First performance evaluation of a Multi-layer Thick Gaseous Electron Multiplier with in-built electrode meshes - MM-THGEM

We describe a new micro-pattern gas detector structure comprising a multi-layer hole-type multiplier (M-THGEM) combined with two in-built electrode meshes: the Multi-Mesh THGEM-type multiplier (MM-THGEM). Suitable potential differences applied between the various electrodes provide an efficient collection of ionization electrons within the MM-THGEM holes and a large charge avalanche multiplication between the meshes. Different from conventional hole-type multipliers (e.g. Gas Electron Multipliers - GEMs, Thick Gas Electron Multipliers - THGEMs, etc.), which are characterized by a variable (dipole-like) field strength inside the avalanche gap, electrons in MM-THGEMs are largely multiplied by a strong uniform field established between the two meshes, like in the parallel-plate avalanche geometry. The presence of the two meshes within the holes allows for the trapping of a large fraction of the positive ions that stream back to the drift region. A gas gain above 10^5 has been achieved for single photo-electron detection with a single MM-THGEM in Ar/(10%)CH4 and He/(10%)CO2, at standard conditions for temperature and pressure. When the MM-THGEM is coupled to a conventional THGEM and used as first cascade element, the maximum achievable gains reach values above 10^6 in He/(10%)CO2, while the IBF approaches of 1.5% in the case of optimum detector-bias configuration. This IBF value is several times lower compared to the one obtained by a double GEM/THGEM detector (5-10%), and equivalent to the performance attained by a Micromegas detector.Comment: 11 pages, 8 figures. Submitted to JINS

Finite-temperature properties of frustrated classical spins coupled to the lattice

We present extensive Monte Carlo simulations for a classical antiferromagnetic Heisenberg model with both nearest ($J_1$) and next-nearest ($J_2$) exchange couplings on the square lattice coupled to the lattice degrees of freedom. The Ising-like phase transition, that appears for $J_2/J_1>1/2$ in the pure spin model, is strengthened by the spin-lattice coupling, and is accompanied by a lattice deformation from a tetragonal symmetry to an orthorhombic one. Evidences that the universality class of the transition does not change with the inclusion of the spin-lattice coupling are reported. Implications for ${\rm Li_2VOSiO_4}$, the prototype for a layered $J_1{-}J_2$ model in the collinear regime, are also discussed.Comment: 6 pages and 8 figure

Ising transition driven by frustration in a 2D classical model with SU(2) symmetry

We study the thermal properties of the classical antiferromagnetic Heisenberg model with both nearest ($J_1$) and next-nearest ($J_2$) exchange couplings on the square lattice by extensive Monte Carlo simulations. We show that, for $J_2/J_1 > 1/2$, thermal fluctuations give rise to an effective $Z_2$ symmetry leading to a {\it finite-temperature} phase transition. We provide strong numerical evidence that this transition is in the 2D Ising universality class, and that $T_c\to 0$ with an infinite slope when $J_2/J_1\to 1/2$.Comment: 4 pages with 4 figure

Biosorption of pharmaceuticals from wastewater using Moringa oleífera as biosorbent

Mestrado de dupla diplomação com a Universidad Nacional de MissionesPharmaceuticals as emerging contaminants have become one of the most controversial environmental issues at global scale. Over the years, there has increased the presence of antibiotics and anti-inflammatory drugs inside rivers, lakes, oceans and even inside drinking water streams. The waste-water treatment plants (WWTPs) lack the necessary technology to remove a concentration between the range ng/l-mg/l and therefore, the need to develop new methods able to remove contaminants in an effective, low cost and environmental friendly way arises. The term “Biosorption” appears as a possible solution. It is a separation process inside the area of Chemical Engineering that follows the same fundaments of adsorption with the only difference that uses biodegradable materials as adsorbent (biosorbent). The present work focuses on studying the potential adsorption capacity of Moringa oleífera (MO) to remove Diclofenac (DCF) and Oxytetracycline (OTC) from waste-water. After different experiments, it was found that in both cases (DCF and OTC) the adsorption processes present high pH dependence, the first one governed by the mechanism of chemisorption while the second one could be controlled by diffusion of the particles between both surfaces. Equilibrium isotherms were determined by Langmuir, Freundlich, and Sips models. In both cases, the adsorption process was best described by the Freundlich model (R2>0.97). Kinetics essays were described by pseudo-first-order, pseudo-second-order, and Intraparticle diffusion models. The experimental data of OTC and DCF removal were best fitted by Intraparticle Diffusion (R2>0.95) and pseudo-second-order (R2>0.93) model respectively. It was possible to obtain a removal percentage of 88% for DCF at a pH of 2 and 50% for OTC at a pH of 10, indicating that MO represents a viable option for the removal of drugs present in contaminated water.Los fármacos en su papel de contaminantes emergentes, se han convertido en uno de los problemas ambientales más preocupantes a escala global. Con el pasar de los años, la presencia de antibióticos y antiinflamatorios dentro de ríos, lagos, océanos e inclusive en corrientes de agua potable, ha ido aumentado. Las plantas de tratamiento de aguas residuales (ETARs) aún no cuentan con los métodos adecuados para remover concentraciones dentro del rango de ng/l-mg/l y por ello, surge la necesidad de desarrollar nuevas tecnologías que sean efectivas, de bajo costo y amigables con el medio ambiente. Como posible solución nace el término de “biosorción”. La biosorción es un proceso de separación dentro del área de Ingeniería Química que sigue los mismos fundamentos de la técnica de adsorción, con la única diferencia que utiliza materiales biodegradables como adsorbentes, conocidos como “biosorbentes”. Es de gran interés en el presente trabajo, estudiar las características, principales propiedades y capacidad de adsorción que posee las cáscaras de la planta Moringa oleífera (MO) para la remoción de Oxitetraciclina (OTC) y Diclofenac (DCF) presentes en aguas residuales. MO es reconocida mundialmente debido a sus propiedades anti-microbiales, nutricionales y coagulantes, mientras que DCF y OTC son considerados dos de los fármacos con mayor contribución a la contaminación del medioambiente. A través de diferentes ensayos, se encontró que en ambos casos (DCF y OTC) se trata de procesos altamente dependientes de pH con la diferencia que el primero es gobernado por el mecanismo de quimisorción mientras que el segundo es controlado bajo la difusión de partículas entre ambas superficies.El modelo de Freundlich (R2>0.98) ha logrado, en ambos casos, el mejor ajuste de los datos empíricos. Mientras que, en modelos de cinética de adsorción, el modelo de Difusión Intraparticular presentó el mejor ajuste para el proceso de remoción de OTC (R2>0.95) y el modelo Pseudo-Segundo-orden, para la adsorción de DCF (R2>0.93). Se ha logrado remover hasta un 88% de DCF a un pH de 2 y hasta 50% de OTC a un pH de 10, indicando que MO representa una opción viable para la remoción de fármacos presentes en aguas contaminadas

Aportaciones de la Etología Humana a los estudios lingüísticos: el caso de la Fraseología

En este texto se reflexiona sobre los vínculos existentes entre la Etología Humana, a partir de algunos de los supuestos teóricos desarrollados por Eibl-Eibesfeldt, y la Lingüística. Se busca establecer una relación entre estos supuestos y una parcela de los estudios lingüísticos, la Fraseología (especialmente, las fórmulas rutinarias). A fin de cumplir este objetivo, se describen, someramente, los principios básicos de la Etología Humana; se considera, asimismo, la atención que ha consagrado esta ciencia a la comunicación humana, el lenguaje y la Lingüística, y de la posibilidad de aplicar la Etolingüística al estudio de la Fraseología. Se defiende la idea de que la Etología Humana puede apoyar la reflexión sobre las bases innatas y culturales que subyacen a diferentes tipos de fraseologismos.In this paper I analyse the connections between Human Ethology and Linguistics. I start out by considering some of the theoretical principles developed by Eibl-Eibesfeldt 1979a, 1979b and 1993 and I try to relate them with a branch of linguistic studies, Phraseology, and more specifically, the routine formulas. In order to achieve this goal, I first describe, briefly, the fundamentals of Human Ethology. Secondly, I show how this science dealt with human communication, language and Linguistics and I also consider the possibility of applying Etholinguistics to the study of Phraseology. I defend the idea that the ethological studies offer different paths that might turn useful to the phraseological research, especially to unravel the innate and cultural bases ruling the construction and use of formulae.Dans ce texte, nous réfléchissons sur les liens entre Éthologie Humaine et Linguistique, à partir de certaines des hypothèses théoriques développés par Eibl-Eibesfeldt (1979a, 1979b, 1993). Nous cherchons à établir une relation entre ces hypothèses et une partie d’études linguistiques, la Phraséologie (et spécifiquement, les formules de routine). Pour atteindre cet objectif, nous décrivons succinctement, les principes de base de l'Éthologie Humaine. Nous parlons alors des efforts que cette science a consacré à la communication humaine, au langage et la Linguistique, et la possibilité d'appliquer l'Etolinguistique à l'étude de la Phraséologie. Nous défendons l'idée que l'Éthologie Humaine peut favoriser une réflexion sur les fondements innés et culturels qui sous-tendent différents types d'unités phraséologiques

Alternatives for programming a low-cost UAV in robotics

The aim of this paper are to present different alternatives to program a commercially available ffying platform, and to discuss what we consider more convenient to be used by our under-graduate students in a regular robotics course to teach them basic vision based control. Due to the background of our students, we will focus more on the description of the software application interface, than on the hardware, although we will describe also both. We also will describ