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  • 1
    Electronic Resource
    Electronic Resource
    Positron lifetimes in V3Si (1978)
    Springer
    Applied physics 17 (1978), S. 421-422 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract From positron annihilation lifetime measurements on V3Si single crystals we estimated that about 17.2% of the positrons annihilate with core electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00886216
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  • 2
    Electronic Resource
    Electronic Resource
    An investigation of point defects in silicon carbide (1995)
    Springer
    Applied physics 61 (1995), S. 55-58 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 68.55 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Positron lifetime measurement on bulk samples of single crystal SiC wafers have shown that both 6H and 4H polytypes exhibit a bulk lifetime of 150±2ps. All samples contained a second, defect-related lifetime component, ranging in value from 250 to about 300 ps with rather low intensities. The defect structure exhibited by the nanocrystalline samples is, not unexpectedly, much more complex. Positron beam experiments on Electron Cyclotron Resonance Chemical Vapour Deposited (ECR-CVD) SiC thin films showed that the positrons are very sensitive to changes in important film parameters as a function of the deposition conditions. It was found that the film density is lower than expected, probably due to hydrogen incorporation; variations in compositions among different films were detected through variations in theS parameters, and differences were observed in the electric field at the film-substrate interface due to hydrogen passivation of dangling bonds and different substrate resistivities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538211
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  • 3
    Electronic Resource
    Electronic Resource
    Crystallinity of pure silica glass studied by positron annihilation (1978)
    Springer
    Applied physics 16 (1978), S. 231-233 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.10 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The crystallinity of silica glass fused from Brasilian quartz is demonstrated by positron annihilation lineshape measurements using a high resolution Ge(Li)-detector as well as by positron lifetime measurement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00885117
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  • 4
    Electronic Resource
    Electronic Resource
    An investigation of point defects in silicon carbide (1995)
    Springer
    Applied physics 61 (1995), S. 55-58 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 61.70; 68.55; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Positron lifetime measurements on bulk samples of single crystal SiC wafers have shown that both 6H and 4H polytypes exhibit a bulk lifetime of 150±2 ps. All samples contained a second, defect-related lifetime component, ranging in value from 250 to about 300 ps with rather low intensities. The defect structure exhibited by the nanocrystalline samples is, not unexpectedly, much more complex. Positron beam experiments on Electron Cyclotron Resonance Chemical Vapour Deposited (ECR-CVD) SiC thin films showed that the positrons are very sensitive to changes in important film parameters as a function of the deposition conditions. It was found that the film density is lower than expected, probably due to hydrogen incorporation; variations in composition among different films were detected through variations in the S parameters, and differences were observed in the electric field at the film–substrate interface due to hydrogen passivation of dangling bonds and different substrate resistivities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538211
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  • 5
    Electronic Resource
    Electronic Resource
    Positron annihilation study of ordering processes in rare-earth cobalt permanent magnets (1987)
    Springer
    Applied physics 42 (1987), S. 287-289 
    Details
    ISSN: 1432-0630
    Keywords: 75 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The ordering process in 1/5 and in 2/17 Sm-Co permanent magnets was followed by positron annihilation lifetime and Doppler broadening measurements. No correlation between magnetic hardness and positron annihilation parameters was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616564
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  • 6
    Electronic Resource
    Electronic Resource
    Positron annihilation in ionic crystals (1975)
    Springer
    Applied physics 6 (1975), S. 21-23 
    Details
    ISSN: 1432-0630
    Keywords: Positron annihilation ; Ionic crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Positron lifetime measurements were made on Ca2+ doped NaCl, Ba2+ doped NaCl and X-ray- and additively-coloured KCl crystals. In the NaCl(Ca) system a correlation which could be approximated by a power equation was found between the dopant concentration and the positron annihilation parameters. In the NaCl(Ba) system the decay parameters do not change significantly as expected and no significant difference in the decay parameters of the coloured and uncoloured crystals could be found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00883544
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  • 7
    Electronic Resource
    Electronic Resource
    Can oral contraceptive steroids influence the elimination of nifedipine and its primary pryidine metabolite in humans? (1998)
    Springer
    European journal of clinical pharmacology 54 (1998), S. 729-734 
    Details
    ISSN: 1432-1041
    Keywords: Key words Oral contraceptives ; Nifedipine ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: To investigate the influence of oral contraceptives on cytochrome P450 3A4 (P450NF) activity. Methods: In 23 healthy women, the pharmacokinetics of nifedipine and its main metabolite dehydronifedipine in plasma were assessed after a single oral dose, prior to and after intake of one of two oral contraceptive formulations, one containing 2 mg dienogest and 0.03 mg ethinylestradiol (group A) and the other containing 0.125 mg levonorgestrel and 0.03 mg ethinylestradiol (group B). Results: While the intake of two oral contraceptives for 21 days did not influence the plasma concentration-time curve of unchanged nifedipine, mean AUC0–23.5 h and the mean Cmax values of dehydronifedipine were significantly lower in both groups tested/(24% in group A and 25% in group B). This observation may indicate a reduced formation rate of metabolites and reflects an inhibition of cytochrome P450 3A4 activity. The activation of the same or other metabolic degradation mechanism(s) could explain this result. Conclusion: The investigation presented demonstrates the importance of metabolite measurement when in vivo studies are undertaken to investigate different influences on drug metabolizing ability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050543
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of ethinylestradiol-containing combination oral contraceptives with gestodene or levonorgestrel on caffeine elimination (1995)
    Springer
    European journal of clinical pharmacology 48 (1995), S. 161-166 
    Details
    ISSN: 1432-1041
    Keywords: Caffeine clearance ; Oral contraceptives ; gestodene ; levonorgestrel ; ethinylestradiol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract In a controlled clinical trial, the elimination of caffeine was examined in 20 healthy women prior to and during one cycle of treatment with either of two oral contraceptive formulations, one containing 0.075 mg gestodene and 0.03 mg ethinylestradiol and one containing 0.125 mg levonorgestrel and 0.03 mg ethinylestradiol. In addition, caffeine clearance was determined 1 month after the last intake of the oral contraceptives. Compared with pretreatment values, the clearance of caffeine was reduced by about 54% and 55% after one treatment cycle with gestodene- and the levonorgestrel-containing oral contraceptive, respectively. Other pharmacokinetic parameters of caffeine, such as t max and C max, were not affected. Clearance values returned to pretreatment values 1 month after the last administration of the oral contraceptives. There was no difference in the reduction of caffeine clearance between contraceptive formulations. A small, but significant difference in the AUC(0–24 h) values of ethinylestradiol was noted between both preparations. There was no correlation between the AUC(model) values of caffeine and the AUC(0–24 h) values of ethinylestradiol. In the present study, a somewhat more pronounced effect on the elimination of caffeine was observed than in previous investigations, where several contraceptive steroids were administered only for a period of 2 weeks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192743
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  • 9
    Electronic Resource
    Electronic Resource
    Altered Elemental Composition of the Cell Wall of a Pseudomonas Strain Having Inducible Tolerance Mechanism to Chromium(VI) (2000)
    Springer
    Bulletin of environmental contamination and toxicology 65 (2000), S. 772-779 
    Details
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s0012800189
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  • 10
    Electronic Resource
    Electronic Resource
    Modulation of glyceraldehyde-3-phosphate dehydrogenase inAnacystis nidulans by glutathione (1982)
    Springer
    Archives of microbiology 133 (1982), S. 2-5 
    Details
    ISSN: 1432-072X
    Keywords: Anacystis nidulans ; Cyanobacterium ; Glutathione ; Glyceraldehyde-3-phosphate dehydrogenase ; Redox modulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13; GAPDH) from the cyanobacteriumAnacystis nidulans was activated up to five-fold by reduced glutathione (GSH) in the physiological concentration range (0.1–2 mM GSH). Non-physiological reductants, like dithiothreitol (DTT) and β-mercaptoethanol, also activated the enzyme. Oxidized glutathione (GSSG) had no effect on the cyanobacterial GAPDH but treatment with H2O2 led to a rapid, reversible deactivation of both untreated and GSH-treated enzyme preparations. GSH reversed the inhibition induced by H2O2. An oligomeric form of the enzyme (apparentM r∼440,000) was dissociated by GSH into a lower-M r, more active enzyme form (M r∼200,000). The enzyme was shown to obey regular Michaelis-Menten kinetics. The activation of GAPDH by GSH was associated with a decrease inK m and an increase inV max values of the enzyme for 3-phosphoglycerate. GSH had virtually no effect on a GAPDH preparation isolated from corn chloroplasts and studied for comparison.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00943760
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