RESUMO
The practical applications of endohedral metallofullerenes (EMFs) are mainly constrained by their low yields. Understanding the formation mechanisms is therefore crucial for developing methods for high-yield and selective synthesis. To address this, a novel force-field parameter set, "CSc.ff", was created using a single-parameter search optimization method, then molecular dynamics simulations of various systems with a carbon-to-scandium atomic ratio of 12.5 were carried out. The simulations were run under a constant atomic number, volume, and energy (NVE) ensemble. The influence of the working gas, helium, as well as temperature gradients on the formation process was examined. Our simulations reveal that the cage growth patterns of Sc-based EMFs (Sc-EMFs) closely resemble those of hollow fullerenes, evolving from free carbon atoms to chains, rings, and, ultimately, to cage-shaped clusters. Importantly, the Sc-EMFs formed in the simulation frequently exhibit structural defects or under-coordinated carbon atoms. Scandium atoms, whether at the periphery or on the surface of these cages, can be incorporated into the cages, forming Sc-EMFs. Helium was found to not only promote the formation of carbon cages but also facilitate the encapsulation of scandium atoms, playing a crucial role in the formation of cluster fullerenes. Moreover, cooling effectively inhibits the uncontrollable growth of the carbon cage and is essential for forming stable, appropriate-sized cages. This study enhances our understanding of the formation of Sc-EMFs and provides valuable insights for developing more efficient synthetic methods.
RESUMO
BACKGROUND: Multiple packed red blood cell (PRBC) transfusions in very low birth weight (VLBW) prematurity have been suggested to be a risk factor for the development of retinopathy of prematurity (ROP) or for chronic lung disease (CLD). The purpose of this study was to examine the effect of PRBC transfusions on the outcome of VLBW prematurity. METHODS: In total, between July 2005 and June 2006, 36 VLBW preterm babies were admitted to our neonatal intensive care unit and were randomly allocated to the "restrictive" (n= 19) or "liberal" (n= 17) criteria for PRBC transfusion. Complete blood count (CBC) was examined at admission and 30 days later. Reticulocyte counts, serum iron and ferritin were examined and compared with the clinical outcomes. RESULTS: Infants in the liberal group received a larger PRBC transfusion volume compared with the restrictive group over 30 days (41.7+/-20.1 vs. 27.2+/-15.9mL, p=0.029). There were no significant differences in the proportion of patients with respiratory distress syndrome, patent ductus arteriosus, severe intraventricular hemorrhage, ROP or CLD between the two groups. The laboratory data, except reticulocyte count, showed no significant difference on day 30. Further analysis of premature babies with and without CLD showed that total transfused blood volume greater than 30mL over 30 days was a risk factor for developing CLD in VLBW infants. CONCLUSION: Both criteria of PRBC transfusion had similar clinical outcomes, although liberal transfusion resulted in a greater amount of blood transfused and a low reticulocyte count at 30 days of age. We suggest restrictive criteria for minimizing the overall amount of transfusion to less than 30 mL may be a better way of preventing CLD in VLBW infants.