Development and testing of galvanic anodes for cathodic protection

Aquest treball resumeix els resultats obtinguts en un projecte de recerca dut a terme en el nostre laboratori i relacionat amb l'assaig electroquímic dels ànodes de sacrifici emprats en protecció catòdica, així com en el desenvolupament de nous ànodes d'alumini -Al- lliures d'indi -In- i de mercuri -Hg. Les aportacions més importants han estat fetes en els aspectes següents: 1. Mecanisme de corrosió durant els assaigs electroquímics. 1.1. Al. Assaig electroquímic d'ànodes de sacrifici de Al. 1.2. Mg. Mecanisme de dissolució dels ànodes de sacrifici de Mg durant l'assaig electroquímic. 1.3. Zn. L'impedància electroquímica com a eina d'assaig dels ànodes de sacrifici de Zn aplicats per projecció tèrmica sobre el formigó. 2. Augment de l'eficiència electroquímica dels ànodes de Mg mitjançant el tractament tèrmic i el control de la seva microestructura. 3. Disseny i desenvolupament de nous ànodes de Al sense In ni Hg. Aquests nous ànodes de Al-Zn-Mg-Li són proposats com una alternativa als actualment en ús. El sistema Al-Mg-Zn ha estat escollit a causa de la presència de precipitats en la matriu de l'alumini, que poden ser capaços de trencar la pel·lícula passiva, però mantenen una alta eficiència electroquímica.This paper summarizes the results obtained in the research project carried out in our laboratory related to the testing of sacrificial anodes used in cathodic protection (CP) systems and the development of new In/Hg-free aluminium-alloy anodes. The main contributions are in the following subjects: 1. Corrosion mechanism during electrochemical testing. 1.1. Al. Electrochemical testing of Al sacrificial anodes. 1.2. Mg. Dissolution mechanism of Mg sacrificial anodes under electrochemical testing. 1.3. Zn. EIS testing of thermal spray Zn anodes for concrete applications. 2. Improving the efficiency of Mg sacrificial anodes by microstructure control and heat treatments. 3. Design and development of new Al-alloy anodes In/Hg free. The evaluation of an Al-Zn-Mg-Li alloy as a potential candidate for Al-sacrificial anode was studied. The Al-Zn-Mg system was particularly selected due to the presence of precipitates in _-Al matrix which are capable of breaking down passive films whilst presenting good electrochemical efficiencies. The effect of Li additions on superficial activation of the anode by means of precipitation of AlLi type compounds was also examined

Análisis modal comparado entre modelos virtuales 2d y 3d aplicado a un Cube Sat

El siguiente trabajo presenta un análisis modal comparado entre modelos virtuales 2D y 3D, para validar la sistematización de una metodología de análisis completo de Ingeniería Asistida por Computadora, ejemplificada en la aplicación a un modelo de nano satélite tipo Cube Sat. Se detallan los requerimientos de las especificaciones técnicas, condiciones estructurales, cargas, restricciones y frecuencias de vibración, que sufre este satélite al momento de su despegue y durante su órbita. Posteriormente se aplica al Diseño Asistido por Computadora la solicitud del análisis de respuesta dinámica al modelo de su estructura principal simplificada, utilizando el Método de los Elementos Finitos. Las simulaciones incluyen el análisis dinámico de frecuencias naturales y modos de vibración libre. La comparación se lleva a cabo con las herramientas de un Sistema de Ingeniería Basada en el Conocimiento que permiten optimizar la elaboración de diseños mecánicos y reducir tiempos de solución ante nuevos retos de simulación

Stochastic Approach to Enantiomeric Excess Amplification and Chiral Symmetry Breaking

Stochastic aspects of chemical reaction models related to the Soai reactions as well as to the homochirality in life are studied analytically and numerically by the use of the master equation and random walk model. For systems with a recycling process, a unique final probability distribution is obtained by means of detailed balance conditions. With a nonlinear autocatalysis the distribution has a double-peak structure, indicating the chiral symmetry breaking. This problem is further analyzed by examining eigenvalues and eigenfunctions of the master equation. In the case without recycling process, final probability distributions depend on the initial conditions. In the nonlinear autocatalytic case, time-evolution starting from a complete achiral state leads to a final distribution which differs from that deduced from the nonzero recycling result. This is due to the absence of the detailed balance, and a directed random walk model is shown to give the correct final profile. When the nonlinear autocatalysis is sufficiently strong and the initial state is achiral, the final probability distribution has a double-peak structure, related to the enantiomeric excess amplification. It is argued that with autocatalyses and a very small but nonzero spontaneous production, a single mother scenario could be a main mechanism to produce the homochirality.Comment: 25 pages, 6 figure

The Hilbert space of Chern-Simons theory on the cylinder. A Loop Quantum Gravity approach

As a laboratory for loop quantum gravity, we consider the canonical quantization of the three-dimensional Chern-Simons theory on a noncompact space with the topology of a cylinder. Working within the loop quantization formalism, we define at the quantum level the constraints appearing in the canonical approach and completely solve them, thus constructing a gauge and diffeomorphism invariant physical Hilbert space for the theory. This space turns out to be infinite dimensional, but separable.Comment: Minor changes and some references added. Latex, 16 pages, 1 figur

Population History and Gene Divergence in Native Mexicans Inferred from 76 Human Exomes.

Native American genetic variation remains underrepresented in most catalogs of human genome sequencing data. Previous genotyping efforts have revealed that Mexico's Indigenous population is highly differentiated and substructured, thus potentially harboring higher proportions of private genetic variants of functional and biomedical relevance. Here we have targeted the coding fraction of the genome and characterized its full site frequency spectrum by sequencing 76 exomes from five Indigenous populations across Mexico. Using diffusion approximations, we modeled the demographic history of Indigenous populations from Mexico with northern and southern ethnic groups splitting 7.2 KYA and subsequently diverging locally 6.5 and 5.7 KYA, respectively. Selection scans for positive selection revealed BCL2L13 and KBTBD8 genes as potential candidates for adaptive evolution in Rarámuris and Triquis, respectively. BCL2L13 is highly expressed in skeletal muscle and could be related to physical endurance, a well-known phenotype of the northern Mexico Rarámuri. The KBTBD8 gene has been associated with idiopathic short stature and we found it to be highly differentiated in Triqui, a southern Indigenous group from Oaxaca whose height is extremely low compared to other Native populations

Hidden Quantum Gravity in 3d Feynman diagrams

In this work we show that 3d Feynman amplitudes of standard QFT in flat and homogeneous space can be naturally expressed as expectation values of a specific topological spin foam model. The main interest of the paper is to set up a framework which gives a background independent perspective on usual field theories and can also be applied in higher dimensions. We also show that this Feynman graph spin foam model, which encodes the geometry of flat space-time, can be purely expressed in terms of algebraic data associated with the Poincare group. This spin foam model turns out to be the spin foam quantization of a BF theory based on the Poincare group, and as such is related to a quantization of 3d gravity in the limit where the Newton constant G_N goes to 0. We investigate the 4d case in a companion paper where the strategy proposed here leads to similar results.Comment: 35 pages, 4 figures, some comments adde

Fomento de las inteligencias múltiples en preescolar por medio de la estrategia del cuento

La presente investigación tiene la finalidad de presentar el diseño y la implementación de una estrategia educativa, a la cual se le llamó Cuento, con la cual se pretendió fomentar el desarrollo de las múltiples inteligencias en los niños. Esta investigación se basa en la Teoría de las Inteligencias Múltiples de Howard Gardner, la cual habla de cómo el conocimiento e identificación de los diferentes tipos de inteligencias (lingüística, lógica-matemática, corporal-cinética, musical, intrapersonal y naturalista) dan rutas alternativas para asegurar el éxito de la inteligencia en los alumnos y refuerzan las ventajas intelectuales para enfatizar los talentos de manera satisfactoria