Morphologies of Precise Polyethylene-Based Acid Copolymers and Ionomers

Acid copolymers and ionomers are polymers that contain a small fraction of covalently bound acidic or ionic groups, respectively. For the specific case of polyethylene (PE), acid and ionic pendants enhance many of the physical properties such as toughness, adhesion and rheological properties. These improved properties result from microphase separated aggregates of the polar pendants in the non-polar PE matrix. Despite the widespread industrial use of these materials, rigorous chemical structure - morphology - property relationships remain elusive due to the inevitable structural heterogeneities in the historically-available acid copolymers and ionomers. Recently, precise acid copolymers and ionomers were successfully synthesized by acyclic diene metathesis (ADMET) polymerization. These precise materials are linear, high molecular weight PEs with pendant acid or ionic functional groups separated by a precisely controlled number of carbon atoms. The morphologies of nine precise acid copolymers and eleven precise ionomers were investigated by X-ray scattering, solid-state 13C nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). For comparison, the morphologies of linear PEs with pseudo-random placement of the pendant groups were also studied. Previous studies of precise copolymers with acrylic acid (AA) found that the microstructural precision produces a new morphology in which PE crystals drive the acid aggregates into layers perpendicular to the chain axes and presumably at the interface between crystalline and amorphous phases. In this dissertation, a second new morphology for acid copolymers is identified in which the aggregates arrange on cubic lattices. The fist report of a cubic morphology was observed at room and elevated temperatures for a copolymer functionalized with two phosphonic acid (PA) groups on every 21st carbon atom. The cubic lattice has been identified as face-centered cubic (FCC). Overall, three morphology types have been identified for precise acid copolymers and ionomers at room temperature: (1) liquid-like order of aggregates dispersed throughout an amorphous PE matrix, (2) one-dimensional long-range order of aggregates in layers coexisting with PE crystals, and (3) three-dimensional periodicity of aggregates in cubic lattices in a PE matrix featuring defective packing. The liquid-like morphology is a result of high content of acid or ionic substituents deterring PE crystallinity due to steric hindrance. The layered morphology occurs when the content of pendants is low and the PE segments are long enough to crystallize. The cubic morphologies occur in precise copolymers with geminal substitution of phosphonic acid (PA) groups and long, flexible PE segments. At temperatures above the thermal transitions of the PE matrix, all but one material present a liquid-like morphology. Those conditions are ideal to study the evolution of the interaggregate spacing (d*) in X-ray scattering as a function of PE segment length between pendants, pendant type and pendant architecture (specifically, mono or geminal substitution). Also at elevated temperatures, the morphologies of precise acrylic acid (AA) copolymers and ionomers were investigated further via atomistic molecular dynamics (MD) simulations. The simulations complement X-ray scattering by providing real space visualization of the aggregates, demonstrating the occurrence of isolated, string-like and even percolated aggregate structures. This is the first dissertation completely devoted to the morphology of precise acid copolymers and precise ionomers. The complete analysis of the morphologies in these novel materials provides new insights into the shapes of aggregates in acid copolymers and ionomers in general. A key aspect of this thesis is the complementary use of experimental and simulation methods to unlock a wealth of new understanding

Unit for service of Guateque – Boyaca, Strategic Planning

Esta investigación se propuso establecer la planeación estratégica de La Unidad Técnica de Servicios Públicos del municipio de Guateque ubicado en el departamento de Boyacá, perteneciente a la Alcaldía municipal y encargada de proveer los servicios de acueducto, alcantarillado y aseo para la población urbana del municipio. Se logró la mejora del plan estratégico actual con la propuesta de una estrategia competitiva orientada al cumplimiento de los objetivos planteados en el plan de gobierno de la Alcaldía, a generar confianza en el ciudadano respecto a la prestación del servicio público domiciliario y a lograr la diferenciación de la entidad a nivel local, departamental y nacional.The purpose of this research was to establish a strategic planning of the Guateque township Public Service Tech Unit located in Boyacá. It belongs to the Municipal town hall and its labor is to provide water, sewage and cleaning service for the urban population of this town. Improving the current strategic plan it was achieved with the proposed competitive strategy that allows to reach the goals planned by the Major goverment, to generate a reliable relationship between citizen and service providers and to show a difference of the service locally, municipally and nationally

Identification and Evolution of Transcription Factors in Stramenopiles

Background. 
Many transcriptional regulatory proteins have been identified and classified into several families on the basis of sequence similarity (Fukami, 2003), these families usually regulate important biological processes, such as development and responses to external stimuli. Transcription factors (TFs) regulate spatial and temporal gene expression by binding to DNA and either activating or repressing the action of RNA polymerases (Latchman, 2004); in addition to TFs, other Transcriptional regulators (TRs) participate in transcriptional modulation by e.g., chromatin remodeling. With the availability of genome sequences for several organisms and computational strategies for gene functional annotation, the entire set of Transcription factors (TFs) and Transcription regulators (TRs) can be identified, described, and compared between species and lineages. The diversity among Stramenopiles is striking; they range from large multicellular seaweeds to tiny unicellular species, they are present in freshwater, marine and terrestrial habitats and embrace many ecologically important algal (e.g. diatoms, brown algae, chrysophytes), and heterotrophic (e.g., Oomycetes) groups.

Methods. 
In order to find TF and TR genes in the deduced proteomes of Stramenopile we followed the approach developed in Perez et al. 2010. Briefly, it exploits the presence of protein domains and their combinations, in the form of boolean rules, that are specific for different families of TFs and TRs. Such rules are represented as a bipartite graph in which a set of nodes represent gene families and the other set of nodes, protein domains. Edges are drawn between nodes of different types indicating whether a protein domain is required in the gene family or it is forbidden.

Results. 
We applied an enlarged set of rules to the deduced proteomes of 8 different Stramenopiles, identifying more than 400 different regulatory genes in each species belonging to up to 59 different gene families.

Conclusions. 
The identification of this class of regulatory genes will constitute and important resource that could be exploited in gene functional characterization and evolutionary analyses. All TFs and TRs families found will be publicly released via a web database.

References.
Pérez-Rodríguez P, Riaño-Pachón DM, Corrêa LG, Rensing SA, Kersten B, Mueller-Roeber B. 2010. Nucleic Acids Res. 38(Database issue):D822-

La doctrina de seguridad nacional: materialización de la guerra fría en América del Sur

El artículo estudia la forma en que el concepto de seguridad nacional fue convertido durante la guerra fría en la Doctrina de Seguridad Nacional, y la manera en que ésta fue aplicada a los países de América Latina bajo la influencia de Estados Unidos. Se destaca el papel de los militares en la aplicación de esta doctrina, así como la lucha contra el enemigo interno y sus implicaciones para la política de los países considerados.The article studies how the concept of national security was transformed during the cold war into the Doctrine of National Security, and the way in which it was applied to the countries of Latin America under the influence of the United States. The role of the military in the application of this doctrine is underlined, as well as the fight against the internal enemy and its implications for the politics of the considered countries

Nota editorial

En el marco de la conmemoración del Bicentenario de Colombia, es necesario generar espacios de reflexión que permitan analizar, en profundidad, tan importante acontecimiento nacional. Para hacerlo, se deben tener en cuenta elementos históricos que, con base en diferentes perspectivas, aporten puntos de vista destinados a enriquecer la actual visión que existe de país y, a la vez, fortalezcan las perspectivas que definirán el futuro de la nación

Evaluación del proceso de habilitación de 47 empresas médicas previsionales Nicaragua, I semestre - 1999.

El presente estudio evalúa y sistematiza el proceso de habilitación de 47 Empresas Medicas Previsionales de Nicaragua, implementado en el I Semestre de 1999. La información se obtuvo mediante revisión de los documentos disponibles en los archivos de la Dirección de Regulación del Ministerio de Salud de Nicaragua (MINSA) y entrevistas a funcionarios que participaron en el proceso, a quienes les fue presentado los resultados preliminares, integrando sus observaciones y asociándose a los resultados obtenidos en la búsqueda de información, dando salida a los objetivos específicos del estudio. Se recomienda descentralizar la habilitación de establecimientos de salud a los 17 SILAIS, de conformidad a como lo establece la Ley General de Salud y su Reglamento; facilitar la regulación de las EMP‟s y demás establecimientos de salud al SILAIS correspondiente en su respectiva jurisdicción, destinando recursos financieros para continuar con el programa de control y seguimiento de la habilitación en las EMP‟s. Integrar a la estructura organizativa de los SILAIS, una oficina de regulación y manuales de la habilitación, actualizando los instrumentos de evaluación cada dos años

Presentación.Nota Editorial:10 Años de la Revista de Estudios Sociales, RES

En agosto de 1998 salió a la luz pública el primer número de la Revista de Estudios Sociales, RES, publicada por la Facultad de Ciencias Sociales de la Universidad de los Andes, con el patrocinio de la Fundación Social. Aunque sólo han transcurrido 10 años desde ese entonces, era un tiempo en el que todavía las revistas académicas eran escasas, efímeras, o tenían poca regularidad. En Los Andes habían nacido y desaparecido varias revistas de contenido social, entre ellas, Razón y Fábula, de gr..

Nota editorial

Los octanos tienen una importancia capital para la humanidad. Fundamentales en la regulación global del clima, el 60% de la población mundial vive a menos de 100 kilómetros de las costas y obtiene de ellos fuentes vitales de alimentación y energía, así como materiales utilizados en diferentes áreas del conocimiento y la investigación. Abarcan el 71% dela superficie de nuestro planeta, almacenan el 90% de los recursos hídricos existentes y albergan más de 250 mil especies