Single-shot implementation of dispersion-scan for the characterization of ultrashort laser pulses

[EN] We demonstrate a single-shot ultrafast diagnostic, based on the dispersion-scan (d-scan) technique. In this implementation, rather than translating wedges to vary the dispersion as in scanning d-scan, the pulse to be measured experiences a spatially varying amount of dispersion in a prism. The resulting beam is then imaged into a second-harmonic generation crystal and an imaging spectrometer is used to measure the two-dimensional trace, which is analyzed using the d-scan retrieval algorithm. We compare the single-shot implementation with the scanning d-scan for the measurement of sub-3.5-fs pulses from a hollow core fiber pulse compressor. We show that the retrieval algorithm used to extract amplitude and phase of the pulse provides comparable results, proving the validity of the new single-shot implementation in the near single-cycle regime. (C)2015 Optical Society of Americ

Continuous spectra in high-harmonic generation driven by multicycle laser pulses

We present observations of the emission of XUV continua in the 20-37 eV region by high harmonic generation (HHG) with $4$-$7\ \mathrm{fs}$ pulses focused onto a Kr gas jet. The underlying mechanism relies on coherent control of the relative delays and phases between individually generated attosecond pulse, achievable by adjusting the chirp of the driving pulses and the interaction geometry. Under adequate negative chirp and phase matching conditions, the resulting interpulse interference yields a continuum XUV spectrum, which is due to both microscopic and macroscopic (propagation) contributions. This technique opens the route for modifying the phase of individual attosecond pulses and for the coherent synthesis of XUV continua from multicycle driving laser pulses without the need of an isolated attosecond burst.Comment: 14 pages, 5 figures. Submitted to Physical Review

An investigation of process contaminants ’ formation during the deep frying of breadcrumbs using a bread coat model

The formation of acrylamide, hydroxymethylfurfural (HMF) and furfural was investigated in a deep fried breadcrumb coat model resembling the coat batter of breaded foods. The influence of the composition of the breadcrumb and the frying conditions on the formation of these contaminants was evaluated. Six wheat-based flour formulations of breadcrumbs were deep fried in sunflower oil at temperatures between 170–200 °C and for frying times of 1–5 minutes. Results showed significant differences in the levels of contaminants according to the concentration of the potential precursors in the breadcrumbs. HMF was influenced by the sugar content in the breadcrumbs whereas levels of acrylamide were significantly correlated with the ratio between asparagine and reducing sugars. Acrylamide, HMF and furfural were directly related to the frying time and temperature. The composition of the breadcrumb and the compounds formed during frying contributed to the total antioxidant capacity of the fried samples. The bread coat model is a useful tool in the formulation of breaded foods since it allows the evaluation of the contribution of breadcrumbs in the formation of process contaminants after frying.This research was partly funded by projects S1013/ABI-3028-AVANSECAL (Comunidad Autonoma of Madrid and FEDER program) and Spanish National Research Council (CSIC-201370E027).Peer reviewe

Risk/benefit considerations of a new formulation of wheat-based biscuit supplemented with different amounts of chia flour

The incorporation of Chia (Salvia hispanica L.) in the formulation of certain foods may be particularly desirable from a nutritional and healthy point of view. The effect of addition of chia flour on the nutritional properties and the formation of process contaminants in wheat flour-based biscuits was investigated. Higher percentage of chia flour in the formula increased the antioxidant capacity, phenolic compounds, protein, fiber and polyunsaturated fatty acids content, then resulting in a nutritionally enhanced product. However levels of process contaminants were also increased and thus acrylamide, hydroxymethylfurfural and furfural ranged between 151 and 1188 mg/kg, 22.8e71.4 mg/kg and 1.3 e5.6 mg/kg, respectively, when chia was added in a range of 0e20% of the total weight. In parallel, the formation of dicarbonyl compounds, such as methylglyoxal and glyoxal, were significantly increased with addition of 5%. Lipid oxidation, particularly polymerization compounds, was accelerated in chiaenriched biscuits, which decreased the shelf-life of the product by promoting a rapid rancidity under accelerated storage conditions. Therefore, although nutritional properties are improved by the incorporation of chia into the biscuits, the increase in the content of process contaminants and the extent of the lipid oxidation should be carefully considered in a context of risk/benefit. © 2016 Elsevier Ltd. All rights reserved.This work was funded by projects S1013/ABI-3028-AVANSECAL (CAM) and CSIC-201370E027.Peer reviewe

Fabrication and creep properties of eutectic-composition Al2O3/YAG/YSZ sintered composites

Three-phase alumina/YAG/yttria-stabilized cubic zirconia (YSZ) composites were fabricated by a solid-state reaction route starting from commercial powders of Al2O3, Y2O3 and monoclinic ZrO2. The final phases Al2O3, YAG and YSZ were obtained after calcination of the powder mixtures at 1400 °C. Dense bulk composites were obtained after sintering, with a homogeneous microstructure of fine and equiaxed grains with sizes of 1 μm. Compressive mechanical tests were performed at 1300–1450 °C in air at constant load and at constant initial strain rate. A brittle-to-ductile transition was found with increasing temperature. Grain boundary sliding is the main deformation mechanism in the ductile regime, characterized by a stress exponent of 2 and by the absence of dislocation activity and changes in grain morphology. Alumina seems to be the rate-controlling phase owing to the improvement in creep resistance by the presence of yttrium and zirconium of the other two phases.Ministerio de Ciencia e Innovación MAT2009-13979-C03-0

Orientaciones de meta en las clases de educación física : un análisis centrado en la educación secundaria obligatoria

This paper explores the subject of motivation in educational environments, more specifically in physical education. The research study it describes is based on the concept of goal perspectives (Nicholls, 1984, Dweck and Legget, 1988, Ames, 1984, Duda, 1992), and the purpose of the study was to identify the (task or ego) goal orientations shown by secondary school students in physical education classes, together with any possible differences based either on gender or the academic stage in the students education. The sample was composed of 203 secondary school students who all answered the POSQ questionnaire. From the results that were obtained, both goal orientations were observed, with a task-basedorientation predominating. It was also shown that boys are more ego oriented than girls

Human Interaction in Learning Ecosystems based on Open Source Solutions

Technological ecosystems are software solutions based on the integration of heterogeneous software components through information flows in order to provide a set of services that each component separately does not offer, as well as to improve the user experience. In particular, the learning ecosystems are technological ecosystems focused on learning and knowledge management in different contexts such as educational institutions or companies. The ecosystem metaphor comes from biology field and it has transferred to technology field to highlight the evolving component of software. Taking into account the definitions of natural ecosystems, a technological ecosystem is a set of people and software components that play the role of organisms; a series of elements that allow the ecosystem works (hardware, networks, etc.); and a set of information flows that establish the relationships between the software components, and between these and the people involved in the ecosystem. Human factor has a main role in the definition and development of this kind of solutions. In previous works, a metamodel has been defined and validated to support Model-Driven Development of learning ecosystems based on Open Source software, but the interaction in the learning ecosystem should be defined in order to complete the proposal to improve the development process of technological ecosystems. This paper presents the definition and modelling of the human interaction in learning ecosystem

Comportamiento en fritura de los aceites extraídos de la aceituna

In this article, the main studies on frying performance of olive-extracted oils, namely, virgin olive oils, olive oils and olive-pomace oils, are reviewed and discussed in relation to other vegetable oils. Firstly, the most relevant compositional data of olive-extracted oils and commonly used vegetable oils are reported, including modified seed oils developed for frying uses. The influence of the degree of unsaturation and of the minor compounds with protective effect during frying are discussed, with special reference to tocopherols, other phenolic compounds, phytosterols and squalene. Results on comparative behavior of olive-extracted oils and other vegetable oils reflect that all olive-extracted oils show great stability to thermal oxidation and are highly suitable for frying, due to their high content of oleic acid, low content of polyunsaturated fatty acids and occurrence of minor components with antioxidant activity or protective effects. Among olive-extracted oils, the scarce information published on used frying pomace-olive oils is noted.En este artículo se revisan los principales estudios sobre el comportamiento en fritura de los aceites extraídos de la aceituna, es decir, aceites de oliva virgen, de oliva y de orujo de oliva. En primer lugar se describe su composición, así como la de los aceites vegetales más utilizados y los aceites de semillas modificadas, y se comenta la influencia en fritura del grado de insaturación y de los componentes menores del aceite, especialmente tocoferoles, otros compuestos fenólicos, fitoesteroles y escualeno. Los estudios realizados en comparación con otros aceites vegetales reflejan la gran resistencia de los aceites extraídos de la aceituna a la oxidación térmica y su aptitud para la fritura, debido a sus altos contenidos en ácido oleico, bajos niveles de ácidos grasos poliinsaturados y presencia de componentes menores con actividad antioxidante o protectora. Entre los aceites extraídos de la aceituna, el comportamiento del aceite de orujo de oliva es el menos estudiado en fritura

Size and shape of supported zirconia nanoparticles determined by x-ray photoelectron spectroscopy

6 pages, 7 figures, 1 table.-- PACS: 68.55.Ac; 68.55.Jk; 79.60.DpThe initial stages of growth of zirconia nanoparticles deposited on SiO2, Y2O3, and CeO2 substrates have been studied by the x-ray photoelectron spectroscopy peak shape analysis. ZrO2 was deposited by plasma decomposition of a volatile Zr(OtBu)4 precursor. The electronic interactions at each particular interface formed have been followed by means of the modified Auger parameter of the deposited Zr cations. They were quantified by means of Wagner plots and the chemical state vectors of the systems. The observed changes in these local electronic probes as the amount of deposit was increased have been correlated to the particular ZrO2 nanostructures identified on each substrate considered. A Volmer-Weber (islands) growth mechanism has been found for all the substrates considered. Moreover, clear indications have been found of a columnar growth for the case of ZrO2 deposited on SiO2.We thank the Spanish Ministry of Science and Education (MAT2004-01558) for financial support.Peer reviewe

Transcranial direct current stimulation (tDCS) over the left prefrontal cortex does not affect time-trial self-paced cycling performance: Evidence from oscillatory brain activity and power output

To test the hypothesis that transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) influences performance in a 20-min time-trial self-paced exercise and electroencephalographic (EEG) oscillatory brain activity in a group of trained male cyclists. There were no differences (F = 0.31, p > 0.05) in power output between the stimulation conditions: anodal (235W[95%CI 222–249 W]; cathodal (235W[95%CI 222–248 W] and sham (234W[95%CI 220–248 W]. Neither heart rate, sRPE nor EEG activity were affected by tDCS (all Ps > 0.05). tDCS over the left DLFC did not affect self-paced exercise performance in trained cyclists. Moreover, tDCS did not elicit any change on oscillatory brain activity either at baseline or during exercise. Our data suggest that the effects of tDCS on endurance performance should be taken with caution.This project was supported by grants from from the Spanish Ministerio de Economía, Industria y Competitividad-PSI2016-75956-P to D. S. and M.Z., a predoctoral grant from the Spanish Ministerio de Economía, Industria y Competitividad (BES-2014-069050) to L.F.C., and a Spanish “Ministerio de Educación, Cultura y Deporte” predoctoral grant (FPU14/06229) to D.H. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript