Are Gauss-Legendre methods useful in molecular dynamics?

AbstractWe apply the two-stage Gauss-Legendre method to the numerical simulation of liquid argon, a typical problem in molecular dynamics. It is found that the scheme is less efficient than the Verlet/leapfrog method, standard in this sort of simulation

Crystal Nucleation by Laser-Induced Cavitation\ud

High-speed and high-resolution photography have been used to investigate the relationship between creation, expansion, and collapse of a vapor cavity induced by a 6 ns laser pulse and the subsequent nucleation of crystals. A thin layer of supersaturated aqueous solutions of (NH4)2SO4 and KMnO4 was confined between two glass plates with a separation of 50 and 100 μm. The expansion and collapse of the laser-induced vapor bubble occurred over a total time scale of 200 μs, while the first identifiable crystal appears one second after the laser pulse. Crystals were observed to form on a ring with a diameter of 70 μm centered in the focal point of the laser. The ring is preceded by an optical disturbance observed through the cavity around 30–50 μs after the laser pulse and vapor cavity formation. This ring-shaped optical disturbance originates from changes in refractive index induced by crystal nuclei formation. The formation of the nuclei most probably coincides with the formation of the bubble, when the rate of evaporation and the supersaturation are at their maxima. Apparently, it takes the nuclei around 30–50 μs to grow to a particle size with a visible optical disturbanc

Ratchet universality in the bidirectional escape from a symmetric potential well

The present work discusses symmetry-breaking-induced bidirectional escape from a symmetric metastable potential well by the application of zero-average periodic forces in the presence of dissipation. We characterized the interplay between heteroclinic instabilities leading to chaotic escape and breaking of a generalized parity symmetry leading to directed ratchet escape to an attractor either at infinity or at -infinity. Optimal enhancement of directed ratchet escape is found to occur when the wave form of the zero-average periodic force acting on the damped driven oscillator matches as closely as possible to a universal wave form, as predicted by the theory of ratchet universality. Specifically, the optimal approximation to the universal force triggers the almost complete destruction of the nonescaping basin for driving amplitudes which are systematically lower than those corresponding to a symmetric periodic force having the same period. We expect that this work could be potentially useful in the control of elementary dynamic processes characterized by multidirectional escape from a potential well, such as forced chaotic scattering and laser-induced dissociation of molecular systems, among others

A modeling framework for predicting the effect of the operating conditions and component sizing on fuel cell degradation and performance for automotive applications

[EN] In this study, durability and performance prediction were integrated in the sizing process of the FC stack of a fuel cell range-extender (FCREx) vehicle together with the design of a dynamics-limited control strategy. For that purpose, a FCREx vehicle model integrating a FC stack, balance of plant, battery, H-2 tank and vehicle body (C-class SUV) validated in previous studies was used. To predict FC stack degradation rate, a novel semi-empirical multi-layered degradation modeling framework for automotive application is proposed and developed. Degradation rates are calculated based on reference degradation rates measured at reference and known conditions (1st layer) and scaled with the electrochemical phenomena (2nd layer) and the operating conditions (3rd layer) through scaling functions based on physical tendencies. Results show how increasing the FC stack power decreases H-2 consumption but increases durability, while increasing the dynamic limitations on the control strategy increases both H-2 consumption and durability. The isolated effect of sizing implied a decrease in H-2 consumption of-3% and an increase in FC stack durability of similar to 53% when comparing the 40 kW and 100 kW designs. In contrast, the effect of dynamic limitations was significantly perceived in the 40 kW design which implied an increase in H-2 consumption close to 8% and an increase in durability of 294% when comparing the infinite dynamics and the highest dynamically restricted cases. Nevertheless, the effect of sizing is neglected under high dynamic limitation and limiting the current density change rate to 0.001 A/cm(2) s may prevent the control strategy from fulfilling the charge sustaining mode in aggressive driving. Based on these results, a set of recommendations were elaborated for FC stack and FCV manufacturers aiming to apply FCREx architecture to passenger car vehicles.This research has been partially funded by the Spanish Ministry of Science, Innovation, and University through the University Faculty Training (FPU) program (FPU19/00550) and FEDER and the Generalitat Valenciana, Consellera dInnovaci, Universitats, Ciencia i Societat Digital through project IDIFEDER/2021/039.Desantes J.M.; Novella Rosa, R.; Pla Moreno, B.; López-Juárez, M. (2022). A modeling framework for predicting the effect of the operating conditions and component sizing on fuel cell degradation and performance for automotive applications. Applied Energy. 317:1-17. https://doi.org/10.1016/j.apenergy.2022.11913711731

Transcriptomics and the mediterranean diet: A systematic review

The Mediterranean diet has been proven to be highly effective in the prevention of cardiovascular diseases and cancer and in decreasing overall mortality. Nowadays, transcriptomics is gaining particular relevance due to the existence of non-coding RNAs capable of regulating many biological processes. The present work describes a systematic review of current evidence supporting the influence of the Mediterranean diet on transcriptomes of different tissues in various experimental models. While information on regulatory RNA is very limited, they seem to contribute to the effect. Special attention has been given to the oily matrix of virgin olive oil. In this regard, monounsaturated fatty acid-rich diets prevented the expression of inflammatory genes in different tissues, an action also observed after the administration of olive oil phenolic compounds. Among these, tyrosol, hydroxytyrosol, and secoiridoids have been found to be particularly effective in cell cycle expression. Less explored terpenes, such as oleanolic acid, are important modulators of circadian clock genes. The wide range of studied tissues and organisms indicate that response to these compounds is universal and poses an important level of complexity considering the different genes expressed in each tissue and the number of different tissues in an organism

La plaqueta pintada del yacimiento epipaleolítico de Picamoixons (Alt Camp, Tarragona) : aproximación al estudio de la cadena operativa

En este trabajo se presenta el estudio realizado sobre una plaqueta pintada localizada en el yacimiento de Picamoixons, cuya cronología oscila entre 9.l70±80 y 11.050±90 B.P. A su vez se desarrolla una metodología referida al medio de aplicación de la pintura mediante las técnicas digital, pincel y "a crayon", en base a un programa experimental. Se describen los primeros resultados y su aplicación a la plaqueta de Picamoixons.In this work we present the study concerning a painted tablet on limestone located at the Picamoixons site, whose dating stands between 9.170±80 and 11.050±90 B.P. At the same time, a methodology is currently being developed regarding the means of application of (he painting through the digital, paintbrush and "a crayon" techniques, based on an experimental programo The frrst results and their application on the Picamoixons tablet are described

Moving towards an Ecosystem Based Management in the Gulf of Cadiz

The concentration of the world's population in coastal regions, in addition to the direct human use, is leading to an accelerated process of change and deterioration of the marine ecosystems worldwide. In the case of the Gulf of Cadiz (GoC), intense fishing throughout history has resulted in the overexploitation of its major commercial stocks. The Ecosystem Based Management (EBM) is the framework currently used for restoration of marine ecosystems. Unlike conventional strategies which only focus on individual components, this new paradigm in ecosystem management implies the consideration of the entire system as a whole. Following the steps of other European seas, this work presents an Integrated Ecosystem Assessment (IEA) for the Gulf of Cadiz as first stone towards an eventual operational EBM. The IEA of the GoC is developed by combining a customized implementation of Levin's cycle with other complementary approaches, commonly used in other European seas. In particular we made use of a traffic light plot to describe the state and trends of the most important descriptors and an Ecopath model to depict the main trophic interactions in this specific ecosystem. From these analyses, we finally come up with candidate indicators suitable to be used within Levin’s cycle framework

Monte Carlo Simulation of a Modified Chi Distribution Considering Asymmetry in the Generating Functions: Application to the Study of Health-Related Variables

[EN] Random variables in biology, social and health sciences commonly follow skewed distributions. Many of these variables can be represented by exGaussian functions; however, in practice, they are sometimes considered as Gaussian functions when statistical analysis is carried out. The asymmetry can play a fundamental role which can not be captured by central tendency estimators such as the mean. By means of Monte Carlo simulations, the effect of a small asymmetry in the generating functions of the chi distribution is studied. To this end, the k generating functions are taken as exGaussian functions. The limits of this approximation are tested numerically for the practical case of three health-related variables: one physical (body mass index) and two cognitive (verbal fluency and short-term memory). This work is in line with our previous works on a physics-inspired mathematical model to represent the reaction times of a group of individuals.This researchwas partially funded by grant number RTI2018-102256-B-I00 of MINECO/FEDER (Spain). N. Ortigosa acknowledges the support from Generalitat Valenciana under grant Prometeo/2017/102, and from Spanish MINECO under grant MTM2016-76647-P.Ortigosa, N.; Orellana-Panchame, M.; Castro-Palacio, JC.; Fernández De Córdoba, P.; Isidro, J. (2021). Monte Carlo Simulation of a Modified Chi Distribution Considering Asymmetry in the Generating Functions: Application to the Study of Health-Related Variables. Symmetry (Basel). 13(6):1-12. https://doi.org/10.3390/sym1306092411213