Large Eddy Simulation based Analysis of Complex Flow Structures within the Volute of a Vaneless Centrifugal Pump

Centrifugal pumps are very common in many fluid handling industrial applications, such as petrochemicals, oil and gas etc. Although the design practices for centrifugal pumps are well established, efforts are directed towards optimising such systems for better operational efficiencies. In order to optimally design centrifugal pumps, it is beneficial to first understand the complex flow phenomena within different sections of the pump for a variety of operating conditions. This is normally achieved through the use of modern techniques, such as Computational Fluid Dynamics (CFD), where the flow within centrifugal pumps can be numerically modelled and important flow features can be analysed for better understanding of interactions amongst different process variables. CFD offers different turbulence modelling techniques with an aim to predict realistic flow approximations. Larger Eddy Simulation (LES) offers a more accurate solution to this, in which the larger eddies are resolved while smaller eddies are modelled, hence predictions using LES are more realistic. Further to turbulence modelling within centrifugal pumps, it is also important to model the complete interaction amongst different variables rather than a simplistic single blade passage flow analysis. In the present work, the complex blade-tongue interactions, and their consequent effects on the pressure fluctuations within the volute have been evaluated. It is seen that the secondary flow features in the near tongue regions due to blade interactions with the tongue, affect the flow characteristics within the volute considerably

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

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 middle-income 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 low-income 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 low-income, 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

Detecting Iron Deficiency in Anemic Patients with Concomitant Medical Problems

OBJECTIVE: To determine the sensitivity and specificity of mean corpuscular volume, transferrin saturation, total iron-binding capacity, and ferritin level in determining iron deficiency in a population of anemic veterans with a wide variety of general medical diagnoses. DESIGN: Retrospective chart review. SETTING: Hospitals of the Department of Veterans Affairs in Madison and Milwaukee, Wisconsin. PARTICIPANTS: One hundred one anemic veterans with any medical condition who underwent bone marrow aspiration and serum iron studies. MEASUREMENTS AND MAIN RESULTS: Using the presence or absence of bone marrow hemosiderin as the reference standard, the sensitivity and specificity of the following serum iron indicators were calculated: mean corpuscular volume, transferrin saturation, total iron-binding capacity, and ferritin level. Of these patients, 41 (40.6%) were categorized as iron deficient, with no stainable bone marrow hemosiderin. A serum ferritin level ≤100 μg/L provided the best sensitivity (64.9%) and specificity (96.1%) for evaluating iron stores in this patient population. When performed within 24 hours of bone marrow examination, a serum ferritin level ≤100 μg/L was 100% accurate in separating iron-deficient from iron-sufficient patients. None of the other serum iron indicators alone or in combination performed better than ferritin level alone. CONCLUSIONS: In a population of anemic veterans with a wide variety of concomitant medical problems, a serum ferritin level ≤100 μg/L was optimal for determining iron deficiency. This is higher than the ferritin level of ≤50 μg/L cited in standard textbooks as evidence of iron deficiency in patients with inflammation, infection, or malignancy