Electrodialysis with bipolar membranes (EDBM) has drawn attention motivated by their application in generating reagents from salts. Due to the water splitting (WS) occurring at the junction of the bipolar membranes (BPMs), where the anion and cation layers are in strict contact, H+ and OH- are released from the BPM producing acid and alkali on the respective compartment. Considering this application, the interest of this work is to provide further understanding of the mechanisms of WS and transport of species in EDBM. This work develops and utilizes, for the first time, an experimentally validated two-dimensional (2-D) computational model, in which the Navier-Stokes and Nernst-Planck equations are coupled with the description of WS given by the Second Wien effect. In addition, a 1-D geometry is also proposed to perform a comparison between electroneutrality and Poisson charge conservation. The model is computationally solved using COMSOL Multiphysics. According to simulations, electroneutrality is valid for 2-D geometries. Moreover, the semipermeable characteristics of the membranes are assessed by means of evidencing a polarization effect resulting in a double-electric layer. The model proposed predicts a significant proton leakage, and facilitates the study of WS within the BPMs.

The Spanish Society for Radiological Protection (SEPR) is a scientific and technical organization that aims to bring together all radioprotection professionals from all the sectors of activity where ionizing and non-ionizing radiation is produced. The development of the SEPR's Strategic Plan every 5 years is the cornerstone of all the different activities that the Society carries out. This document establishes the SEPR goals and objectives for that period, as well as the activities planned to achieve them. It is a living and open document that draws on past experiences while looking to the future. The Strategic Plan 2019-2023, approved on June 2019, is the Third Strategic Plan of the SEPR. In its preparation, account has been taken of the experience obtained in the application of the two previous Strategic Plans, as well as of the new demands of the general public and of professionals in the area of radiological protection that have become apparent during the previous period. This paper describes the development of the current Strategic Plan, as well as the Plan itself, and briefly analyzes its implementation in the Conclusion.

El presente artículo analiza el proceso de integración del componente investigativo en el currículo de Ingeniería Agrónoma del Centro Universitario de Banes (Cuba) específicamente en metodología de la investigación. El diseño teórico – documental se fundamenta en el análisis de contenido del currículo de la mencionada oferta académica trabajada en condiciones de semipresencialidad. También se aborda un componente propositivo a través de la concepción de una propuesta centrada en tareas integradoras cuya validación se hace a través de grupos de discusión entre expertos. Como principal resultado destaca que las tareas integradoras como base de la mediación didáctica en metodología de la investigación, permiten contribuir a la problematización y profesionalización de los contenidos de la asignatura en el plan de estudio. Entre las conclusiones se evidencia la necesidad de un tratamiento metodológico interdisciplinar orientado a los objetivos de la carrera, para favorecer el desarrollo de competencias científicas en los estudiantes.

We present an apparatus for performing gas phase high-harmonic generation spectroscopy of molecules primarily found in the liquid phase. Liquid molecular samples are heated in a temperature controlled bath and their vapour is used to back a continuous flow gas jet, with vapour pressures of over 1 bar possible. In order to demonstrate the system, we perform high harmonic spectroscopy experiments in benzene with a 1.8 μm driving field. Using the unique capabilities of the system, we obtain spectra that are nearly free from the effects of longitudinal phase-matching, amenable to comparison with advanced numerical modelling.

The Spanish Pulsed Laser Centre (CLPU) is a new high-power laser facility for users. Its main system, VEGA, is a CPA Ti:Sapphire laser which, in its final phase, will be able to reach Petawatt peak powers in pulses of 30fs with a pulse contrast of 1:1010 at 1ps. The extremely low level of pre-pulse intensity makes this system ideally suited for studying the laser interaction with ultrathin targets. We have used the particle-in-cell (PIC) code OSIRIS to carry out 2D simulations of the acceleration of ions from ultrathin solid targets under the unique conditions provided by VEGA, with laser intensities up to 1022Wcm−2 impinging normally on 20–60nm thick overdense plasmas, with different polarizations and pre-plasma scale lengths. We show how signatures of the radiation pressure-dominated regime, such as layer compression and bunch formation, are only present with circular polarization. By passively shaping the density gradient of the plasma, we demonstrate an enhancement in peak energy up to tens of MeV and monoenergetic features. On the contrary linear polarization at the same intensity level causes the target to blow up, resulting in much lower energies and broader spectra. One limiting factor of Radiation Pressure Acceleration is the development of Rayleigh–Taylor like instabilities at the interface of the plasma and photon fluid. This results in the formation of bubbles in the spatial profile of laser-accelerated proton beams. These structures were previously evidenced both experimentally and theoretically. We have performed 2D simulations to characterize this bubble-like structure and report on the dependency on laser and target parameters.

We present high harmonic generation spectroscopy of haloand methy-substitued benzenes using 1.8 μm driving pulses. Compared to that of benzene, the spectra from substituted molecules decay more rapidly at higher orders. The dependence of the effect on the driving laser intensity suggests an origin in the dynamics of the ion rather than the static photorecombination cross section. The ultrafast rearrangement of atoms and molecules following excitation by an ultrashort laser pulse is of fundamental interest and is pertinent to topical open questions such as the nature of charge migration in biomolecules. Highorder harmonic generation (HHG) in a strong laser field is sensitive to electronic [1] and nuclear [2] rearrangement that occurs in the sub-cycle interval between ionization and recombination, and as such enables observation of electronic motion on the few-femtosecond timescale. Most previous studies, using 800 nm driving pulses, have examined molecules with ionization potentials above 10 eV. However many interesting and more complex molecules, such as benzene and its derivatives, have ionization potentials of 8-10 eV, so that ionization saturation prevents the generation of HHG continua at 800 nm. Additionally, dynamics are expected on timescales longer than the 2 fs available at 800 nm. Here, we present HHG spectroscopy in benzene and its haloand methyl-substituted derivatives using 1.8 μm pulses. Figure 1(a) shows the harmonic spectrum produced by 60 fs, 500 μJ, 1.8 μm pulses focused with a 50 cm lens into jet of benzene vapour produced by backing a 200 μm hole with 0.3 bar. The molecules, liquids at room temperature, are delivered by a novel heated delivery system which allows precise pressure control and convenient switching of samples. Figure 1(b) shows the harmonic amplitudes obtained in bromoand chlorobenzene normalized to those in benzene. There is a reduction in the higher orders, with the effect being stronger in chlorobenzene. Figure 1(c) shows similar behaviour in the doubly methyl-substituted mand o-xylene. We probe the origin of these differences by reducing the laser intensity and hence the spectral region sampled by the plateau. Figure 2(a) shows harmonic spectra in bromobenzene at 20 and 30 TW/cm, and Fig. 2(b) shows the harmonic amplitudes normalized to those of benzene under the same conditions. The steeper decline at the lower intensity suggests that the differences from benzene are due to dynamical processes such as nuclear motion or ionic eigenstate evolution which occur during the electron's excursion in the continuum, rather than differences in the static photorecombination cross section which depend on the harmonic frequency only.

One of the issues that needs to be studied in order to improve the durability of a PEM fuel cell system is the management of the hydrogen feeding procedure. It has been demonstrated that its efficiency and durability are improved when using a hydrogen recirculation system. In the recirculation mode, the unused gas is returned to the inlet by a pump or a compressor or using a passive device such as an ejector. Ejectors are devices used to induce a secondary fluid by momentum and energy transfer from a high energy primary jet. Their application for the recirculation system of a fuel cell is very beneficial due to their low maintenance, no moving parts and no parasitic power. In this work, an ejector has been designed to be implemented in a PEM fuel cell test station to analyze how ejector based hydrogen recirculation systems affect PEM fuel cells. The proper design of an ejector must take into account several geometrical parameters that can only be studied using Computational Fluid Dynamics (CFD). Thus, a CFD model has been implemented using the High Mach Number Flow interface in COMSOL Multiphysics with the CFD Module. The model proposed solves the problem of the ejector using an axisymmetric 2D geometry. As the density of the fluid is variable, the Favre averaged Navier-Stokes equations are used. These equations are approximated using the standard k-ε turbulence model and assuming that the gas follows the ideal gas law. The thermodynamics and transport properties for the gas are held constant. Both consistent and inconsistent stabilization methods are used. Isotropic diffusion is added to obtain an initial solution and then the problem is solved again without using it. An experimental ejector has been designed using the model and manufactured. Then, it has been tested experimentally with air to validate the model. Results showed that the model is capable of capturing the mass flows obtained for different operative conditions (Figure 1). After validating the model, the geometry of the ejector to be implemented for the PEM fuel cell test station has been obtained by carrying out a parametric study to find the optimum geometrical parameters. All the experimental tests were performed at the PEM Fuel Cells Laboratory of the "Institut de Robòtica i Informàtica Industrial" (CSIC-UPC, Barcelona, Spain) and only possible due to its advanced equipment and proficient technical staff. This work has been partially funded by the Spanish national project MESPEM (Ref. DPI2011-25649) and the Spanish Ministry of Education, Culture and Sport and UPC Fluid Mechanics Department "Beca de Colaboración". Reference He S et al. , Progress of mathematical modeling on ejectors, Renewable and Sustainable Energy Reviews 13, 1760-1780 (2009). Zhu Y, Li Y, New theoretical model for convergent nozzle ejector in the proton exchange membrane fuel cell system, Journal of Power Sources 191, 510-519 (2009). Zhu Y et al. , Numerical investigations of geometry parameters for design of high performance ejectors, Applied Thermal Engineering 29, 898-905 (2009). Figures used in the abstract Figure 1: Mass flows vs primary pressure obtained experimentally and with the model. The gas used is air. Figure 2: Results for primary pressure equal to 1.75 bar absolute. a) Temperature. b) Pressure. c) Mach Number. Figure 3: Results for primary pressure equal to 4.5 bar absolute. a) Temperature. b) Pressure. c) Mach Number.

The Spanish Pulsed Laser Centre (CLPU) is a new high-power laser facility for users. Its main system, VEGA, is a CPA Ti:Sapphire laser which, in its final phase, will be able to reach petawatt peak powers in pulses of 30 fs with a pulse contrast of 1 : 1010 at 1 ps. The extremely low level of pre-pulse intensity makes this system ideally suited for studying the laser interaction with ultrathin targets. We have used the particle-in-cell (PIC) code OSIRIS to carry out 2D simulations of the acceleration of ions from ultrathin solid targets under the unique conditions provided by VEGA, with laser intensities up to 1022Wcm-2 impinging normally on 5 - 40 nm thick overdense plasmas, with different polarizations and pre-plasma scale lengths. We show how signatures of the radiation pressure dominated regime, such as layer compression and bunch formation, are only present with circular polarization. By passively shaping the density gradient of the plasma, we demonstrate an enhancement in peak energy up to tens of MeV and monoenergetic features. On the contrary linear polarization at the same intensity level causes the target to blow up, resulting in much lower energies and broader spectra. One limiting factor of Radiation Pressure Acceleration is the development of Rayleigh-Taylor like instabilities at the interface of the plasma and photon fluid. This results in the formation of bubbles in the spatial profile of laser-accelerated proton beams. These structures were previously evidenced both experimentally and theoretically. We have performed 2D simulations to characterize this bubble-like structure and report on the dependency on laser and target parameters.

The highly increasing energy demand and reduction of available fossil energy sources have made it important to develop new techniques for energy storage, being hydrogen a good alternative for the future. That is the reason why the storage of hydrogen as an absorbed element in metal hydride bottles has been studied. To this end, a three-dimensional model of a charging process in a metal hydride container has been developed. This mathematical model has been implemented into COMSOL Multiphysics to allow obtaining results on the charging variables at different studied scenarios in order to be able to create a state of charge estimator in the future. The absorption process of hydrogen includes several mechanisms. First, hydrogen flows through the pores of the metal. Then, it is absorbed into the metal through an exothermic reaction. Consequently the metal hydride density increases due to the addition of hydrogen. A 2D-axisymmetrical model has been implemented as the bottle is cylindrical and a time dependent study has been carried out as the proposed problem has an evolution over time. Fluid flow in porous media has been modeled using Brinkman equations, temperature evolution is included with the Heat Transfer in Fluids interface and finally the density growth is calculated by the Domain ODE and DAE application mode. The generated heat is extracted applying a heat transfer coefficient between the walls of the bottle and the surrounding air, which will force the temperature to decrease in the wall region (Figure 1). The effect of the cooling level has great impact on the charging process as the hydrogen absorption rate depends on the bottle temperature. The cooler the bottle is, the higher the absorption rate and the faster the bottle will be filled (Figure 2). Besides analyzing the effect of the cooling level, a lot of parametric studies regarding metal properties have been carried out in order to discover their influence on the process. The model has been experimentally validated showing a good agreement in different operating conditions. All the experimental tests were performed at the PEM Fuel Cells Laboratory of the Institut de Robòtica i Informàtica Industrial (CSIC-UPC, Barcelona, Spain) and only possible due to its advanced equipment and proficient technical staff. This work has been partially funded by the Spanish national project MESPEM (Ref. DPI2011-25649) and the Spanish Council for Scientific Investigations JAE-INTRO2014. Reference H. Dhaou et. al., Measurement and modeling of kinetics of hydrogen sorption by LaNi5 and two related pseudobinary compounds, International Journal of Hydrogen Energy 32: 1922-27 (2007) K. Jiao et. al., Effects of various operating conditions on the hydrogen absorption processes in a metal hydride tank, Applied Energy 94: 257-269 (2012) J. Nam et. al., Three-dimensional modeling and simulation of hydrogen absorption in metal hydride hydrogen storage vessels, Applied Energy 89: 164-175 (2012) Figures used in the abstract Figure 1: Temperature Distribution inside the bottle. Time=250s and h=1652 W m-2 K-1 Figure 2: Effect of heat transfer coefficient on the evolution of temperature (left) and absorbed hydrogen fraction (right)

The collective behaviour of pondermotively-driven electrons in the interaction of an ultraintense laser pulse with a relativistically transparent target is investigated both numerically and experimentally. The 2D profile of the electrons is found to lengthen along the laser polarisation axis in the case of limited transparency. At higher degrees of transparency a double lobe structure forms in the electron beam in the orthorgonal plane to the polarisation direction. Numerical results demonstrate good agreement with the experimentally measured degree of transparency and elucidate the laser-electron dynamics of the transition to transparency.

High-order harmonic generation is as a powerful tool for the study of molecular properties. Up to now this investigation tool has been confined to simple molecules, with a relatively high ionization potential, since ionization saturation hindered its exploitation to fragile molecules. In this work we show that such limitation can be overcome by using mid-IR ultrashort driving pulses; as prototypical molecules we considered hydrocarbons. Clear signatures of the highest occupied molecular orbital were found in the harmonic spectra generated in unsaturated aligned hydrocarbons like acetylene, ethylene, allene and 1,3-butadiene. Our findings demonstrate that high-order harmonic generation spectroscopy can be extended to complex molecular species.

We make a concise review on the current research lines at the Centro de Laseres Pulsados Ultracortos Ultraintensos (CLPU) associated with Universidad de Salamanca (USAL). A broad spectrum of fundamental research and applications on intense lasers is covered in our installations.

Exploiting a few-cycle, mid-infrared laser source, we produced extended harmonic spectra in several molecules with low ionization potentials. These results pave the way to the extension of high harmonic spectroscopy to complex species like biomolecules.

We make a review of the high harmonic generation (HHG) process, its characteristics and properties, presenting our main results in the field. The HHG is a very interesting source on the deep ultraviolet region with high potential in applications such as time resolved measurements and high spatial resolution imaging.

Generation of low-order harmonics (third and fifth) of the fundamental radiation of a Q-switched Nd:YAG laser (1064 nm, pulse 15 ns) was observed in a CaF2 laser ablation plume. The ablation process is triggered by a second Q-switched Nd: YAG laser operating at 532 or 266 nm. In the scheme employed, the fundamental laser beam propagates parallel to the target surface at controllable distance and temporal delay, allowing to the probing of different regions of the freely expanding plume. The intensity of the harmonics is shown to decrease rapidly as the distance to the target is increased, and for each distance, an optimum time delay between the ablating laser pulse and the fundamental beam is found. In situ diagnosis of the plume by optical emission spectroscopy and laser-induced fluorescence serves to correlate the observed harmonic behavior with the temporally and spatially resolved composition and velocity of flight of species in the plume. It is concluded that harmonics are selectively generated by CaF species through a two-photon resonantly enhanced sum-mixing process exploiting the (B-2 Sigma(+)-X-2 Sigma(+), Delta nu = 0) transition of the molecule in the region of 530 nm. In this work polar molecules have been shown to be the dominating species for harmonic generation in an ablation plume. Implications of these results for the generation of high harmonics in strongly polar molecules which can be aligned in the ablation plasma are discussed.

The Artemis facility for ultrafast XUV science is constructed around a high average power carrier-envelope phasestabilised system, which is used to generate tuneable pulses across a wavelength range spanning the UV to the far infrared, few-cycle pulses at 800nm and short pulses of XUV radiation produced through high harmonic generation. The XUV pulses can be delivered to interaction stations for materials science and atomic and molecular physics and chemistry through two vacuum beamlines for broadband XUV or narrow-band tuneable XUV pulses. The novel XUV monochromator provides bandwidth selection and tunability while preserving the pulse duration to within 10 fs. Measurements of the XUV pulse duration using an XUV-pump IR-probe technique demonstrate that the XUV pulselength is below 30 fs for a 28 fs drive laser pulse. The materials science station, which contains a hemispherical electron analyser and five-axis manipulator cooled to 14K, is optimised for photoemission experiments with the XUV. The end-station for atomic and molecular physics and chemistry includes a velocity-map imaging detector and molecular beam source for gas-phase experiments. The facility is now fully operational and open to UK and European users for twenty weeks per year. Some of the key new scientific results obtained on the facility include: the extension of HHG imaging spectroscopy to the mid-infrared; a technique for enhancing the conversion efficiency of the XUV by combining two laser fields with non-harmonically related wavelengths; and observation of D3+ photodissociation in intense laser fields.

The emerging techniques of molecular spectroscopy by high order harmonic generation have hitherto been conducted only with Ti:Sapphire lasers which are restricted to molecules with high ionization potentials. In order to gain information on the molecular structure, a broad enough range of harmonics is required. This implies using high laser intensities which would saturate the ionization of most molecular systems of interest, e.g. organic molecules. Using a laser at 1300 nm, we are able to extend the technique to molecules with relatively low ionization potentials (approximately 11 eV), observing wide harmonic spectra reaching up to 60 eV. This energy range improves spatial resolution of the high harmonic spectroscopy to the point where interference minima in harmonic spectra of N(2)O and C(2)H(2) can be observed.

We report observations and analysis of high harmonic generation driven by a superposition of fields at 1290 nm and 780 nm. These fields are not commensurate in frequency and the superposition leads to an increase in the yield of the mid-plateau harmonics of more than two orders of magnitude compared to using the 1290 nm field alone. Significant extension of the cut-off photon energy is seen even by adding only a small amount of the 780 nm field. These observations are explained by calculations performed in the strong field approximation. Most importantly we find that enhancement is found to arise as a consequence of both increased ionization in the sum-field and modification of the electron trajectories leading to an earlier return time. The enhanced yield even when using modest intensity fields of 5 x 10(13) Wcm(-2) is extended to the 80 eV range and is a promising route to provide a greater photon number for applications in XUV imaging and time-resolved experiments at a high repetition rate.

High-order harmonic generation (HHG) from molecules produces spectra that are modulated by interferences that encode both the static structure and the electron dynamics initiated by interaction with the laser field. Using a midinfrared (mid-IR) laser at 1300 nm, we are able to study the region of the harmonic spectrum containing such interferences in CO2 over a wide range of intensities. This allows for isolation and characterization of interference minima arising due to subcycle electronic dynamics triggered by the laser field, which had previously been identified but not systematically separated. Our experimental and theoretical results demonstrate important steps toward combining attosecond temporal and angstrom-scale spatial resolution in molecular HHG imaging.

We demonstrate enhancement by 1 order of magnitude of the high-order harmonics generated in argon by combining a fundamental field at 1300 nm (10(14) W cm(-2)) and its orthogonally polarized second harmonic at 650 nm (2 × 10(13) W cm(-2)) and by controlling the relative phase between them. This extends earlier work by ensuring that the main effect is the combined field steering the electron trajectory with negligible contribution from multiphoton effects compared to the previous schemes with 800/400 nm fields. We access a broad energy range of harmonics (from 20 eV to 80 eV) at a low laser intensity (far below the ionization saturation limit) and observe deep modulation of the harmonic yield with a period of π in the relative phase. Strong field theoretical analysis reveals that this is principally due to the steering of the recolliding electron wave packet by the two-color field. Our modeling also shows that the atto chirp can be controlled, leading to production of shorter pulses.