mode) discharges with low toroidal rotation, the ion thermal diffusivity, χi, has an approximately Heaviside function dependence on the major radius divided by the radial scale length of the ion temperature, R/LTi. When R/LTi is less than a critical value, the χi's are very small. When R/LTi is about equal to the critical value, χi increases rapidly. Although the gradient profiles for high confinement (H-mode) have a different shape, they still show a critical gradient type of behavior. This type of dependence is consistent with the predictions for transport, which is dominated by ion temperature gradient modes and is a strong indicator that these modes are the main contributors toward L-mode transport in DIII-D and a major contributor to transport in a certain region of DIII-D H-mode discharges. When strong rotational shear is present, the thermal confinement is improved in regions of the plasma. In these regions, the dependence of the diffusivities on the gradients is changed. The type of change is consistent with the physical picture that when the E×B shearing frequency is greater than the maximum linear growth rate of the modes as calculated without shear, then the modes are stabilized and the transport is reduced. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1395567
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of accumulation period and harvest date in spring on dry-matter yield and forage quality in mixed swards containing Lolium spp. and Trifolium subterraneum in Western Australia (2001)
    Oxford UK : Blackwell Science Ltd
    Grass and forage science 56 (2001), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The object of this study was to determine the effect of closing date and date of harvest for conservation (accumulation period), on dry-matter (DM) yield and forage quality of annual pasture in Western Australia. The field study comprised 48 plots, 2 m × 2 m, sown with either annual ryegrass (Lolium rigidum Gaud.) or Italian ryegrass (L. multiflorum Lam.), and mixed with subterranean clover (Trifolium subterraneum L.). Defoliation of swards until the end of winter was at the three leaves tiller–1 stage. In spring, once stem nodal development had commenced, swards were defoliated every 3–4 weeks. Swards were defoliated either twice with three leaves tiller–1 (accumulation period 1 commenced on 15 August); twice with three leaves tiller–1 and then once after 4 weeks (accumulation period 2 commenced on 11 September); twice with three leaves tiller–1 and then twice after 4-week intervals (accumulation period 3 commenced on 9 October) or; twice with 3 leaves tiller–1 and then twice after 4-week intervals and then once after 3 weeks (accumulation period 4 commenced on 30 October). From the commencement of the accumulation period, tiller density, DM yield and forage quality were determined weekly for up to 10 weeks.There was a positive quadratic association between DM yield and days after the commencement of the accumulation period. Yields were maximized from accumulation period 1 with 5·3, 6·6 and 9·5 t DM ha–1, and growth rates were 140, 128 and 145 kg DM ha–1 d–1, for Wimmera annual ryegrass and Richmond and Concord cultivars of Italian ryegrass respectively. In contrast, in vitro dry-matter digestibility (IVDMD) and crude protein (CP) content were negatively associated with days after the commencement of the accumulation period, and initial values were greater than 0·80 and 180 g kg DM–1 for IVDMD and CP content respectively. The rate of decline in IVDMD d–1 for Wimmera annual ryegrass was 0·005, 0·019 and 0·012 d–1 for accumulation periods 1, 2 and 3, respectively, while for Italian ryegrass cultivars Richmond was 0·015, 0·011, 0·02 and 0·012 d–1 and Concord was 0·014, 0·009, 0·013 and 0·01 d–1, for the 4 accumulation periods respectively.It is recommended that annual and Italian ryegrass pastures be harvested between 10% and 20% inflorescence emergence when IVDMD will exceed 0·70 regardless of cultivar and/or defoliation practice prior to the commencement of the accumulation period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2494.2001.00242.x
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  • 6
    Electronic Resource
    Electronic Resource
    Observation of pinching in the compact toroid injection experiment: Implications for a plasma opening switch (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1237-1239 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A compact toroid inductively stores the energy released by a capacitor bank as it is being accelerated. This energy can be stored for a period of more than ten microseconds and then transferred to a load on a much shorter time scale. This article presents framing camera images of the radial compression of plasma trailing behind a compact toroid as the compact toroid leaves its inner electrode. This compression illustrates the basic principles of a compact toroid plasma opening switch which could be used to drive fast z pinches. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1400773
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  • 7
    Electronic Resource
    Electronic Resource
    Enhanced peak power and short pulse operation of planar waveguide CO2 lasers (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 2276-2278 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a large peak power enhancement and reduction in pulse width for planar waveguide carbon dioxide lasers. Gain modulation through rf discharge power switching produces trains of laser pulses with peak power levels at up to 38 times the cw power level, with a pulse duration as low as 10 μs. Operation at repetition rates in the kHz region preserves the average power (100 W) of the normal cw/long pulse mode of operation. The laser is shown to operate close to the predicted boundaries dictated by thermal loading of the discharge. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1359148
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  • 8
    Electronic Resource
    Electronic Resource
    Electric field induced instabilities at liquid/liquid interfaces (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 2377-2381 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: External electric fields were used to amplify thermal fluctuations at the interface between two thin liquid films. Similar to the results shown previously for the enhancement of fluctuations at the polymer/air interface, interfacial fluctuations having a well-defined wavelength were enhanced with a characteristic growth rate. A simple theoretical framework to describe the experimental observations is presented. Both experiment and model calculation show a substantial reduction in feature size as a result of the change in surface/interfacial energy when going from the thin film to the bilayer case. Experimentally, features develop nearly 50 times faster for the bilayers in comparison to the polymer/air case. These results point to a simple route by which the nanoscopic feature can be easily and rapidly produced or replicated. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1338125
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  • 9
    Electronic Resource
    Electronic Resource
    Will rising CO2 protect plants from the midday sun? A study of photoinhibition of Quercus myrtifolia in a scrub-oak community in two seasons (2001)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 24 (2001), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Over a large part of the photoperiod, light energy absorbed by upper canopy leaves saturates photosynthesis and exceeds the energetic requirements for light-saturated linear electron flow through photosystem II (JPSII), so that photoinhibition results. From a theoretical consideration of the response of light-saturated photosynthesis to elevated atmospheric CO2 partial pressure (pCO2) it may be predicted that, where light-saturated photosynthesis is Rubisco-limited, an increase in pCO2 will stimulate JPSII. Therefore, the proportion of absorbed quanta dissipated photochemically will increase and the potential for photoinhibition of photosynthesis will decrease. This was tested by measuring modulated chlorophyll a fluorescence from Quercus myrtifolia Willd. growing in the field in open-top chambers, at either current ambient or elevated (ambient + 35 Pa) pCO2 on Merritt Island, Florida, USA. During spring and summer, light-saturated photosynthesis at current ambient pCO2 was Rubisco-limited. Consistent with theoretical prediction, JPSII was increased and photoinhibition decreased by elevated pCO2 in spring. In the summer, when growth had largely ceased, an acclimatory decrease in the maximum Ribulose 1,5 bisphosphate saturated carboxylation capacity (Vc max) removed the stimulation of JPSII seen in the spring, and photoinhibition was increased in elevated pCO2. It is concluded that, for Q. myrtifolia growing in the field, the effects of elevated pCO2 on JPSII and photoinhibition will reflect seasonal differences in photosynthetic acclimation to elevated pCO2 in a predictable manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2001.00792.x
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  • 10
    Electronic Resource
    Electronic Resource
    A global perspective of ground level, ‘ambient’ carbon dioxide for assessing the response of plants to atmospheric CO2 (2001)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 7 (2001), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: For most studies involving the response of plants to future concentrations of atmospheric carbon dioxide (CO2), a current concentration of 360–370 μatm is assumed, based on recent data obtained from the Mauna Loa observatory. In the present study, average seasonal diurnal values of ambient CO2 obtained at ground level from three global locations (Australia, Japan and the USA) indicated that the average CO2 (at canopy height) can vary from over 500 μatm at night to 350 μatm during the day with average 24-h values ranging from 390 to 465 μatm. At all sites sampled, ambient CO2 rose to a maximum value during the pre-dawn period (03.00–06.00 hours); at sunrise, CO2 remained elevated for several hours before declining to a steady-state concentration between 350 and 400 μatm by mid-morning (08.00–10.00 hours). Responses of plant growth to simulations of the observed variation of in situ CO2 were compared to growth at a constant CO2 concentration in controlled environment chambers. Three diurnal patterns were used (constant 370 μatm CO2, constant 370 during the day (07.00–19.00 hours), high CO2 (500 μatm) at night; or, high CO2 (500 μatm) at night and during the early morning (07.00–09.00 hours) decreasing to 370 μatm by 10.00 hours). Three plant species − soybean (Glycine max, L (Merr.), velvetleaf (Abutilon theophrasti L.) and tomato (Lycopersicon esculentum L.) − were grown in each of these environments. For soybean, high night-time CO2 resulted in a significant increase in net assimilation rate (NAR), plant growth, leaf area and biomass relative to a constant ambient value of CO2 by 29 days after sowing. Significant increases in NAR for all three species, and significant increases in leaf area, growth and total biomass for two of the three C3 species tested (velvetleaf and soybean) were also observed after 29 days post sowing for the high night/early morning diurnal pattern of CO2. Data from these experiments suggest that the ambient CO2 concentration experienced by some plants is higher than the Mauna Loa average, and that growth of some agricultural species at in situ CO2 levels can differ significantly from the constant CO2 value used as a control in many CO2 experiments. This suggests that a reassessment of control conditions used to quantify the response of plants to future, elevated CO2 may be required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.2001.00436.x
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