The use of a ns-pulsed, high repetition rate green laser for SLM of 99.9% pure Cu

The most common laser type used in selective laser melting (SLM) machines is continuous fiber laser emitting at 1 m. The low optical absorptivity of Cu to ~1 m wavelength renders pure Cu a highly demanding material for SLM . The low optical absorptivity along with high thermal conductivity causes unstable processing conditions when standard SLM machine are used with pure Cu. Conversely, Cu has a much higher optical absorptivity at the green wavelength. Until recently, high power green lasers have not been available for material processing. This work investigates the use of a novel ns-pulsed fiber laser operating at the second harmonic (532 nm) for SLM of 99.9% pure Cu powder. In particular, the laser source operates at 30 MHz repetition rate providing ns regime and up to 110 W average power. The green laser is implemented to a bespoke open SLM platform. Results show that cubic specimens with densities >99.5% could be achieved

High speed videography of gap bridging with beam oscillation and wire feeding during the laser welding of stainless steel and aluminum alloys

Laser beam welding is known for its quality and speed. Given its susceptibility to gaps, the technology is applied in the industrial field with hard automation and dedicated fixtures rather than small-batch production. The latter cannot always guarantee the strict conditions on the fit-up of joints, especially with complex geometries. Gap-bridging techniques may be exploited to overcome these inaccuracies. The present work investigates the simultaneous use of low frequency circular beam oscillation and wire feeding as means to produce a continuous weld seam in the presence of constant air gaps. Lap joint welding of 2 mm-thick AISI301LN and butt joint welding of 3 mm-thick AW6005A-T6 alloy were conducted with gaps up to 1mm. High-speed imaging at 10kHz provided an insight in the dynamics of the oscillating weld pool and spatter formation. Optical inspection and metallographic analyses were used to verify the gap-bridging capability as well as the resulting seam quality

Long-Term Outcome of Acute Coronary Syndromes in Young Patients

Introduction: Acute coronary syndromes (ACS) in young patients are uncommon and their influence on morbidity and mortality in this population is still debated. Aim: We investigated clinical and angiographic characteristics, risk factors and outcome in young patients diagnosed with ACS, compared with those of older patients, evaluating survival free from death and/or nonfatal myocardial infarction (MI) and/or coronary revascularization (primary endpoint), and then with respect to each component of the primary endpoint. Methods: We retrospectively analyzed 1696 patients diagnosed with ACS between 2007 and 2013. 116 were aged ≤45 years (young adults), 1116 were >45 and <75 years (older adults) and 464 were ≥75 years. Results: Young adults were mostly male, with a prevalent diagnosis of STEMI, had less frequently typical cardiovascular risk factors and lower prevalence of extensive coronary artery disease. Over a median 3 years follow up, survival free from composite endpoint was better in young than in older adult patients (11.2 vs. 24.2%; p = 0.001), mainly due to a lower rate of death while the occurrence of non fatal MI and of coronary revascularization was similar (7.8 vs. 8.7%, p = 0.86; 8.7 vs. 12.9%, p = 0.23 respectively). Diabetes was the strongest independent risk factor of worse prognosis in the young cohort (OR 3.47; 95% CI 1.01–11.9; p = 0.04). Conclusions: Young adults showed peculiar clinical features and lower mortality compared with older adults. Morbidity was not different between the two populations, with diabetes independently associated with a worse prognosis

Under-dilated TIPS Associate With Efficacy and Reduced Encephalopathy in a Prospective, Non-randomized Study of Patients With Cirrhosis

Portosystemic encephalopathy (PSE) is a major complication of trans-jugular intrahepatic porto-systemic shunt (TIPS) placement. Most devices are self-expandable polytetrafluoroethylene-covered stent grafts (PTFE-SGs) that are dilated to their nominal diameter (8 or 10 mm). We investigated whether PTFE-SGs dilated to a smaller caliber (under-dilated TIPS) reduce PSE yet maintain clinical and hemodynamic efficacy. We also studied whether under-dilated TIPS self-expand to nominal diameter over time. METHODS: We performed a prospective, non-randomized study of 42 unselected patients with cirrhosis who received under-dilated TIPS (7 and 6 mm) and 53 patients who received PTFE-SGs of 8 mm or more (controls) at referral centers in Italy. After completion of this study, dilation to 6 mm became the standard and 47 patients were included in a validation study. All patients were followed for 6 months; Doppler ultrasonography was performed 2 weeks and 3 months after TIPS placement and every 6 months thereafter. Stability of PTFE-SG diameter was evaluated by computed tomography analysis of 226 patients with cirrhosis whose stent grafts increased to 6, 7, 8, 9, or 10 mm. The primary outcomes were incidence of at least 1 episode of PSE grade 2 or higher during follow up, incidence of recurrent variceal hemorrhage or ascites (based on need for at least 1 large-volume paracentesis by 4 weeks after TIPS placement), incidence of shunt dysfunction requiring TIPS recanalization, and reduction in porto-caval pressure gradient. RESULTS: PSE developed in a significantly lower proportion of patients with under-dilated TIPS (46%) than controls (73%) during the first year after the procedure (P=.015), but the proportions of patients with recurrent variceal hemorrhage or ascites did not differ significantly between groups. No TIPS occlusions were observed. These results were confirmed in the validation cohort. In an analysis of self-expansion of stent grafts, during a mean follow-up period of 252 days after placement, none of the PTFE-SGs self-expanded to the nominal diameter in hemodynamically relevant sites (such as portal and hepatic vein vascular walls). CONCLUSION: In prospective, non-randomized study of patients with cirrhosis, we found under-dilation of PTFE-SGs during TIPS placement to be feasible, associated with lower rates of PSE, and effectiv