Background The precise mechanism of takotsubo-like left ventricular (LV) dysfunction remains unclear. Methods and Results Eight consecutive patients with takotsubo-like LV dysfunction were studied. ...In the acute phase and 3 weeks later, the coronary flow velocity spectrum and coronary flow velocity reserve (CFVR) were recorded by Doppler guidewire. The deceleration time of diastolic velocity (DDT; ms) was measured from the peak diastolic velocity to the point where the extrapolated line intersected the baseline. In all cases, CFVR of the 3 coronary arteries increased during follow-up (1.7±0.5 to 2.4±0.5 for the left anterior descending artery (p<0.05), 1.7±0.5 to 2.7±0.8 for the left circumflex artery (p<0.05) and 1.7±0.3 to 2.5±0.4 for the right coronary artery (p<0.05)). In addition, the DDT of all coronary arteries increased during follow-up. Conclusions Decreased CFVR and short DDT were demonstrated in patients with takotsubo-like transient LV dysfunction in the acute phase, and these findings improved 3 weeks later, which suggests that coronary microvascular dysfunction may be a causative mechanism. (Circ J 2005; 69: 934 - 939)
Visualisation of the microscopic deformation of a stainless steel was attempted. A mirror polished, flat surface specimen was subjected to a simple tension test, and the deformation of a fine lattice ...drawn by a focused ion beam (FIB) of Ga
+
was observed. The depth of the lattice was of the order of a few tens of nanometres. The penetration depth of Ga
+
was estimated using SRIM software, and the result indicated that the use of a FIB might not cause serious detriment to the mechanical properties of the lattice surface. After testing, lattices were examined by field emission scanning electron microscopy (FESEM). The results showed that displacement was continuous in the grain as well as across the grain boundary, and the microscopic deformation was categorised into three patterns: (a) a clear thin layer of shear deformation which was discontinuous across the grain boundary, (b) an area of uniform deformation inside this thin layer and (c) microscopic shear bands appearing sporadically in the grains.
Background Optical coherence tomography (OCT) is a new imaging method. With a resolution of approximately 10-20 Ém, which is approximately 10-fold higher than that of intravascular ultrasound (IVUS). ...Methods and Results This study compared the coronary intima - media thickness (IMT) and the intimal thickness of 54 coronary arterial segments evaluated by histological examination with the results of OCT and IVUS. There was better agreement in IMT between OCT and histological examination than between IVUS and histological examination (r=0.95, p<0.001, mean difference =-0.01±0.07 mm for OCT; r=0.88, p<0.001, mean difference =-0.03±0.10 mm for IVUS). There was good agreement in the intimal thickness between OCT and histological examination (r=0.98, p<0.001, mean difference =0.01±0.04 mm). Conclusions IMT could be measured more accurately by OCT than IVUS. In addition, the intimal thickness could be evaluated by OCT and correlated well with the histological examination. (Circ J 2005; 69: 903 - 907)
Hot compression tests were conducted on an austenitic stainless steel, BS 304S31, to clarify the origin of the grain coarsening phenomenon that is observed for carbon steels deformed slightly at a ...high temperature. The grain size was measured after hot compression testing, and the distribution was compared with that of the equivalent plastic strain ϵ
eq
calculated using a rigid plastic finite element analysis technique. Similarly to carbon steels, a clear band zone was observed, although in a different region, in the plane difined by working temperature and ϵ
eq
. The adoption of a material without a phase transformation has provided strong evidence supporting the hypothesis presented for carbon steels that the grain coarsening phenomenon is strain induced grain growth in the austenite region. A peculiar, staggered grain boundary was observed as the equivalent plastic strain approached the threshold value for the initiation of grain coarsening.
Investigations were carried out to clarify the independence of two factors that govern the occurrence of the grain coarsening phenomenon: equivalent plastic strain and temperature. The material used ...was BS 304S31 stainless steel which exhibits no phase transformation. It was quickly heated after a cold compression test was carried out to evaluate separately the influences of equivalent plastic strain and temperature. It was found that, in the plane spanned by temperature and equivalent plastic strain given by cold working, there is a clear line at which initiation of grain coarsening occurs. This line exactly coincides with one obtained by a hot compression test, and it was concluded that equivalent plastic strain and temperature are two factors that govern the grain coarsening phenomenon. Additional experiments showed that a small amount of prestrain shortens the incubation time for the initiation of grain coarsening behaviour.
Curious behaviour has been found in a heavily reduced high carbon steel AISI 1070. A wire of 1˙5 mm in diameter manufactured through tandem cold die drawing with total elongation of 13˙4 was ...subjected to heating. When it was heated above 473 K, remarkably, the length of specimen slightly increased after cooling. The ratio of increase in length was about 0˙1%. The decrease in diameter was slightly larger than the expected value to ensure the volume constancy condition owing to plastic metal working. This change in dimensions did not occur in the parent wire of 5˙5 mm in diameter, and it was concluded that this change was induced by heavy reduction by cold tandem drawing. SEM observation showed the occurrence of new isolated cementite when the heating temperature exceeded 473 K and it was assumed that it might be closely related to the mechanism through which increase in length occurs.
A new drawing die designed to reduce the residual stresses in bar after drawing is presented. The die design consists of two consecutive straight taper portions, and the outlet portion has a very ...small die angle. The marked beneficial effect of adding the outlet portion was predicted by finite element modelling (FEM), and subsequently verified by measuring the residual stresses in drawn bars. The optimum range of the outlet die angle was determined using FEM. The new design requires a slightly longer die length than the conventional one, but it is short enough to be adopted in current production lines.
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