Direct transformation of equilateral hexagonal Frank vacancy loops to stacking fault tetrahedra under thermal fluctuation.

Stacking fault tetrahedra (SFTs) are highly interesting three-dimensional vacancy defects in quenched, plastically deformed or irradiated face-centered-cubic metals and have a significant impact on the properties and subsequent microstructural evolution of the materials. Their formation mechanism and stability relative to two-dimensional vacancy loops are still debated. Equilateral hexagonal Frank vacancy loops (faulted, sessile) observed in microscopy have been considered unable to directly transform to SFTs due to separation of Shockley partial dislocations as well as embryonic stacking faults. Here using sufficiently long (up to tens of nanoseconds) molecular dynamic simulations, we demonstrate that such a transformation can in fact take place spontaneously at elevated temperatures under thermal fluctuation, reducing potential energy of defected atoms by <0.05 eV/atom. The transformation becomes easier with increasing temperature or decreasing loop size.

Peritoneal-mediastinal communication complication in peritoneal dialysis.

Peritoneal-mediastinal communication is a rare complication of peritoneal dialysis (PD). We report the first case of peritoneal-mediastinal communication complication in a 36-year-old Caucasian man on continuous cycler peritoneal dialysis (CCPD) after undergoing cardiac surgery. He developed end-stage kidney disease (ESKD) due to calcineurin inhibitor nephrotoxicity and BK virus nephropathy in the setting of prior heart transplantation. He was initially started on intermittent hemodialysis (iHD) and was switched to CCPD 1 year later. He presented with increased drainage from his sternal incision site and reduced ultrafiltration. A contrast-enhanced chest computed tomography scan revealed an anterior chest wall subcutaneous fluid collection. He was found to have a peritoneal-mediastinal communication intraoperatively. He was successfully managed with "low-volume" PD by using reduced fill volumes for all his exchanges and did not require transition to iHD. He also had no vascular access options because of multiple prior thromboses, which would have made transitioning to iHD not feasible. This case further highlights the complex management of an ESKD patient who cannot do iHD and only do low-volume PD because of a surgical complication and the need for a multidisciplinary approach to ensure appropriate patient care.

Effect of prosthesis patient mismatch in mitral position on pulmonary hypertension.

OBJECTIVES: Pulmonary arterial hypertension (PAH) is associated with poor outcome after mitral valve replacement (MVR). We proposed to evaluate the effect of valve prosthesis patient mismatch (PPM) on pulmonary arterial (PA) pressure following MVR. METHODS: Five hundred patients who have undergone MVR were studied retrospectively. Postoperative PA systolic pressure (PASP) measured 6 months postoperatively by Doppler echocardiography was compared with preoperative values. PASP ≥ 40 mmHg was defined as PAH. Mitral valve effective orifice area was calculated by the continuity equation and indexed for body surface area. PPM was defined as indexed effective orifice area ≤ 1.2 cm2/m2. A multivariate model was constructed to ascertain the independent determinants of systolic PA pressure. Also, a propensity score model was constructed to overcome the baseline differences between the PPM and no PPM groups. RESULTS: The incidence of PPM in this study was 37.2%. The average postoperative PASPs were 30.49 and 42.35 mmHg in the no PPM and PPM groups, respectively; (P < 0.001). Regression of PAH in the PPM and no PPM groups was 76.26% and 20.64%, respectively; (P < 0.001). The indexed effective orifice area correlated well with postoperative PASP (r = 0.71). The overall survival and freedom from cardiac death at 10 years were 79.8% and 85.3%; and at 20 years were 66.5% and 74.3%, respectively. Both, overall survival and the freedom from cardiac death were higher in the no PPM group than in the PPM group; (P < 0.001). Propensity score matching analysis yielded 112 pairs of the PPM and no PPM cohorts, which revealed higher overall survival and freedom from cardiac death in the no PPM group; (P = 0.028 and 0.012, respectively). CONCLUSIONS: Mitral PPM is an independent predictor of persistent PAH after MVR along with associated morbidity and reduced survival.