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  • Analytical Chemistry and Spectroscopy  (7)
  • Muscle contraction  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Electromyographic basis of inaccurate movement; its dependence upon the mode of muscle contraction (1991)
    Springer
    European journal of applied physiology 62 (1991), S. 162-170 
    Details
    ISSN: 1439-6327
    Keywords: Motor control ; Electromyography ; Muscle contraction ; Inaccurate movement ; Motor skill
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The electromyographic basis of inaccurate performance was investigated in two rapid precision-grip skills controlled by concentric and eccentric muscle contractions respectively. Surface electromyograms, recorded from the first dorsal interosseous (DI), adductor pollicis (AP) and abductor pollicis brevis, were utilised to identify changes in the timing and intensity of muscle activation which may be responsible for inaccurate performance. The results showed that when fast precision-grip skills were controlled by concentric DI and AP muscle contractions, variations in the intensity of muscle contraction were responsible for inaccurate performance. However, when these skills were controlled by eccentric DI and AP muscle contractions, inaccurate performance resulted from variations in the timing of muscle activation. It was concluded that the nature of the deficiency in the patterns of muscle activation resulting in inaccurate performance was dependent upon the type of muscle contraction used in the skill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00643736
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of muscle activation dynamics on reaction time in the elderly (1994)
    Springer
    European journal of applied physiology 69 (1994), S. 344-349 
    Details
    ISSN: 1439-6327
    Keywords: Aging ; Electromyography ; Reaction time ; Motor control ; Muscle contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this investigation was to determine whether age-related changes in the dynamics of muscle activation were, in part, responsible for longer reaction times (RT) in the elderly. A group of 12 young (mean age, 20.6 years) and 12 elderly (mean age, 64.3 years) women performed a series of ballistic forearm supination movements in response to an auditory stimulus while using a simple reaction time test. Surface electromyographic waveforms from biceps brachii (agonist) and pronator teres (antagonist) muscles were recorded, together with the angle-time curves representing the motion of the forearm, on to an IBM compatible microcomputer. The results showed that an age-related increase (P〈0.05) in motor reaction time (MRT) contributed to longer RT in the elderly. In addition, the longer (P〈0.05) MRTs in the elderly were associated with a significantly slower rate (P〈0.05) of biceps brachii muscle activation and a significantly increased proportion (P〈0.05) of the initial biceps brachii muscle burst required to initiate the movement. This data suggested that an important part of the slowing of motor behaviour, commonly observed with increasing age, may be due to either decreases in the ability of aged skeletal muscle to rapidly generate tension or to a reduction in motor drive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392041
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Transition from slow to ballistic movement: development of triphasic electromyogram patterns (1991)
    Springer
    European journal of applied physiology 63 (1991), S. 381-386 
    Details
    ISSN: 1439-6327
    Keywords: Motor control ; Electromyography ; Motor skill ; Triphasic electromyogram ; Muscle contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this investigation was to determine how the triphasic electromyogram (EMG) pattern of muscle activation developed from the agonist muscle only pattern as movement time (t mov) decreased. Six adult women produced a series of 30° elbow extension movements in the horizontal plane at speeds ranging from ballistic (〈 400-ms t mov) to very slow (〉 800-ms t mov). Surface EMG from triceps brachii (agonist) and biceps brachii (antagonist) muscles were recorded, together with elbow angle, on a microcomputer. The results showed that triphasic EMG patterns developed systematically as t mov decreased from 1000 ms to 〈 200 ms. In trials with very long t mov, many elbow extension movements were produced by a single continuous activation of the agonist triceps brachii muscle. As t mov decreased however, agonist activation became predominantly burst-like and other components of the triphasic EMG pattern [activation of the antagonist (Ant) and second agonist activation (Ag2)] began to appear. At the fastest movement speeds, triphasic EMG patterns (Ag1-Ant-Ag2, Ag1 being first activation of agonist muscle) were always present. This data indicated that the triphasic pattern of muscle activation was not switched on when a particular t mov was achieved. Rather, each component systematically developed until all were present, as distinctive bursts of activity, in most trials with t mov less than 400 ms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00364466
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Microprobe analysis. C.A. Andersen (Ed.), Wiley Interscience, 1973. $24.95 (1974)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 3 (1974), S. A28 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300030415
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  • 5
    Electronic Resource
    Electronic Resource
    X-ray production as a function of depth for low electron energies (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 5 (1976), S. 36-40 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Depth distributions of X-ray production by electrons in the energy range of six to fifteen key have been measured for Si and Cu characteristic X-rays in matrices of Al, Ni, Ag and Au. Corrections from these curves show that the modified Philibert absorption correction predicts the wrong dependence on matrix atomic number at these low electron energies, while the Duncomb and Reed atomic number correction shows too strong a dependence on atomic number. The curves should be valuable for comparison with both theoretical and empirical models for quantitative analysis at low energies.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300050109
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Conference reports (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 6 (1977), S. xi 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300060112
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    The atomic number and absorption corrections in electron microprobe analysis at low electron energies (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 7 (1978), S. 26-30 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: From an extensive series of measurements of φ(ρz) curves, at electron energies between 6 and 15 KeV, an empirical formula;φ(R)=DKn(KR)n-1 exp(-(KR)n) where R=ρz+ρzo, was developed to accurately describe the shape and magnitude of the measured curves. On the basis of this equation a quantitative correction for absorprion and atomic mumber effects has been derived for low electron energies. A comparision of quantitative analysis using the above equation wit other absorption and atomic number corrections shows better agreement between calculated and known concenequation to a correction for fluorescence due to characteristic lines is outlined.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300070109
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  • 8
    Electronic Resource
    Electronic Resource
    Quantitative electron probe microanalysis using Gaussian φ(ρz) Curves (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 11 (1982), S. 187-193 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The Gaussian expression for φ(ρz) has been used as the basis of a computer program for quantitative electron probe microanalysis. Corrections for absorption and atomic number are combined within the expression for φ(ρz) whereas the fluorescence correction is based on numerical integration over the primary and secondary intensities. Error histograms based on about 500 published analyses of standard specimens have been used to adjust the parameters in the Gaussian expression for optimum accuracy. The resultant error histograms are as narrow as those obtained for the most accurate of the current ZAF correction procedures. Extension of the method to non-normal electron incidence is relatively straightforward.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300110411
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  • 9
    Electronic Resource
    Electronic Resource
    A Gaussian expression to describe φ(ρz) curves for quantitative electron probe microanalysis (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 10 (1981), S. 138-146 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: It is shown that the depth distribution of X-ray production in the electron microprobe can be accurately described by a Gaussian modified at the sample surface by a transient. Assuming that the Gaussian is a consequence of the electrons undergoing a random walk in the sample and that the transient corresponds with the change from collimated to random electron trajectories enables theoretical values for the amplitudes and coefficients of the two functions to be predicted. There is excellent agreement between the predicted and the observed values. The Lenard coefficient and the electron range can both be estimated from the coefficient in the Gaussian. It is suggested that for microprobe work, Lenard's law for electron absorption be replaced by this revised law. Both the absorption and atomic number corrections of the traditional ZAF approach are replaced by the new function.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300100311
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  • 10
    Electronic Resource
    Electronic Resource
    F. Maurice, L. Meny and R. Fixier (Editors), Microanalyse et Microscopie Electronique à Bayalage and its English translation Microanalysis and Scanning Electron Microscopy (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 10 (1981), S. 153-153 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300100314
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