The role of Engineering and Engineering Science in Environmental Licensing, Case Study: Chile

En este artículo se analiza el rol de la ingeniería y la investigación en el proceso de licenciamiento ambiental a la luz del cambio institucional realizado en Chile a partir de 2010: la creación del Ministerio de Ambiente y el Servicio de Evaluación Ambiental. Para ello, se mostrarán los desafíos existentes a la hora de implementar esa nueva institucionalidad, las oportunidades detectadas y el trabajo realizado para hacer frente a esos cambios. Finalmente, se presentarán los resultados obtenidos hasta este momento teniendo como modelo el proyecto Punta Alcalde.In this paper, we analyze the role of engineering and research in the environmental licensing process in the light of institutional changes made in Chile since 2010: the creation of the Ministry of Environment and the Environmental Assessment Service. To do this, we will show the challenges posed by these new institutions, the opportunities identified and the work undertaken to address those changes. Finally, the results will be presented taking the Punta Alcalde project as a model

Exploring the Nature of the Energy Barriers on the Mechanism of the Zirconocene-Catalyzed Ethylene Polymerization: A Quantitative Study from Reaction Force Analysis

Ethylene polymerization mediated by methyl-bis(cyclopentadienyl)-zirconium or zirconocene catalyst, [ZrCp₂CH₃]⁺, is one of the most popular catalytic reaction for polyethylene production. Rationalizing the major effects that control the polymer growth result in a challenge for computational studies. Through quantum chemical calculations, we characterized the zirconocene ethylene polymerization reaction mechanism: chain initiation (I; first ethylene insertion) [ZrCp₂CH₂CH₂CH₃]⁺, chain propagation (P; from second (P₁) to ninth (P₉) ethylene insertion) [ZrCp₂ (CH₂)₂₀CH₃]⁺, and chain termination processes (T; β-hydrogen elimination from P₅ or P₉) [ZrHCp₂ (H₂C═CH(CH₂)₁₈CH₃]⁺ are analyzed through the potential energy surface (PES) and reaction force analysis (RFA). The RFA approach involves pulling out the portion of an activation barrier that corresponds to distorting reactants into the geometries they adopt in a transition state structure until it reaches the structural relaxation toward the equilibrium geometry of the product. Because the interactions between the zirconocene and the ethylene molecule are influenced by a combination of several kinds of steric and electronic effects, it is indispensable to understanding these interactions in order to rationalize and predict in a quantitative manner the reaction barrier heights and the concomitant polymer growth. In the present work, we employ a simple procedure within the framework of the RFA and the density functional steric energy decomposition analysis (EDA) approach to quantitatively separate the different types of interactions; steric (ΔE_s), electrostatic (ΔE_e), and quantum (ΔE_q) effects in order to predict the impact of each factor on the course of the polymerization process as well as for the polymer control and design

Internal Rotation of Disilane and Related Molecules:a Density Functional Study

DFT calculations performed on Si_2H_6, Si_2F_6, Si_2Cl_6, and Si_2Br_6 are reported. The evolution of the energy, the chemical potential and the molecular hardness, as a function of torsion angle, is studied. Results at the DFT-B3LYP/6-311++G** level show that the molecules always favor the stable staggered conformations, with low but significant energy barriers that hinder internal rotation. The chemical potential and hardness of Si_2H_6 remains quite constant as the sylil groups rotate around the Si-Si axis, whereas the other systems exhibit different degrees of rearrangement of the electronic density as a function of the torsion angle. A qualitative analysis of the frontier orbitals shows that the effect of torsional motion on electrophilic attack is negligible, whereas this internal rotation may generate different specific mechanisms for nucleophilic attack.Comment: LATeX file, 7 figures, uses elsart.cls, natbib, graphic

Relations among several nuclear and electronic density functional reactivity indexes

A set of connections among several nuclear and electronic indexes of reactivity in the framework of the conceptual Density Functional Theory by using an expansion ofthe energy functional in terms of the total number of electrons and the normal coordinates within a canonical ensemble was derived. The relations obtained provided explicit links between important quantities related to the chemical reactivity of a system. This paper particularly demonstrates that the derivative of the electronic energy with respect to the external potential of a system in its equilibrium geometry was equal to the negative of the nuclear repulsion derivative with respect to the external potentia

Reaction Electronic Flux Perspective on the Mechanism of the Zimmerman Di-π-methane Rearrangement

The reaction electronic flux (REF) offers a powerful tool in the analysis of reaction mechanisms. Noteworthy, the relationship between aromaticity and REF can eventually reveal subtle electronic events associated with reactivity in aromatic systems. In this work, this relationship was studied for the triplet Zimmerman di-π-methane rearrangement. The aromaticity loss and gain taking place during the reaction is well acquainted by the REF, thus shedding light on the electronic nature of reactions involving dibenzobarrelenes

Políticas gubernamentales sobre envejecimiento: el caso de Chile

El análisis de las políticas gubernamentales sobre el envejecimiento en Chile consta de 3 secciones. La primera contiene un diagnóstico demográfico y socioeconómico de la tercera edad. La segunda sección aborda los objetivos de las políticas, cuyo propósito central es definido como el mejoramiento de la calidad de vida del adulto mayor a través del fomento de la actividad independiente, de su dignidad de vida y de sus lazos con la familia y la comunidad. La tercera sección reúne un conjunto de recomendaciones de políticas específicas en las áreas de salud, educación, vivienda y medio ambiente, trabajo y seguridad social, uso del tiempo libre y participación social

Chile: diferenciales de fecundidad y mortalidad por estrato social. Trabajo de investigacion

Incluye BibliografíaLa estimacion de los niveles de fecundidad y mortalidad en Chile se basa en la aplicacion de metodos indirectos a la Encuesta Demografica y Socioeconomica de 1976 y agrupa a la poblacion en estratos sociales, a partir del nivel de instruccion: sin instruccion, con instruccion basica, con instruccion media y con instruccion universitaria (al menos un ano). Los resultados evidencian la presencia de niveles de fecundidad decrecientes a medida que aumenta el nivel de instruccion de las mujeres, desde una tasa global de 5,7 hijos entre las analfabetas, a una tasa de 4,5 entre las con instruccion basica y de 2,8 y 2,2 entre aquellas con instruccion media y universitaria, respectivamente. Asimismo, a medida que aumenta la instruccion, disminuye la mortalidad en los dos primeros anos de vida