The Near-Sightedness of Many-Body Interactions in Anharmonic Vibrational Couplings.

Couplings between vibrational motions are driven by electronic interactions, and these couplings carry special significance in vibrational energy transfer, multidimensional spectroscopy experiments, and simulations of vibrational spectra. In this investigation, the many-body contributions to these couplings are analyzed computationally in the context of clathrate-like alkali metal cation hydrates, including Cs(HO), Rb(HO), and K(HO), using both analytic and quantum-chemistry potential energy surfaces. Although the harmonic spectra and one-dimensional anharmonic spectra depend strongly on these many-body interactions, the mode-pair couplings were, perhaps surprisingly, found to be dominated by one-body effects, even in cases of couplings to low-frequency modes that involved the motion of multiple water molecules.

Impact of Atrial Pacing in Fontan Patients with Junctional Rhythm: A Prospective Echocardiographic Study.

Sinus node dysfunction (SND) with junctional rhythm (JR) is common after the Fontan operation. Atrial pacing (AP) restores atrioventricular (AV) synchrony, but the placement of a pacemaker carries significant morbidity. To study the impact of AP on echocardiographic parameters of function in Fontan patients with SND and JR.

Pitfalls in the n-mode representation of vibrational potentials.

Simulations of anharmonic vibrational motion rely on computationally expedient representations of the governing potential energy surface. The n-mode representation (n-MR)-effectively a many-body expansion in the space of molecular vibrations-is a general and efficient approach that is often used for this purpose in vibrational self-consistent field (VSCF) calculations and correlated analogues thereof. In the present analysis, a lack of convergence in many VSCF calculations is shown to originate from negative and unbound potentials at truncated orders of the n-MR expansion.

Accelerating and stabilizing the convergence of vibrational self-consistent field calculations via the direct inversion of the iterative subspace (vDIIS) algorithm.

The vibrational self-consistent field (VSCF) method yields anharmonic states and spectra for molecular vibrations, and it serves as the starting point for more sophisticated correlated-vibration methods. Convergence of the iterative, non-linear optimization in VSCF calculations can be erratic or altogether unsuccessful, particularly for chemical systems involving low-frequency motions. In this work, a vibrational formulation of the Direct Inversion of the Iterative Subspace method of Pulay is presented and investigated.

Accelerating Anharmonic Spectroscopy Simulations via Local-Mode, Multilevel Methods.

computer simulations of anharmonic vibrational spectra provide nuanced insight into the vibrational behavior of molecules and complexes. The computational bottleneck in such simulations, particularly for potentials, is often the generation of mode-coupling potentials. Focusing specifically on two-mode couplings in this analysis, the combination of a local-mode representation and multilevel methods is demonstrated to be particularly symbiotic.

Aortic valve atresia and type C interrupted aortic arch with circle of Willis dependent circulation: a case of successful biventricular repair in the neonatal period.

We report a rare case of aortic valve atresia and type C interrupted aortic arch with retrograde filling of the ascending aorta via the right common carotid artery through intracranial collateralisation and a presumed intact circle of Willis, who successfully underwent a complete biventricular repair in the neonatal period.

The Clinical and Cost Utility of Cardiac Catheterizations in Infants with Bronchopulmonary Dysplasia.

Objective: To evaluate the cost-utility of catheterization-obligate treatment in preterm infants with pulmonary hypertension, as compared with empiric initiation of sildenafil based on echocardiographic findings alone.

Study Design: A Markov state transition model was constructed to simulate the clinical scenario of a preterm infant with echocardiographic evidence of pulmonary hypertension associated with bronchopulmonary dysplasia (BPD) and without congenital heart disease under consideration for the initiation of pulmonary vasodilator therapy via one of two modeled treatment strategies-empiric or catheterization-obligate. Transitional probabilities, costs and utilities were extracted from the literature.

Is biventricular vascular coupling a better indicator of ventriculo-ventricular interaction in congenital heart disease?

Background: Ventriculo-ventricular interactions are known to exist, though not well quantified. We hypothesised that the ventricular-vascular coupling ratio assessed by cardiovascular MRI would provide insight into this relationship. We also sought to compare MRI-derived ventricular-vascular coupling ratio to echocardiography and patient outcomes.