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The energy of protons accelerated by ultra-intense lasers in the target normal sheath acceleration (TNSA) mechanism can be greatly enhanced by the laser parameter optimization. We propose to investigate the optimization of laser parameters for proton acceleration using double laser pulses in TNSA mechanism. The sheath field generation at the rear side of the target is significantly affected by the introduction of second laser pulse in TNSA mechanism, and consequently, the energy of the accelerated protons is also modified. The second laser pulse was introduced with different delays to study its impact on proton acceleration. Our study shows that the interplay of laser intensity and pulse duration of both laser pulses affects the proton acceleration. It was found that the proton maximum energy is the function of both laser intensity and pulse duration. A number of simulations have been performed to obtain maximum proton energy data under different combinations of laser intensity and pulse duration for the two laser pulses. The simulation results account for the underline physics for the proton bunch energy and the sheath field as a function of pulse intensity and pulse delay.
Arterial switch operation is the treatment of choice in infants with transposed arterial trunks. It is technically challenging to perform in patients having usual atrial arrangement and concordant atrioventricular connections but having a left-sided aorta. Correction in this setting requires surgical expertise and precision. Here we review our experience with such patients.
Between January, 2002 and October, 2013, the arterial switch operation was performed in 20 patients in the combination emphasised above. Patient records were analysed in detail for coronary arterial patterns, and for the techniques used for transfer of the coronary arteries and reconstruction of the great arteries. Outcomes were recorded in terms of in-hospital survival and left ventricular function at the most recent follow-up.
All patients survived the procedure. Ages ranged from 3 days to 18 months, with a median of 75 days; the weight of the patients ranged from 3 to 8.8 kg, with a median of 3.85 kg. The LeCompte manoeuvre was performed in only nine patients. The mean cardiopulmonary bypass time was 157.5±24.9, with a median of 161 minutes, and the mean aortic cross-clamp time was 101.2±23.8, with a median of 102 minutes. Subsequently, two patients died: the first due to a sudden onset of ventricular fibrillation and the second during a crisis of severe pulmonary hypertension. At the last follow-up, which ranged from 23 to 41 months, with a mean of 38.04±2.32 and a median of 38.4 months, all 18 survivors were in NYHA class I, with none requiring cardiac medications and all having normal bi-ventricular function without residual defects.
With appropriate technical modifications, patients with concordant atrioventricular and discordant ventriculo-arterial connections with a left-sided aorta can undergo successful anatomical repair.
This research article addresses the effect of fillers on the high-temperature corrosion behavior of AISI 347 weld joints. Multi-pass pulsed current gas tungsten arc welding was carried out on 6.67 mm thick plates of AISI 347 using three different fillers namely ER347, ER2553, and ERNiCrMo-3. The fusion zone microstructures of AISI 347 employing ER2553 and ERNiCrMo-3 exhibited columnar and dendritic grain growth; whereas vermicular delta ferrite was observed at the fusion zone of ER347 welds. Tensile studies showed that the weld employing ERNiCrMo-3 exhibited better tensile strength than the parent metal. High-temperature corrosion studies were carried out on the fusion zones by exposing the coupons to an aggressive, synthetic molten-salt incinerator environment containing 40% Na2SO4–40% K2SO4–10% NaCl–10% KCl at 650 °C for 50 cycles. The studies attested that the fusion zone employing ERNiCrMo-3 exhibited better corrosion resistance than the other two fillers used in the study. Spallation of oxides was witnessed due to the dissolution of Cr2O3 in the ER347 and ER2553 fusion zones. The hot corroded samples were characterized using surface analytical techniques.