Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Validación de un modelo CFD frío para el flujo gas-sólidos en un riser del Proceso de Desintegración Catalítica, (FCC)

En el presente trabajo se valida un modelo numérico propuesto en 2D para el flujo gas-sólidos en un riser (tubo elevador) del Proceso de Desintegración Catalítica en Lecho Fluidizado (FCC). El riser tiene 0.2 m de diámetro y 14.2 m de altura y por el fondo del riser se alimenta aire de fluidización con una velocidad de 5.2 m/s, mientras que la mezcla aire­ catalizador se alimenta por las entradas laterales a una velocidad de 0.476 m/s y una fracción volumétrica de 0.6. El modelo se resuelve considerando una aproximación Euleriana-Euleriana transitoria junto con la Teorla Cinética del Flujo Granular (KTGF), con el programa ANSYS® 12.0, y usando un tamaño de paso de 1 ms, para un total de 40 s de tiempo de simulación. El modelo se valida contra datos experimentales disponibles en la literatura, y se compara con resultados numéricos obtenidos por otros investigadores. Se observa que el modelo de arrastre utilizado no estima adecuadamente el intercambio de momentum gas-sólidos y sobre-predice las velocidades axiales de las fases. Los resultados numéricos obtenidos muestran una tendencia favorable con los datos experimentales, y con los resultados numéricos previos. Para mejorar la predicción de los perfiles de flujo, en una etapa posterior se utilizará un modelo de arrastre capaz de predecir la formación de grupos (clusters) de partículas

Caracterización numérico-experimental del vórtice adyacente al escalón de un conducto con contracción

En este trabajo se presenta el análisis del comportamiento del flujo en un conducto rectangular con escalón

A Mechanical Picture of Fractal Darcy’s Law

The main goal of this manuscript is to generalize Darcy’s law from conventional calculus to fractal calculus in order to quantify the fluid flow in subterranean heterogeneous reservoirs. For this purpose, the inherent features of fractal sets are scrutinized. A set of fractal dimensions is incorporated to describe the geometry, morphology, and fractal topology of the domain under study. These characteristics are known through their Hausdorff, chemical, shortest path, and elastic backbone dimensions. Afterward, fractal continuum Darcy’s law is suggested based on the mapping of the fractal reservoir domain given in Cartesian coordinates xi into the corresponding fractal continuum domain expressed in fractal coordinates ξi by applying the relationship ξi=ϵ0(xi/ϵ0)αi−1, which possesses local fractional differential operators used in the fractal continuum calculus framework. This generalized version of Darcy’s law describes the relationship between the hydraulic gradient and flow velocity in fractal porous media at any scale including their geometry and fractal topology using the αi-parameter as the Hausdorff dimension in the fractal directions ξi, so the model captures the fractal heterogeneity and anisotropy. The equation can easily collapse to the classical Darcy’s law once we select the value of 1 for the alpha parameter. Several flow velocities are plotted to show the nonlinearity of the flow when the generalized Darcy’s law is used. These results are compared with the experimental data documented in the literature that show a good agreement in both high-velocity and low-velocity fractal Darcian flow with values of alpha equal to 0α11 and 1α12, respectively, whereas α1=1 represents the standard Darcy’s law. In that way, the alpha parameter describes the expected flow behavior which depends on two fractal dimensions: the Hausdorff dimension of a porous matrix and the fractal dimension of a cross-section area given by the intersection between the fractal matrix and a two-dimensional Cartesian plane. Also, some physical implications are discussed

Experimental numerical comparision of the pressure drop through an hydrocyclone

This paper shows the comparative results of an experimental and numerical study. The numerical simulations were performed with the ANSYS/Fluent software by means of CFD applying RNG k-&epsilon; and standard k-&omega; turbulence models. Experimental data were recorded of a hydrocyclone mounted on a test bench which operates with a water flow. The values extracted are the inlet pressure, outlet pressure, inlet velocity and outlet velocity. In order to investigate the pressure drop underwent by a hydrocyclone, a pressure assessment was carried out in different areas of the divice geometry. The results of the numerical study were compared and correlated with the experimental data. The numerical values report a percentage difference of 10.45% for the RNG k-&epsilon; model and 1.57% for the standard k-&omega; model, with respect to the experimentally obtained output pressure. The percentage difference between experimental and numerical pressure drop is 0.04% for standard k-&omega; model and 0.24% for RNG k-&epsilon; model. By studying finite volumes, the components of axial velocity, tangential velocity and turbulence intensity are calculated. These phenomena are studied simultaneously in this work. The turbulence models used to generate the corresponding analyzes in this work show similarity between both results and flow behavior. The concordance between the computational results and the experimental data is acceptable, so that the numerical simulations applied reach the purpose of this investigation

Design and Numerical Analysis of an Annular Combustion Chamber

Designing a combustion chamber for gas turbines is considered both a science and an art. This study presents a comprehensive methodology for designing an annular combustion chamber tailored to the operating conditions of a CFM-56 engine, a widely used high bypass ratio turbofan engine. The design process involved calculating the basic criteria and dimensions for the casing, liner, diffuser, and swirl, followed by an analysis of the cooling sections of the liner. Numerical simulations using NUMECA software and the HEXPRESS meshing tool were conducted to predict the combustion chamber’s behavior and performance, employing the κ-ε turbulence model and the Flamelet combustion model. Methane was used as the fuel, and simulations were performed for three fuel injection angles: axial, 45°, and 60°. Results demonstrate that the combustion chamber is properly dimensioned and achieves complete combustion for all configurations. The pressure ratio is 0.96, exceeding the minimum design criteria. Additionally, the emissions of unburned hydrocarbons are zero, while nitrogen oxides and carbon monoxide levels are below regulatory limits. These findings validate the proposed design methodology, ensuring efficient and environmentally compliant combustion chamber performance