Drift instability of standing Faraday waves

We consider the weakly nonlinear evolution of the Faraday waves produced in a vertically vibrated two-dimensional liquid layer, at small viscosity. It is seen that the surface wave evolves to a drifting standing wave, namely a wave that is standing in a moving reference frame. This wave is determined up to a spatial phase, whose calculation requires consideration of the associated mean flow. This is just the streaming flow generated in the boundary layer attached to the lower plate supporting the liquid. A system of equations is derived for the coupled slow evolution of the spatial phase and the streaming flow. These equations are numerically integrated to show that the simplest reflection symmetric steady state (the usual array of counter-rotating eddies below the surface wave) becomes unstable for realistic values of the parameters. The new states include limit cycles (the array of eddies oscillating laterally), drifted standing waves (patterns that are standing in a uniformly propagating reference frame) and some more complex attractors

The effect of surface contamination on the drift instability of standing Faraday waves

We consider the effect of surface contamination, modelled by Marangoni elasticity with insoluble surfactant and surface viscosity, in promoting drift instabilities in spatially uniform standing Faraday waves. It is seen that contamination enhances drift instabilities that lead to various steadily propagating and (both standing and propagating) oscillatory patterns. In particular, steadily propagating waves appear to be quite robust, as a seminal experiment by Douady, Fauve & Thual (1989)

Effect of a Thin Floating Fluid Layer in Parametrically Forced Waves

In order to describe correctly on-board experiments, where residual acceleration can have a significant impact in the fluid motion, we consider the effect of a thin immiscible fluid layer on top of a liquid substrate in incrementing the damping and promoting drift instabilities in spatially uniform standing Faraday waves. It is seen that the effective surface viscosity of the newtonian liquid film enhances drift instabilities that lead to various steadily travelling and standing and travelling oscillatory patterns, among others. In particular, travelling waves appear to be the primary instability of the basic standing wave for deep water problem

Methanol and ammonia as emerging green fuels: Evaluation of a new power generation paradigm

[EN]In the current context of the energy transition, the use of liquid fuels is attracting attention to be used as energy storage, due to the inherent fluctuations of the main renewable energy sources. In addition, these liquid fuels have also been proposed as energy carriers, to introduce renewables in hard-to-electrify applications. Methanol and ammonia emerge as the two most promising green liquid fuels for energy purposes. In this work, a systematic assessment of the transformation of methanol/ammonia into power is performed. Two different routes have been studied: thermochemical (through fuel combustion) and electrochemical (using fuel cells). From a technical analysis, the methanol process reaches the highest efficiency, around 38%. In general, thermochemical processes show better performance in terms of energy efficiency. From an economic perspective, the current costs of the thermochemical route are around 0.3 €/kWh and 0.6-1 €/kWh for the electrochemical. Electricity cost is expected to be reduced as process efficiency increases down to values of around 0.1 €/kWh. A progressive introduction of these green liquid fuels will be necessary to achieve a 100% renewable energy system in all areas, guaranteeing the long-term sustainability of the planet

Evaluating ammonia as green fuel for power generation: A thermo-chemical perspective

[EN]Energy storage will be necessary for a future power system with high penetration of renewable sources, mainly, wind and solar, to ensure the stability of the grid. In this context, power-to-chemicals is a promising concept for a medium/long-term storage horizon and a wide range of capacities. Within this alternative, ammonia rises as one of the fuels with the highest potential in a scenario targeting decarbonization. The first step is the production of ammonia using renewable energy sources, followed by its transfor mation into energy. This second area requires a deeper analysis at process scale in order to introduce this technology into the future power system. In this work, an assessment of an ammonia-based power plant is presented, focusing on the thermo-chemical route. A combined cycle is evaluated, considering different gas clean-up technologies to re cover valuable components and comply with environmental restrictions. As a result, the total efficiency of the power facility reaches about 40%, limited by the maximum temperature allowed in the gas turbine. The influence of the price of ammonia is also evaluated due to the paramount importance of this parameter. The production cost ranges from 0.2 to 0.6 €/kWh, with the lowest level corresponding to a scenario in which there is a significant reduction in the cost of renewable power generation and electrol ysis technology. Therefore, the feasibility of the use of ammonia as an energy storage alternative is demonstrated, providing a powerful platform for the implementation of a power grid with high penetration of fluctuating sources

Optimisation of the production of fermentable monosaccharides from algal biomass grown in photobioreactors treating wastewater

Producción CientíficaBiomass grown in wastewater treatment photobioreactors is a cheap raw material with high contents of carbohydrates, proteins and lipids. This work studies the production of fermentable monosaccharides from three biomasses grown in piggery wastewater (P), domestic wastewater (W) and synthetic medium (S) by applying chemical pretreatment and enzymatic hydrolysis, using a Taguchi design. ANOVA identified temperature, chemical reagent type and chemical reagent concentration as significant operational parameters. However, the biomass concentration, pretreatment time, enzyme dosage and enzymatic hydrolysis time had no remarkable effect. The bacterial content of the biomass had no relevant impact on carbohydrate and protein solubilisation but had a remarkable effect on the degradation of the released carbohydrates (57, 60 and 37% for P, W and S), while also affecting lipid solubilisation. Pretreatment with HCl 2 M at 120 °C resulted the optimal conditions, achieving a monosaccharide recovery of 53, 59 and 80% for P, W and S biomasses, respectively.Gobierno regional de Castilla y León (UIC 071, CLU 2017-09 and VA080G18)Ministerio de Ciencia, Innovación y Universidades (project CTQ2017-84006-C3-1-R)Unión Europea - FEDER (CLU 2017-09 and CTQ2017-84006-C3-1-R

Mean Flow Effects in the Faraday Instability

We study the weakly nonlinear evolution of Faraday waves in a 2D container that is vertically vibrated. In the small viscosity limit, the evolution of the surface waves is coupled to a non-oscillatory mean flow that develops in the bulk of the container. The corresponding long time (Navier-Stokes+amplitude) equations are derived and analyzed numerically. The results indicate that the (usually ignored) mean flow plays an essential role in the stability of the surface waves and in the bifurcated wave patterns

Mathematical formulation and comparison of solution approaches for the vehicle routing problem with access time windows

The application of the principles of sustainability to the implementation of urban freight policies requires the estimation of all the costs and externalities involved. We focus here on the case of access time windows, which ban the access of freight vehicles to central urban areas in many European cities. Even though this measure seeks to reduce congestion and emissions in the most crowded periods of the day, it also imposes additional costs for carriers and results in higher emissions and energy consumption. We present here a mathematical model for the Vehicle Routing Problem with Access TimeWindows, a variant of the VRP suitable for planning delivery routes in a city subject to this type of accessibility restriction.We use the model to find exact solutions to small problem instances based on a case study and then compare the performance over larger instances of a modified savings algorithm, a genetic algorithm, and a tabu search procedure, with the results showing no clear prevalence of any of them, but confirming the significance of those additional costs and externalities.Ministerio de Economía y Competitividad EC2013-47286-C3-3-

Nuevas estrategias farmacológicas en el tratamiento de las complicaciones de la obesidad. Alirocumab y Evolocumab como nuevo tratamiento para la dislipemia

La dislipemia es una de las principales consecuencias de la obesidad. Las estatinas están consideradas como un tratamiento seguro y eficaz de esta patología pero en ciertas situaciones clínicas el riesgo cardiovascular todavía permanece. Sin embargo, anticuerpos monoclonales como alirocumab y evolocumab se han introducido recientemente en el mercado. Su diana terapéutica es la PCSK9, proproteína convertasa subtilisina /kexina tipo 9, que se une al receptor LDL bloqueando la eliminación del colesterol de la sangre. La inhibición de la PCSK9 incrementará proporcionalmente los R-LDL y disminuirá los niveles de colesterol LDL. Discutiremos los beneficios de estas alternativas farmacológicas usando como base ensayos clínicos que han sido desarrollados en dos programas importantes

Oncogenic Sox2 regulates and cooperates with VRK1 in cell cycle progression and differentiation.

Sox2 is a pluripotency transcription factor that as an oncogene can also regulate cell proliferation. Therefore, genes implicated in several different aspects of cell proliferation, such as the VRK1 chromatin-kinase, are candidates to be targets of Sox2. Sox 2 and VRK1 colocalize in nuclei of proliferating cells forming a stable complex. Sox2 knockdown abrogates VRK1 gene expression. Depletion of either Sox2 or VRK1 caused a reduction of cell proliferation. Sox2 up-regulates VRK1 expression and both proteins cooperate in the activation of CCND1. The accumulation of VRK1 protein downregulates SOX2 expression and both proteins are lost in terminally differentiated cells. Induction of neural differentiation with retinoic acid resulted in downregulation of Sox2 and VRK1 that inversely correlated with the expression of differentiation markers such as N-cadherin, Pax6, mH2A1.2 and mH2A2. Differentiation-associated macro histones mH2A1.2and mH2A2 inhibit CCND1 and VRK1 expression and also block the activation of the VRK1 promoter by Sox2. VRK1 is a downstream target of Sox2 and both form an autoregulatory loop in epithelial cell differentiation.Ministerio de Economía y Competitividad [SAF2013-44810R, SAF2014-57791-REDC].Consejería de Educación de la Junta de Castilla y León [CSI002U14 and UIC-017] to P.A.L