946 resultados para Peroxyl radical


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Comentarios de Jaime Rodríguez, sobre su libro La revolución política durante la época de la Independencia. El Reino de Quito, 1808-1822, Quito, Universidad Andina Simón Bolívar (UASB-E)/Corporación Editora Nacional (CEN), 2006 y los comentarios y reseñas publicadas en la Revista Procesos No. 27.

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Con el presente trabajo pretendo revisar el concepto de liberalismo radical como movimiento político en su configuración estatal de Colombia y Ecuador. Ambos países comparten, para su fortuna, vidas políticas paralelas que pudieron confluir en su historia, formación y política. El primer capítulo se ocupa de la noción de radicalismo e función del liberalismo y el conservadurismo; en el capítulo segundo se desarrollan aquellas condiciones necesarias que vieron nacer al liberalismo radical y le propiciaron su oportunidad en el poder; finalmente, el capítulo tercero se concentra en ilustrar las acciones de los gobiernos radicales, sus protagonistas y su coherencia conforme obedecen a una doctrina liberal radical. Pongo de presente no solo las coincidencias políticas que permitieron el surgimiento de una fuerte corriente liberal radical sino que también destacó las consecuencias positivas y negativas que pudieron dejar sus gobiernos en la praxis y la memoria de sus pueblos. Sin duda, su momento histórico funda en cada nación una esperanza social importante y una revolución que marcaría un devenir muy favorable a los estados nacientes y su reformulación de la forma colonial de administración y la política en manos de una fuerte tradición criolla o militarista. Creo que el liberalismo radical, que con sus matices gobernó en Colombia y Ecuador, puso de presente al individuo como protagonista de la historia y a las sociedades que éstos conformaban. También lucha contra las instituciones coloniales que requieren de lo religioso para sobrevivir. Incuba, en la formación y la educación, el proyecto genuino de un hombre moderno, racional y autónomo que puede construir su futuro y autodeterminarse. Lamentablemente, fracasa en su férreo espíritu de combatir de manera compulsiva a la semilla de religión que había sido legada tres siglos antes pero sienta el Estado laico que permitirá la consolidación estatal con un definitivo quiebre de la política colonial y en la aplicación de un igualitarismo que pueda regular la sociedad naciente.

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Este libro estudia la agenda educativa del liberalismo-radical que gobernó el Ecuador entre 1895 y 1912, luego de la Revolución liberal. Procura responder algunos interrogantes en torno a los temas de educación en la agenda pública de los dirigentes políticos de esa tendencia, al tiempo que busca desvelar lo que lograron ejecutar y aquello que quedó como asignatura pendiente. Su propósito también es revisar si dicha agenda constituyó una ruptura con lo que hasta ese momento se había realizado en cuanto a instrucción pública primaria, en general, y de las mujeres, en particular, o si continuó con la lógica de los gobiernos anteriores respecto al fortalecimiento del Estado y la ampliación de su control hacia periferias que aún se encontraban fuera de su poder en el período analizado. La autora, mediante el análisis de los documentos de la época, demuestra que el proyecto de instrucción pública laica y gratuita del liberalismo-radical tuvo demoras y dificultades para concretarse en el caso de los varones, y no llegó a ejecutarse en lo que se refiere a la formación de las niñas, pese a los esfuerzos que en ello empeñaron.

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1. Soy isoflavones have been extensively studied because of their possible health-promoting effects. Genistein and daidzein, the major isoflavone aglycones, have received most attention; however, they undergo extensive metabolism in the gut and liver, which might affect their biological properties. 2. The antioxidant activity, free radical-scavenging properties and selected cellular effects of the isoflavone metabolites equol, 8-hydroxydaidzein, O-desmethylangiolensin, and 1,3,5 trihydroxybenzene were investigated in comparison with their parent aglycones, genistein and daidzein. 3. Electron spin resonance spectroscopy indicated that 8-hydroxydaidzein was the most potent scavenger of hydroxyl and superoxide anion radicals. Isoflavone metabolites also exhibited higher antioxidant activity than parent compounds in standard antioxidant (FRAP and TEAC) assays. However, for the suppression of nitric oxide production by activated macrophages, genistein showed the highest potency, followed by equol and daidzein. 4. The metabolism of isoflavones affects their free radical scavenging and antioxidant properties, and their cellular activity, but the effects are complex.

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beta-Lactones have, for the first time, been prepared by 4-exo-trig radical cyclization. Thus, alpha-ethenoyloxy radicals react in the presence of tributylstannane in a photothermal process to give beta-lactones. Highest yields were obtained when groups capable of stabilizing a carboncentered radical were present at the 3-position of the alkenoate acceptor.

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DiGrignard reagents of the form XMg(CH2)(n)MgX, where X = Br or I and n = 6, 8, 10 or 12, were allowed to react with PhSnCl3 to produce highly cross-linked Ph-Sn polymeric networks. The Sn-H moiety was incorporated into these insoluble network polymers by treatment with Br-2 and NaBH4. Excellent accessibility of the Sn-H was displayed by these solvent penetrable but insoluble networks, giving them higher Sn-H loadings than all previously reported supported reagents. These reagents were totally regenerable in NaBH4 for radical assisted organic synthesis and no detectable leaching of the Sn into solution was observed during these reactions.

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The three lowest (1(2)A('), 2(2)A('), and 1(2)A(')) potential-energy surfaces of the C2Cl radical, correlating at linear geometries with (2)Sigma(+) and (2)Pi states, have been studied ab initio using a large basis set and multireference configuration-interaction techniques. The electronic ground state is confirmed to be bent with a very low barrier to linearity, due to the strong nonadiabatic electronic interactions taking place in this system. The rovibronic energy levels of the (CCCl)-C-12-C-12-Cl-35 isotopomer and the absolute absorption intensities at a temperature of 5 K have been calculated, to an upper limit of 2000 cm(-1), using diabatic potential-energy and dipole moment surfaces and a recently developed variational method. The resulting vibronic states arise from a strong mixture of all the three electronic components and their assignments are intrinsically ambiguous. (c) 2005 American Institute of Physics.

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The first three electronic states (1(2)A', 2(2)A', 1(2)A '') of the C2Br radical, correlating at linear geometries with (2)Sigma(+) and (2)Pi states, have been studied ab initio, using Multi Reference Configuration Interaction techniques. The electronic ground state is found to have a bent equilibrium geometry, R-CC = 1.2621 angstrom, R-CBr = 1.7967 angstrom, < CCBr 156.1 degrees, with a very low barrier to linearity. Similarly to the valence isoelectronic radicals C2F and C2Cl, this anomalous behaviour is attributed to a strong three-state non-adiabatic electronic interaction. The Sigma, Pi(1/2), Pi(3/2) vibronic energy levels and their absolute infrared absorption intensities at a temperature of 5K have been calculated for the (CCBr)-C-12-C-12-Br-79 isotopomer, to an upper limit of 2000 cm(-1), using ab initio diabatic potential energy and dipole moment surfaces and a recently developed variational method.

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1. Soy isoflavones have been extensively studied because of their possible health-promoting effects. Genistein and daidzein, the major isoflavone aglycones, have received most attention; however, they undergo extensive metabolism in the gut and liver, which might affect their biological properties. 2. The antioxidant activity, free radical-scavenging properties and selected cellular effects of the isoflavone metabolites equol, 8-hydroxydaidzein, O-desmethylangiolensin, and 1,3,5 trihydroxybenzene were investigated in comparison with their parent aglycones, genistein and daidzein. 3. Electron spin resonance spectroscopy indicated that 8-hydroxydaidzein was the most potent scavenger of hydroxyl and superoxide anion radicals. Isoflavone metabolites also exhibited higher antioxidant activity than parent compounds in standard antioxidant (FRAP and TEAC) assays. However, for the suppression of nitric oxide production by activated macrophages, genistein showed the highest potency, followed by equol and daidzein. 4. The metabolism of isoflavones affects their free radical scavenging and antioxidant properties, and their cellular activity, but the effects are complex.

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A discharge-flow system, coupled to cavity-enhanced absorption spectroscopy (CEAS) detection systems for NO3 at lambda = 662 nm and NO2 at lambda = 404 nm, was used to investigate the kinetics of the reactions of NO3 with eight peroxy radicals at P similar to 5 Torr and T similar to 295 K. Values of the rate constants obtained were (k/10(-12) cm(3) molecule(-1) s(-1)): CH3O2 (1.1 +/- 0.5), C2H5O2 (2.3 +/- 0.7), CH2FO2 (1.4 +/- 0.9), CH2ClO2 (3.8(-2.6)(+1.4)), c-C5H9O2 (1.2(-0.5)(+1.1)), c-C6H11O2 (1.9 +/- 0.7), CF3O2 (0.62 +/- 0.17) and CF3CFO2CF3 (0.24 +/- 0.13). We explore possible relationships between k and the orbital energies of the reactants. We also provide a brief discussion of the potential impact of the reactions of NO3 with RO2 on the chemistry of the night-time atmosphere.

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One-electron oxidation of 3,6-diphenyl-1,2-dithiin yields the corresponding radical cation. The product is stable at low temperatures and can be distinguished by a triplet EPR signal. Cyclic voltammetric, UV-vis spectroelectrochemical, and DFT studies were performed to elucidate its molecular structure and electronic properties. Time-dependent DFT calculations reproduce appreciably well the UV-vis spectral changes observed during the oxidation. The results reveal a moderately twisted structure of the 1,2-dithiin heterocycle in the radical cation.

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Peroxy radicals were measured onboard two scientific aircrafts during the AMMA (African Monsoon Multidisciplinary Analysis) campaign in summer 2006. This paper reports results from the flight on 16 August 2006 during which measurements of HO2 by laser induced fluorescence spectroscopy at low pressure (LIF-FAGE) and total peroxy radicals (RO2* = HO2+ΣRO2, R = organic chain) by two similar instruments based on the peroxy radical chemical amplification (PeRCA) technique were subject of a blind intercomparison. The German DLR-Falcon and the British FAAM-BAe-146 flew wing tip to wing tip for about 30 min making concurrent measurements on 2 horizontal level runs at 697 and 485 hPa over the same geographical area in Burkina Faso. A full set of supporting measurements comprising photolysis frequencies, and relevant trace gases like CO, NO, NO2, NOy, O3 and a wider range of VOCs were collected simultaneously. Results are discussed on the basis of the characteristics and limitations of the different instruments used. Generally, no data bias are identified and the RO2* data available agree quite reasonably within the instrumental errors. The [RO2*]/[HO2] ratios, which vary between 1:1 and 3:1, as well as the peroxy radical variability, concur with variations in photolysis rates and in other potential radical precursors. Model results provide additional information about dominant radical formation and loss processes.