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The relation between muscle pain, muscle activity, and muscle co-ordination is still controversial. The present human study investigates the influence of experimental muscle pain on resting, static, and dynamic muscle activity. In the resting and static experiments, the electromyography (EMG) activity and the contraction force of m. tibialis anterior were assessed before and after injection of 0.5 ml hypertonic saline (5%) into the same muscle. In the dynamic experiment, injections of 0.5 ml hypertonic saline (5%) were performed into either m. tibialis anterior (TA) or m. gastrocnemius (GA) and the muscle activity and co-ordination were investigated during gait on a treadmill by EMG recordings from m. TA and m. GA. At rest no evidence of EMG hyperactivity was found during muscle pain. The maximal voluntary contraction (MVC) during muscle pain was significantly lower than the control condition (P < 0.05). During a static contraction at 80% of the pre-pain MVC muscle pain caused a significant reduction in endurance time (P < 0.043). During dynamic contractions, muscle pain resulted in a significant decrease of the EMG activity in the muscle, agonistic to the painful muscle (P < 0.05), and a significant increase of the EMG activity of the muscle, antagonistic to the painful muscle (P < 0.05). Muscle pain seems to cause a general protection of painful muscles during both static and dynamic contractions. The increased EMG activity of the muscle antagonistic to the painful muscle is probably a functional adaptation of muscle co-ordination in order to limit movements. Modulation of muscle activity by muscle pain could be controlled via inhibition of muscles agonistic to the movement and/or excitation of muscles antagonistic to the movement. The present results are in accordance with the pain-adaptation model (Lund, J.P., Stohler, C.S. and Widmer, C.G. In: H. Vaer?y and H. Merskey (Eds.), Progress in Fibromyalgia and Myofascial Pain. Elsevier, Amsterdam, 1993, pp. 311-327.) which predicts increased activity of antagonistic muscle and decreased activity of agonistic muscle during experimental and clinical muscle pain. 相似文献
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The influence of NaCl and CO2 on the atmospheric corrosion of magnesium alloy AZ91 is studied in the laboratory. Samples were exposed under carefully controlled air and flow conditions; the relative humidity was 95%, the temperature was 22.0°C and the concentration of CO2 was < 1 ppm or 350 ppm. Different amounts of sodium chloride (0–70 μg/cm2) were added before exposure. The corrosion products were analyzed by gravimetry, ion chromatography, X‐ray diffraction and scanning electron microscopy. Mass gain and metal loss results are reported. The combination of high humidity and NaCl is very corrosive towards AZ91. However, the NaCl‐induced corrosion is inhibited by ambient concentrations of CO2. Exposure in the absence of CO2 gives rise to heavy pitting, with brucite, Mg(OH)2, being the dominant corrosion product. In the presence of CO2 a layer of hydrated magnesium hydroxy carbonate, Mg5(CO3)4(OH)2 · 5 H2O forms. A tentative corrosion mechanism is presented that explains the behavior in the two environments. 相似文献
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Lateral buckling of beams analysed as elastically supported columns subject to a varying axial force
S.E. Svensson 《Journal of Constructional Steel Research》1985,5(3):179-193
The stability problem for an elasticallu supported column subject to a varying axial force has been solved by means of a general numerical procedure based on Galerkin's method. Apart from the intrinsic value of the solution itself, its possible value modelling some complex stability problems in the area of restrained lateral-torsional stability problems is demonstrated and specific numerical solutions are applied to the case of lateral buckling of the free flange of a composite girder. The results obtained are discussed and suggestions for additional investigations are presented. 相似文献
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W. Montfrooij E. C. Svensson I. M. de Schepper 《Journal of Low Temperature Physics》1992,89(3-4):437-440
We correct for the effect of temperature induced frequency shifts on the observed dynamic structure factor S(q,) and find that the intrinsic behavior for non-superfluid4He is remarkably similar to that for other noble-gas fluids. 相似文献
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Lipase-catalyzed transesterification of phosphatidylcholine at controlled water activity 总被引:2,自引:0,他引:2
Ingemar Svensson Patrick Adlercreutz Bo Mattiasson 《Journal of the American Oil Chemists' Society》1992,69(10):986-991
The incorporation of a free fatty acid into thesn-1 position of phosphatidylcholine by lipase-catalyzed transesterification was investigated. The thermodynamic water activity
of both the enzyme preparation and the substrate solution was adjusted to the same value prior to the reaction. The reaction
rate increased with increasing water activity but the yield of modified phosphatidylcholine decreased due to hydrolysis. By
using a large excess of the free fatty acid (heptadecanoic acid), the hydrolysis reaction was slowed down, so a higher yield
was obtained at a given degree of incorporation. The best results were obtained withRhizopus arrhizus lipase immobilized by adsorption on a polypropylene support. With this preparation, a yield of 60% and nearly 50% incorporation
of heptadecanoic acid (100% incorporation in thesn-1 position) was obtained at a water activity of 0.064. The enzyme preparation had good operational stability and position
specificity. Little incorporation (<1%) was observed in thesn-2 position, when almost all the fatty acid in thesn-1 position was exchanged. 相似文献