6 research outputs found
Life test of a high temperature PEM fuel cell prepared by electrospray
A life test has been conducted to a PBI-based membrane-electrode assembly (MEA) in which the anode and cathode catalyst layers were prepared by electrospray and results were compared with a previous study in which the catalyst layer was prepared by airbrushing. During the study, the average and local current density were continually monitored and several diagnostic techniques were periodically applied, including polarization curves, cyclic voltammetries, electrochemical impedance spectroscopy and computational fluid dynamics modelling (CFD). Results show that significantly better fuel cell performance is achieved by the electrosprayed MEA, by about 40%, as compared with the MEA prepared by traditional airbrushing with the same catalyst loading. According to the experimental measurements, the higher electrochemical active surface area and more favourable mass transport are the main responsible for the improved yield. Modelling estimations agree with experimental observations and corroborate better mass transport properties of the catalyst layer when using electrospray. This can be explained by a more appropriate morphology of the layer. No evidence of positive effects on the lifetime of the fuel cell was found out. At the end of the lifetest, the local concentrations of platinum (Pt) and phosphorus (P) in the degraded MEA were analysed and a correlation between Pt loading profile and local current distribution could be established.Se ha realizado una prueba de vida a un conjunto de membrana-electrodo (MEA) basado en PBI en el que las capas de catalizador de ánodo y cátodo se prepararon mediante electropulverizaciĂłn y los resultados se compararon con un estudio anterior en el que la capa de catalizador se preparĂł mediante aerografĂa. Durante el estudio, se monitoreĂł continuamente la densidad de corriente promedio y local y se aplicaron periĂłdicamente varias tĂ©cnicas de diagnĂłstico, incluidas curvas de polarizaciĂłn, voltamperometrĂas cĂclicas, espectroscopĂa de impedancia electroquĂmica y modelado de dinámica de fluidos computacional (CFD). Los resultados muestran que se logra un rendimiento significativamente mejor de la celda de combustible mediante el MEA electropulverizado, en aproximadamente un 40%, en comparaciĂłn con el MEA preparado mediante aerografĂa tradicional con la misma carga de catalizador. SegĂşn las mediciones experimentales, la mayor superficie activa electroquĂmica y el transporte de masa más favorable son los principales responsables de la mejora del rendimiento. Las estimaciones de modelado concuerdan con las observaciones experimentales y corroboran mejores propiedades de transporte de masa de la capa de catalizador cuando se usa electropulverizaciĂłn. Esto puede explicarse por una morfologĂa más apropiada de la capa. No se encontrĂł evidencia de efectos positivos sobre la vida Ăştil de la pila de combustible. Al final de la prueba de vida, se analizaron las concentraciones locales de platino (Pt) y fĂłsforo (P) en el MEA degradado y se pudo establecer una correlaciĂłn entre el perfil de carga de Pt y la distribuciĂłn de la corriente local. Las estimaciones de modelado concuerdan con las observaciones experimentales y corroboran mejores propiedades de transporte de masa de la capa de catalizador cuando se usa electropulverizaciĂłn. Esto puede explicarse por una morfologĂa más apropiada de la capa. No se encontrĂł evidencia de efectos positivos sobre la vida Ăştil de la pila de combustible. Al final de la prueba de vida, se analizaron las concentraciones locales de platino (Pt) y fĂłsforo (P) en el MEA degradado y se pudo establecer una correlaciĂłn entre el perfil de carga de Pt y la distribuciĂłn de la corriente local. Las estimaciones de modelado concuerdan con las observaciones experimentales y corroboran mejores propiedades de transporte de masa de la capa de catalizador cuando se usa electropulverizaciĂłn. Esto puede explicarse por una morfologĂa más apropiada de la capa. No se encontrĂł evidencia de efectos positivos sobre la vida Ăştil de la pila de combustible. Al final de la prueba de vida, se analizaron las concentraciones locales de platino (Pt) y fĂłsforo (P) en el MEA degradado y se pudo establecer una correlaciĂłn entre el perfil de carga de Pt y la distribuciĂłn de la corriente local
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
Desarrollo de catalizadores metálicos soportados para la reacción de reformado seco de metano
Tesis doctoral inĂ©dita leĂda en la Universidad AutĂłnoma de Madrid, Facultad de Ciencias, Departamento de FĂsica-QuĂmica Aplicada. Fecha de lectura: 18-03-199
Durable corrosion-resistant coating based in graphene oxide for cost-effective fuel cells components
Summary: The current imperative transition to environmentally friendly technologies for power generation requires the reduction of their production costs. In the case of proton exchange membrane fuel cells, current collectors, which are usually integrated as flow field plates in the cells, constitute a critical component due to its weight and cost. In this paper, a cost-effective alternative is proposed, which is based in copper as conductive substrate. The protection of this metal in the aggressive media resulting from the operation conditions is the principal challenge. A continuous reduced graphene oxide coating has been developed to avoid corrosion under operation. The results of the protection behavior of this coating under accelerated stress tests performed in a real fuel cell reveal that the cost-effective procedure for copper coating is able to compete with gold-plated nickel collectors and constitute a real alternative to reduce the production costs and the weight of these systems