Non covalent interactions are quite common in all kinds of π-systems, such as π-π interactions, long range/short range van der waal force of interactions, ion-π interactions etc. Ab initio calculations are well es...Non covalent interactions are quite common in all kinds of π-systems, such as π-π interactions, long range/short range van der waal force of interactions, ion-π interactions etc. Ab initio calculations are well established and account well for the experimental long range interaction energies for small clusters of aromatic molecules and most of the calculations were carried out using the MPn methods. If a reasonably large basis set is used to calculate the stacking interaction energies for a cluster (dimer, trimer etc.) of aromatic molecules then the electron-electron correlation energy may be properly calculated. Moreover, ab initio calculations for aromatic π-systems show that the calculated stacking interaction energies highly depend on the basis set used and the electron correlation energy. In this investigation, the electron correlation of the stacked hydrated phenol systems has been accounted at MP2 level of calculations. We have calculated the π-π stacking interaction energies of the hydrated phenolic systems with different conformations.展开更多
Aromatic systems like phenol, diphenol, cyano benzene, chloro benzene, aniline etc shows effective π-π stacking interactions, long range van der Waals forces;ion-π interactions etc. and these forces of interactions...Aromatic systems like phenol, diphenol, cyano benzene, chloro benzene, aniline etc shows effective π-π stacking interactions, long range van der Waals forces;ion-π interactions etc. and these forces of interactions play an crucial role in the stability of stacked π-dimeric system. On the other hand, substituents and conformational change in the stacked dimmers of aromatic system may also change the stability of different stacked dimers. In this current study, stacked phenolic dimmers (both phenol and diphenol) have been taken for investigation of the stacking π-π interaction. But, the stacking interactions are also greatly affected by the conformational change with internal rotation (i.e. dihedral angle, φ) between the stacked dimers. It is generally accepted that larger basis sets are required for the highly accurate calculation of interaction energies for any stacked aromatic models. But, it has recently been reported that M062X/6-311++G(d,p) basis set is effectively better than that of B3LYP/6-311++G(d,p) for determining the interaction energies for any kind of long range interaction in aromatic systems. Therefore, all the calculations were carried out by using M062X/6-311++G(d,p) basis set. However, in most of the cases the calculated π-π stacking interaction energies show almost same result for both DFT and ab initio methods.展开更多
Objective To describe phenotype, perioperative events, and early morbidity among infants with esophageal atresia with or without tracheoesophageal fistula(EA/TEF), and to evaluate how gap length relates to postoperati...Objective To describe phenotype, perioperative events, and early morbidity among infants with esophageal atresia with or without tracheoesophageal fistula(EA/TEF), and to evaluate how gap length relates to postoperative and follow-up outcomes.Methods A retrospective single-center cohort study was conducted in a tertiary neonatal and pediatric surgery service, Riyadh, Saudi Arabia. All infants with EA/TEF managed between January 1, 2016 and December 31, 2024. Clinical data include early clinical anastomotic leak(≤14 days), recurrent fistula, anastomotic stricture and time-to-event outcomes including hospital length of stay, time to full oral feeding, duration of postoperative ventilation and duration of parenteral nutrition. Followup outcomes included respiratory morbidity and feeding support requirements.Results Sixty-seven infants were included;gross type C was most frequent(73.1%). Gap length was assessable in 63 non-H-type cases, with 31.7% classified as long-gap EA. Survival to discharge was 86% after excluding three trisomy 18 infants managed palliatively. Primary repair was achieved in 67.2% overall but in only 10% of long-gap infants, among whom staged repair or gastric pull-up predominated. Early anastomotic leak occurred in 26.9%, recurrent fistula in 14.9% and anastomotic stricture in 32.8%. In multivariable logistic regression, long-gap EA was the only independent predictor of stricture(adjusted odds ratio(OR) 4.44;95% confidence interval(CI) 1.27 to 15.55;p=0.020). Recovery was substantially longer for long-gap infants: median hospital stay 186 vs. 53 days(p<0.001) and time to full oral feeding 209 vs. 29 days(p<0.001). At follow-up(n=55), 34.5% required gastrostomy, 20% had feeding aversion, 36.4% experienced recurrent respiratory infections, and 10.9% had tracheomalacia.Conclusions Gap length was the principal determinant of anastomotic stricture and prolonged recovery after EA/TEF repair. These data provide a baseline for ongoing quality improvement and support early referral of long-gap cases to specialized multidisciplinary centers with structured follow-up programs.展开更多
文摘Non covalent interactions are quite common in all kinds of π-systems, such as π-π interactions, long range/short range van der waal force of interactions, ion-π interactions etc. Ab initio calculations are well established and account well for the experimental long range interaction energies for small clusters of aromatic molecules and most of the calculations were carried out using the MPn methods. If a reasonably large basis set is used to calculate the stacking interaction energies for a cluster (dimer, trimer etc.) of aromatic molecules then the electron-electron correlation energy may be properly calculated. Moreover, ab initio calculations for aromatic π-systems show that the calculated stacking interaction energies highly depend on the basis set used and the electron correlation energy. In this investigation, the electron correlation of the stacked hydrated phenol systems has been accounted at MP2 level of calculations. We have calculated the π-π stacking interaction energies of the hydrated phenolic systems with different conformations.
文摘Aromatic systems like phenol, diphenol, cyano benzene, chloro benzene, aniline etc shows effective π-π stacking interactions, long range van der Waals forces;ion-π interactions etc. and these forces of interactions play an crucial role in the stability of stacked π-dimeric system. On the other hand, substituents and conformational change in the stacked dimmers of aromatic system may also change the stability of different stacked dimers. In this current study, stacked phenolic dimmers (both phenol and diphenol) have been taken for investigation of the stacking π-π interaction. But, the stacking interactions are also greatly affected by the conformational change with internal rotation (i.e. dihedral angle, φ) between the stacked dimers. It is generally accepted that larger basis sets are required for the highly accurate calculation of interaction energies for any stacked aromatic models. But, it has recently been reported that M062X/6-311++G(d,p) basis set is effectively better than that of B3LYP/6-311++G(d,p) for determining the interaction energies for any kind of long range interaction in aromatic systems. Therefore, all the calculations were carried out by using M062X/6-311++G(d,p) basis set. However, in most of the cases the calculated π-π stacking interaction energies show almost same result for both DFT and ab initio methods.
文摘Objective To describe phenotype, perioperative events, and early morbidity among infants with esophageal atresia with or without tracheoesophageal fistula(EA/TEF), and to evaluate how gap length relates to postoperative and follow-up outcomes.Methods A retrospective single-center cohort study was conducted in a tertiary neonatal and pediatric surgery service, Riyadh, Saudi Arabia. All infants with EA/TEF managed between January 1, 2016 and December 31, 2024. Clinical data include early clinical anastomotic leak(≤14 days), recurrent fistula, anastomotic stricture and time-to-event outcomes including hospital length of stay, time to full oral feeding, duration of postoperative ventilation and duration of parenteral nutrition. Followup outcomes included respiratory morbidity and feeding support requirements.Results Sixty-seven infants were included;gross type C was most frequent(73.1%). Gap length was assessable in 63 non-H-type cases, with 31.7% classified as long-gap EA. Survival to discharge was 86% after excluding three trisomy 18 infants managed palliatively. Primary repair was achieved in 67.2% overall but in only 10% of long-gap infants, among whom staged repair or gastric pull-up predominated. Early anastomotic leak occurred in 26.9%, recurrent fistula in 14.9% and anastomotic stricture in 32.8%. In multivariable logistic regression, long-gap EA was the only independent predictor of stricture(adjusted odds ratio(OR) 4.44;95% confidence interval(CI) 1.27 to 15.55;p=0.020). Recovery was substantially longer for long-gap infants: median hospital stay 186 vs. 53 days(p<0.001) and time to full oral feeding 209 vs. 29 days(p<0.001). At follow-up(n=55), 34.5% required gastrostomy, 20% had feeding aversion, 36.4% experienced recurrent respiratory infections, and 10.9% had tracheomalacia.Conclusions Gap length was the principal determinant of anastomotic stricture and prolonged recovery after EA/TEF repair. These data provide a baseline for ongoing quality improvement and support early referral of long-gap cases to specialized multidisciplinary centers with structured follow-up programs.
