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  • 1
    Electronic Resource
    Electronic Resource
    Observation of Doppler shifted Tα emission from TFTR tritium neutral beams : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 632-634 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: 195 tritium ion source shots were injected into Tokamak Fusion Test Reactor (TFTR) high power plasmas during December 1993–March 1994. In addition, four highly diagnosed pulses were fired into the calorimeter. Analysis of the Doppler shifted Tα emission of the beam in the neutralizer has revealed that the extracted ion compositions for deuterium and tritium are indistinguishable: 0.72±0.04 D+; 0.22±0.02 D+2; 0.07±0.01 D+3 compared to 0.72±0.04 T+; 0.23±0.02 T+2; 0.05±0.01 T+3. The resultant tritium full-energy neutral fraction is higher than for deuterium due to the increased neutralization efficiency at lower velocity. To conserve tritium, it was used only for injection and a few calorimeter test shots, never for ion source conditioning. When used, the gas species were switched to tritium only for the shot in question. This resulted in an approximately 2% deuterium contamination of the tritium beam and vice versa for the first deuterium pulse following tritium. Data from the calorimeter shots indicate that tritium contamination of the deuterium beam cleans up in five to six beam pulses, and is reduced to immeasurable quantities prior to deuterium beam injection. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146309
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of object potentials on the wake of a flowing plasma (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2675-2679 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements and calculations have been carried out to determine the structure of electric potential and ion density in the near wake created by the flow of a high-Mach-number plasma past a conducting plate biased with respect to the undisturbed plasma. Results are obtained for a molecular nitrogen plasma with ambient electron densities N of the order of 105 cm−3, ion temperatures of θi(approximately-equal-to)0.025 eV, electron temperatures of θ∼0.3 eV, and plasma flow velocities of V0(approximately-equal-to)106 cm/s, corresponding to V0/(θ/M)1/2(approximately-equal-to)11. For high-Mach-number flow past an unbiased object, the wake structure is very nearly that predicted for the expansion of an initially uniform plasma half-space into vacuum; in this case there is a sharply defined ion front moving under the influence of an electric field produced by charge separation between ions and electrons near the front. With bias potential φp such that qφp/θ is in the range −1 to −10, a well-defined ion front still exists, but its motion is strongly affected by the imposed potential. This effect can be explained in terms of the impulse received by those ions passing through the sheath region near the plate edge. Two-dimensional simulations of the laboratory experiments were performed by using a multiple waterbag technique. The results for both zero and finite ion temperatures are almost noise-free and support the approximate analytical model. The calculated density for 10 θ negative bias on the plate is compared with the measured profile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339418
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  • 3
    Electronic Resource
    Electronic Resource
    Instrument for differential ion flux vector measurements on Spacelab 2 (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1897-1902 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The differential ion flux probe (DIF probe) is a scientific instrument capable of deconvolving a multiplicity of ion streams, differing in flow direction and/or energy, and independently determining the flow direction, current density, temperature, and energy of each stream. The original instrument concept was developed for laboratory investigations in the area of plasma dynamics and was reported [N. H. Stone, Rev. Sci. Instrum. 48, 1458 (1977). Since then, the DIF probe has been redesigned and developed into a flight instrument to provide measurements of disturbed plasma flow conditions within the terrestrial ionosphere. It has flown on the STS-3 Space Shuttle mission, on sounding rockets, and recently on the Spacelab-2 mission as part of the plasma diagnostics package (PDP) experiment. Herein, we discuss the unique design and operational characteristics required for the flight model of the DIF probe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138441
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  • 4
    Electronic Resource
    Electronic Resource
    Operation of large "field-free'' ion sources in the presence of magnetic fields (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 596-600 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Large area 10×40-cm Lawrence Berkeley Laboratory "field-free'' ion sources were used during the first 2.5 yr of the neutral beam injection heating experiment on the tokamak fusion test reactor. Although these ion sources were located inside magnetic shielding structures, interference from tokamak magnetic fields prevented beam operation under certain conditions when using hydrogen. The fields causing this interference have been studied, and modifications which allow operation of such sources in these fields have been made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139839
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  • 5
    Electronic Resource
    Electronic Resource
    The persistence of seeds of 16 weed species over six years in two arable fields (2002)
    Oxford, UK : Blackwell Science Ltd
    Weed research 42 (2002), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two experiments have investigated the persistence of 16 arable, annual broad-leaved weed species over 6 years in a silty loam and a clay soil. Small plastic beads were included as an ‘inert’ comparison. Seeds were broadcast in October on to plots at the start of the experiment, and these were either tine cultivated or ploughed annually thereafter. Plots were sown with either spring or winter wheat. As far as possible, weed seeding was prevented each year. For some species, the seed decline appeared to be slower on the ploughed plots than on the tined plots and in the winter wheat compared with the spring wheat. Seed decline also tended to be slower on the clay soil at Rothamsted than on the silty loam at Long Ashton. Some species declined rapidly (e.g. Brassica napus, Chrysanthemum segetum, Galium aparine, Galeopsis tetrahit), with annual decline rates in excess of 58%, whereas others declined very little (e.g. Papaver rhoeas decline rate 9%). Most of the other species had decline rates between 20% and 40%. The results are discussed in relation to the development of population dynamics models to predict long-term consequences of alternative weed management strategies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3180.2002.00281.x
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  • 6
    Electronic Resource
    Electronic Resource
    Crop canopy development and structure influence weed suppression (1999)
    Oxford UK : Blackwell Science Ltd
    Weed research 39 (1999), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Weed suppression characteristics of different winter cereal species and cultivars were studied in two field experiments in two successive years. Two cultivars each of barley, oats and wheat were studied using the weed Galium aparine L. at a range of densities. Significant differences were found in the suppressive abilities of the crop species: oats being the most suppressive, followed by barley and then wheat. Percentage yield loss was related to G. aparine density using a rectangular hyperbolic model. In 1995–96, significant differences between the two wheat cultivars were found, with cv. Avalon being able to suppress G. aparine growth much more effectively than cv. Spark. However, in 1996–97, high rainfall in May, June and July enabled G. aparine to escape suppression by the cultivars. Cultivar competitive ability was associated with high overall leaf area, resistance to loss of tillers under competitive pressure, greater height, canopy structure and development. The oat cultivars were more competitive at early growth stages than could be accounted for by their canopy structure; the possible contribution of allelopathic exudates to their suppressive ability is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3180.1999.00148.x
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  • 7
    Electronic Resource
    Electronic Resource
    Predicting the competitive effects of weed and crop density on weed biomass, weed seed production and crop yield in wheat (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 35 (1995), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Competition between winter-sown wheat and Viola arvensis Murray or Papaver rhoeas L. was studied in two experiments in two successive years. The effects of varying crop and weed density were modelled in terms of weed biomass over time, weed seed production and crop yield. Biomass model parameters, representing maximum weed biomass and intra- and interspecific competition, were obtained for different assessment dates, enabling biomass levels to be predicted during the two growing seasons. Weed biomass declined, and its maximum level was reached earlier, with increasing crop density. Intraspecific competition was higher in the absence than in the presence of crop, increasing with time and with weed density. Halving the wheat population increased June biomass of V. arvensis by 74% and of P. rhoeas by 63%. Crop yield losses with increasing weed density were greater with low than with medium and high crop populations. P. rhoeas was significantly more competitive than V. arvensis in both years. Weed biomass in 1989 responded more to reductions in crop density following the milder winter of 1988/89 than in the previous year; however crop yields were less affected in 1989 due to summer drought, restricting late weed growth and competition. Weed seed production was related to weed biomass; the progressive lowering of crop density increased seed production, and both species were very prolific in the absence of crop. By combining models, seed production could be derived for a given competitive effect on the crop. Threshold weed populations, based on low weed levels that are not economic to control, could then be equated with the accompanying weed seed production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.1995.tb01789.x
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of soil moisture on the competitive ability and seed dormancy of Sinapis arvensis in spring wheat (1999)
    Oxford UK : Blackwell Science Ltd
    Weed research 39 (1999), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Two experiments were carried out, one in 1995 and one in 1997, to investigate the competitive abilities of two spring wheat cultivars with Sinapis arvensis L. The spring wheat cultivars (Baldus and Canon) of contrasting growth habit were grown with and without S. arvensis under two different moisture regimes (10% and 70% of field capacity). In 1995, S. arvensis was found to be less competitive when subjected to moisture stress, resulting in smaller wheat yield losses in dry soil than in moist soil. In both years, seed production of S. arvensis was reduced by competition and moisture stress, and the seeds produced by plants that had been grown in drier soil were small and had negligible dormancy. Hence, in dry conditions, the competitiveness of S. arvensis and its potential to produce persistent seed may be reduced. Some differences between the two wheat cultivars were evident: cv. Baldus was more competitive against S. arvensis than cv. Canon. This could be attributed to differences in canopy structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3180.1999.00147.x
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  • 9
    Electronic Resource
    Electronic Resource
    Computer-mediated social support, older adults, and coping (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of communication 50 (2000), S. 0 
    Details
    ISSN: 1460-2466
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Media Resources and Communication Sciences, Journalism
    Notes: One important new context of communication for older adults is computer-mediated communication (CMC). Although the Internet has become an important resource for information, little is known about the ways in which individuals use this technology for social support. Older adults (mean age = 62) using SeniorNet and other related websites completed an on-line questionnaire (N = 136) investigating social support in the computer-mediated environment. Satisfaction with Internet providers of social support was significantly higher for high Internet users than for low Internet users whereas low Internet users were more satisfied with their non-Internet support networks than high Internet users. Internet companionship network size was significantly larger than Internet social support network size. Greater involvement with the on-line community was predictive of lower perceived life stress. Social support and companionship satisfaction were not related to the types of coping strategies used; however, the results indicate that direct action was the most common coping strategy for the sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2466.2000.tb02855.x
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  • 10
    Electronic Resource
    Electronic Resource
    Composition of Atriplex hortensis, Sweet and Bitter Chenopodium quinoa Seeds (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 67 (2002), 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: Composition and amino acid profiles of seeds from garden orach (A triplex hortensis) and sweet quinoa (Chenopodium quinoa Willd. ‘Surumi’) were compared with bitter quinoa (Chenopodium quinoa Willd.). Protein content was 14.8 and 15.7% for sweet and bitter quinoa, respectively. Garden orach seeds had a protein content of 25.7%, similar to that found in legumes. Fat and ash contents were similar for all three samples (5.3 to 6.2% fat; 2.6 to 3.2% ash). Amino acid profiles showed a balanced content of essential amino acids for all three samples when compared with reference patterns from the World Health Organization. Garden orach and quinoa seed proteins contained higher lysine contents compared with cereals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2002.tb10294.x
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