Listar Química por título
Mostrando ítems 253-272 de 360
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Photoisomerization of 5-Membered Heterocycles
(1987-06-07)Photolysis of substituted furans, thiophenes, and pyrroles resulted in positional isomerization as a consequence of the scrambling of the ring carbon atoms, Two intermediates have been proposed for this photoisomerization, ... -
Photoreactivity of Oil and Alcoholic Diterpenic Varnishes: Key Role of the Polymerization Process
(2020)he conservation of artworks is a key issue in cultural heritage. The alterations of the varnish could be linked mainly to the photopolymerization of the natural resin. The photodegrada- tion of sandarac and rosin under ... -
Phytochemical study of endemic Costa Rican Annonaceae species Annona pittieri and Cymbopetalum costaricense
(2021)Phytochemical profile of the Central American rainforest endemic Annonaceae species, Annona pittieri and Cymbonopetallum costaricense, were studied in search of novel bioactive compounds. The acetogenin squamocin (1) ... -
Polifenoides de Uncaria Tormentosa y propiedades fitoterapéuticas de uña de gato costarricense
(2012-12-18)Esta invención se refiere a extractos fenólicos conteniendo procianidinas, propelargonidinas y flavanolignanos, con propiedades/actividades potencialmente beneficiosas para la salud humana, y obtenidos a partir de las ... -
Polyphenolic HRMS Characterization, Contents and Antioxidant Activity of Curcuma longa rhizomes from Costa Rica
(2022-03)Curcuma longa constitutes an important source of secondary metabolites that have been associated with multiple health benefits. For instance, curcumin, demethoxycurcumin and bisdemethoxy-curcumin, have been found to perform ... -
Potent nor-triterpenoid blockers of the voltage-gated potassium channel Kv1.3 from Spachea correae
(1998)The isolation and structure elucidation of two novel nor-triterpenoid KV1.3 potassium channel blockers correolide and dehydrocorreolide from the Costa Rican tree Spachea correae are reported. The first potent and selective ... -
Predation of the Rolled-Leaf Beetle Cephaloleia kressi García-Robledo (Coleoptera: Chrysomelidae: Cassidinae) by the Rove Beetle Phanolinus Sp. (Coleoptera: Staphylinidae: Xanthopygina) in a Montane Forest of Costa Rica
(2020-12-22)The genus Cephaloleia Chevrolat includes 215 species, known as rolled-leaf beetles, all of which are restricted to the Neotropics (Garcı́a-Robledo et al. 2015; Staines and Garcı́a-Robledo 2014). These beetles complete their ... -
Pristine but metal-rich Río Sucio (Dirty River) is dominated by Gallionella and other iron-sulfur oxidizing microbes
(2017-03)Whether the extreme conditions of acidity and heavy metal pollution of streams and rivers originating in pyritic formations are caused primarily by mining activities or by natural activities of metal-oxidizing microbes ... -
Producción de un detergente líquido ambientalmente preferible y estrategia de lanzamiento al mercado del Valle Central Occidental de Costa Rica
(2009)Se determinó la viabilidad de instalar una empresa de productos químicos preferibles para el ambiente, en el cantón de Poás de Alajuela, Costa Rica. Con este propósito se seleccionó una formulación de un detergente líquido ... -
Propargylation of Alkyl Halides: (E)-6,10-dimethyl-5,9-undecadien-1-yne and (E)-7,11-dimethyl-6,10-dodecadien-2-yn-1-ol
(1990)El siguiente documento es parte de un experimento científico que se titula “Propargylation of Alkyl Halides: (E)-6,10-dimethyl-5,9-undecadien-1-yne and (E)-7,11-dimethyl-6,10-dodecadien-2-yn-1-ol”. El mismo fue realizado ... -
Propargylation of Carbonyl Compounds: An Efficient Method for the Synthesis of Homopropargyl Alcohols
(1998)Controlled dilithiation of allene, with two equivalents of n-butytlithium, produces the propargyl dianion 5. The latter couple efficiently with carbonyl compounds to produce homopropargyl alcohols in high yields. -
Purpureocillium roseum sp. nov. A new ocular pathogen for humans and mice resistant to antifungals
(2020)Background Infectious keratitis is the main cause of preventable blindness worldwide, with about 1.5–2.0 million new cases occurring per year. This inflammatory response may be due to infections caused by bacteria, fungi, ... -
Quimica Orgánica Experimental
(1978)Los autores han tratado de reunir en este libro un conjunto de experimentos que permiten al profesor ejemplarizar todas las técnicas fundamentales del laboratorio de Química Orgánica y también ejemplarizar los compuestos ... -
Rapid Determination of the ‘Legal Highs’ 4-MMC and 4-MEC by Spectroelectrochemistry: Simultaneous Cyclic Voltammetry and In Situ Surface-Enhanced Raman Spectroscopy
(2021-12-31)The synthetic cathinones mephedrone (4-MMC) and 4-methylethcathinone (4-MEC) are two designer drugs that represent the rise and fall effect of this drug category within the stimulants market and are still available in ... -
Rapid shift in microbial community structure in a neutral hydrothermal hot spring from Costa Rica
(2020)In this work, we characterize the geochemistry and microbial community of Bajo las Peñas, a neutral (pH 6.5-7.4), hot spring (T = 62.0-68.0°C) located near Turrialba Volcano, Costa Rica. The microbiota at its two sources ... -
Reacciones del 2,2´-Tio-benzimidazol con Sulfato de Dimetilo
(1979)Se efectuó la reacción del 2,2´-tiobis-benzimidazol con el sulfato de dimetilo por pasos. Se comprobó la formación de: 1,1´-dimetil-2,2´-tiobis-benzimidazol (2) y del diperclorato del 1,1´,3,3´-tetrametil-2,2´-tiobisbenz ... -
Reacción del Oxido de Etileno con Clorhidratos de Aminoácidos
(1978)Se estudió la reacción del óxido de etileno con clorhidratos de aminoácidos a bajas temperaturas. Esta reacción conduce a la obtención de los aminoácidos libres. Se probó la eficiencia de este nuevo método de purificación ... -
Reactive Intermediates in the Photolysis of Furan, Thiophene and Pyrrole: The Dewar and the Ring Contraction forms
(1985-07-14)Five-member aromatic heterocycles have been known to undergo scrambling of the ring atoms upon photolysis. These reactions are characterized by their selectivity and several mechanisms have been proposed involving the ... -
Reactivity and structure of derivatives of 2-hydroxy-1,4-naphthoquinone (lawsone)
(2007-11)The structures of two derivatives of 2-hydroxy-1,4-naphthoquinone (lawsone) are examined using the density functional theory (DFT) hybrid functional B3LYP. Using the optimized structure of lawsone acetate, the reactivity ... -
Recolección y preservación de muestras para la medición de variables del sistema de CO2 en aguas marino - costeras
(2021-10)El texto tiene como objetivo establecer el procedimiento de recolección y preservación de muestras de agua de mar para la medición de variables del sistema de carbonatos.