First Principle Computation of Random Pinning Glass Transition, Glass Cooperative Length-Scales and Numerical Comparisons

As a guideline for experimental tests of the ideal glass transition (Random Pinning Glass Transition, RPGT) that shall be induced in a system by randomly pinning particles, we performed first-principle computations within the Hypernetted chain approximation and numerical simulations of a Hard Sphere model of glass-former. We obtain confirmation of the expected enhancement of glassy behaviour under the procedure of random pinning, which consists in freezing a fraction $c$ of randomly chosen particles in the positions they have in an equilibrium configuration. We present the analytical phase diagram as a function of $c$ and of the packing fraction $\phi$, showing a line of RPGT ending in a critical point. We also obtain first microscopic results on cooperative length-scales characterizing medium-range amorphous order in Hard Spere glasses and indirect quantitative information on a key thermodynamic quantity defined in proximity of ideal glass transitions, the amorphous surface tension. Finally, we present numerical results of pair correlation functions able to differentiate the liquid and the glass phases, as predicted by the analytic computations.Comment: Working draft, comments are welcom

La experiencia a favor del cambio

[Resumen] Objetivo: Explorar la percepción de la participación social en personas mayores con déficit auditivo desde su perspectiva, identificando fortalezas y barreras de comunicación y de información en su vida diaria, profundizando en sus relaciones y de las personas de su entorno más cercano, así como su desempeño ocupacional en salud y calidad de vida. Metodología: Estudio de tipo cualitativo con enfoque fenomenológico realizado en el período comprendido enseis meses. La muestra está compuesta por 5 personas con déficit auditivo de una Residencia Gerontológica. Las técnicas utilizadas fueron la entrevista y el uso de audio. Resultados: La mayoría de los participantes presentan problemas de comunicación y acceso a la información oral, tanto con sus semejantes como con los de su entorno más cercano (familia), referenciando una limitación en la participación social. Se aprecia el importante papel de la comunicación, el acceso a la información y los productos de apoyo (por ej., las prótesis auditivas). Y, por tanto, se observa un desajuste entre los recursos de apoyo y las necesidades de las personas mayores con déficit auditivo. Conclusiones:Las personas mayores con déficit auditivo perciben su participación social como algo “normal”, debido a las circunstancias personales y sociales. Se percibe que se encuentran en un estado de acomodo en su “problema” para aquellas personas que portan prótesis auditivas, en cambio, aquellas que no poseen de dichas prótesisTraballo fin de grao (UDC.FCS). Terapia ocupacional. Curso 2013/2014

An Ising Model for Metal-Organic Frameworks

We present a three-dimensional Ising model where lines of equal spins are frozen in such that they form an ordered framework structure. The frame spins impose an external field on the rest of the spins (active spins). We demonstrate that this "porous Ising model" can be seen as a minimal model for condensation transitions of gas molecules in metal-organic frameworks. Using Monte Carlo simulation techniques, we compare the phase behavior of a porous Ising model with that of a particle-based model for the condensation of methane (CH$_4$) in the isoreticular metal-organic framework IRMOF-16. For both models, we find a line of first-order phase transitions that end in a critical point. We show that the critical behavior in both cases belongs to the 3D Ising universality class, in contrast to other phase transitions in confinement such as capillary condensation.Comment: 11 pages, 9 figure

Low-temperature anomalies of a vapor deposited glass

We investigate the low temperature properties of two-dimensional Lennard-Jones glass films, prepared in silico both by liquid cooling and by physical vapor deposition. We identify deep in the solid phase a crossover temperature $T^*$, at which slow dynamics and enhanced heterogeneity emerge. Around $T^*$, localized defects become visible, leading to vibrational anomalies as compared to standard solids. We find that on average, $T^*$ decreases in samples with lower inherent structure energy, suggesting that such anomalies will be suppressed in ultra-stable glass films, prepared both by very slow liquid cooling and vapor deposition.Comment: 10 pages including appendices, 8 figures. Version accepted for Physical Review Material

Numerical detection of the Gardner transition in a mean-field glass former

Recent theoretical advances predict the existence, deep into the glass phase, of a novel phase transition, the so-called Gardner transition. This transition is associated with the emergence of a complex free energy landscape composed of many marginally stable sub-basins within a glass metabasin. In this study, we explore several methods to detect numerically the Gardner transition in a simple structural glass former, the infinite-range Mari-Kurchan model. The transition point is robustly located from three independent approaches: (i) the divergence of the characteristic relaxation time, (ii) the divergence of the caging susceptibility, and (iii) the abnormal tail in the probability distribution function of cage order parameters. We show that the numerical results are fully consistent with the theoretical expectation. The methods we propose may also be generalized to more realistic numerical models as well as to experimental systems.Comment: 17 pages, 16 figure

Growing timescales and lengthscales characterizing vibrations of amorphous solids

Low-temperature properties of crystalline solids can be understood using harmonic perturbations around a perfect lattice, as in Debye's theory. Low-temperature properties of amorphous solids, however, strongly depart from such descriptions, displaying enhanced transport, activated slow dynamics across energy barriers, excess vibrational modes with respect to Debye's theory (i.e., a Boson Peak), and complex irreversible responses to small mechanical deformations. These experimental observations indirectly suggest that the dynamics of amorphous solids becomes anomalous at low temperatures. Here, we present direct numerical evidence that vibrations change nature at a well-defined location deep inside the glass phase of a simple glass former. We provide a real-space description of this transition and of the rapidly growing time and length scales that accompany it. Our results provide the seed for a universal understanding of low-temperature glass anomalies within the theoretical framework of the recently discovered Gardner phase transition.Comment: 12 pages, 20 figures. Accepted for publication in PNA

Unsupervised hierarchical clustering using the learning dynamics of RBMs

Datasets in the real world are often complex and to some degree hierarchical, with groups and sub-groups of data sharing common characteristics at different levels of abstraction. Understanding and uncovering the hidden structure of these datasets is an important task that has many practical applications. To address this challenge, we present a new and general method for building relational data trees by exploiting the learning dynamics of the Restricted Boltzmann Machine (RBM). Our method is based on the mean-field approach, derived from the Plefka expansion, and developed in the context of disordered systems. It is designed to be easily interpretable. We tested our method in an artificially created hierarchical dataset and on three different real-world datasets (images of digits, mutations in the human genome, and a homologous family of proteins). The method is able to automatically identify the hierarchical structure of the data. This could be useful in the study of homologous protein sequences, where the relationships between proteins are critical for understanding their function and evolution.Comment: Version accepted in Physical Review

Port-City Development: The Spanish Case

[Abstract]: The objective of this paper is to try to evaluate the port-city relationship from its onset, taking into account the challenges of port 4.0. Indicators such as the percentage of employees participating in training programs, the percentage of female employees in Galician ports, the percentage of merchandise moved by private operators and the percentage of companies with quality certification in Galician ports are evaluated. The fourth revolution is based on the transition from current fossil fuel-based energy models to alternative energy sources, changes in the logistics and transport parameters and finally, on the elimination of intermediation. The key component of the third pillar of new Economy 4.0 is complete digitalization. The optimum port-city solution must address the need of both the urban planner and the port manager to evaluate potential measures that would alleviate the pressure of dedicated port facilities on the city and vice versa to the greatest extent possible

Industria agroalimentaria en Extremadura: obstáculos a la innovación, disposición a innovar y políticas públicas demandadas

The purpose of this paper is to analyse the barriers perceived by agribusiness companies in Extremadura; how these barriers influence their disposition to innovate and the type of public actions demanded by these companies in order to boost innovation. Data comes from an ad hoc survey conducted in 2013. The methodology used combines descriptive analysis with factor analysis and econometric analysis. Main results show that high costs and risks, lack of human resources and difficulties of appropriability are the barriers that reduce the probability to innovate, and that there are important differences among the perceived factors of obstacles and demands of public actions. This can be a reference to develop government policies specifically geared towards boosting innovation in this kind of industry.El objetivo de este trabajo es analizar las barreras percibidas por las empresas agroalimentarias en Extremadura; cómo estas barreras influyen en su disposición a innovar y el tipo de acciones públicas que demandan estas empresas para impulsar la innovación. Los datos provienen de una encuesta ad hoc realizada en 2013. La metodología utilizada combina el análisis descriptivo con el análisis factorial y econométrico. Los principales resultados muestran que los costes y riesgos elevados, la falta de recursos humanos y las dificultades de apropiabilidad son las barreras que reducen la probabilidad de innovar, y que existen diferencias importantes entre los factores de obstáculos percibidos y las demandas de las acciones públicas. Esto puede ser una referencia para desarrollar políticas gubernamentales orientadas específicamente a impulsar la innovación en este tipo de industria