Effect of trace elements on the interface reactions between two lead-free solders and copper or nickel substrates

Traditional Sn-Pb solder alloys are being replaced, because of environmental and health concerns about lead toxicity. Among some alternative alloy systems, the Sn-Zn and Sn-Cu base alloy systems have been studied and reveal promising properties. The reliability of a solder joint is affected by the solder/substrate interaction and the nature of the layers formed at the interface. The solder/substrate reactions, for Sn-Zn and Sn-Cu base solder alloys, were evaluated in what concerns the morphology and chemical composition of the interface layers. The effect of the addition of P, at low levels, on the chemical composition of the layers present at the interface was studied. The phases formed at the interface between the Cu or Ni substrate and a molten lead-free solder at 250º C, were studied for different stage times and alloy compositions. The melting temperatures, of the studied alloys, were determined by Differential Scanning Calorimetry (DSC). Identification of equilibrium phases formed at the interface layer, and the evaluation of their chemical composition were performed by Scanning Electron Microscopy (SEM/EDS). Different interface characteristics were obtained, namely for the alloys containing Zn. The obtained IML layer thickness was compared, for both types of alloy systems.FCT - Fundação para a Ciência e Tecnologi

English as a foreign language (EFL) homework diaries: Evaluating gains and constraints for selfregulated learning and achievement

A pesar de la importancia de la realización de los deberes escolares (tareas para casa, TPC) en el aprovechamiento académico, hoy en día existe una enorme preocupación por la baja implicación de muchos alumnos en la realización de las TPC y su efecto en el alto fracaso escolar. En este estudio, centrado en el área académica del inglés (lengua extranjera), y en base a una muestra de 591 alumnos de 5º y 6º de Educación Primaria, se analiza el rol de diferentes variables relativas a las TPC en la determinación del rendimiento académico de los estudiantes (proximal y distal), teniendo en cuenta el papel potencialmente mediador de dicha relación del uso de estrategias de autorregulación del aprendizaje y la efi cacia percibida. Los resultados obtenidos muestran que el efecto de las TPC sobre el rendimiento es indirecto, a través de las variables cognitivo-motivacionales consideradas (uso de estrategias de autorregulación del aprendizaje y la autoefi cacia). Estos resultados son discutidos en la línea de convertir la realización de las TPC como elemento clave para afrontar el elevado fracaso escolar.English as a foreign language (EFL) homework diaries: Evaluating gains and constraints for selfregulated learning and achievement. Although homework completion is said to be rather important to achievement, nowadays there is a growing concern of educators about the increasing number of students who do not engage properly on doing the homework tasks and the subsequent impact on school failure rates. Focusing on English as a Foreign Language (EFL) and using a sample of 591 Portuguese fi fth and sixth graders, the present study analyses the role played by a number of homework variables on students’ achievement (proximal and distal), and their mediating role on the use of self-regulated learning strategies and perceived self-effi cacy in the domain. Data confi rm the indirect effect of homework on school achievement, by means of the referred cognitive and motivational variables (use of self-regulated learning strategies and self-effi cacy). These fi ndings are further discussed in order to highlight the signifi cant role homework completion can play on fi ghting school failure

Grupo Trabalho Utilizadores - GTU

QRE

Revealing the last 13,500 years of environmental history from the multiproxy record of a mountain lake (Lago Enol, northern Iberian Peninsula)

This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s10933-009-9387-7.We present the Holocene sequence from Lago Enol (43°16′N, 4°59′W, 1,070 m a.s.l.), Cantabrian Mountains, northern Spain. A multiproxy analysis provided comprehensive information about regional humidity and temperature changes. The analysis included sedimentological descriptions, physical properties, organic carbon and carbonate content, mineralogy and geochemical composition together with biological proxies including diatom and ostracod assemblages. A detailed pollen study enabled reconstruction of variations in vegetation cover, which were interpreted in the context of climate changes and human impact. Four distinct stages were recognized for the last 13,500 years: (1) a cold and dry episode that includes the Younger Dryas event (13,500–11,600 cal. year BP); (2) a humid and warmer period characterizing the onset of the Holocene (11,600–8,700 cal. year BP); (3) a tendency toward a drier climate during the middle Holocene (8,700–4,650 cal. year BP); and (4) a return to humid conditions following landscape modification by human activity (pastoral activities, deforestation) in the late Holocene (4,650–2,200 cal. year BP). Superimposed on relatively stable landscape conditions (e.g. maintenance of well established forests), the typical environmental variability of the southern European region is observed at this site.The Spanish Inter-Ministry Commission of Science and Technology (CICYT), the Spanish National Parks agency, the European Commission, the Spanish Ministry of Science, and the European Social Fund

Revealing the last 13,500 years of environmental history from the multiproxy record of a mountain lake (Lago Enol, northern Iberian Peninsula)

This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s10933-009-9387-7.We present the Holocene sequence from Lago Enol (43°16′N, 4°59′W, 1,070 m a.s.l.), Cantabrian Mountains, northern Spain. A multiproxy analysis provided comprehensive information about regional humidity and temperature changes. The analysis included sedimentological descriptions, physical properties, organic carbon and carbonate content, mineralogy and geochemical composition together with biological proxies including diatom and ostracod assemblages. A detailed pollen study enabled reconstruction of variations in vegetation cover, which were interpreted in the context of climate changes and human impact. Four distinct stages were recognized for the last 13,500 years: (1) a cold and dry episode that includes the Younger Dryas event (13,500–11,600 cal. year BP); (2) a humid and warmer period characterizing the onset of the Holocene (11,600–8,700 cal. year BP); (3) a tendency toward a drier climate during the middle Holocene (8,700–4,650 cal. year BP); and (4) a return to humid conditions following landscape modification by human activity (pastoral activities, deforestation) in the late Holocene (4,650–2,200 cal. year BP). Superimposed on relatively stable landscape conditions (e.g. maintenance of well established forests), the typical environmental variability of the southern European region is observed at this site.The Spanish Inter-Ministry Commission of Science and Technology (CICYT), the Spanish National Parks agency, the European Commission, the Spanish Ministry of Science, and the European Social Fund

Farmland biodiversity and agricultural management on 237 farms in 13 European and two African regions

Farmland is a major land cover type in Europe and Africa and provides habitat for numerous species. The severe decline in farmland biodiversity of the last decades has been attributed to changes in farming practices, and organic and low-input farming are assumed to mitigate detrimental effects of agricultural intensification on biodiversity. Since the farm enterprise is the primary unit of agricultural decision making, management-related effects at the field scale need to be assessed at the farm level. Therefore, in this study, data were collected on habitat characteristics, vascular plant, earthworm, spider, and bee communities and on the corresponding agricultural management in 237 farms in 13 European and two African regions. In 15 environmental and agricultural homogeneous regions, 6–20 farms with the same farm type (e.g., arable crops, grassland, or specific permanent crops) were selected. If available, an equal number of organic and non-organic farms were randomly selected. Alternatively, farms were sampled along a gradient of management intensity. For all selected farms, the entire farmed area was mapped, which resulted in total in the mapping of 11 338 units attributed to 194 standardized habitat types, provided together with additional descriptors. On each farm, one site per available habitat type was randomly selected for species diversity investigations. Species were sampled on 2115 sites and identified to the species level by expert taxonomists. Species lists and abundance estimates are provided for each site and sampling date (one date for plants and earthworms, three dates for spiders and bees). In addition, farmers provided information about their management practices in face-to-face interviews following a standardized questionnaire. Farm management indicators for each farm are available (e.g., nitrogen input, pesticide applications, or energy input). Analyses revealed a positive effect of unproductive areas and a negative effect of intensive management on biodiversity. Communities of the four taxonomic groups strongly differed in their response to habitat characteristics, agricultural management, and regional circumstances. The data has potential for further insights into interactions of farmland biodiversity and agricultural management at site, farm, and regional scale

Propuestas y perspectivas de investigación en el área de Didáctica de la Lengua y la Literatura: nuevos horizontes en la era de lo emocional y lo poscomunicativo

Innovation in Didactics of Language and Literature is the mail core of the present monographic edition

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Mecanismos de muerte neuronal asociados a la hipoglucemia

La concentración fisiológica de la glucosa sanguínea en los humanos (80-90 mg/dl) se mantiene en este rango a través de mecanismos sistémicos altamente regulados. Cuando estos mecanismos no operan adecuadamente, la glucosa sanguínea disminuye dando lugar a un estado de hipoglucemia. La disminución de glucosa por debajo de los 20 mg/dl induce un estado de coma hipoglucémico caracterizado por el cese o aplanamiento de la actividad cerebral eléctrica. Dicho estado puede revertirse a través de la administración intravenosa de glucosa. Como consecuencia de un episodio hipoglucémico ocurre daño neuronal debido a que el cerebro es altamente dependiente del aporte sanguíneo de glucosa; la cual es la fuente de energía principal necesaria para su correcto funcionamiento. Una gran variedad de funciones celulares se alteran en condiciones de deficiencia energética; como tales: el mantenimiento de los gradientes iónicos, la liberación y recaptura de neurotransmisores, la regulación de la concentración intracelular de calcio y la función mitocondrial. Muchas evidencias señalan la articipación del glutamato como excitotoxina en la muerte neuronal hipoglucémica y recientemente; se ha propuesto que el estrés oxidativo juega un papel importante en este proceso. En esta revisión analizamos los factores que contribuyen al desarrollo de daño cerebral en hipoglucemia

Effects of glucagon-like peptide-1 and exendins on kinase activity, glucose transport and lipid metabolism in adipocytes from normal and type-2 diabetic rats

SCOPUS: ar.jinfo:eu-repo/semantics/publishe