Optimization of Aging Temperature and Heat-Treatment Pathways in Additively Manufactured 17-4PH Stainless Steel.

This study investigates the tensile behaviors of additively manufactured (AM) 17-4PH stainless steels heat-treated within various temperature ranges from 400 °C to 700 °C in order to identify the effective aging temperature. Despite an aging treatment of 400-460 °C increasing the retained austenite content, an enhancement of the tensile properties was achieved without a strength-ductility trade-off owing to precipitation hardening by the Cu particles. Due to the intricate evolution of the microstructure, aging treatments above 490 °C led to a loss in yield strength and ductility. A considerable rise in strength and a decrease in ductility were brought about by the increase in the fraction of precipitation-hardened martensitic matrix in aging treatments over 640 °C. The impact of heat-treatment pathways on aging effectiveness and tensile anisotropy was then examined. Direct aging at 482 °C for an hour had hardly any effect on wrought 17-4PH, but it increased the yield strength of AM counterparts from 436-457 to 588-604 MPa. A solid-solution treatment at 1038 °C for one hour resulted in a significant drop in the austenite fraction, which led to an increase in the yield (from 436-457 to 841-919 MPa) and tensile strengths (from 1106-1127 to 1254-1256 MPa) with a sacrifice in ductility. Improved strength and ductility were realized by a solid-solution followed by an aging treatment, achieving 1371-1399 MPa. The tensile behaviors of AM 17-4PH were isotropic both parallel and perpendicular to the building direction.

Cardioprotective effects of rosuvastatin and carvedilol on delayed cardiotoxicity of doxorubicin in rats.

CONTEXT: Doxorubicin is widely used anti-neoplastic drug but has serious cardiotoxicity. Long-term cardioprotective effects of statin and carvedilol against delayed cardiotoxicity of doxorubicin was not well elucidated. OBJECTIVE: To evaluate long-term cardioprotective effects of co-administered rosuvastatin and carvedilol against chronic doxorubicin-induced cardiomyopathy (DIC) in rats. METHODS: Sixty-one rats were assigned to six groups: group I, control; group II, doxorubicin only (1.25 mg/kg, bi-daily, I.P.); group III, doxorubicin + rosuvastatin (2 mg/kg/day, P.O.); group IV, doxorubicin + rosuvastatin(10 mg/kg/day, P.O.); group V, doxorubicin + carvedilol (5 mg/kg/day, P.O.); group VI, doxorubicin + carvedilol (10 mg/kg/day, P.O.). Drugs were administered for 4 weeks (by week 4) and rats were observed without drugs for 4 weeks (by week 8). RESULTS: After 4 weeks discontinuation of drugs (week 8), group III showed higher +dP/dt (p = 0.058), lower -dP/dt (p = 0.009), lower left ventricular (LV) tissue malondialdehyde (MDA; p = 0.022), and less LV fibrosis (p = 0.011) than group II. Group IV showed similar results to group III. However, in group V and VI, carvedilol failed to reduce LV dysfunction, elevation of troponin or myocardial fibrosis, although group V showed lower LV tissue MDA (p = 0.004) than group II. DISCUSSION AND CONCLUSIONS: Myocardial injury and LV systolic/diastolic dysfunction at week 8 was alleviated by co-administered rosuvastatin, but not by carvedilol. It is unclear whether the cardioprotective effect of rosuvastatin is attributed to a suppression of oxidative stress induced by doxorubicin, because carvedilol did not exhibit a cardioprotective effect despite its antioxidant effects.

Simultaneous and spontaneous multivessel coronary artery dissection presenting as congestive heart failure.

Spontaneous coronary artery dissection (SCAD) is a rare cause of myocardial ischemia. Multivessel SCAD is much rarer than single vessel involvement and acute coronary syndrome is the most frequent clinical presentation of a patient with SCAD. The patient in this report had SCAD in both the left anterior descending and right coronary arteries at the same time. However, the clinical manifestation was not acute coronary syndrome but rather congestive heart failure. Successful angioplasty and stent placement was performed and the symptoms of congestive heart failure were successfully resolved with medical treatment.