Pressure Dependence of Superconducting Properties, Pinning Mechanism, and Crystal Structure of the Fe0.99Mn0.01Se0.5Te0.5 Superconductor.

We have investigated the pressure (P) effect on structural (up to 10 GPa), transport [R(T): up to 10 GPa], and magnetic [(M(T): up to 1 GPa)] properties and analyzed the flux pinning mechanism of the Fe0.99Mn0.01Se0.5Te0.5 superconductor. The maximum superconducting transition temperature (T c) of 22 K with the P coefficient of T c dT c/dP = +2.6 K/GPa up to 3 GPa (dT c/dP = -3.6 K/GPa, 3 ≤ P ≥ 9 GPa) was evidenced from R(T) measurements. The high-pressure diffraction and density functional theory (DFT) calculations reveal structural phase transformation from tetragonal to hexagonal at 5.9 GPa, and a remarkable change in the unit cell volume is observed at ∼3 GPa where the T c starts to decrease, which may be due to the reduction of charge carriers, as evidenced by a reduction in the density of states (DOS) close to the Fermi level. At higher pressures of 7.7 GPa ≤ P ≥ 10.2 GPa, a mixed phase (tetragonal + hexagonal phase) is observed, and the T c completely vanishes at 9 GPa. A significant enhancement in the critical current density (J C) is observed due to the increase of pinning centers induced by external pressure. The field dependence of the critical current density under pressure shows a crossover from the δl pinning mechanism (at 0 GPa) to the δT c pinning mechanism (at 1.2 GPa). The field dependence of the pinning force at ambient condition and under pressure reveals the dense point pinning mechanism of Fe0.99Mn0.01Se0.5Te0.5. Moreover, both upper critical field (H C2) and J C are enhanced significantly by the application of an external P and change over to a high P phase (hexagonal ∼5.9 GPa) faster than a Fe0.99Ni0.01Se0.5Te0.5 (7.7 GPa) superconductor.

Clinical Results of Ascending Aorta-Abdominal Aorta Bypass / 日本心臓血管外科学会雑誌

Ascending aorta-infrarenal abdominal aorta bypass was performed in 8 patients: 4 patients with dissecting aortic aneurysm, 3 patients with thoracic aneurysm and 1 patient with stenosis of the thoracic aorta after grafting for congenital thoracic aneurysm. Four patients who had aortic dissection underwent the thromboexclusion method, but thromboexclusion of the thoracic aorta occured in only one patient after additional clamp to the distal thoracic aorta. He is the only long-term survival in this series. The thromboexclusion method was also performed in two patients with infectious thoracic aortic aneurysm, but they died of aneurysmal rupture within 13 months after operation. One patient who undewent resection of a thoracic aneurysm with extra-anatomic bypass, developed respiratory insufficiency and paraplegia, and died of pneumonia. The patient with thoracic aortic stenosis is alive and well 11 years after operation. The indications of the thromboexclusion method for thoracic aneurysm should be limited only to very poor-risk patients who seem to be inaccessible to a direct approach. Ascending aorta-abdominal aorta bypass is recommended in cases of thoracic aortic stenosis.

Long-term Results of Direct Surgical Approach to Left Main Coronary Artery / 日本心臓血管外科学会雑誌

Five patients with isolated stenosis of the left main coronary artery or stenotic ostial lesions underwent direct coronary artery surgery. These surgical approaches included vein patch angioplasty in 2 cases, punch out endarterectomy in 1 case, and resection of the thickened aortic wall and transaortic endarterectomy in 2 cases. Early results were satisfactory, except for one case who died due to severe LOS and MOF. In the late postoperative period, one case of vein patch angioplasty died due to cerebral bleeding, and in the other case, stenosis existed in position of distal patch anastomosis. Since direct coronary artery surgery was successful in both early and late postoperative fidings, it is believed to be useful and safe technique if the candidates are selected properly.

Clinical Experience of Right Heart Bypass Using Heparin-coated Tube and Roller Pump System / 日本心臓血管外科学会雑誌

A 47 year-old man with frequent attacks of ventricular tachycardia (VT) due to arrhythmogenic right ventricular dysplasia (ARVD) developed severe right heart failure following cryoablation of the multiple VT focuses. Inotropic support and intraaortic balloon pumping failed to maintain the systemic circulation, so that we performed the right heart bypass (RHB) using a heparin-coated tube and roller pump. With the use of RHB, systemic circulation improved. We attempted to wean the patient off after 14 days RHB support. However this was unsuccessful because of poor RV function, and RHB was recommenced. The patient finally died of multiple organ failure on the 21st postoperative day, but the major organ function was well maintained for at least two weeks. The heparin-coated tube and roller pump system is easy to handle, and is suitable as a short term lifesaving adjunct for severe right ventricular failure.

An Experimental Evaluation for Blood Compatibility of Mock Cardiopulmonary Bypass Systems / 日本心臓血管外科学会雑誌

To estimate the blood compatibility during extracorporeal circulation, we designed mock circulation system consisted of a membrane oxygenator and vinyl circuit with roller pump. Primed with 200ml Ringer's acetate and 200ml of fresh whole human blood, mock circulation was worked at flow rate 0.5<i>l</i>/min for 6hr. Heparin was not primed, oxygenator did not fill any gases and circulation was keeping at 37°C. The thrombin-antthrombin complex and fibrinopeptide-A showed progressive increase and fibrinogen correspondingly decrease. Nevertheless, the plasmin α2 plasmin inhibitor complex and D-dimer showed minimal changes within normal range in spite of increasing fibrinopeptide B β 15-42. We can not find any signs of secondary fibrinolytic activity. On the other hand, the platelet was persistently activated as shown statistically significant increase in β-thrombogloblin and platelet factor IV. Significant elevations of complement 3a and 4a were seen with increase of complement 5a and activated oxygen productivity by neutrophilic leucocytes. In conclusion, moderate and limited blood alterations occurred in mock cardiopulmonary bypass circuit.