Electrochemical behaviour of copper in potassium thiocyanate : I. Dissolution, passivation and pitting processes

The electrochemical behaviour of copper in borate buffers containing KSCN is studied by potentiostatic and potentiodynamic techniques complemented with scanning electron microscopy and EDAX. The voltammetric response can be divided into three regions. Region I is related to the formation of a Cu(SCN)ad monolayer followed by a porous tridimensional growth of CuSCN(s). A complex oxide layer containing a Cu(I) inner and a Cu(II) outer layer is formed under the CuSCN layer leading to metal passivation. At this stage of the process soluble Cu(I) and Cu(II) species are detected. Region II corresponds to the onset of Cu passivity through the formation of a complex film. The passive region extends up to a certain critical value (breakdown potential) associated with the localized corrosion of base Cu (region III). The breakdown potential decreases linearly as the KSCN concentration increases. The localized corrosion process is apparently related to the nucleation and growth of an unstable Cu(SCN)2 layer in equilibrium with Cu(SCN)−3(I). A reaction pathway is presented to account for the overall electrochemical behaviour of Cu in borate buffers containing KSCN.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Electrochemical behaviour of copper in potassium thiocyanate solution : II. Analysis of potentiostatic current transients

The kinetics of passivity and pitting corrosion of copper in borate-boric acid buffer containing potassium thiocyanate is studied at 25°C by means of potentiostatic transients recorded at different constant potential values. Three different potential regions are distinguished. Region I, as the applied potential is increased, implies the successive formation of cuprous thiocyanate, cuprous and cupric oxide. This corresponds to the formation of a composite anodic layer. Region II extends from the potential of the third anodic voltammetric peak up to the breakdown potential. Region III involves the breakdown of the passive layer caused by thiocyanate ions, and the formation of different copper salts in the pits. The kinetics of the various stages is discussed in terms of an extension of the nucleation and growth mechanism following an approach which was earlier applied for explaining the initiation and growth of pitting corrosion of metals.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Electrochemical behaviour of copper in potassium thiocyanate : I. Dissolution, passivation and pitting processes

The electrochemical behaviour of copper in borate buffers containing KSCN is studied by potentiostatic and potentiodynamic techniques complemented with scanning electron microscopy and EDAX. The voltammetric response can be divided into three regions. Region I is related to the formation of a Cu(SCN)ad monolayer followed by a porous tridimensional growth of CuSCN(s). A complex oxide layer containing a Cu(I) inner and a Cu(II) outer layer is formed under the CuSCN layer leading to metal passivation. At this stage of the process soluble Cu(I) and Cu(II) species are detected. Region II corresponds to the onset of Cu passivity through the formation of a complex film. The passive region extends up to a certain critical value (breakdown potential) associated with the localized corrosion of base Cu (region III). The breakdown potential decreases linearly as the KSCN concentration increases. The localized corrosion process is apparently related to the nucleation and growth of an unstable Cu(SCN)2 layer in equilibrium with Cu(SCN)−3(I). A reaction pathway is presented to account for the overall electrochemical behaviour of Cu in borate buffers containing KSCN.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Electrochemical behaviour of copper in potassium thiocyanate solution : II. Analysis of potentiostatic current transients

The kinetics of passivity and pitting corrosion of copper in borate-boric acid buffer containing potassium thiocyanate is studied at 25°C by means of potentiostatic transients recorded at different constant potential values. Three different potential regions are distinguished. Region I, as the applied potential is increased, implies the successive formation of cuprous thiocyanate, cuprous and cupric oxide. This corresponds to the formation of a composite anodic layer. Region II extends from the potential of the third anodic voltammetric peak up to the breakdown potential. Region III involves the breakdown of the passive layer caused by thiocyanate ions, and the formation of different copper salts in the pits. The kinetics of the various stages is discussed in terms of an extension of the nucleation and growth mechanism following an approach which was earlier applied for explaining the initiation and growth of pitting corrosion of metals.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Extralimital Senegalese species during Marine Isotope Stages 5.5 and 11 in the Canary Islands (29° N): Sea surface temperature estimates

The presence of Harpa doris Röding, 1798 in marine deposits of the last interglacial period, ~130-120 ka (marine isotope stage or MIS 5.5) in the Canary Islands (Gran Canaria, Lanzarote and Fuerteventura) enabled us to compare this occurrence with its present habitat in the Gulf of Guinea and the Cape Verde Islands, well to the south. This comparison leads to the conclusion that sea surface temperatures (SSTs) in the waters around the Canary Islands during the last interglacial period were at least 3.3 °C higher than today. H. doris is found in association with the large gastropod Persististrombus latus (Gmelin, 1791) as well as the coral Siderastrea radians (Pallas, 1766). The presence of these extralimital southern,warm-water species in the Canary Islands during the last interglacial period also implies a northward expansion of plankton-feeding larvae in seawater with a high chlorophyll-a content. Such conditionswould require a shortening of the southern arm of the cool Canary Current that dominates the waters around the Canary Islands at present. Marine deposits dating to ~400 ka (MIS 11) are also found on the Canary Islands. In these deposits, the presence of Saccostrea cucullata (Born, 1778) allows a comparison with its present habitat in the Gulf of Guinea. In this analysis, we conclude that SSTs in waters around the Canary Islands during this major interglacial period were at least 4.2 °C higher than today. Middle Pleistocene fossils of S. cucullata have also been found in the western Mediterranean Sea and Morocco, as well as the Cape Verde Islands. If these deposits also date to MIS 11, SST warming could have been a regional phenomenon, including much of the eastern Atlantic Ocean and Mediterranean Sea

Un recorrido por la arqueología del Noroeste argentino: trayectorias, diálogos y saberes (segunda parte)

Presentamos en esta oportunidad el Número Especial 2, producto de un segundo y último conjunto de trabajos presentados en las Primeras Jornadas de Arqueología del Noroeste Argentino (I JAN), organizadas por la Sociedad Argentina de Antropología (SAA) y realizadas entre el 28 de marzo y 1 de abril del año 2022 en la localidad de Tilcara (Jujuy). Estas primeras jornadas fueron un espacio de análisis y discusión para quienes investigamos en el Noroeste argentino (NOA) desde la Arqueología, provocando un encuentro académico por demás necesario luego del período de aislamiento producido por la pandemia. Las jornadas desarrolladas en salones y patios del Museo Regional de Pintura José Antonio Terry y del Instituto Interdisciplinario Tilcara (IIT-FFyL-UBA) estuvieron plagadas de intercambios formales e informales que sin duda enriquecieron el desarrollo de nuestras investigaciones. Al igual que en el Número Especial anterior, las contribuciones presentadas previamente como ponencias y posters fueron reelaboradas por sus autores en formato artículo y sometidas al sistema de arbitraje, políticas editoriales y aspectos éticos sostenidos por revista Relaciones. Este segundo número está integrado por quince artículos que abordan una amplia variedad de casos referidos a tópicos como materialidades y tecnologías, paisajes, interacciones, identidades, relaciones sociales y difusión del patrimonio.Sociedad Argentina de Antropologí

Incidence, associated factors and clinical impact of severe infections in a large, multicentric cohort of patients with systemic lupus erythematosus

OBJECTIVES: To estimate the incidence of severe infection and investigate the associated factors and clinical impact in a large systemic lupus erythematosus (SLE) retrospective cohort. METHODS: All patients in the Spanish Rheumatology Society Lupus Registry (RELESSER) who meet ?4 ACR-97 SLE criteria were retrospectively investigated for severe infections. Patients with and without infections were compared in terms of SLE severity, damage, comorbidities, and demographic characteristics. A multivariable Cox regression model was built to calculate hazard ratios (HRs) for the first infection. RESULTS: A total of 3658 SLE patients were included: 90% female, median age 32.9 years (DQ 9.7), and mean follow-up (months) 120.2 (±87.6). A total of 705 (19.3%) patients suffered ?1 severe infection. Total severe infections recorded in these patients numbered 1227. The incidence rate was 29.2 (95% CI: 27.6-30.9) infections per 1000 patient years. Time from first infection to second infection was significantly shorter than time from diagnosis to first infection (p < 0.000). Although respiratory infections were the most common (35.5%), bloodstream infections were the most frequent cause of mortality by infection (42.0%). In the Cox regression analysis, the following were all associated with infection: age at diagnosis (HR = 1.016, 95% CI: 1.009-1.023), Latin-American (Amerindian-Mestizo) ethnicity (HR = 2.151, 95% CI: 1.539-3.005), corticosteroids (?10mg/day) (HR = 1.271, 95% CI: 1.034-1.561), immunosuppressors (HR = 1.348, 95% CI: 1.079-1.684), hospitalization by SLE (HR = 2.567, 95% CI: 1.905-3.459), Katz severity index (HR = 1.160, 95% CI: 1.105-1.217), SLICC/ACR damage index (HR = 1.069, 95% CI: 1.031-1.108), and smoking (HR = 1.332, 95% CI: 1.121-1.583). Duration of antimalarial use (months) proved protective (HR = 0.998, 95% CI: 0.997-0.999). CONCLUSIONS: Severe infection constitutes a predictor of poor prognosis in SLE patients, is more common in Latin-Americans and is associated with age, previous infection, and smoking. Antimalarials exerted a protective effect.Spanish Foundation of Rheumatology. FIS/ISCIII (grant number PI11/02857). Dr. Pego-Reigosa is supported by Grant 316265 (BIOCAPS) from the European Union 7th Framework Programme (FP7/REGPOT-2012–2013.1)

Puesta en marcha y operación de un sistema combinado de tratamiento de líquidos cloacales con reactores UASB y lagunas de estabilización

Se presenta la puesta en marcha y operación de una planta piloto para el tratamiento de líquidos cloacales, consistente en dos reactores UASB (reactores anaeróbicos de flujo ascendente y manto de lodos) seguidos de cinco lagunas de estabilización (LDE) en serie. La puesta en marcha del sistema fue realizada en aproximadamente un mes. La eficiencia de remoción de Demanda Química de Oxígeno (DQO) en las etapas anaeróbicas alcanzó el 90%, con Tiempos de Retención Hidráulica (TRH) de 6 + 6 h, mientras que la eficiencia de remoción de Sólidos Suspendidos Totales y Volátiles fue 98,1 y 99,1%, respectivamente. La remoción de Coliformes Fecales (CF) en el sistema completo fue 99.9999%, con 15 d de TRH en las LDE. La remoción total de huevos de helmintos fue 99.3%. El sistema estudiado es una opción atractiva para el tratamiento de líquidos cloacales en regiones subtropicales.In this work, the start-up and operation of a pilot-scale sewage treatment plant are described. The plant consists of two UASB (upflow anaerobic sludge blanket) reactors in series followed by five waste stabilization ponds (WSP), also in series. The start-up was accomplished in approximately one month. Chemical oxygen demand (COD) removal efficiency in the anaerobic steps reached 90%, with hydraulic retention times (HRT) of 6 + 6 h, while total and volatile suspended solids (TSS/VSS) removal was 98,1 and 99,1%, respectively. Faecal Coliforms (FC) removal in the entire system was 99.9999%, with 15 d HRT in the WSP. Total removal of helminth eggs was 99.3%. The studied system is an attractive option for sewage treatment in subtropical regions.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES