Improvements to the interfacial curvature of interFoam based on (i) the smoothing of the liquid fraction field and (ii) the creation of a signed distance function (ϕ-based) are implemented. While previous work in this area has focused on evaluating spurious currents and similar configurations, the tests implemented in this work are more applicable to sprays and hydrodynamic breakup problems. For the ϕ-based method, a dual approach is developed based on a geometric reconstruction of the interface at interfacial cells and the solution of the Hamilton-Jacobi equation away from these cells. The more promising results are from this method, where the lack of convergence of Laplace pressure predictions existing in the standard version of interFoam is fixed, resulting in second-order convergence. Similar but less drastic improvements are observed for other exercises consisting of the oscillation of a droplet, a 2-phase Orr–Sommerfeld problem, the Rayleigh–Plateau instability, and the retraction of a liquid column. It is only when the dynamics are either entirely governed by surface tension or are heavily influenced by it that we see the need to substitute the standard interFoam curvature approach with a more accurate scheme. For more realistic problems, which naturally include more complicated dynamics, the difference between the standard approach and the ϕ-based approach is minimal.

PySPH is an open-source, Python-based, framework for particle methods in general and Smoothed Particle Hydrodynamics (SPH) in particular. PySPH allows a user to define a complete SPH simulation using pure Python. High-performance code is generated from this high-level Python code and executed on either multiple cores, or on GPUs, seamlessly. It also supports distributed execution using MPI. PySPH supports a wide variety of SPH schemes and formulations. These include, incompressible and compressible fluid flow, elastic dynamics, rigid body dynamics, shallow water equations, and other problems. PySPH supports a variety of boundary conditions including mirror, periodic, solid wall, and inlet/outlet boundary conditions. The package is written to facilitate reuse and reproducibility. This article discusses the overall design of PySPH and demonstrates many of its features. Several example results are shown to demonstrate the range of features that PySPH provides.

Predicting the outcome of liquid droplet collisions is an extensively studied phenomenon but the current physics based models for predicting the outcomes are poor (accuracy $\approx 43\%$). The key weakness of these models is their limited complexity. They only account for 3 features while there are many more relevant features that go unaccounted for. This limitation of traditional models can be easily overcome through machine learning modeling of the problem. In an ML setting this problem directly translates to a classification problem with 4 classes. Here we compile a large labelled dataset and tune different ML classifiers over this dataset. We evaluate the accuracy and robustness of the classifiers. ML classifiers, with accuracies over 90\%, significantly outperform the physics based models. Another key question we try to answer in this paper is whether existing knowledge of the physics based models can be exploited to boost the accuracy of the ML classifiers. We find that while this knowledge improves the accuracy marginally for small datasets, it does not improve accuracy with if larger datasets are used for training the models.

Tetralogy of Fallot with absent pulmonary valve syndrome is a rare form of congenital heart disease. Among the different variations with this rare anomaly is nonconfluent pulmonary artery branches with anomalous origin of the left pulmonary artery from the ductus arteriosus. The authors present one such case which was diagnosed prenatally to have tetralogy of Fallot with absent pulmonary valve and identified postnatally to have nonconfluent pulmonary artery branches in addition. We discuss the conundrum of respiratory management in this patient pre- and postoperatively due to a unique ventilation perfusion mismatch problem, which varies between the two lungs.

The effect of nozzle surface features on the overall atomization behavior of a liquid jet is analyzed in the present computational work by adopting three representative geometries, namely a single X-ray tomography scan of the Engine Combustion Network’s Spray A nozzle (Unprocessed), a spline reconstruction of multiple scans (Educated), and a purely external flow configuration. The latter configuration is often used in fundamental jet atomization studies. Numerically, the two-phase flow is solved based on algebraic volume-of-fluid methodology utilizing the OpenFoam solver, interFoam. Quantitative characterization of the surface features concerning the first two geometries reveals that while both of them have similar levels of cylindrical asymmetries, the nozzle configuration pertaining to the Unprocessed geometry has much larger surface features along the streamwise direction than the Educated geometry. This produces for the Unprocessed configuration a much larger degree of non-axial velocity components in the flow exiting the orifice and also a more pronounced disturbance of the liquid surface in the first few diameters downstream of the nozzle orifice. Furthermore, this heightened level of surface destabilization generates a much shorter intact liquid core length, that is, it produces faster primary atomization. The surprising aspect of this finding is that the differences between the Unprocessed and Educated geometries are of [Formula: see text](1) μm, and they are able to produce [Formula: see text](1) mm effects in the intact liquid core length. In spite of more pronounced atomization for the Unprocessed geometry, the magnitude of the turbulent liquid kinetic energy is roughly the same as the Educated geometry. This highlights the important role of mean field quantities, in particular, non-axial velocity components, in precipitating primary atomization. At the other end of the spectrum, the external-only configuration has the mildest level of surface disturbances in the near field resulting in the longest intact liquid core length.

We assessed the value of existing guidelines for the evaluation of suspected congenital heart disease (CHD) in term neonates and propose a revised algorithm. Retrospective chart review of newborns referred for cardiac evaluation at a tertiary care center was performed. A total of 777 newborns qualified for the study. Among these, 3 critical and 8 major CHD were identified. The sensitivity of the combination of abnormal physical examination and pulse oximetry screening for major and critical CHD was 100%. The cost to detect a case of critical CHD, based on echocardiograms done for all abnormal electrocardiograms, was 3.4 times more than that incurred for performing this test on the basis of abnormal pulse oximetry and physical examination. Adding electrocardiogram to CHD screening increases cost without adding diagnostic yield. Based on our findings, we propose a revised algorithm for a systematic cost-effective approach to cardiac evaluation of term newborns with suspected CHD.

BACKGROUND:Enlargement of the left atrium is a non-invasive marker of diastolic dysfunction of the left ventricle, a determinant of prognosis in children with cardiomyopathy. Similarly, N-terminal prohormone brain natriuretic peptide is a useful marker in the management of children with cardiomyopathy and heart failure. The aim of this study is to evaluate the association of left atrial pressures with left atrial volume and N-terminal prohormone brain natriuretic peptide in children with cardiomyopathy.METHODS:This was a retrospective study reviewing the medical records of patients <18 years of age, who were diagnosed with cardiomyopathy or acute myocarditis with eventual development of cardiomyopathy. Left atrial volume by transthoracic echocardiogram and pulmonary capillary wedge pressure, a surrogate of left atrial pressure, obtained by means of cardiac catheterisation were analysed. In addition, N-terminal prohormone brain natriuretic peptide levels obtained at the time of the cardiac catheterisation were also reviewed. Statistical analysis was performed to evaluate the association of left atrial pressures with left atrial volume and N-terminal prohormone brain natriuretic peptide levels.RESULTS:There was a linear correlation of left atrial pressure estimated in the cardiac catheterisation with indexed left atrial volume (r=0.63; p<0.001) and left atrial volume z-scores (r=0.59; p<0.001). We found no statistically significant association between the left atrial pressure and N-terminal prohormone brain natriuretic peptide levels.CONCLUSIONS:Left atrial volume measured non-invasively by echocardiography can be used as a surrogate for left atrial pressure in assessing diastolic dysfunction of the left ventricle in children with cardiomyopathy. The larger the size of the left atrium, worse is the diastolic function of the left ventricle.

The common Lagrangian-Eulerian modeling of liquid sprays is largely based on linear stability theory, where the associated growth rates and most unstable wavelengths are used in prescribing initial Lagrangian droplet characteristics. Using highly-resolved VoF simulations, the present work is aimed at examining the extent to which this linear stability and associated flow characteristics hold in a realistic spray configuration under normal operating conditions using the ECN spray A geometry. This involves a comparison between linear stability wavelength predictions, originating from two-phase Orr-Sommerfeld solutions, and those obtained from the VoF simulations. The results show that within the first 4 diameters beyond the orifice, the non-linear components of the Navier-Stokes have grown to 10% of the corresponding linear part in both the liquid and the gas phase, and continue to grow exponentially. The non-axial and non-fully developed flow profiles are particularly significant even within one diameter but do not develop as strongly as the non-linear components. Linear stability theory is able to adequately capture the initial surface disturbances, and there is reasonable agreement with VoF simulations, despite the fact that the base flow is not exactly the conventional one. A main finding from the work shows that while the most unstable modes are captured in the simulations and agree with theoretical predictions, these modes are not directly responsible for fragmenting the liquid core or causing primary atomization. Their action is limited to breaking up the surface of the jet, while the liquid core of the jet remains intact for another 20 jet diameters downstream. (C) 2018 Elsevier Ltd. All rights reserved.

The interphase momentum coupling and growth in interfacial mass flow rate corresponding to liquid jet injection into a quiescent gas are studied in the present work via highly-resolved simulations. It is shown that the spray formation process is composed of three regimes. In the first regime, which is closest to the nozzle, the surface of the jet undergoes interfacial perturbations and breakup; however, the internal liquid core remains intact, and the interphase momentum exchange is weak. In the second regime, primary atomization occurs, resulting in the breakup of the entire jet. Besides the creation of relatively large amounts of interfacial area, this second regime is characterized by a huge increase in the momentum coupling between the gas and liquid phases. In the last regime, both phases merge into a quasi-equilibrium state, where the atomization process is essentially complete, and both phasic velocities converge to a unique average value. In a subsequent analysis, this unique value is shown to be given by (U-inj rho(L)Omega(L)) / (rho(L)Omega(L) + rho(G)Omega(G)).

Background: Large mediastinal teratomas in the fetus are rare and can present with direct compression of intrathoracic structures as well as pericardial and pleural effusions. Mediastinal fetal teratoma may be detected as a mass in the chest during a routine prenatal ultrasound. Because of the pressure on mediastinal structures it may result in non-immune fetal hydrops (NIFH) and polyhydramnios. The development of hydrops may lead to fetal demise. Timely obstetric and/or surgical intervention is important to improve survival in this patient population. Case review: We report a case of a large mediastinal teratoma in a fetus who presented with a large pericardial effusion at 28 weeks gestation. The fetus developed NIFH at 31 weeks gestation. The fetus was successfully managed with an ex utero intrapartum therapy (EXIT) procedure which involved pericardiocentesis and surgical resection of the large teratoma. Histological examination revealed an encapsulated immature teratoma. Discussion: Mediastinal teratomas are usually detected by routine second- and third-trimester ultrasound. Large teratomas have been described to present with airway compromise and NIFH. Some cases have been managed by postnatal surgery and rare cases by EXIT procedure. Conclusions: This is the first reported case of a fetal mediastinal teratoma and severe pericardial effusion who developed NIFH, in whom EXIT procedure was successfully employed to simultaneously drain the effusion and resect the tumor.

Objective The objective of this study was to investigate the association between contrast enema (CE) and clinical sepsis (CS) in premature babies (PB) and the role of antibiotics (ABs) in its prevention.Study Design A retrospective electronic chart review of preterm babies, who underwent CE during their stay in the neonatal intensive care unit. Group I includes CEs of babies exposed to AB during or within 48 hours of the procedure. Group II represents CEs of babies, not exposed to AB. Variables for both groups were collected and analyzed.Results There were 161 CEs performed in 133 babies. The overall incidence of CS after CE in preterm babies was 21/160 cases (13%). The incidence was significantly lower in Group I (1/79, 1.2%), compared with Group II (20/81, 24.7%) (p < 0.001). Six (30%) of the 20 babies from Group II had positive blood culture and all 20 required AB after the CE. There were no statistical differences in the variables between the two groups.Conclusion There is a possible association between CE and CS in preterm babies. ABs given during or before the procedure prevent this complication.