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  • 2000-2004  (5)
  • 1980-1984  (2)
  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Regulation and interaction of cholesterol, bile salt and lipoprotein synthesis in liver (1983)
    Springer
    Journal of molecular medicine 61 (1983), S. 1163-1170 
    Details
    ISSN: 1432-1440
    Keywords: Triglyceride ; Cholesterol ; Very low density Lipoproteins ; Synthesis ; Secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The liver is the junction of several interorgan metabolic cycles which are essential for the homeostasis of mammalian metabolism. Two of these are described in greater detail and their role in control of lipid metabolism will be presented. The fatty acid-triglyceride cycle is of particular importance for our understanding of the mechanisms governing serum lipid levels. This is due to the fact that the lipoprotein secreted by the liver in the course of this metabolic cycle — very low density lipoprotein — has a relatively long half-life in the plasma compartment. Data have been collected from the literature to show that different nutritional and pharmacological stimuli affecting serum lipid levels do so by interfering with the rate of very low density lipoprotein input into the plasma compartment. The enterohepatic circulation of steroids is another cycle which contributes to control of lipid metabolism. Data are presented which show that bile acids, the major steroids circulating in this cycle, exert direct feedback control of hepatic cholesterol synthesis. This characteristic of bile acids may explain why certain bile acids, when given orally, reduce serum cholesterol levels. Several clinical and experimental observations suggest a close relation between bile acid and triglyceride metabolism. It is characterized by an inverse relation between bile acid pool size and serum triglyceride levels. Moreover, a reduction of the bile acid pool size is accompanied by an enhanced hepatic fatty acid and triglyceride synthesis and secretion into blood. The molecular basis and physiological significance of these observations have still to be explored. Special emphasis is put on the advantage of monolayer cultures of liver cells which had to be used in order to reach much of the experimental evidence outlined herein. This cellular model endowed with the physiology and phenotype of the normal adult liver cell is particularly suited to the study of long-term regulation of metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01537427
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  • 7
    Electronic Resource
    Electronic Resource
    Metabolic abnormalities in a patient with muscular carnitine deficiency (1981)
    Springer
    Journal of inherited metabolic disease 4 (1981), S. 133-133 
    Details
    ISSN: 1573-2665
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A patient with muscular carnitine deficiency showed little clinical improvement with carnitine supplementation but responded well to the addition of medium-chain triglycerides to the diet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263626
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