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  • 1
    Electronic Resource
    Electronic Resource
    Morphology of experimentally denervated and reinnervated rat facial muscle I. Histochemical and histological findings (1994)
    Springer
    European archives of oto-rhino-laryngology and head & neck 251 (1994), S. 36-40 
    Details
    ISSN: 1434-4726
    Keywords: Facial muscle ; Enzyme histochemistry ; Facial palsy ; Experimental denervation ; Reinnervation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The morphological changes in rat facial muscles were evaluated after permanent denervation and were compared with findings after immediate reinnervation. Thirty rats underwent transection of the left and right facial nerves immediately followed by hypoglossal-facial nerve anastomosis on the right side (muscular reinnervation) and removal of 8–10 mm of the facial plexus on the left side (permanent muscular denervation). Levator labii muscle samples of both sides were collected sequentially at 2, 6, 7, 10, 20, and 24 weeks after surgery and submitted to routine histological and enzyme histochemical staining procedures. In normal levator labii muscles a typical “chessboard” pattern was found, with type I fibers being smaller than type II fibers. These latter fibers also were more prevalent than the type I fibers. Among the type II fiber subtypes, the type IIB fibers were larger and more frequent. Two weeks after surgery, there were no differences between denervated facial muscles and those undergoing reinnervation. Both showed atrophic myofibers among normal-sized fibers and slight fibrosis. Those muscles denervated for more than 2 weeks displayed increasing fiber atrophy with frequent loss of typability, as well as proliferation of connective tissue and fat cells in perimysial and endomysial sites. After denervation for 20 weeks only a few atrophic fibers were found in wide areas of fibrosis and fat cells. Following nerve anastomosis the reinnervated levator labii muscle showed much less fiber atrophy. Regrowth to normal fiber diameters was found with only a few atrophic myofibers 10 weeks after anastomosis although a moderate fibrosis predominated at perimysial sites. Reinnervated facial muscle fibers displayed a typical type-grouping pattern and also frequent lack of typability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175955
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Design of an electrical impedance tomography phantom using active elements (2000)
    Springer
    Medical & biological engineering & computing 38 (2000), S. 390-394 
    Details
    ISSN: 1741-0444
    Keywords: Electrical impedance tomography (EIT) ; Electrical phantom ; Impedance spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The architecture of a novel phantom for electrical impedance tomography (EIT) is proposed. The design employs active elements, which include multiplying digital to analogue converters (MDAC), so that the impedance distribution in the phantom may be varied dynamically using computer control. The phantom is designed to assist in the validation of an EIT system under test. A number of published layouts for passive phantoms are analysed, and the requirements for an active element are specified for the most applicable of these. The use of active elements throughout a phantom imposes significant costs because of the need for each active element to operate independently. This proposal limits the cost and complexity by employing active elements in a restricted region of the phantom. Currently available technology, principally due to the limited analogue bandwidth of the MDAC, precludes the construction of a fully capable phantom from active elements. However, a design is specified that would enable its future development to cover the frequency range from 10kHz to 1 MHz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02345007
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of a digitally controlled impedance element (2000)
    Springer
    Medical & biological engineering & computing 38 (2000), S. 395-400 
    Details
    ISSN: 1741-0444
    Keywords: Electrical impedance tomography (EIT) ; Synthesised impedance ; Multiplying DAC ; Impedance spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A practical design for the synthesis of a digitally controlled electrical impedance element is presented. The impedance element comprises a real impedance element in series with a voltage source whose magnitude is determined by the applied voltage multiplied by a factor k. The value of k is shown strongly to affect the circuit's performance. Results are presented which demonstrate the correspondence between circuit models and practical measurements. When negative values for k were employed the circuit element offered a controlled impedance range of 1:1000 and was stable to at least 1.5MHz, providing that low source impedance values were used. With a positive k, a restricted range of impedance values could be obtained and the value of source impedance was less critical, though the circuit's performance was acceptable only to about 100 kHz. Consideration is given to the specification of a multiplier that would permit the circuit's range of application to be extended to low megahertz frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02345008
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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