Evaluation of Precise Measurements of Young\u27s Modulus and Shear Modulus by the Electro-static Driving Method

The relationship between the flexural and torsional resonance frequencies and Young\u27s modulus, E, and shear modulus, G, is derived semiempirically for rectangular and cylindrical bars of mild steel. The measured resonance frequency, f_i, of flexural vibration is given by f_i=M_i^2k/2π^2l^2・√, where T_i is the geometrical factor, M_i a constant obtained under the boundary condition of the vibration, k, the radius of gyration of the cross section of a bar with its length, l, ρ is the density and E Young\u27s modulus which is the physical quantity of main interest here. The subscript, i, assigned for the respective quantities in the i-th mode of vibration. The geometrical factor is determined experimentally from the measurement on samples of similar shape but different in k/l. The resonance frequency, f_i\u27 for the torsional vibration is given by f_i\u27=i/2l・√ where I_p is the polar itnerita of the cross section and K is the constant as defined by T/G×l/θ for the torsional angle, θ, induced by the moment, T, which is applied at the end of the bar. The geometrical factor, T_i\u27, depends upon the ratio S/l, where S is the cross sectional area, and it is determined experimentally by the method similar to that for determining T_i. Corrected values of E and G of mild steel are 2.110 and 0.816 T dyne/cm^2, respectively, and the compressibility, κ and Possion\u27s ratio, μ, calculated from the corrected values of E and G are 0.59 pcm^2/dyne and 0.29, respectively

DIRECT EFFECT OF PERCUTANEOUS TRANSLUMINAL ANGIOPLASTY ON THE HEART IN PATIENT WITH PERIPHERAL ARTERY DISEASE

Background and Purpose : The patient with peripheral artery disease (PAD) is known to have a poor prognosis for life. Recently, it has been reported that percutaneous transluminal angioplasty (PTA) for PAD improves the prognosis. However, the detailed mechanisms remain unclear.Augmentation index (AIx) or central aortic pressure (CAP) is shown to increase myocardial mechanical stress and facilitate myocardial hypertrophy. The aim of this study is to clarify the direct cardioprotective effects of PTA mediated by decreasing CAP and AIx.Methods : 28 patients with PAD were enrolled. They were divided into two groups ; control group (n=12) and PTA group (n=16). Both radial AIx and CAP were measured by using pulse waveform analysis of arterial waveform recorded non-invasively by applanation tonometry in radial artery. We used a plasma B-type natriuretic peptide (BNP) level as a marker of myocardial mechanical stress. Plasma BNP levels, radial AIx and CAP which were measured after PTA or angiography, were compared with the data on admission.Result : Although plasma BNP levels in the control group were not changed, those in the PTA group were significantly decreased from 68.44 to 42.08 pg/ml (p<0.05). Pulse waveform analysis demonstrated that radial AIx and CAP in the control group remain unchanged. On the other hand, radial AIx and CAP were significantly reduced in the PTA group. The reduction rates of radial AIx, CAP and plasma BNP levels were −11.3%, −8.9% and −34% respectively.Conclusion : These results suggest that PTA can decrease myocardial mechanical stress in patients with PAD. The mechanisms may be mediated in part by reduction of radial AIx and CAP