Discrete Spectrum of Quantum Hall Effect Hamiltonians I. Monotone Edge Potential

We consider the unperturbed operator $H_0 : = (-i \nabla - A)^2 + W$, self-adjoint in $L^2(\R^2)$. Here $A$ is a magnetic potential which generates a constant magnetic field $b>0$, and the edge potential $W$ is a non-decreasing non constant bounded function depending only on the first coordinate $x \in \R$ of $(x,y) \in \R^2$. Then the spectrum of $H_0$ has a band structure and is absolutely continuous; moreover, the assumption $\lim_{x \to \infty}(W(x) - W(-x)) < 2b$ implies the existence of infinitely many spectral gaps for $H_0$. We consider the perturbed operators $H_{\pm} = H_0 \pm V$ where the electric potential $V \in L^{\infty}(\R^2)$ is non-negative and decays at infinity. We investigate the asymptotic distribution of the discrete spectrum of $H_\pm$ in the spectral gaps of $H_0$. We introduce an effective Hamiltonian which governs the main asymptotic term; this Hamiltonian involves a pseudo-differential operator with generalized anti-Wick symbol equal to $V$. Further, we restrict our attention on perturbations $V$ of compact support and constant sign. We establish a geometric condition on the support of $V$ which guarantees the finiteness of the eigenvalues of $H_{\pm}$ in any spectral gap of $H_0$. In the case where this condition is violated, we show that, generically, the convergence of the infinite series of eigenvalues of $H_+$ (resp. $H_-$) to the left (resp. right) edge of a given spectral gap, is Gaussian.Comment: 32 page

High-pressure phase equilibrium in a carbon dioxide-acetone isopropanol ternary system: obtaining and analysing new datasets

This paper describes the work carried out to obtain and analyse the thermodynamic equilibrium dataset for the ternary mixture of carbon dioxide, acetone and isopropanol in a range of temperatures between 308.15 and 328.15 K and pressures between approximately 5 MPa and 14 MPa. The composition (molar fraction) of each compound was varied approximately in the ranges 2 ∶ (0.7; 0.99); ∶ (0.003; 0.24); ∶ (0.001; 0.14) maintaining 3 different volumetric ratios of acetone/isopropanol: 1:1, 3:1 and 5:1. The measurements are based on the use of a static synthetic method in which the opacity and redissolution points are visually observed in a high-pressure, variable volume view-cell. The system has not been previously studied and therefore represents a novel contribution to high-pressure phase equilibria investigation. The text can be divided into three main parts: (i) where the characteristics of supercritical fluids, especially supercritical CO2 and the importance of phase equilibrium measurement in these systems are addressed; (ii) in which the experimental process carried out in the laboratory to obtain the data, as well as the equipment, the different existing phase equilibrium measurement methods and the one used in this work are explained; and (iii) in which the results obtained are analysed with the aim of predicting and understanding the behaviour of the system. To this end, a discussion of the raw data is conducted and the thermodynamic modelling using the Peng-Robinson and Soave Redlich-Kwong equations of state is carried outDepartamento de Ingeniería Química y Tecnología del Medio AmbienteMáster en Ingeniería Químic

Continuum limit for a discrete Hodge-Dirac operator on square lattices

We study the continuum limit for Dirac-Hodge operators defined on the $n$ dimensional square lattice $h\mathbb{Z}^n$ as $h$ goes to $0$. This result extends to a first order discrete differential operator the known convergence of discrete Schr\"odinger operators to their continuous counterpart. To be able to define such a discrete analog, we start by defining an alternative framework for a higher-dimensional discrete differential calculus. We believe that this framework, that generalize the standard one defined on simplicial complexes, could be of independent interest. We then express our operator as a differential operator acting on discrete forms to finally be able to show the limit to the continuous Dirac-Hodge operator

RAD-UNAM: Genesis and evolution of a repository administrators group

In this talk, we will present RAD-UNAM, the Network of Digital Collections (Red de Acervos Digitales). UNAM is Mexico's (and Latin America's) largest university, with over 300,000 students, and produces close to half of all of the country's academic publications. Due to its size, in many aspects, the university operates almost as a federation of faculties and research centers, lacking coordination in several key areas. RAD-UNAM is a network, firstly, among people interested in promoting awareness on the need for having properly set up digital repositories (that is, beyond being digital dumps, adhering to internationally recognized catalogation standards), as well as on the need to offer our academic material under Open Access licensing terms, and only as a logical consequence, a network of actual repositories using OAI-PMH and DublinCore as a technological basis. Given the social characteristics of the professors and researchers of UNAM (mainly, an aging faculty which struggles coming to grips with the modern flows of information, and anachronic evaluation mechanisms), an important part of our job has been to convince the faculty on the importance of Open Access, and how it does not undermine their research. RAD-UNAM is currently made up by nine repositories, not only spanning very different knowledge fields but also organizationally very different entities, each of them with objects of very different nature, and a central harvester. Our group has become a referent for repository creation and management in our region, and is slowly advancing towards incorporating as an institutional project

Effectiveness if traditional games compared with technological games in classroom climate and student's performance in the EFL classroom : a quasi-experimental research

Tesis (Pedagogía en Inglés)The present study intended to corroborate the hypothesis that both technological and traditional games can help school students in their learning process and that traditional games unlike technological ones, also help in the creation of a better classroom climate. Through a quasi-experiment in three different educational settings, control groups and experimental ones were going to be measured both in students’ performance expressed in marks and in classroom climate measured with a sociometric test. Chile’s current national contingency has prevented this study to be concluded as expected. As an alternative outcome, the researchers carried out a perception study that compared student’s acceptance of both technological and traditional games. The result of this study shows that current students, who are digital natives, showed a slight preference for traditional games over the technological ones, defying the common belief that students only react positively to technology.El presente estudio pretende corroborar la hipótesis de que tanto los juegos tecnológicos como los tradicionales pueden ayudar a los alumnos en su proceso de aprendizaje y que los juegos tradicionales a diferencia de los tecnológicos pueden ayudar, además en la creación de un mejor clima de aula. A través de un cuasi-experimento en tres diferentes establecimientos educacionales, en los grupo de control y experimentales se iba a medir tanto el rendimiento de los estudiantes expresado a través de sus calificaciones, como el clima de aula medido a través de un cuestionario sociométrico. La actual contingencia nacional de Chile ha impedido que este estudio concluya según lo previsto. Como alternativa, los investigadores llevaron a cabo un estudio de percepción que comparó la aceptación de los estudiantes hacia los juegos tecnológicos y tradicionales. El resultado de este estudio muestra que los estudiantes, siendo nativos digitales. mostraron una ligera preferencia por los juegos tradicionales por sobre los tecnológicos, desafiando la creencia general de que los estudiantes solo reaccionan positivamente ante la tecnología

Sino-Africa Cooperation: Promoting an Enabling Environment for Higher Levels of Investment and Financial Sector Development

In many fields connected to architecture and urban design, the term ‘resilience’ has grown common and tends to stand for a variety of different things. What this paper intends to do is to work with the term under a rather basic understanding – that of systems capable of performing even after being altered. Specifically, this means the extent to which a spatial configuration is sensitive to smaller or larger changes, where these sensitivities can be found and the degree of impact should the links be severed. Building on investigations by Hillier, Shpuza, and Conroy Dalton and Kirsan, the intent is to take one step further and set the term in relation to what a spatial configuration operates as social and cultural interface. Thus, a system that is considered as syntactically resilient is a system where inhabitance (use, identity) can follow similar principles as before the change, whereas a non-resilient system is one that can suffer big changes in the spatial logic by ostensibly minor local changes, thereby putting considerable strain on or enforcing change of inhabitance. The paper furthermore establishes some basic methods and measures for how to measure and analyse this, and also discusses the pros and cons of different spatial models for the ability of analyzing the question at hand. Concretely, the investigation begins with a conceptual, methodological discussion that is then followed by analysis of a small number of buildings to investigate the validity of the proposed methods and measures. The paper investigates the use of a series of existing measures as well as proposes new measures of configurational sensitivity. Finally it discusses how these measures relate to on the one hand security issues, and on the other generic questions in architectural design.QC 20140107Resilient Infrastructure and Building Security (RIBS

Los Tettigoniidae (Insecta, Orthoptera) del Parque Natural de Montesinho (Portugal)

El Parque Natural de Montesinho, situado en la frontera norte de Portugal, en la región denominada Nordeste Transmontano es singular entre los espacios protegidos portugueses por la gran diversidad de hábitats y la relativamente escasa perturbación sufrida., lo que le confiere un carácter propio. EI estudio de su entomofauna es precario y se limita a citas puntuales de determinados grupos taxonómicos, a excepción del trabajo de Ribeiro et al. (1982) sobre Culícidos (Insecta, Diptera)