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941.
Preliminary theoretical and empirical work suggest that increased thyroarytenoid muscle activity may either increase or decrease fundamental frequency, depending on cricothyroid muscle activity and a new cross-sectional area parameter. This parameter is defined as the ratio of muscular tissue in vibration to total tissue in vibration. Canine laryngeal nerves were stimulated to measure vocal-fold length changes. These data, combined with previously reported tissue density, passive stress, and passive frequency data, were used to construct a set of curves predicting canine fundamental frequency from thyroarytenoid and cricothyroid muscle activity and the area ratio. The results suggest that high cricothyroid muscle activity and small area ratios tend to cause fundamental frequency lowering with increased thyroarytenoid muscle activity. 相似文献
942.
943.
A.V. Clark 《Ultrasonics》1985,23(1):21-30
To assess the integrity of a structure containing a (known) flaw, it is necessary to know the stresses acting on the flaw. Many common structural elements (e.g. beams and plates) are subjected to either true plane stress or generalized plane stress. For either of these cases, there are three in-plane stresses (one shear stress and two normal stresses) to be determined in general.In this paper, we consider the application of the acoustic birefringence method to generalized plane stress states, where the thickness-averaged values of the shear and normal stresses are sought. It is shown that the times-of-flight are thickness-averaged effects, whereas the polarization directions depend upon local values of stress. Consequently, when the symmetric (axial) component of the stresses dominates the antisymmetric (bending) component, the acoustic birefringence method can be used to determine all three stresses, if the boundary conditions are known. For unknown boundary conditions, the normal stresses can be determined to within arbitrary functions.Problems arise in using the normal incidence technique when either the shear stress vanishes, or the symmetric (membrane) components of generalized plane stress do not dominate the bending components. In the former case, the thickness-averaged difference in normal stresses can be obtained, provided that the birefringence in the unstressed state is known. In the latter case, the (averaged) difference in normal stresses can be obtained by measuring time-of-flight differences of off-axis SH-waves propagating in the planes of material symmetry of the plate. 相似文献
944.
The general high-frequency, rough-surface reflection process is treated by the method of stationary phase. In particular, the principle of stationary phase is applied to each of the local reflection events, which appear to depend on surface curvature as well as slope. However, we show that the number of reflecting highlights also depends on curvature and cancels the curvature dependence. These results agree fully with those obtained by Beckmann and Spizzichino for the special case of the Gaussian process. 相似文献
945.
The antioxidant activity of a novel artificial glutathione peroxidase-like enzyme, selenium-containing glutathione 5-transferase
from Lucilia cuprina (seleno-LuGST1-1), was studied by using a ferrous sulfate/ascorbate-induced mitochondrial damage model system. Swelling of
mitochondria, lipid peroxidation, and cytochrome-c oxidase activity were selected to evaluate the preservation of mitochondrial integrity in this system. Seleno-LuGST1-1 could
effectively protect the mitochondria against oxidative damage in a dose-dependent manner and exhibited both higher catalytic
activity and greater antioxidant ability than the classic mimic, 2-phenyl-1,2-benziososelenazol-3(2H)-one (Ebselen). This
novel artificial biocatalyst therefore may have great protential for pharmacologic application in the treatment of reactive
oxygen species-related diseases. 相似文献
946.
947.
Zusammenfassung Die rheologischen Eigenschaften gesunder menschlicher Gelenksflüssigkeiten im Geschwindigkeitsgefällebereich vonD = 10–3-103 s–1 wurden untersucht. Es wurden die Scherviskosität und die erste Normalspannungsdifferenz gemessen. Gesunde Synovialflüssigkeiten besitzen hohe Anfangsviskosität (~40 Pa · s) und zeigen eine starke Abhängigkeit vom Geschwindigkeitsgefälle. Der SchermodulG ist im Gegensatz zu pathologischen Proben niedrig und über weite Bereiche konstant. Die längsten Relaxationszeiten betragen 5–10 s. Die kritische Konzentration, bei der Netzwerkbildung einsetzt, beträgt 0,75 10–3 g/ml. Die Proben lassen sich zu einer Masterkurve vereinigen, die als verallgemeinertes Fließgesetz für gesunde Synovia aufgefaßt werden kann. Eine Untersuchung über die zeitliche Abhängigkeit der post-mortem-Synovia zeigt, daß innerhalb von 12 Stunden keine nennenswerten Veränderungen eintreten.
The rheology of healthy human synovial fluids has been investigated at a shear-rate between 10–3-103 s–1. Shear viscosity and first normal-stress difference were measured. Healthy synovial fluids show high zero-shear viscosity (about 40 Pa · s) and a strong shear rate dependence. The modulusG is constant over a large range, in contrast to pathological samples. The longest relaxation times are 5–10 s. The critical concentrationc cr , at which entanglement occurs is about 0.75 10–3 g/ml. The samples can be represented by a master-curve, which may be regarded as the constitutive equation of healthy synovial fluids. An investigation of the time dependency of synovial fluids indicated no changes within 12 hours post mortem.
Herrn Prof. Dr. DDr. h. c. O. Kratky zum 80. Geburtstag mit den besten Wünschen gewidmet. 相似文献
948.
Ravi Kant 《Proceedings Mathematical Sciences》1978,87(9):219-225
An investigation is made of the flow of an electrically conducting rarefied gas due to the time-varying motion of an infinite
porous plate, the gas being permeated by a transverse magnetic field. The suction is taken to be a constant and the magnetic
lines of force are taken to be fixed relative to the fluid. The effects of magnetic field, rarefaction parameter, suction
parameter are shown by means of some tables. The expressions of the skin friction for the two particular cases have also been
obtained. 相似文献
949.
谈高校基础实验室仪器设备配置的几个问题 总被引:1,自引:0,他引:1
本文提出高校物理实验室,仪器设备购置中应注意的几条原则。并提出一套估算办法。 相似文献
950.