Quantum Monte Carlo study of few- and many-body Bose systems in one and two dimensions

In this Thesis, we report a detailed study of the ground-state properties of a set of quantum few- and many-body systems in one and two dimensions with different types of interactions by using Quantum Monte Carlo methods. Nevertheless, the main focus of this work is the study of the ground-state properties of an ultracold Bose system with dipole-dipole interaction between the particles. We consider the cases where the bosons are confined to a bilayer and multilayer geometries, that consist of equally spaced two-dimensional layers. These layers can be experimentally realized by imposing tight confinement in one direction. We specifically address the study of new quantum phases, their properties, and transitions between them. One expects these systems to have a rich collection of few- and many-body phases because the dipole-dipole interaction is anisotropic and quasi long-range.Comment: Author's PhD thesis defended on December 21st, 2020 at Universitat Polit\`ecnica de Catalunya, Spain. Supervisors: Grigory Astrakharchik and Jordi Boronat Medico. 148 pages. This dissertation is also available at https://atenea-phd.upc.edu/mod/finalthesis/download.php?file=1fdcb9aad2c827491e96b7a142f2179

The role of potassium orbitals in the metallic behavior of K3picene

Detailed electronic structure calculations of picene clusters doped by potassium modeling the crystalline K3picene structure show that while two electrons are completely transferred from potassium atoms to the LUMO of pristine picene, the third one remains closely attached to both material components. Multiconfigurational analysis is necessary to show that many structures of almost degenerate total energies compete to define the cluster ground state. Our results prove that the 4s orbital of potassium should be included in any interaction model describing the material. We propose a quarter filled two orbital model as the most simple model capable of describing the electronic structure of K-intercalated picene. Precise solutions obtained by a development of Lanczos method show low energy electronic excitations involving orbitals located at different positions. Consequently, metallic transport is possible in spite of the clear dominance of interaction over hopping.Comment: 12 pages, 10 figures (6 of them really heavy

Few-body bound states of two-dimensional bosons

We study clusters of the type A$_N$B$_M$ with $N\leq M\leq 3$ in a two-dimensional mixture of A and B bosons, with attractive AB and equally repulsive AA and BB interactions. In order to check universal aspects of the problem, we choose two very different models: dipolar bosons in a bilayer geometry and particles interacting via separable Gaussian potentials. We find that all the considered clusters are bound and that their energies are universal functions of the scattering lengths $a_{AB}$ and $a_{AA}=a_{BB}$, for sufficiently large attraction-to-repulsion ratios $a_{AB}/a_{BB}$. When $a_{AB}/a_{BB}$ decreases below $\approx 10$, the dimer-dimer interaction changes from attractive to repulsive and the population-balanced AABB and AAABBB clusters break into AB dimers. Calculating the AAABBB hexamer energy just below this threshold, we find an effective three-dimer repulsion which may have important implications for the many-body problem, particularly for observing liquid and supersolid states of dipolar dimers in the bilayer geometry. The population-imbalanced ABB trimer, ABBB tetramer, and AABBB pentamer remain bound beyond the dimer-dimer threshold. In the dipolar model, they break up at $a_{AB}\approx 2 a_{BB}$ where the atom-dimer interaction switches to repulsion.Comment: 3 figure

Daily rainfall variability in the Spanish Mediterranean area

Ponencias presentadas en: 2nd European Conference on Applied Climatology (ECAC) celebrada en Viena del 19 al 23 de octubre de 2018

Sequencing of folding events in Go-like proteins

We have studied folding mechanisms of three small globular proteins: crambin (CRN), chymotrypsin inhibitor 2 (CI2) and the fyn Src Homology 3 domain (SH3) which are modelled by a Go-like Hamiltonian with the Lennard-Jones interactions. It is shown that folding is dominated by a well-defined sequencing of events as determined by establishment of particular contacts. The order of events depends primarily on the geometry of the native state. Variations in temperature, coupling strengths and viscosity affect the sequencing scenarios to a rather small extent. The sequencing is strongly correlated with the distance of the contacting aminoacids along the sequence. Thus $\alpha$-helices get established first. Crambin is found to behave like a single-route folder, whereas in CI2 and SH3 the folding trajectories are more diversified. The folding scenarios for CI2 and SH3 are consistent with experimental studies of their transition states.Comment: REVTeX, 12 pages, 11 EPS figures, J. Chem. Phys (in press

Does Circular Economy Affect Financial Performance? The Mediating Role of Sustainable Sup-ply Chain Management in the Automotive Industry

The implementation of stricter sustainable policies and the tightening of environmental laws are forcing manufacturing companies, particularly those that make up the automotive industry, to make changes and improvements involving Circular Economy (CE) practices. However, CE practices do not always lead to an improvement in firm performance. This study analyzes the effects of the implementation of CE practices on the financial performance (FIP) of manufacturing companies in the automotive industry of Mexico, considering the mediating effect exerted by sustainable supply chain management (SSCM). The proposed model is validated through PLS-SEM using a sample of 460 companies. The results show that the FIP is strengthened through the implementation of the CE and that this effect is mediated by the commitment of the company to promote a better SSCM. This study contributes to the CE and SSCM theories by providing evidence about the positive effect that the implementation of these activities has on the performance of the automotive industry and how a SSCM equally exerts a direct and indirect effect on this. In the same way, managers can use this study and its results to make their operations more efficient and to demonstrate the effects of sustainability on the financial performance of the company

Revalorization of Posidonia oceanica Waste for the Thermochemical Production of Biochar

Every year, many tonnes of Posidonia oceanica are removed from Mediterranean beaches to maintain the quality and pleasure of use of the beaches. Most of this waste ends up in landfills, entailing removal costs. In this work, the Posidonia oceanica material was characterised, and a washing system was developed to obtain biochar. An adequate washing of the starting biomass was shown to play a key role as it led to an over 90% salt content reduction and, therefore, a decrease in conductivity values. The use of biochar as a soil remediator improves soil properties, carbon sequestration, and plant growth. However, not all types of biochars are suitable for this type of application. Therefore, the properties of biochar made from Posidonia oceanica at different temperatures (300, 400, and 500 °C) were studied. All the biochars obtained showed to exceed 10% organic carbon, which is the lower limit to be applied to soils, the maximum percentage having been obtained at 300 °C. In addition, all presented pH values (8.02, 10.32, and 10.38 for the temperatures of 300, 400, and 500 °C, respectively) that were similar to those of other effective biochars for the remediation of acid soils.The present study was funded by the Ministry of Science and Innovation (Spain) [grant number PID2019-108632RB-I00] and by Prometheus Programme (Spain) [grant number CIPROM/2021/027]