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  • Chemistry  (1)
  • Timing  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 120 (1998), S. 325-334 
    ISSN: 1432-1106
    Keywords: Key words Eye movements ; Timing ; Saccades ; Human ; Wing and Kristofferson model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We assessed the suitability of using the Wing and Kristofferson model for timing repetitive motor responses to analyse timing variability during repetitive saccadic eye movements. The model decomposes total timing variability (TV) into a central timing component (CV) and a peripheral motor delay component (MV). Eight normal subjects made voluntary horizontal saccades, in darkness, in synchrony with a regular auditory metronome. After 20 saccades had been produced, the metronome was switched off and subjects continued responding at the same frequency until 31 further saccades had been made. Inter-saccade intervals (ISIs) from the unpaced phase were used to calculate TV, CV and MV. Three different target intervals, paced by auditory cues, were used – 496 ms, 752 ms and 1000 ms. In the paced phase, subjects’ ISIs closely matched the auditory cue intervals. In the unpaced phase, subjects were clearly able to respond at three different frequencies. As predicted by the Wing and Kristofferson model, the durations of successive ISIs tended to be negatively correlated. As expected, TV and CV increased with increasing ISI. Contrary to the expectation of the model that MV would remain constant, we found that it increased with increasing interval. Our results do not conclusively demonstrate the validity of applying the Wing and Kristofferson model to the analysis of timing variability during repetitive saccadic eye movements. However, comparison with previous studies shows that, at least in normal subjects, it is equally valid to apply the model to the analysis of repetitive saccadic eye movements as it is to apply it to the analysis of data from other effectors.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1992), S. 165-175 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A combination of constant neutral loss (CNL) and daughter ion scanning tandem mass spectrometry was used to identify nine metabolites of the antimuscarinic drug cimetropium bromide. CNL mass spectrometry (-54 Da, corresponding to loss of -CH2-cyclopropyl with a concomitant gain of H) was used to rapidly screen an extract from a rat liver microsomal incubate. This sample had been subjected to only minimal purification involving zinc sulphate precipitation of the microsomal proteins followed by solid-phase extraction using a Sep-Pak C-18 reversed-phase cartridge. The ions detected in CNL mass spectrometry were subjected to collisionally activated dissociation and the resulting daughter ion spectra were compared with those acquired for synthetic standards. Four ions observed in CNL mass spectrometry were shown to be artifacts, produced either by the fast atom bombardment (FAB) ionization process or the incubation and/or extraction conditions. Their structures were determined from the daughter ion spectra acquired. It was also demonstrated that in the presence of high concentrations of the unmetabolized drug substrate, ions were formed during FAB ionization that possessed identical daughter ion spectra to previously identified metabolites. This observation highlighted the need to conduct adequate control experiments to ensure that artifacts from the FAB process, as well as from the incubation procedures, were distinguished from ions attributable to metabolites.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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