Dependence of the elastic strain coefficient of copper on the pre-treatment

The effect of various pre-treatments on the elastic strain coefficient (alpha) (defined as the reciprocal of the modulus of elasticity E) (Epsilon) and on the mechanical hysteresis of copper has been investigated. Variables comprising the pre-treatments were pre-straining by stretching in a tensile testing machine and by drawing through a die, aging at room and elevated temperatures and annealing. The variation of the elastic strain coefficient with test stress was also investigated

Abhängigkeit der elastischen Dehnungszahl des Kupfers von der Vorbehandlung

The effect of various pre-treatments on the elastic strain coefficient (alpha) (defined as the reciprocal of the modulus of elasticity E) (Epsilon) and on the mechanical hysteresis of copper has been investigated. Variables comprising the pre-treatments were pre-straining by stretching in a tensile testing machine and by drawing through a die, aging at room and elevated temperatures and annealing. The variation of the elastic strain coefficient with test stress was also investigated

Quadratur der Segmente des Cirkels nach der Art des Hippocrates

v. Wilhelm Friedrich Kuntze (Pastor zu Dippoldiswalde

Surgical risk of preoperative malperfusion in acute type A aortic dissection

OBJECTIVE: Patients who have type A dissection with preoperative malperfusion syndromes are believed to be at extremely high surgical risk. Our aim was to evaluate perioperative and long-term results of patients with preoperative malperfusion. METHODS: A total of 276 patients (174 men; mean age 59.5 +/- 13.4 years) underwent surgery for acute type A dissection between October 1994 and January 2008. Preoperative malperfusion syndromes were diagnosed in 93 (33.7%) patients (group I) and involved coronary circulation in 41 (15%) patients, central nervous system in 39 (14%) patients, limb ischemia in 32 (11.6%) patients, and mesenteric circulation in 8 (3%) patients. Postoperative results were compared between patients with preoperative malperfusion and those without this complication (group II, n = 183). RESULTS: In-hospital mortality was 29.0% in group I versus 13.6% in group II (P = .002). The postoperative intensive care unit stay was longer (11.4 +/- 9.7 vs 7.7 +/- 6.9 days; P = .04) in the malperfusion group. A total of 6 (75%) patients with mesenteric malperfusion died. Long-term follow-up (range, 1-122 months postoperatively) was available in 100% of survivors. One-year and 5-year overall survivals were 49.8% +/- 11.8% and 41.8% +/- 12.6% in group I versus 70.4% +/- 7.6% and 56% +/- 10.4% in group II (P = .005). Cox regression analysis identified preoperative malperfusion as a significant risk factor for long-term mortality after surgery for type A dissection (hazard ratio, 1.7; 95% confidence intervals, 1.2-3.1). CONCLUSIONS: Preoperative malperfusion is a significant risk factor influencing perioperative and long-term survival after surgery for acute type A dissection. Percutaneous interventional procedures and delayed surgery should be considered in patients with clinically apparent mesenteric malperfusion because of the dismal prognosis of immediate surgical therapy