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  • 1
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Lithium fluoride, field-enhanced ion source experiments are being performed on PBFA II. The source consists of a thin coating of LiF on a microscopically rough substrate. Diagnostics to measure ion beam energy, purity, and transport include electrical monitors, Faraday cups, nuclear activation, ion pinhole camera, Rutherford magnetic spectrograph, and shadowbox aperture array. With PBFA II operating at three-quarters energy, the source has produced 16 TW of ion power and 550 kJ of ion energy with 70% diode efficiency. Over 26 kJ of lithium beam energy has been focused to the diode center axis with a peak energy density of about 1.3 kJ/cm2 . PICDIAG simulations of the lithium focus indicate the intrinsic source divergence is about 45 mrad with a 20-μm-grade porous stainless-steel substrate.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 589 (1990), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3075-3080 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a new visible spectroscopy diagnostic system for measuring plasma properties in the PBFA II applied-B ion diode. The system transports light from the ion diode to a remote screen room where it is recorded by a spectrograph coupled to a streak camera. We developed extensive calibration techniques for measuring the collection efficiency into the fiber link, the effects of the background bremsstrahlung radiation on the fibers, the fiber transmission as a function of wavelength, and the absolute streaked-spectrograph sensitivity as a function of wavelength. We have recorded time-dependent spectral line profiles and intensities from the PBFA II plasma opening switch, the beam-transport gas cell, and the anode plasma. The Stark shift of the LiI 2s-2p transition observed on LiF-anode shots shows that the time-resolved electric field peaks at 7–8 MV/cm, the highest field ever measured using the Stark effect. The potential of these measurements to expand our knowledge of ion-diode physics is being explored.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Recent experiments were performed at PBFA II to characterize the ion beam on-axis. The targets were comprised of two parts. One was a conical gold foil whose beam-induced fluorescence was used to obtain a beam footprint and a measurement of beam voltage. The gold also served as a Rutherford scattering source for an ion pinhole camera. The other part was an on-axis Li cylinder, contained within the gold cone, whose gamma output was used as a beam calorimeter. We present the results of this data.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 31 (1991), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: An in-vitro growth system for investigating the behaviour of S. gesnerioides on cowpea has been developed. The roots of young cowpea plants were spread over glass fibre filter paper in a shallow plastic tray, and a known number of germinated Striga seeds were placed on the cowpea root surface. This allowed the infection process of the parasite to be quantified. Good access to the host-parasite association enabled the entire infection process to be easily monitored and tissue removed for cytological studies. Observations revealed for the first time that contact of S. gesnerioides radicles with host roots stimulated the development of radicular hairs and swelling of the tip of these radicles. Furthermore, penetration of cowpea roots by Striga was shown to be localized and to cause very little damage to the host roots. Swollen parasite tubercles developed on the surface of the roots only after the host stele had been penetrated by invading Striga cells. This growth system is suitable for in-vestigating the mechanisms of host resistance. and also for rapidly screening cowpea germplasm for new sources of resistance to the Parasite. Resistant cowpea cultivars offer the best potential solution for control of this Parasite.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 37 (1990), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 8 (1990), S. 0 
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: New aeromagnetic data, K-Ar age determinations of dredged marine igneous rocks, as well as other geophysical evidence have shed light on the chronology, nature and evolution of the northern Iceland Plateau. Correspondence between seismic refraction profiles taken on the Jan Mayen Ridge and westward through Jan Mayen Island, suppressed aeromagnetic anomalies, earthquake surface wave studies, and ages of dredged igneous rocks suggest these strata may form an extended region of thickened crust, possibly of Caledonian age, extending westward toward the Kolbeinsey Ridge and northwest to the south wall of the Jan Mayen Fracture Zone.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Bioprocess and biosystems engineering 6 (1991), S. 273-284 
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Manipulation of cellular metabolism to maximize the yield and rate of formation of desired products may be achieved through genetic modification. Batch fermentations utilizing glucose as a carbon source were performed for three recombinant strains of Saccharomyces cerevisiae in which the glucose phosphorylation step was altered by mutation and genetic engineering. The host strain (hxk1 hxk2 glk) is unable to grow on glucose or fructose; the three plasmids investigated expressed hexokinase PI, hexokinase PII, or glucokinase, respectively, enabling more rapid glucose and fructose phosphorylation in vivo than that provided by wild-type yeast. Intracellular metabolic state variables were determined by 31P NMR measurements of in vivo fermentations under nongrowth conditions for high cell density suspensions. Glucose consumption, ethanol and glycerol production, and polysaccharide formation were determined by 13C NMR measurements under the same experimental conditions as used in the 31P NMR measurements. The trends observed in ethanol yields for the strains under growth conditions were mimicked in the nongrowth NMR conditions. Only the strain with hexokinase PI had higher rates of glucose consumption and ethanol production in comparison to healthy diploid strains in the literature. The hexokinase PII strain drastically underutilized its glucose-phosphorylating capacity. A regulation difference in the use of magnesium-free ATP for this strain could be a possible explanation. Differences in ATP levels and cytoplasmic pH values among the strains were observed that could not have been foreseen. However, cytoplasmic pH values do not account for the differences observed among in vivo and in vitro glucose phosphorylation activities of the three recombinant strains.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effects of dissolved oxygen concentration on hybridoma cell growth, metabolism, and antibody production were studied. A mouse hybridoma cell line producing an IgG1 directed at a consensus α-interferon was grown in batch cultures in a 5 dm3 stirred bioreactor at dissolved oxygen (DO) concentrations of 5, 30, 90 and 95% or air saturation. High oxygen tension (95% of air saturation) reduced specific growth rate without affecting cell viability. At lower dissolved oxygen levels, specific growth rates were approximately independent of DO, although changes in mitochondrial function and antibody production were observed. Flow cytometry assays of a fluorescent mitochondria-specific marker (Rhodamine 123) show significant single-cell heterogeneities during late exponential growth and greater average fluorescence in cultures grown at 95% DO. The quantity of cell-surface immunoglobulin, measured by an immunofluorescent flow cytometric technique, was the same at high (95%) and low (5%) dissolved oxygen concentrations. Myeloma cells of the type used in constructing the above hybridoma line were much less sensitive to dissolved oxygen level. Specific respiration rate, pyruvate utilization rate, cytochrome oxidase activity, and succinate-cytochrome c oxidoreductase activity were significantly greater (62–116%) for the hybridoma cells than for the myeloma cells in T-flask cultures.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Bioprocess and biosystems engineering 6 (1990), S. 49-61 
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effect of NH4Cl addition on intracellular pH (pH i ) was determined by flow cytometric measurements of the fluorescence of a pH-sensitive dye. The effects of NH4Cl on growth were determined for batch growth of cells in flasks in an incubator. The addition of NH4Cl caused a cytoplasmic acidification. A new lower steady-state value of pH i was attained within 20–40 min of NH4Cl addition. A correlation was found between the effects of NH4Cl on growth and on pH i : whereas 3 mM NH4Cl had little effect on growth and on pH i , 10 mM NH4Cl caused a substantial growth inhibition and a pH i decrease of 0.2–0.3 units. The effects of NH4Cl on growth and on pH i were found to be independent of the external pH value (pH e over the range 6.8 to 7.6, except that 10 mM NH4Cl was more toxic at pH e 7.6. The addition of NH4Cl caused an increase in the average cell volume at pH e 7.6, but had no effect on the average cell volume at pH e 's 6.8 and 7.2. For comparison, the effects of pH e alone on growth and on pH i were determined. There was little difference in cell growth at pH e 's 6.8, 7.2 and 7.6. At pH e 6.6, there was a substantial growth inhibition. Some measurements of the effects of pH e on pH i were made, although the steady-state value of pH i as a function of pH e was not determined due to limitations in the pH i -measuring technique. These measurements showed that pH i remained constant from pH e 7.6 to 6.8, but fell by 0.2 units at pH e 6.6, in agreement with the growth results.
    Type of Medium: Electronic Resource
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