Beam formulation and FE framework for architected structures under finite deformations

The breakthrough in additive manufacturing (AM) techniques is opening new routes into the conceptualisation of novel architected materials. However, there are still important roadblocks impeding the full implementation of these technologies in different application fields such as soft robotics or bioengineering. One of the main bottlenecks is the difficulty to perform topological optimisation of the structures and their functional design. To help this endeavour, computational models are essential. Although 3D formulations provide the most reliable tools, these usually present very high computational costs. Beam models based on 1D formulations may overcome this limitation but they need to incorporate all the relevant mechanical features of the 3D problem. Here, we propose a mixed formulation for Timoshenko-type beams to consistently account for axial, shear and bending contributions under finite deformation theory. The framework is formulated on general bases and is suitable for most types of materials, allowing for the straightforward particularisation of the constitutive description. To prove validity of the model, we provide original experimental data on a 3D printed elastomeric material. We first validate the computational framework using a benchmark problem and compare the beam formulation predictions with numerical results from an equivalent 3D model. Then, we further validate the framework and illustrate its flexibility to predict the mechanical response of beam-based structures. To this end, we perform original experiments and numerical simulations on two types of relevant structures: a rhomboid lattice and a bi-stable beam structure. In both cases, the numerical results provide a very good agreement with the experiments by means of both quantitative and qualitative results. Overall, the proposed formulation provides a useful tool to help at designing new architected materials and metamaterial structures based on beam components. The framework presented may open new opportunities to guide AM techniques by feeding machine learning optimisation algorithms.The authors acknowledge support from Ministerio de Ciencia e Innovacion MCIN/AEI/10.13039/501100011033 under Grant number PID2020-117894GA-I00, and the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 947723, project: 4D-BIOMAP). DGG acknowledges support from the Talent Attraction grant (CM 2018 - 2018-T2/IND-9992) from the Comunidad de Madrid. JAR acknowledges support from the Programa de Apoyo a la Realización de Proyectos Interdiscisplinares de I + D para Jóvenes Investigadores de la Universidad Carlos III de Madrid and Comunidad de Madrid, Spain (project: OPTIMUM)

Homogenization of magnetoelastic heterogeneous solid bodies based on micropolar magnetoelasticity

A variational-based homogenization method for magnetoelastic composite materials is established in a small strains framework. The existence of a non-symmetrical stress tensor motivates the elaboration of a homogenized Cosserat type magnetoelastic effective medium at the macroscale. Generic expressions of the effective magnetic and elastic properties are derived, showing the existence of couplings between the elastic and magnetic behaviors at the macrolevel. Applications of the developed homogenization methodology are done for periodic heterogeneous media prone to local bending at the scale of a few unit cells. The validation of the homogenized medium is performed by comparing its predictions versus those of fully resolved computations. The influence of the magnetic field intensity and orientation on the strength of micropolar effects is assessed. The proposed formulation opens new possibilities for the efficient design of multifunctional metamaterials via computational modelling.The authors acknowledge support from MCIN/ AEI /10.13039/501100011033 under Grant number PID2020-117894GA-I00. The authors acknowledge support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 947723, project: 4D-BIOMAP). DGG acknowledges support from the Talent Attraction grant (CM 2018-2018-T2/IND-9992) from the Comunidad de Madrid

Electric field and charged cluster dual model for Potential Depdendent Surface-Enhanced Raman Spectroscopy

The computation of electrochemical systems is very challenging because of the many variables involved.1 Among them, the effect of the electrode potential is particularly complex to be introduced in atomistic models. In this work, we propose a model where the surface excess of charge has been modelled with the tetrahedral-like clusters [Ag19]+, [Ag20]0 and [Ag19]-. We then modulate the effect of other surface charges implicitly as an external electric field and correlated a calculated magnitude like the electric charge on the adsorbate with the electrode potential, a purely experimental one. This model is tested with the potential-dependent Surface-Enhanced Raman Scattering (SERS) of pyridine. Namely, we investigated the changes in the Raman shifts and relative intensities due to the potential, and evaluated the different contributions (electromagnetic, charge-transfer) to the SERS spectra. Our preliminary results nicely reproduce the experimental trends and reveal that enhancement factors up to 107 are achieved when the charge-transfer state interact with the bright local excitations of the metal cluster.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Comparative performance of theoretical tools in order to quantify the effect of the electric potential on the vibrational wavenumbers and intensities of the SERS of 2-methylpyrazine adsorbed on a nanostructured silver electrode

The effect of the electrode potential in surface-enhanced Raman scattering (SERS) intensities and wavenumbers of 2-methylpyrazine (2MP) was analyzed on the basis of a resonant charge transfer (CT) mechanism by using a simple theoretical model in which the metallic surface and its charge density were simulated by atomic silver clusters of different size (n) and charge (q), [Agn]q. Two linear silver atoms (n = 2) with zero charge (q = 0) and three linear silver atoms (n = 3) with positive and negative charges (q = ±1) linked to the two nonequivalent aromatic nitrogen atoms in 2MP were taken into account. The wavenumber shifts of the most intense bands and the SERS-CT spectra of these two types of metal-adsorbate supermolecule, [Agn-N1]q and [Agn-N4]q, were calculated by using a time-dependent density functional theory (TD-DFT) method and the independent mode displaced harmonic oscillator (IMDHO) approximation. A comparison of the effect of different levels of calculation, ab initio/DFT, on the predictions from the two theoretical models (isolated adsorbate/supermolecule) is also performed. Only DFT theoretical results of the metal-adsorbate supermolecule allow to explain the main role of the pair of bands assigned to totally symmetric ring-stretching 8a,b modes. The 8a vibration is the strongest band at any electrode potential, whereas the 8b mode reaches a maximum enhancement at −0.50 V and then decreases at −0.75 V. This model of a charged metal-adsorbate interface allows for detecting the presence of a CT mechanism in a SERS record.Consejería de Conocimiento, Investigación y Universidad, Junta de Andalucía, Grant/Award Numbers: P18-RT-4592, UMA18-FEDERJA-049; Generalitat Valenciana, Grant/Award Number: APOSTD/2021/025; Junta de Andalucía/FEDER; University of Málaga and Generalitat Valenciana/European Social Fund // Funding for open access charge: Universidad de Málaga / CBU

Influence of weight status on physical and mental health in Moroccan perimenopausal women

Introduction: There is a lack of information about fitness and other health indicators in women from countries such as Morocco. This study aims to explore the association of weight status with physical and mental health in Moroccan perimenopausal women. Methods: 151 women (45-65 years) from the North of Morocco were analyzed by standardized field-based fitness tests to assess cardiorespiratory fitness, muscular strength, flexibility, agility and balance. Quality of life was assessed by means of the Short-Form-36 Health Survey. Resting heart rate, blood pressure and plasma fasting glucose, total cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides were also measured. Results: Blood pressure (P=0.001), plasma triglycerides (P=0.041) and the prevalence of metabolic syndrome (P<0.001) increased as weight status increased. Levels of cardiorespiratory fitness, upper-body flexibility (both, P<0.001), static balance (P<0.05) and dynamic balance (P<0.01) decreased as weight status increased. Pairwise comparisons showed differences mainly between normal-weight and overweight vs. obese groups. No differences between groups were observed on quality of life. Conclusion: Cardiovascular and lipid profile and fitness, important indicators of cardiovascular disease risk, worsened as weight status increased, whereas quality of life appears to be independent of weight status. Exercise and nutritional programs focus on weight management may be advisable in this under studied population.Pan African Medical Journal 2016; 2

About the Unexpected Structure and Properties of Molecules Bonded to Metal Nanoclusters.

SERS (Surface-Enhanced Raman Scattering) is a very powerful technique to gain insight into the nature of metal-molecule hybrids on a molecular level. We show the results of combining SERS and theoretical calculations (1) to analyze the subtle electronic structure of metal-molecule (M-A) interfaces, especially to study the dependence of their structure and properties on applied electric potentials or fields. An example of this is the huge efficiency of the potential (EV) in tuning the energies (E) of metal-molecule charge transfer (CT) states. An equivalence between both quantities is expected on the basis of classical electrochemistry (G=E/EV=1 eV/V) but observed energy gains up to G=4 or 5 eV/V can be explained by combining the dependence of the CT energies (E) on the excess of charge of the metal (qeff) (see Graphical Abstract) and the capacitive enhancement located at metallic nanostructures (2). Moreover, theoretical calculations predict a dual electronic structure of the M-A surface complex in the case of charged molecules bonded to charged metals. These two types of surface states of the same hybrid system are of a very different nature and are selected by the sign of the metal charge (qeff). It is predicted that a single M-A complex can be very strongly bonded (chemisorbed) or form weak and very polarizable complexes (physisorbed) depending on the charges of both the ionic species and the surface excess of the metal which is modulated by the applied potential. These two types of complexes determine the properties of the overall system in the ground electronic state, like the behavior of the wavenumbers of the CN stretching band adsorbed on metals (3-4), as well as in excited states, like the forward and reverse metal-molecule CT states of the isonicotinate anion bonded to positive (chemisorbed, G~0 eV/V) or negative (physisorbed, high G) silver clusters (5), respectively (see Graphical Abstract).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The influence of electrode potential on SERS through the electronic structure of nanostructured metal-cyanide interfaces

Experimental and theoretical calculations confirm the existence of two different electronic structures of a surface complex formed by a particular molecule bonded to charged metal electrodes, clusters, or nanoparticles. Each electronic structure of the metal-molecule hybrid system is selected by sign of the surface excess of charge of the metal at potentials more negative or positive than its potential of zero charge (PZC). Surface-enhanced Raman scattering (SERS) of cyanine adsorbed on a silver electrode shows two regions, which are selected by the voltage and characterized by the differentiated response of the vibrational wavenumbers of the ν(CN) stretching band. The combination between the experimental SERS and theoretical DFT calculations has allowed for relating the two regions to chemisorbed (C-hybrid, region A) and physisorbed (P-hybrid, region B) surface complexes, where cyanide is bonded through the carbon on top of a single silver atom of the surface. The electrode potential selects one or another type of electronic structure of the system, which are of different nature having a differentiated response to the applied voltage. Electric potentials tune smoothly the wavenumbers, bond energies, and injected charges of the P-hybrid at more negative potentials than PZC, but the very strong C-hybrid prevents significant changes of these properties at positive excesses of charge. The existence of the dual electronic structure of metal-molecule interfaces might require reinterpreting experiments that are usually discussed by resorting to, for instance, the reorientation of the adsorbate, the formation of complexes with different stoichiometries, the existence of nonequivalent local sites on the surface, or to instrumental artifacts. Moreover, this dual behaviour also determines the properties and responses of technological devices where metal-molecule interfaces are involved.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Effectiveness and implementation of an online intervention (MINDxYOU) for reducing stress and promote mental health among healthcare workers in Spain : a study protocol for a stepped-wedge cluster randomized trial

The World Health Organization has formally recognized that healthcare professionals are at risk of developing mental health problems; finding ways to reduce their stress is mandatory to improve both their quality of life and, indirectly, their job performance. In recent years, particularly since the COVID-19 pandemic outbreak, there has been a proliferation of online interventions with promising results. The purpose of the present study is twofold: to test the effectiveness of an online, self-guided intervention, MINDxYOU, to reduce the stress levels of healthcare workers; and to conduct an implementation study of this intervention. Additionally, an economic evaluation of the intervention will be conducted. The current study has a hybrid effectiveness-implementation type 2 design. A stepped wedge cluster randomized trial design will be used, with a cohort of 180 healthcare workers recruited in two Spanish provinces (Malaga and Zaragoza). The recruitment stage will commence in October 2022. Frontline health workers who provide direct care to people in a hospital, primary care center, or nursing home setting in both regions will participate. The effectiveness of the intervention will be studied, with perceived stress as the main outcome (Perceived Stress Scale), while other psychopathological symptoms and process variables (e.g., mindfulness, compassion, resilience, and psychological flexibility) will be also assessed as secondary outcomes. The implementation study will include analysis of feasibility, acceptability, adoption, appropriateness, fidelity, penetration, and sustainability. The incremental costs and benefits, in terms of quality-adjusted life years, will be examined by means of cost-utility and cost-effectiveness analyses. MINDxYOU is designed to reduce healthcare workers' stress levels through the practice of mindfulness, acceptance, and compassion, with a special focus on how to apply these skills to healthy habits and considering the particular stressors that these professionals face on a daily basis. The present study will show how implementation studies are useful for establishing the framework in which to address barriers to and promote facilitators for acceptability, appropriateness, adoption, feasibility, fidelity, penetration, and sustainability of online interventions. The ultimate goal is to reduce the research-to-practice gap. This study was registered in ClinicalTrials.gov on 29/06/2022; registration number: NCT05436717

High-Throughput Synthesis of Pillared-Layered Magnesium Tetraphosphonate Coordination Polymers: Framework Interconversions and Proton Conductivity Studies

Novel pillared-layered framework materials were synthesized by high-throughput or microwave-assisted methodology that contain Mg2+ and the zwitterionic linker HDTMP (hexamethylenediamine-N,N,N0,N0-tetrakis(methylenephosphonic acid)). Three compounds were structurally characterized by X-ray powder diffraction. In the compound {Mg[(HO3PCH2)2N(CH2)6N (CH2PO3H2)2](H2O)}n(1), obtained at 140 ºC by hydrothermal or microwave-assisted reaction, the layers are built by isolated Mg2+ octahedra coordinated by oxygen atoms from six different zwitterionic HDTMP ligands. Each amino-bis(methylenephosphonate) moiety links three Mg2+ ions, bridging two of them through one phosphonate group and connecting the third polyhedron in a monodentate fashion. In Compound 2, {Mg[(HO3PCH2)2N(CH2)6N(CH2PO3H2)2]}n, hydrothermally synthesized at 180 C, the layers are composed of bidentate amino-bis(methylenephosphonate) moieties connected to three Mg2+ ions, with one of the phosphonate groups acting as a bridging ligand. Various subtle structural changes are noted for the other two compounds. Thermodiffraction of 1 reveals that a crystalline-to-crystalline phase transformation occurs concomitantly with its dehydration, leading to a new anhydrous phase, namely, {Mg[(HO3PCH2)2N(CH2)6N(CH2PO3H2)2]}n(1deh). This process is fully reversible upon equilibrating the solid at room temperature. The reported compounds can adsorb ammonia and CO2. Compound 1 exhibits a moderate proton conductivity, ~1.5 x 10-5 S·cm-1 at 80 ºC and 95% RH, that increases a half order of magnitude after experiencing a complete dehydration/rehydration process

Escribir en la universidad: aplicación de nuevas tecnologías

Depto. de Lengua Española y Teoría de la LiteraturaFac. de FilologíaFALSEsubmitte