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Muscles within muscles: the neuromotor control of intra-muscular segments (1998)

Wickham, J. B. ; Brown, J. M. M.

Springer

European journal of applied physiology 78 (1998), S. 219-225

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ISSN: 1439-6327

Keywords: Key words Functional differentiation ; Electromyography ; Deltoid ; Motor control ; Muscle function

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract The aim of this investigation was to anatomically identify, and then determine the function of, individual segments within the human deltoid muscle. The anatomical structure of the deltoid was determined through dissection and/or observation of the shoulder girdles of 11 male cadavers (aged 65–84 years). These results indicate that the deltoid consists of seven anatomical segments (D1–D7) based upon the distinctive arrangement of each segment's origin and insertion. Radiographic analysis of a cadaveric shoulder joint suggested that only the postero-medial segment D7 has a line of action directed below the shoulder joint's axis of rotation. The functional role of each individual segment was then determined utilising an electromyographic (EMG) technique. Seven miniature (1 mm active plate; 7 mm interelectrode distance) bipolar surface electrodes were positioned over the proximal portion of each segment's muscle belly in 18 male and female subjects (18–30 years). EMG waveforms were then recorded during the production of rapid isometric shoulder abduction and adduction force impulses with the shoulder joint in 40 degrees of abduction in the plane of the scapula. Each subject randomly performed 15 abduction and 15 adduction isometric force impulses following a short familiarisation period. All subjects received visual feed back on the duration and amplitude of each isometric force impulse produced via a visual force-time display which compared subject performance to a criterion force-time curve. Movement time was 400 ms (time-to-peak isometric force) at an intensity level of 50% maximal voluntary contraction. Temporal and intensity analyses of the EMG waveforms, as well as temporal analysis of the isometric force impulses, revealed the neuromotor control strategies utilised by the CNS to control the activity of each muscle segment. The results showed that segmental neuromotor control strategies differ across the breadth of the muscle and that individual segments of the deltoid can be identified as having either “prime mover”, “synergist”, “stabiliser” or “antagonist” functions; functional classifications normally associated with whole muscle function. Therefore, it was concluded that the CNS can “fine tune” the activity of at least six discrete segments within the human deltoid muscle to efficiently meet the demands of the imposed motor task.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004210050410

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Fire-retardant performance of some surface coatings for naval ship interior applications (1995)

Brown, J. R. ; Mathys, Z. ; Riddell, S. Z. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Fire and Materials 19 (1995), S. 109-118

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ISSN: 0308-0501

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: The fire-retardant performances of various surface coatings for naval ship interior applications have been evaluated by a number of small-scale fire test methods. The coatings were eveluated as topcoats by cone calorimetry and limiting oxygen index methods and as primer/topcoat systems by radiat heating, direct flame impingement and reverse panel heating procedures. The coatings investigated were (1) a solvent-based epoxy polyester, (2) a solvent-based fireretardant alkyd,(3) a solvent-based chlorimated alkyd and (4) a water-based acrylic. In terms of the measured parameters, the chlorinated alkyd has superior fire properties while the epoxy polyserter, the fire-retardant alkyd and parameters, the chlorinated alkyd has superior fire properties while the epoxy polyester, the fire-retardant alkyd and the acrylic have significat disadvantages in relation to fire propagation. The relatively low amount of hydrogen chloride (∼ 0.3% - mass per initial mass) evolved by the chlorinated alkyd during cone calorimetric combustion and its outstanding fire-retardant properties have resulted in it being considered acceptable for naval ship interior applications.

Additional Material: 6 Ill.