Anomalous precursor diamagnetism at low reduced magnetic fields and the role of Tc inhomogeneities in the superconductors Pb55In45 and underdoped La1.9Sr0.1CuO4

The magnetic field dependence of the magnetization was measured above the superconducting transition in a high-Tc underdoped cuprate La1.9Sr0.1CuO4 and in a low-Tc alloy (Pb55In45). Near the superconducting transition [typically for (T-Tc)/Tc<0.05] and under low applied magnetic field amplitudes [typically for H/Hc2(0)<0.01, where Hc2(0) is the corresponding upper critical field extrapolated to T=0 K] the magnetization of both samples presents a diamagnetic contribution much larger than the one predicted by the Gaussian Ginzburg-Landau (GGL) approach for superconducting fluctuations. These anomalies have been already observed in cuprate compounds by various groups and attributed to intrinsic effects associated with the own nature of these high-Tc superconductors. However, we will see here that our results in both high and low-Tc superconductors may be explained quantitatively, and consistently with the GGL behavior observed at higher fields, by just taking into account the presence in the samples of an uniform distribution of Tc inhomogeneities. These Tc inhomogeneities, which may be in turn associated with stoichiometric inhomogeneities, were estimated from independent measurements of the temperature dependence of the field-cooled magnetic susceptibility under low applied magnetic fields.Comment: 25 pages, including 6 figures and 1 table. Typos corrected. Compacte

Autonomía y orientación en el Espacio Europeo de Educación Superior mediante el portafolio y la tutoría

En el nuevo rol del profesor y del estudiante universitario, según el cual el primero asume funciones de guía, orientador, asesor y facilitador de recursos para el aprendizaje activo del segundo, se le da más importancia al aprendizaje que a la enseñanza. En este trabajo mostramos la percepción que tienen 290 estudiantes de distintas especialidades de Magisterio y Fisioterapia sobre el uso del portafolios y de la tutoría como elementos de interés para los procesos de innovación docente (Espacio Europeo de Educación Superior). Para tal fin se ha pasado un cuestionario, efectuándose un análisis descriptivo y comparativo, obteniendo evidencias de interés

Equivariant Poincar\'e series of filtrations and topology

Earlier, for an action of a finite group $G$ on a germ of an analytic variety, an equivariant $G$-Poincar\'e series of a multi-index filtration in the ring of germs of functions on the variety was defined as an element of the Grothendieck ring of $G$-sets with an additional structure. We discuss to which extend the $G$-Poincar\'e series of a filtration defined by a set of curve or divisorial valuations on the ring of germs of analytic functions in two variables determines the (equivariant) topology of the curve or of the set of divisors

XANES Study of the Radiation Damage on Alkanethiolates-Capped Au Nanoparticles

The radiation damage during XANES experiments on alkanethiols capped gold nanoparticles has been investigated. Different carbon length chains and nanoparticle sizes have been studied. Changes in the spectra after 45 minutes of irradiation, using a bend magnet, were observed for chains with more than 6 carbon atoms and are associated with the cleavage of S-C bonds and formation of atomic sulphur on the nanoparticle surface.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

XANES Study of the Radiation Damage on Alkanethiolates-Capped Au Nanoparticles

The radiation damage during XANES experiments on alkanethiols capped gold nanoparticles has been investigated. Different carbon length chains and nanoparticle sizes have been studied. Changes in the spectra after 45 minutes of irradiation, using a bend magnet, were observed for chains with more than 6 carbon atoms and are associated with the cleavage of S-C bonds and formation of atomic sulphur on the nanoparticle surface.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Metal and semimetal loadings in sediments and water from mangrove ecosystems: A preliminary assessment of anthropogenic enrichment in São Tomé island (central Africa)

Mangroves act as buffer areas for marine systems, providing a barrier to contamination from continental sources by retaining metal pollutants. This study evaluates metal and semimetal contamination in the water column and sediments of four mangroves located on the volcanic island of São Tomé. Several metals had a widespread distribution, with occasional high concentrations, linked to potential sources of contamination. However, the two smaller mangroves, located in the northern part of the island, tended to have high metal concentrations. Arsenic and chromium concentrations were notably concerning, particularly if we consider this is an isolated and non-industrialized island. This work highlights the need for further assessments and a better understanding of processes and implications of metal contamination in mangroves. This assumes a particular relevance in areas that have specific geochemical compositions (i.e., volcanic origin) and in developing countries, where people often rely directly and heavily on resources obtained from these ecosystems.info:eu-repo/semantics/publishedVersio

Branqueamento e caracterização físico-química de fibras do cacho/ráquis de bocaiuva no Pantanal Sul Mato-Grossense.

O presente trabalho tem por objetivo realizar o branqueamento e a caracterização das fibras do cacho com ráquis da bocaiuva

Desempenho de desfibrador comercial para espécies vegetais do Pantanal.

Este trabalho teve por finalidade avaliar o desempenho de um desfibrador mecânico comercial de cana-de-açúcar quanto à sua eficiência para a remoção de fibras para as espécies do gravatá, carandá e da bocaiuva em escala de bancada

Avaliação de um desfibrador mecânico comercial para algumas espécies nativas do Pantanal de Corumbá.

No Brasil, a produção de fibras de coco, sisal e curauá são feitas por comunidades nos estados do Norte e Nordeste exemplos de biomassas vegetais usualmente empregadas, em vários países, como fonte de celulose e lignina. A celulose extraída pode ser tratada, por hidrólise ácida, para obtenção de nanocristais de celulose, material de alto valor agregado, reforço em matrizes poliméricas, que melhora as suas propriedades mecânicas e de barreira. A lignina é um coproduto usualmente obtido a partir da produção de pastas celulósicas e de papel. Seu interesse vem crescendo em virtude do aumento na sua demanda para uso como ligante, dispersante, dentre outros, não se limitando apenas a produção de energia. O processo de extração da fibra é feito por esmagamento e raspagem mecânica para remoção da fibra e posterior secagem. O desfibramento mecânico do sisal é geralmente feito com uma desfibradora conhecida como “paraibana”, do tipo itinerante e de baixa capacidade de processamento e alimentação manual, em que todo o resíduo da extração é descartado no campo. Este equipamento de fabricação rústica oferece riscos para o operador, apesar de algumas modificações terem sido introduzidas para a melhoria de sua segurança. Os equipamentos utilizados para a extração da fibra de sisal são também utilizados para a extração de outras fibras vegetais, dentre as quais são incluídas as fibras do cânhamo, abacá, juta e correlatas. Portanto, há necessidade de avanços tecnológicos de processos e de equipamentos voltados para a extração de fibra de espécies vegetais no Brasil. Esse gargalo fica mais evidente pois pouco se conhece sobre o uso e/ou a adaptação de desfibradores mecânicos comerciais ou protótipos visando a extração de fibras de espécies vegetais nativas

Abundance of Anchovy eggs by CUFES: Inter-annual fluctuations and spatial patterns.

Data on the abundance of Anchovy eggs in the Gulf of Cadiz as collected by CUFES are explored in the present work in relation to their spatial pattern and inter-annual fluctuations. These data were gathered in 12 summer surveys, both acoustic (ECOCADIZ series) and DEPM (BOCADEVA series) ones, since 2004 to date (no survey in 2012). A total of 1499 CUFES stations were sampled, which distributed from the strait of Gibraltar, in Spain, to Cape San Vicente, in Portugal (in 2010 to Cape Sta. Maria only). The sampling scheme consisted in a grid of 21 parallel transects, normal to the shoreline and inter-spaced 8 nm, with the samples being collected every 3 nm at a c.a. 600 l/min flow with a 335 μm mesh size net and at a sampling depth of 5 m from the surface. A continuous record of SST and SSS at 5 m (termosalinometer) was coupled to the CUFES sampling. The surveys were carried out in June, July or August depending on the year. Oceanographic variables such as temperature, salinity and chlorophyll, and even the bottom topography of the shelf as well, they all showed significantly different in two regions: to the East and West of the Cape S. Mª. The density of Anchovy eggs presents a high variability between stations showing a very patched distribution. The stations with most eggs are located to the East of Cape Sta. Mª. Egg abundance also showed a very high between-year variability, ranging from 2955 eggs in 2005 to 41941 eggs collected in 2014. Regarding the spatial pattern of egg distribution, the 84.9% of the total egg density (all the surveys pooled) was collected in the area east of the Cape Sta. Mª (37.4 % in 2016), and the 89.8 % of total egg density in stations bellow 100 m depth (47.9 % in 2016). What happened in 2016? The mean temperature registered in 2016 in the Western stratum (22.0ºC) was practically the same that the mean temperature registered from 2004 to 2015 in the Eastern stratum (21.7ºC). The analysis of the centers of gravity of the eggs densities vs longitude and depth show significant trends, but not for latitude, which indicate a displacement towards the West in 2016. However, no trends were found in the centers of gravity of the acoustic energy (NASC) as a proxy of adults. Is then the westward displacement of the spawning in 2016 caused by an advective transport (currents and/or winds) or by other causes? What will be the further effect on recruitment? It would be good to obtain a statistical model in order to explain how the different variables affect the abundance of eggs, including other variables like the wind, tide... The presence of deep canyons crossing the shelf in the East of Cape Sta. Mª indicates that distance to the coast would be a better variable than depth