Theoretical Studies of Homogeneous Catalysts Mimicking Nitrogenase

The conversion of molecular nitrogen to ammonia is a key biological and chemical process and represents one of the most challenging topics in chemistry and biology. In Nature the Mo-containing nitrogenase enzymes perform nitrogen 'fixation' via an iron molybdenum cofactor (FeMo-co) under ambient conditions. In contrast, industrially, the Haber-Bosch process reduces molecular nitrogen and hydrogen to ammonia with a heterogeneous iron catalyst under drastic conditions of temperature and pressure. This process accounts for the production of millions of tons of nitrogen compounds used for agricultural and industrial purposes, but the high temperature and pressure required result in a large energy loss, leading to several economic and environmental issues. During the last 40 years many attempts have been made to synthesize simple homogeneous catalysts that can activate dinitrogen under the same mild conditions of the nitrogenase enzymes. Several compounds, almost all containing transition metals, have been shown to bind and activate N(2) to various degrees. However, to date Mo(N(2))(HIPTN)(3)N with (HIPTN)(3)N= hexaisopropyl-terphenyl-triamidoamine is the only compound performing this process catalytically. In this review we describe how Density Functional Theory calculations have been of help in elucidating the reaction mechanisms of the inorganic compounds that activate or fix N(2). These studies provided important insights that rationalize and complement the experimental findings about the reaction mechanisms of known catalysts, predicting the reactivity of new potential catalysts and helping in tailoring new efficient catalytic compounds

Innovación turística y desarrollo regional

Libro que se compila 14 capítulos asociados a las temáticas de innovación y desarrollo tecnológico en el sector turístico, emprendimiento y tecnologías emergentes, políticas estratégicas y tácticas para mejorar la competitividad en las empresas, políticas públicas y educación para el desarrollo regional y responsabilidad social ambientalBook that compiles 14 chapters associated to the themes of innovation and technological development in the tourism sector, entrepreneurship and emerging technologies, strategic and tactical policies to improve competitiveness in companies, public policies and education for regional development and environmental social responsibilityInnovación social como estrategia para el desarrollo de las poblaciones palafíticas de la ciénaga grande de santa marta mediante la oferta de productos turísticos / Gregoria Polo de Lobatón; José Luis Rosenstiehl Martínez; Daulis Lobatón Polo -- Uso de las tic para mejorar la competitividad turística en San Basilio de Palenque / Jesús Llerena Cabrera; Raúl José Martelo Gómez; David Franco Borré -- Plataforma web niu (nuevo, ideas y usados) / Néstor José Ocampo Ardila -- Posicionamiento estratégico del turismo urbano de eventos como atributo de la personalidad del espacio territorial de la ciudad de santa marta / Zuleidy María Ruíz Torres -- Identificación competitiva de la oferta exportadora de la región ariari para fortalecer el desarrollo social y económico en zonas de posconflicto basado en el comercio exterior y logística / Keyla Karina González Martínez -- Tecnologías integradas en gestión sostenible de operadores turísticos en zonas de posconflicto del departamento del meta / Carlos Hernán Cruz Castro; óscar Eduardo Sarmiento Saavedra -- Herramienta online de control de ingresos y facturación: una solución dinámica para las pequeñas y medianas empresas / Esmerlis Camargo Torres; Antonio José González Liñán; Marieth Orcasitas Peñaloza; Yerson Monroy Contreras -- Modelo de cadena productiva dinamizado a través de la educación y las estrategias TIC para el desarrollo regional sostenible en Risaralda / Beatriz Elena Franco Cárdenas; Patricia Henao Montoya; Marco Aurelio Aristizabal Valencia -- Evaluación físico - química de adhesivo de yuca (manihot esculenta) como alternativa comercial para la Orinoquia / Yarithza Molina Caro; Wilfran Hernán Cortes Conde -- Formulaciones nutracéuticas alimenticias para estilos de vida saludables / Daldo Araujo Vidal; Daniel Mendoza Cujia; Maresa Anaya de oro -- Competencias tecnológicas como estrategia formativa en los aprendices de gestión de redes de datos del SENA regional guajira / Carlos Antonio Salas Solano; Alejandro Jesús Osorio Amaya; Alda Pérez Campuzano; Duvan Andrés rondón bravo -- Uso y apropiación del computador como herramienta para las prácticas educativas de los docentes / Alda Pérez Campuzano; Carlos Antonio Salas Solano; Elkin Fuentes Jiménez; Kira Rodríguez Moscote -- El aviturismo como eje transformador de cultura ambiental y desarrollo sustentable / Lina María Gamarra Pineda; Néstor Alejandro Tascón Arias -- Huella ecológica (he), indicador de condición ambiental para evaluar la sostenibilidad en instituciones de educación (ie) / Cristian David Trujillo CardonaPrimera ediciónna169 página

Influencia del BIM en una estructura de tres niveles

Este proyecto se desarrolló con el fin de modelar una edificación existente para conocer cómo influye el programa en el proceso constructivo, este trabajo se llevó a cabo por medio de dos programas de ingeniería tales como ETABS y REVIT; Inicialmente, se obtuvo el plano estructural y arquitectónico de una edificación de uso residencial de 3 niveles con una altura total de 12,8m y un área en planta de 243m2, ubicado en el barrio las Catleyas de la ciudad de Neiva. Como primera medida, se utiliza el programa ETABS y por medio de esté se modela la estructura con la finalidad de verificar las derivas de acuerdo a las especificaciones de la NSR-10 Titulo A y B, adicionalmente, se realizó el diseño del espectro elástico, el cual se introdujo al modelo para luego observar el comportamiento de la estructura cuando se presente un movimiento sísmico. Finalmente, se hace la verificación de la deriva máxima donde se observó que no cumple de acuerdo a lo especificado en la norma. Con el fin de observar la parte arquitectónica y estructural de la edificación al mismo tiempo, se modeló los elementos estructurales por medio del software REVIT, tales como: zapatas, columnas, vigas, vigas cargueras, viga canal, escaleras; asimismo, se propuso dos tipos de losas, para el piso 1 y cubierta una placa maciza de 10 cm de espesor y una losa nervada para los pisos 2 y 3 con una dimensión de 5 cm de espesor y los nervios 10 x 20 cada 70 cm. El modelo estructural se exporta a una plantilla arquitectónica en REVIT, donde se modelan los planos arquitectónicos de la edificación. Finalmente, se obtuvo las cantidades de obra para cada material el cual es exportado a Excel para observarlas detalladamente.Introducción. -- 1. Alcance. -- 2. Objetivos. -- 2.1 Objetivo general. -- 2.2 Objetivos especificos. -- 3. Generalidades. -- 3.1 Descripción general del proyecto. -- 3.2 Localización del proyecto. -- 4. Diseño metodológico. -- 4.1 Espectro elástico de diseño. -- 4.1.1 Definición del nivel de amenaza sísmica y el espectro de diseño. -- 5. Modelación en etabs. -- 6. Modelo estructural. -- 7. Modelo arquitectonico. -- 8. Cantidades de obra . -- 9. Conclusiones. -- Bibliografía. [email protected]@[email protected]

Structural Role of Uracil DNA Glycosylase for the Recognition of Uracil in DNA Duplexes. Clues from Atomistic Simulations

In the first stage of the base excision repair pathway the enzyme uracil DNA glycosylase (UNG) recognizes and excises uracil (U) from DNA filaments. U repair is believed to occur via a multistep base-flipping process, through which the damaged U base is initially detected and then engulfed into the enzyme active site, where it is cleaved. The subtle recognition mechanism by which UNG discriminates between U and the other similar pyrimidine nucleobases is still a matter of active debate. Detailed structural information on the different steps of the base-flipping pathway may provide insights on it. However, to date only two intermediates have been trapped crystallographically thanks to chemical modifications of the target and/or of its complementary base. Here, we performed force-field based molecular dynamics (MD) simulations to explore the structural and dynamical properties of distinct UNG/dsDNA adducts, containing A:U, A:T, G:U, or G:C base pairs, at different stages of the base-flipping pathway. Our simulations reveal that if U is present in the DNA sequence a short-lived extra-helical (EH) intermediate exists. This is stabilized by a water-mediated H-bond network, which connects U with His148, a residue pointed out by mutational studies to play a key role for U recognition and catalysis. Moreover, in this EH intermediate, UNG induces a remarkable overall axis bend to DNA. We believe this aspect may facilitate the flipping of U, with respect to other similar nucleobases, in the latter part of the base-extrusion process. In fact, a large DNA bend has been demonstrated to be associated with a lowering of the free energy barrier for base-flipping. A detailed comparison of our results with partially flipped intermediates identified crystallographically or computationally for other base-flipping enzymes allows us to validate our results and to formulate hypothesis on the recognition mechanism of UNG. Our study provides a first ground for a detailed understanding of the UNG repair pathway, which is necessary to devise new pharmaceutical strategies for targeting DNA-related pathologies

Oral contraceptive pill, progestogen or estrogen pre-treatment for ovarian stimulation protocols for women undergoing assisted reproductive techniques.

Contains fulltext : 89927.pdf (publisher's version ) (Open Access)BACKGROUND: For many subfertile women, assisted reproductive techniques (ART) is the only hope for a pregnancy and live birth. The combined oral contraceptive pill (OCP) given prior to the hormone therapy in an IVF cycle may result in better pregnancy outcomes of ART. OBJECTIVES: To assess whether pre-treatment with combined OCPs, progestogens or estrogens in ovarian stimulation protocols affects outcomes in subfertile couples undergoing ART. SEARCH STRATEGY: We searched the Cochrane Menstrual Disorders and Subfertility Group Specialised Register, The Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, PsycINFO. Other electronic resources on the Internet, reference list of relevant articles were also searched as well as the ESHRE abstracts (2008). All these searches were conducted in November 2008. SELECTION CRITERIA: Randomised controlled trials of pre-treatment with combined OCP, progestogen or estrogen in subfertile women undergoing IVF/ICSI. DATA COLLECTION AND ANALYSIS: Two authors independently extracted the data and assessed risk of bias. We calculated Peto odds ratios for dichotomous data and weighted mean difference for continuous variables. Authors of trials were contacted in case of missing data. MAIN RESULTS: No evidence of effect was found with regard to the number of live births when using a pre-treatment. However, the combined OCP in GnRH antagonist cycles, compared to no pre-treatment, is associated with fewer clinical pregnancies (Peto OR 0.69, P = 0.03) and more days and a higher amount of gonadotrophin therapy (respectively: MD 1.44, P < 0.00001; and MD 691.69, P < 0.00001). Also compared to placebo or no pre-treatment, a progestogen pre-treatment in GnRH agonist cycles, is associated with more clinical pregnancies (Peto OR 1.95, P = 0.007) and fewer ovarian cysts (Peto OR 0.21, P < 0.00001). At last, in estrogen pre-treated GnRH antagonist cycles, compared to no pre-treatment, more oocytes are retrieved (MD 2.01, P < 0.00001), but a higher amount of gonadotrophin therapy is needed (MD 207.08, P < 0.00001). For the other outcomes no evidence of effect was found or there were not enough studies available in the subgroup for pooling. AUTHORS' CONCLUSIONS: There was evidence of improved pregnancy outcomes with progestogen pre-treatment and poorer pregnancy outcomes with a combined OCP pre-treatment. However, we conclude that major changes in ART protocols should not be made at this time, since the number of overall studies in the subgroups is small and reporting of the major outcomes is inadequate

Structural Role of Uracil DNA Glycosylase for the Recognition of Uracil in DNA Duplexes. Clues from Atomistic Simulations

In the \ufb01rst stage of the base excision repair pathway the enzyme uracil DNA glycosylase (UNG) recognizes and excises uracil (U) from DNA \ufb01laments. U repair is believed to occur via a multistep base-\ufb02ipping process, through which the damaged U base is initially detected and then engulfed into the enzyme active site, where it is cleaved. The subtle recognition mechanism by which UNG discriminates between U and the other similar pyrimidine nucleobases is still a matter of active debate. Detailed structural information on the di\ufb00erent steps of the base-\ufb02ipping pathway may provide insights on it. However, to date only two intermediates have been trapped crystallographically thanks to chemical modi\ufb01cations of the target and/or of its complementary base. Here, we performed force-\ufb01eld based molecular dynamics (MD) simulations to explore the structural and dynamical properties of distinct UNG/dsDNA adducts, containing A:U, A:T, G:U, or G:C base pairs, at di\ufb00erent stages of the base-\ufb02ipping pathway. Our simulations reveal that if U is present in the DNA sequence a shortlived extra-helical (EH) intermediate exists. This is stabilized by a water-mediated H-bond network, which connects U with His148, a residue pointed out by mutational studies to play a key role for U recognition and catalysis. Moreover, in this EH intermediate, UNG induces a remarkable overall axis bend to DNA. We believe this aspect may facilitate the \ufb02ipping of U, with respect to other similar nucleobases, in the latter part of the base-extrusion process. In fact, a large DNA bend has been demonstrated to be associated with a lowering of the free energy barrier for base-\ufb02ipping. A detailed comparison of our results with partially \ufb02ipped intermediates identi\ufb01ed crystallographically or computationally for other base-\ufb02ipping enzymes allows us to validate our results and to formulate hypothesis on the recognition mechanism of UNG. Our study provides a \ufb01rst ground for a detailed understanding of the UNG repair pathway, which is necessary to devise new pharmaceutical strategies for targeting DNA-related pathologies