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  • 2000-2004  (5)
  • 1970-1974  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    New diagnostics for physics studies on TEXTOR-94 (invited) : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 1046-1053 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Recently the Dutch, Belgian, and North-Rhine Westphalian Fusion Institutes have consolidated their fusion research on the medium-sized tokamak TEXTOR-94 in the so-called Trilateral Euregio Cluster. To aid the new physics program of TEC, a large number of advanced core diagnostics has recently been implemented. In this article we will discuss the reasoning that has led to the choices of the various diagnostics. Furthermore, we will briefly describe the new diagnostics systems. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1321740
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Calibration procedure and data processing for a TV Thomson scattering system (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 3514-3527 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Calibration procedures for Thomson scattering systems based on television-like cameras, so-called TVTS systems, are described. The TVTS systems of the Rijnhuizen Tokamak Project (RTP), the TJ-II stellarator, and the Torus Experiment for Technology Oriented Research (TEXTOR) tokamak combine a 10–15 J ruby laser as a source with an intensified charge coupled device camera as a detector. A tungsten strip lamp in combination with an integrating sphere is used to calibrate all ∼105 pixels of the camera relatively to each other. Rayleigh scattering on hydrogen or nitrogen is used to perform an absolute calibration of the complete detection system. Great emphasis is placed on possible systematic errors on the determination of the electron temperature Te and density ne due to the calibration, such as tungsten lamp temperature, detoriation of the detection window, long term stability, laser beam alignment, and detector linearity. The long term stability of the system was tested by comparing different sets of calibration factors. Over a period of 1/2 yr the values of the calibration factors varied by less than 5%. Using the same Thomson scattering data but different sets of calibration factors the Te values varied even less than 1%. A two camera technique was used to search for possible unknown systematic errors in the determination of Te profiles. It appears that these systematic errors are about half of the observational error on Te. Density fluctuations can be determined with an accuracy equal to the statistical error of ∼3%, while the systematic error on ne appeared to be ∼10%, which can be corrected for using interferometer data. As a result, these TVTS systems can measure Te and ne profiles with ∼100 (RTP) or 120 (TEXTOR) spatial elements along the full plasma diameter with observational errors on Te of ∼6% in the range of 25 eV–6 keV, at ne=2×1019 m−3 and 10 J laser energy. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1386896
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  • 3
    Electronic Resource
    Electronic Resource
    High resolution multiposition Thomson scattering for the TEXTOR tokamak : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 1138-1142 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article, the recently installed high resolution multiposition Thomson scattering (TS) system of the TEXTOR tokamak is presented. Light from a pulsed ruby laser is scattered by the free electrons of the plasma and transmitted by fiber optics to a polychromator for spectral analysis. The Doppler broadened spectrum of the scattered light is analyzed with a Littrow spectrometer, detected with an image intensifier, and recorded with two intensified charge coupled device cameras. Values of the electron temperature (Te) in the range of 50 eV up to 4 keV can be measured at 450 spatial elements of 2 mm along a chord of 900 mm, with a resolution of 8 mm. The observational error on Te was found to be 〈3% at an electron density (ne) of 3.5×1019 m−3 using a laser energy of ∼8 J. These features make—to our knowledge—the multiposition TS system of TEXTOR to be the one with the highest spatial and spectral resolution in the world. In this article the first results of this powerful diagnostic will be presented. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1322602
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  • 4
    Electronic Resource
    Electronic Resource
    The Atmosphere of Mars (1974)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Earth and Planetary Sciences 2 (1974), S. 333-367 
    Details
    ISSN: 0084-6597
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.ea.02.050174.002001
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  • 5
    Electronic Resource
    Electronic Resource
    Responses of photosystem I compared with photosystem II to high-light stress in tropical shade and sun leaves (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: Sun and shade leaves of several plant species from a neotropical forest were exposed to excessive light to evaluate the responses of photosystem I in comparison to those of photosystem II. Potential photosystem I activity was determined by means of the maximum P700 absorbance change around 810 nm (ΔA810max) in saturating far-red light. Leaf absorbance changes in dependence of increasing far-red light fluence rates were used to calculate a ‘saturation constant’, Ks, representing the far-red irradiance at which half of the maximal absorbance change (ΔA810max/2) was reached in the steady state. Photosystem II efficiency was assessed by measuring the ratio of variable to maximum chlorophyll fluorescence, Fv/Fm, in dark-adapted leaf samples. Strong illumination caused a high degree of photo-inhibition of photosystem II in all leaves, particularly in shade leaves. Exposure to 1800–2000 μmol photons m−2 s−1 for 75 min did not substantially affect the potential activity of photosystem I in all species tested, but caused a more than 40-fold increase of Ks in shade leaves, and a three-fold increase of Ks in sun leaves. The increase in Ks was reversible during recovery under low light, and the recovery process was much faster in sun than in shade leaves. The novel effect of high-light stress on the light saturation of P700 oxidation described here may represent a complex reversible mechanism within photosystem I that regulates light-energy dissipation and thus protects photosystem I from photo-oxidative damage. Moreover, we show that under high-light stress a high proportion of P700 accumulates in the oxidized state, P700+. Presumably, conversion of excitation energy to heat by this cation radical may efficiently contribute to photoprotection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2001.00673.x
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  • 6
    Electronic Resource
    Electronic Resource
    Ascorbic acid, a familiar small molecule intertwined in the response of plants to ozone, pathogens, and the onset of senescence (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ascorbic acid is a well-known antioxidant and cellular reductant with an intimate and complex role in the response of plants to ozone. It is clear from a number of studies that sensitivity to ozone is correlated with total ascorbic acid levels, and that a first line of defence against the reactive oxygen species generated in the apoplastic space by ozone is ascorbic acid. For activity, ascorbic acid must be in the fully reduced state. Therefore, both the rate of ascorbic acid synthesis and recycling via dehydroascorbate and monodehydroascorbate reductases are critical in the maintenance of a high ascorbic acid redox state. Active transport of ascorbic acid across the plasma membrane is necessary to achieve reduction of oxidized ascorbic acid by cytoplasm-localized reductases. It has been known for some time that the chlorotic lesions produced by exposure to ozone are not unlike lesions produced by the hypersensitive response to avirulent pathogen attack. Surprisingly, activation of a defence gene-signalling network by both ozone and pathogens is influenced by the level of ascorbic acid. Indeed, in addition to acting simply as an antioxidant in the apoplastic space, ascorbic acid appears to be involved in a complex phytohormone-mediated signalling network that ties together ozone and pathogen responses and influences the onset of senescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2004.01203.x
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