Disordered hyperuniformity in two-component non-additive hard disk plasmas

We study the behavior of a two-component plasma made up of non-additive hard disks with a logarithmic Coulomb interaction. Due to the Coulomb repulsion, long-wavelength total density fluctuations are suppressed and the system is globally hyperuniform. Short-range volume effects lead to phase separation or to hetero-coordination for positive or negative non-additivities, respectively. These effects compete with the hidden long-range order imposed by hyperuniformity. As a result, the critical behavior of the mixture is modified, with long-wavelength concentration fluctuations partially damped when the system is charged. It is also shown that the decrease of configurational entropy due to hyperuniformity originates from contributions beyond the two-particle level. Finally, despite global hyperuniformity, we show that in our system, the spatial configuration associated with each component separately is not hyperuniform, i.e., the system is not "multihyperuniform.

A computational study of electrolyte adsorption in a simple model for intercalated clays

12 p., 10 fig.A pillared interlayered clay is represented by a two-dimensional quenched charged disordered medium, in which the pillar configuration is produced by the quench of a two-dimensional electrolyte and the subsequent removal of the anions (that act as a template). The cation charge is counterbalanced by a neutralizing background that is an ideal representation of the layer's negative charge in the experimental system. In this paper we investigate the adsorption of electrolyte particles in this charged disordered medium resorting both to the use of the replica Ornstein-Zernike equation in the hypernetted chain approximation and grand canonical Monte Carlo simulations. The theoretical approach qualitatively reproduces the simulated behavior of the adsorbed fluids. Theoretical estimates of the material porosities obtained for various types of pillar distributions are in good agreement with the simulation. We investigate the influence of the matrix on correlation functions and adsorption isotherms. © 2010 American Institute of Physics.E.L. gratefully acknowledges the support from the Dirección General de Investigación Científica y Técnica under Grant No. MAT2007-65711-C04-04 and from the Dirección General de Universidades e Investigación de la Comunidad de Madrid under Grant No. S0505/ESP/0299 and Program MOSSNOHO-CM

Hyperuniformity on spherical surfaces

In this work we present a study on the characterization of ordered and disordered hyperuniform point distributions on spherical surfaces. In spite of the extensive literature on disordered hyperuniform systems in Euclidean geometries, to date few works have dealt with the problem of hyperuniformity in curved spaces. As a matter of fact, some systems that display disordered hyperuniformity, like the space distribution of photoreceptors in avian retina, actually occur on curved surfaces. Here we will focus on the local particle number variance and its dependence on the size of the sampling window (which we take to be a spherical cap) for regular and uniform point distributions, as well as for equilibrium configurations of fluid particles interacting through Lennard-Jones, dipole-dipole and charge-charge potentials. We will show how the scaling of the local number variance enables the characterization of hyperuniform point patterns also on spherical surfaces

Pattern formation in binary fluid mixtures induced by short-range competing interactions

Molecular dynamics simulations and integral equation calculations of a simple equimolar mixture of diatomic molecules and monomers interacting via attractive and repulsive short-range potentials show the existence of pattern formation (microheterogeneity), mostly due to depletion forces away from the demixing region. Effective site-site potentials extracted from the pair correlation functions using an inverse Monte Carlo approach and an integral equation inversion procedure exhibit the features characteristic of a short-range attractive and long-range repulsive potential. When charges are incorporated into the model, this becomes a coarse grained representation of a room temperature ionic liquid, and as expected, intermediate range order becomes more pronounced and stable

A PORTABLE AND INEXPENSIVE DO-IT-YOURSELF TEMPERATURE SENSOR

Nowadays it is important to have commercial solutions to be used in teaching and research laboratories for the needs. We can have different equipment according to the necessary parameters of control being related to the influence of parameters internal or external to the laboratory practice. However they can't be straightforward to use, their costs can be considerable.  In this context, the do-it-yourself approach is an interesting alternative. In this paper we report the construction of a temperature sensor made by students. Based on a probe taken from a deactivated equipment, the sensor development and validation encompassed its design and building up, the establishment of a connection to a personal computer via USB, the setup of computer-controlled processes, which included remote control, graphical and numerical displaying and signal acquisition, and finally its testing. Tests were performed in water containers with different temperatures, namely boiling, room and ice. The obtained results are comparable to those from a commercial thermometer. This student experiment project allowed not only to contact different disciplines such as chemistry, electronics, and programming but also to gain competencies that can be used outside the class context. We proved it is possible to build tailor-made electronic devices capable of providing useful measurements to chemical purposes old equipment in an inexpensive and trustworthy way

Phase diagram of a two-dimensional lattice gas model of a ramp system

Using Monte Carlo Simulation and fundamental measure theory we study the phase diagram of a two-dimensional lattice gas model with a nearest neighbor hard core exclusion and a next-to-nearest neighbors finite repulsive interaction. The model presents two competing ranges of interaction and, in common with many experimental systems, exhibits a low density solid phase, which melts back to the fluid phase upon compression. The theoretical approach is found to provide a qualitatively correct picture of the phase diagram of our model system.Comment: 14 pages, 8 figures, uses RevTex

Photo-induced volume changes in selenium. Tight-binding molecular dynamics study

Tight-binding molecular dynamics simulations of photo-excitations in small Se clusters (isolated Se$_8$ ring and helical Se chain) and glassy Se networks (containing 162 atoms) were carried out in order to analyse the photo induced instability inside the amorphous selenium. In the cluster systems after taking an electron from the highest occupied molecular orbital to the lowest unoccupied molecular orbital a bond breaking occurs. In the glassy networks photoinduced volume expansion was observed and at the same time the number of coordination defects changed significantly due to illumination

In Situ Synthesis of Artificial Lipids

This review comes from a themed issue on Synthetic Biomolecules (2022); Edited by Neal K. Devaraj and Shinya TsukijiFinanciado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] Lipids constitute one of the most enigmatic family of biological molecules. Although the importance of lipids as basic units of compartmental structure and energy storage is well-acknowledged, deciphering the biosynthesis and precise roles of specific lipid species has been challenging. To better understand the structure and function of these biomolecules, there is a burgeoning interest in developing strategies to produce noncanonical lipids in a controlled manner. This review covers recent advances in the area of in situ generation of synthetic lipids. Specifically, we report several approaches that constitute a powerful toolbox for achieving noncanonical lipid synthesis. We describe how these methodologies enable the direct construction of synthetic lipids, helping to address fundamental questions related to the cell biology of lipid biosynthesis, trafficking, and signaling. We envision that highlighting the current advances in artificial lipid synthesis will pave the way for broader interest into this emerging class of biomimetic molecules.Roberto J. Brea acknowledges support from Xunta de Galicia through the “Atracción de talento investigador” programme (ED431H2020/19). Roberto J. Brea also thanks the Agencia Estatal de Investigación (AEI) and the Ministerio de Ciencia e Innovación (MICINN) for his Ramón y Cajal contract (RYC2020-030065-I). The authors acknowledge funding for open access charge from Universidade da Coruña/Consorcio Interuniversitario de Galicia (CISUG)Xunta de Galicia; ED431H2020/1

Dos apuestas: Robinson Crusoe y Havy Ibn Yadän.

Sin resume

Avempace. Tratado de la unión del intelecto con el hombre

Este tratado, que se titula Risala Ittisal al-'aql bi-l-insan, Tratado de la unión del Inntelecto con el hombre, fue editado y traducido al español por primera vez por Miguel Asín, Palacios, precediéndolo de un magnifico estudio. Posteriormente Vincent Lagardère tradujo al francés la versión española de Asín, con otro estudio introductorio, en el que, aparte de dar algunos datos nuevos (habían pasado 38años), presentaba muy bien, actualizando la situación histórica, el ambiente intelectual de al-Andalus y de la Zaragoza musulmana, marco en que escribió Avempace su tratado