[en] Programmable pacemakers (PPM) can be programmed to sense, stimulate, or inhibit atrial (A) and/or ventricular (V) electrical activity, and include variable A-V delays and other options. Selecting the optimum combination of settings for an individual patient can be a formidable task in the absence of noninvasive, objective, quantifiable measures of cardiac function. The authors attempt to determine whether the MUGA study could be adapted to such a task. MUGA studies were performed on 13 patients (pts) with PPM who had varying degrees of A-V block, during various settings of the PPM's. Studies were carried out 5-10 min. after pacing mode and A-V delay were changed, with the pt resting and supine. All 5 MUGA studies were carried out after a single injection of Tc-99m labeled autologous red blood cells. The results show that the VDD mode brings about a higher left ventricular ejection fraction (LVEF) and cardiac output (CO) than the DVI mode, and that either of these dual-chamber pacing modes produces a higher LVEF and CO than single-chamber pacing (VVI). Furthermore, a longer A-V delay was shown to improve LVEF and CO in patients with initially low LVEF. The MUGA study is simple, noninvasive, objective, and quantifiable, and can easily be repeated several times following a single injection. It can be used to ''fine tune'' programmable pacemakers for optimum hemodynamic performance

[en] In this paper, the damping mechanism model of Fe-Mn alloy was analyzed using dislocation theory. Moreover, as an important parameter in Fe-Mn based alloy, the effect of stacking fault probability on the damping capacity of Fe-19.35Mn alloy after deep-cooling or tensile deformation was also studied. The damping capacity was measured using reversal torsion pendulum. The stacking fault probability of γ-austenite and ε-martensite was determined by means of X-ray diffraction (XRD) profile analysis. The microstructure was observed using scanning electronic microscope (SEM). The results indicated that with the strain amplitude increasing above a critical value, the damping capacity of Fe-19.35Mn alloy increased rapidly which could be explained using the breakaway model of Shockley partial dislocations. Deep-cooling and suitable tensile deformation could improve the damping capacity owning to the increasing of stacking fault probability of Fe-19.35Mn alloy

[en] Influences of transformation behavior and precipitates on the deformation behavior of Ni-rich NiTi alloys were thermodynamically and experimentally investigated in present work. According to the thermodynamic analysis, the critical stress presents the same linear relationship with martensitic transformation temperature for all Ni-rich NiTi alloys. The thermodynamic results were demonstrated by the experimental results after aging treatment of Ni-rich NiTi alloys with compositions of 51.5, 51 and 50.5 at% Ni, even for the aged alloys with R phase transformation. Meanwhile, evolution of precipitate size and volume fraction was clearly discussed for Ni-rich NiTi alloys with different aging conditions. Different from the critical stress, transformation behavior presents no obvious influence on the yield stress of the Ni-rich NiTi alloys. The yield stress is mainly determined by Ni₄Ti₃ precipitates, which increases with increasing the precipitate volume fraction and decreases with increasing the precipitate size.

[en] Highlights: • Ni₄Ti₃ precipitation changes to β-Nb precipitation with increasing Nb addition. • Ni₄Ti₃ precipitates cause no change of phase transformation in Nb2 alloy. • β-Nb precipitates decrease Ms in NiTiNb alloy. • The critical yield stresses present same minus linear relationship with Ms. -- Abstract: Ni-rich Ni_xTi_yNb_z (x/y = 1.0645/x-y ≈ 3, z = 0, 2, 4, 6, 9 at.%) alloys were designed and prepared in this work. Based on these alloys, the precipitation evolution of Ni-rich NiTiNb alloys and its influence on phase transformation and mechanical properties were investigated. Ni₄Ti₃ precipitates are observed in Nb0 and Nb2 alloys after aging and furnace cooling. Ni₄Ti₃ precipitation sharply increases Ms in Nb0 alloy, however, causes no obvious change of Ms in Nb2 alloy. With increasing Nb addition, large numbers of β-Nb precipitates densely distribute among eutectic regions of Nb6 and Nb9 alloys. β-Nb precipitates and eutectic β-Nb particles decrease Ms. The critical yield stresses of all Ni-rich NiTiNb alloys are determined by Ms, and present same minus linear relationship with Ms. Precipitation and element variation change Ms and then influence mechanical properties. Meanwhile, this result is demonstrated by thermodynamic analysis.