Propuesta de delimitación y revitalización del Núcleo Fundacional de Ciudad Antigua, Nueva Segovia, 2020

Los núcleos fundacionales de las ciudades coloniales o iberoamericanas, son en sí, el resultado de las “ideas urbanísticas generadas durante los siglos XV y XVI en Europa”, cuya función fue posicionarse como “centros administrativos, políticos y religiosos”, con el objetivo de “evangelizar a los indígenas y crear ciudades defensivas” (Covarrubias Gaitán, 2008); se estableció una retícula partiendo desde una plaza mayor, creando así una trama ortogonal que dio origen a la ciudad. En este sentido, se reconoce el núcleo histórico de Ciudad Antigua, como referente importantísimo del período de la colonización en Nicaragua, este posee un alto valor patrimonial que refleja el testimonio vivo de las huellas recorridas a través de la historia por más de cuatro siglos. No obstante, dado a las múltiples transformaciones sociales y territoriales ocurridas en torno a su progreso, se encuentra actualmente en un proceso de desvalorización y deterioro, lo cual ha limitado su avance en diferentes aspectos; partiendo de este problema, se plantea la realización de una propuesta de delimitación y revitalización del núcleo fundacional de Ciudad Antigua, como parte de una estrategia que aportará al desarrollo económico, social y cultural, mediante el aprovechamiento de los recursos patrimoniales existentes y el rescate de la identidad cultural del sitio. Para este estudio investigativo se utilizaron técnicas cualitativas como: entrevistas, observación, revisión documental y levantamientos en campo, en relación a la estructura esta se fundamenta en un proceso metodológico secuencial que engloba la parte teórica con el análisis y discusión de los resultados obtenidos. Finalmente, se delimito el núcleo fundacional mediante la aplicación de criterios específicos basados en especialistas en la temática, fundamentado por un análisis histórico y urbanístico de la ciudad, además se realizó un análisis urbano-arquitectónico que permitió conocer las problemáticas y potencialidades del sector, concluyendo con la presentación de la propuesta de revitalizació

The double [3+2] photocycloaddition reaction

One of a synthetic organic chemists‟ greatest challenges is to create step-efficient routes toward compounds with high molecular complexity. Therefore, reactions such as the meta photocycloaddition of an olefin to a benzene derivative, which provide more than one bond in a single step are of significant importance. It this remarkable reaction three new σ bonds, three new rings and up to six new stereocenters are formed simultaneously. Additional complexity can be added by tethering the two reacting partners together and this form of the reaction has found many uses in natural product synthesis. In this work a remarkable double [3+2] photocycloaddition reaction is reported that results in the formation of a complex cis, cis, cis, trans-[5, 5, 5, 5] fenestrane derivative from a simple flat aromatic acetal with two branching alkenes. During this dramatic transformation four carboncarbon bonds, five new rings and seven new stereocenters are created in a single one-pot process using only UV light. The reaction occurs in a sequential manner from the linear meta photocycloadduct, via a secondary [3+2] addition of the alkene across the cyclopropane of the adduct. In addition, an angular meta photocycloadduct also produced in the initial addition step, undergoes an alternative fragmentation-translocation photoreaction to afford a silphinene-like angular tricyclic compound. In this work the investigation of this newly discovered process is discussed via the synthesis and subsequent irradiation of a series of photosubstrates containing different functional groups in the arene-alkene tether. In addition, attempts toward the synthesis of alternative structures using the same double [3+2] photocycloaddition are reported

Studies on Toxic Substances of Locoweeds, Astragalus earlei and Others.

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Highly efficient synthesis of the tricyclic core of Taxol by cascade metathesis

An efficient enantioselective synthesis of the ABC tricyclic core of the anticancer drug Taxol is reported. The key step of this synthesis is a cascade metathesis reaction, which leads in one operation to the required tricycle if appropriate fine-tuning of the dienyne precursor is performed

Modulating attentional load affects numerosity estimation: evidence against a pre-attentive subitizing mechanism

Traditionally, the visual enumeration of a small number of items (1 to about 4), referred to as subitizing, has been thought of as a parallel and pre-attentive process and functionally different from the serial attentive enumeration of larger numerosities. We tested this hypothesis by employing a dual task paradigm that systematically manipulated the attentional resources available to an enumeration task. Enumeration accuracy for small numerosities was severely decreased as more attentional resources were taken away from the numerical task, challenging the traditionally held notion of subitizing as a pre-attentive, capacity-independent process. Judgement of larger numerosities was also affected by dual task conditions and attentional load. These results challenge the proposal that small numerosities are enumerated by a mechanism separate from large numerosities and support the idea of a single, attention-demanding enumeration mechanism

Comparison of three video laryngoscopy devices to direct laryngoscopy for intubating obese patients: a randomized controlled trial

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