137 research outputs found
Reforming of biomass-derived producer gas using toluene as model tar: Deactivation and regeneration studies in Ni and K-Ni catalysts
No full textChemicals and CAS Registry Numbers
carbon dioxide 124-38-9, 58561-67-4
nickel 7440-02-0
toluene 108-88-3
Carbon Dioxide
Nickel
TolueneWithin the syngas production from biomass gasification, tar removal constitutes a chief issue to overcome for advanced catalytic systems. This work investigates the performance of Ni and Ni-K catalysts for reforming of derived-biomass producer gas using toluene as model tar. At 750 °C and 60Lg-1h-1, the stability test (70 h) revealed stable performances (CO2, CH4 and C7H8 conversions of 60, 95 and 100%, correspondingly) uniquely for the Ni-K catalyst. Although the efficient protection towards coking let by K was demonstrated, TPO studies over the post-reacted systems still evidenced the presence of carbon deposits for both samples. Conducting three successive reaction/regeneration cycles with different gasifying agents (air, steam and CO2) at 800 °C for 1h, the capability towards regeneration of both catalytic systems was assessed and the spent catalysts were characterized by XRD, SEM and TEM. While none of the regeneration treatments recovered the performance of the unpromoted catalyst, the Ni-K catalysts demonstrated the capability of being fully regenerated by air and CO2 and exhibited analogous catalytic performances after a series of reaction/regeneration cycles. Hence, it is proved that the addition of K into Ni catalysts not only enhances the resistance against deactivation but enables rather facile regenerative procedures under certain atmospheres (air and CO2).Financial support for this work has been obtained from the Spanish Ministerio de Economía y Competitividad – MINECO (RTI2018-096294-B-C33 and ENE2015-66975-C3-2-R projects) co-financed by FEDER funds from the European Union and the Universidad de Sevilla-Junta de Andalucía Program under contract US-1263288. Lola Azancot acknowledges the MINECO for her associated PhD fellowship (BES-2016-0077475).Peer reviewe
[Dos Carlos (Málaga.1971)]
No full textCopia digital. España : Ministerio de Cultura y Deporte. Subdirección General de Cooperación Bibliotecari
Región e historia en la América Hispano-Colonial: Ensayo de método e hipótesis sobre la regionalización, c.1520 -c.1720
No full text
New aspects in cardiorenal syndrome and HFpEF
No full textCardiorenal syndrome (CRS) is a complex disease in which the heart and kidneys are simultaneously affected, and subsequently, the malfunction of one organ promotes the deterioration of the other. Heart failure (HF) with preserved ejection fraction (HFpEF) is the most common form of HF. The pathophysiology of CRS is not well known and several mechanisms have been proposed. An elevation of central venous pressure seems to be one of the key points to consider, among others such as an increase in intraabdominal pressure. Several diagnostic tools have been identified to establish the diagnosis of CRS in patients with HFpEF. Currently, the availability of biomarkers of renal and cardiac injury, the use of pulmonary ultrasound, the monitoring of the size of the inferior vena cava and the study of the renal venous pattern offer a new dimension in accurately diagnosing and quantifying organ damage in CRS. Beyond the symptomatic treatment of congestion, until recently specific therapeutic tools for patients with CRS and HFpEF were not available. Interestingly, the development of new drugs such as the angiotensin/neprilysin inhibitors and sodium-glucose cotransporter-2 (SGLT-2) inhibitors offer new therapeutic strategies with potential benefits in reduction of cardiorenal adverse outcomes in this population. Randomized clinical trials that focus on patients with HFpEF are currently ongoing to delineate optimal new treatments that may be able to modify their prognosis. In addition, multidisciplinary teamwork (nephrologist, cardiologist and nurse) is expected to decrease the number of visits and the rate of hospitalizations, with a subsequent patient benefit
Alteraciones de la inmunidad innata, inflamación de bajo grado y progresión de la aterosclerosis subclínica en pacientes con enfermedad renal crónica y en trasplantados renales
No full textIntroducción: La enfermedad cardiovascular se presenta de forma muy precoz en los pacientes con enfermedad renal crónica (ERC) y trasplantados renales, siendo la principal causa de mortalidad en estas poblaciones. Los factores de riesgo clásicos de enfermedad cardiovascular como la hipertensión y la diabetes son muy prevalentes en la enfermedad renal crónica pero esto no explica el enorme incremento del riesgo cardiovascular. Los factores de riesgo no clásicos como la disfunción endotelial, inflamación subclínica, las alteraciones de la Mannose binding lectin (MBL) que es un componente de la inmunidad innata, son un hecho importante en la ERC y trasplante. La presencia y progresión de aterosclerosis subclínica evaluada mediante ecografía carotidea, permite la mejor estratificación del riesgo cardiovascular. Dicho esto, el objetivo de esta tesis es evaluar si el trasplante modifica de forma independiente del grado de insuficiencia renal la presencia y progresión aterosclerosis subclínica.
Material y métodos: En dos cohortes de pacientes con enfermedad renal crónica y trasplantados renales con filtrado glomerular estimado (FG-e) <60 ml/min/1.73 m2 no en diálisis, se determinaron en la visita basal, niveles de ADMA, VEGF, ICAM-1, IL-6, TNFR2, MCP-1 y MBL, se cuantificaron el número de células progenitoras endoteliales y células circulantes endoteliales. Se realizó monitorización ambulatoria de presión arterial de 24 horas (MAPA), índice tobillo brazo, velocidad de onda de pulso (VOP) y ecografía carotidea con la cuantificación del grosor de intima media y número de placas carotideas. Se realizó seguimiento de los pacientes a los 18 meses con realización de VOP y ecografía carotidea y a los 36 meses, se realizaron MAPA 24 horas, ITB, VOP y ecografía carotidea, y se registraron los eventos renales y cardiovasculares.
Resultados: la presión arterial en la consulta fue similar en ambos grupos. La presión arterial por MAPA de 24h (133.9±14.3 vs. 126.2±16.1, P=0.014), PAS diurna (135.6±15.2 vs. 128.7±16.2, P=0.042), y PAS nocturna (131.2±16.2 vs. 120.2±17.9, P=0.0014) fue más elevada en los trasplantados renales. Además, presentaban una mayor proporción de pacientes con hipertensión arterial nocturna y non dipper (68.5% vs. 47.4%,P=0.03). Para estudiar la contribución del trasplante a esta diferencia, se incluyó en el modelo multivariado el hecho de ser trasplantado como una variable independiente, resultando que para la PAS 24h, diurna y nocturna, el trasplante era un predictor independiente para un incremento de PAS. Se observó que los trasplantados renales presentaban unos niveles de IL-6 más elevados así como una mayor proporción de pacientes con placas carotideas (55.4% vs 30%, P=.016) con respecto a los pacientes con ERC. Las variables que se asociaban a la PAS 24 horas fueron la proteinuria y los monocitos circulantes (P=.001), mientras que IL-6, creatinina sérica y el número total de placas se asociaban de forma independiente a la ausencia de caída de la presión arterial nocturna (P=.0001).
Conclusiones: La MAPA de 24 horas está más elevada en los trasplantados, a expensas de la hipertensión nocturna y presentan una mayor proporción de pacientes con hipertensión arterial nocturna y patrón "non dipper", lo que sugiere un peor perfil de riesgo cardiovascular. Existe un mayor grado de inflamación subclínica en el paciente trasplantado renal evaluado mediante el número de monocitos circulantes y los niveles de IL-6. Los pacientes trasplantados tienen más aterosclerosis subclínica que los pacientes con ERC a igualdad de función renal y proteinuria. La ausencia de caída de presión arterial o patrón "non dipper" en el trasplante se asocia a la inflamación sistémica medida mediante la IL-6 y a la carga aterosclerótica.Introduction: Cardiovascular disease is prevalent in patients with chronic kidney disease (CKD) and kidney transplants and constitutes a main cause of death in these patients. The classical cardiovascular risk factors (i.e. hypertension and diabetes) are very prevalent but they do not explain the increase of cardiovascular risk and mortality. Moreover, non-traditional cardiovascular risk factors such as endothelial dysfunction, subclinical inflammation, mannose binding lectin alterations, are important in CKD and kidney transplants recipients. The presence and progression of subclinical atherosclerosis evaluated by carotid ultrasound, allows a better stratification of cardiovascular risk in general populations and populations at risk. Thus, the aim of this doctoral thesis is evaluate if kidney transplants modify the presence and progression of subclinical atherosclerosis independently of renal function.
Material and methods: Two cohorts of patients with CKD and kidney transplants recipients with glomerular filtration rate (GFR-e) < 60 ml/min/1.73 m2 not on dialysis were included. In basal visit levels of ADMA, VEGF, ICAM-1, IL-6, TNFR2, MCP-1 and MBL were determined, number of endothelial progenitor cells and circulating endothelial cells were quantified. Ambulatory blood pressure monitoring (ABPM), ankle-brachial index, pulse wave velocity (PWV) and carotid ultrasound were performed at basal visit and 36 months of follow-up. At 18 months of follow up, a PWV and carotid ultrasound were recorded. In each visit, cardiovascular and renal events were registered.
Results: Office BP was not different between transplants and CKD patients (139.5±14.3 vs. 135.2±19.3, P=1.00, respectively). ABPM 24-hr systolic blood pressure (SBP) (133.9±14.3 vs. 126.2±16.1, P=0.014), awake SBP (135.6±15.2 vs. 128.7±16.2, P=0.042), and sleep SBP (131.2±16.2 vs. 120.2±17.9, P=0.0014) were higher in renal transplants. When patients were classified according to BP patterns associated with highest cardiovascular risk, the proportion of
patients with both nocturnal hypertension and non-dipper pattern was higher in transplants (68.5% vs. 47.4%,P=0.03). In the multivariate regression analysis, transplantation was an independent predictor of 24-hr, awake, and sleep SBP. Log IL-6 (P=.011), and total number of carotid plaques (P=.013) were higher, while the percentage decline of SBP from day to night was lower in kidney transplant recipients (P=.003). Independent predictors of 24-hour SBP were urinary protein/creatinine ratio and circulating monocytes (P=.001), while Log IL-6, serum creatinine, and total number of carotid plaques (P=.0001) were independent predictors of percentage decline of SBP from day to night.
Conclusions: Office BP is similar in kidney transplants and CKD patients with similar renal function. On the contrary, hypertension is more severe in kidney transplants when evaluated with ABPM mainly as a result of increased sleep systolic BP. Thus, precise evaluation of hypertension in kidney transplants requires ABPM. Kidney transplants presents a higher levels of IL-6 and more subclinical atherosclerosis, and subclinical atherosclerosis and systemic inflammation are associated with hypertension after transplantation
Fe-based catalysts on cellulose-derived carbon towards low-temperature RWGS
No full textThe RWGS reaction is a key pathway for converting CO2 into CO, a crucial intermediate to produce synthetic fuels and chemicals. Optimizing RWGS catalysts to enhance CO selectivity at lower temperatures facilitates integration with downstream processes such as Fischer-Tropsch synthesis. This study investigates the promotional effects of Mo, Cr, Mn, and Ce on Fe/CDC catalysts for RWGS. The catalysts were synthesized using cellulose as a biotemplate, yielding Fe/cellulose-derived carbon (Fe/CDC) catalysts. The catalysts were characterized by analyzing metal dispersion, metal-support interactions, and CO2 adsorption properties. The results for the different promoters indicate that Fe-Cr forms alloys, Fe-O-Mo species are generated, while Fe-Mn and Fe-Ce promote strong Fe-Me interactions through surface migration of the promoter. The Fe/CDC catalyst exhibited the highest CO2 conversion but the lowest CO selectivity. In contrast, Fe-Ce/CDC and Fe-Mn/CDC, which exhibit higher basicity, showed lower CO2 conversion but higher CO selectivity. This behavior is likely due to strong CO2 adsorption, which inhibits the reaction, as well as lower surface exposure of Fe, given that Ce and Mn cover Fe active sites, further affecting catalytic performance. Conversely, Fe-Mo/CDC, which has intermediate basicity, achieved the highest CO selectivity despite a lower CO2 conversion compared to the unpromoted catalyst. This suggests that Mo, not only influences adsorption properties, but also induces electronic effects through Fe-O-Mo species, promoting CO formation. These findings highlight Fe-Mo/CDC as a promising catalyst for low-temperature RWGS. Further studies are needed to elucidate the specific role of Mo in Fe-based catalysts and to optimize its catalytic performance
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