969 resultados para LIE-ALGEBRAS


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Resumen: La fuerte crisis financiera y los hechos internacionales más recientes están atravesados por grandes cuestionamientos acerca de la relación entre la ética y la economía, y la responsabilidad que la economía de mercado pueda tener en problemas sociales y políticos más profundos. En este artículo se presentan algunas de las dimensiones del debate entre la ética y la economía que están detrás de la cuestión fundamental del rol de las responsabilidades éticas en la crisis financiera. El tema es abordado desde una perspectiva que considera que existe un fuerte vínculo entre la ética y la economía. Esta visión representa un desafío frente al punto de vista tradicional, que sostiene que debe haber una separación estricta entre la racionalidad ética y la racionalidad económica.

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Resumen: Krzysztof Penderecki (Dębica, 1933) ha sido considerado una ‘verdadera leyenda de la historia de la música’ y ‘el compositor vivo más reconocido por el público en general’. ¿Cuál es la estética de este artista polaco que compone para príncipes, catedrales y ciudades, y ha recibido más de medio centenar de honores y reconocimientos internacionales? A dicha estética, plasmada en la producción musical pendereckiana, nos aproximaremos a través de un enfoque diacrónico-sincrónico y descriptivo-normativo, debido a la naturaleza de ésta. Después de exponer los estímulos musicales de la infancia y juventud de Penderecki, describiremos las distintas fases de su producción, deteniéndonos en sus respectivas obras y particularidades; luego, a modo de síntesis, examinaremos las características inherentes a la totalidad de dicha producción, resumida gráficamente a través de un modelo funcional; por último, abordaremos las concepciones subyacentes en lo más profundo de la creación del artista polaco con quien hemos tenido el privilegio de estudiar.

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For a n-dimensional vector fields preserving some n-form, the following conclusion is reached by the method of Lie group. That is, if it admits an one-parameter, n-form preserving symmetry group, a transformation independent of the vector field is constructed explicitly, which can reduce not only dimesion of the vector field by one, but also make the reduced vector field preserve the corresponding ( n - 1)-form. In partic ular, while n = 3, an important result can be directly got which is given by Me,ie and Wiggins in 1994.

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[ES] Este trabajo propone una lectura de los seis primeros cuadernos del diario que Alejandra Pizarnik escribió a lo largo de toda su vida, desde los 18 años y hasta que murió a la edad de 36. El análisis de estos cuadernos, escritos entre 1954 y 1958, nos permite recorrer el itinerario que Alejandra Pizarnik realiza por la cuestión genérica, la cuestión nacional y la cuestión sexual. Desde su experiencia en cuanto sujeto, la escritura registra esta primera fase en la construcción del yo que Pizarnik desea para su diario. Esta fase, que se puede denominar etapa-derribo, está dominada por el desafío a las ideas del discurso hegemónico. Una vez haya resuelto este escollo en la construcción del yo de su diario, la escritura de Pizarnik no volverá sobre estos temas. Sin embargo, la búsqueda el “verdadero” yo se registra como proceso en el que a un movimiento de construcción del yo, le sigue un movimiento de destrucción de lo que las palabras han conformado, en secuencias en las que la apelación a la mentira de lo escrito o la desconfi anza en la capacidad del lenguaje para expresarlo, son la pauta de dicha escritura.

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[EN] Progress in methodology in specific fields is usually very closely linked to the technological progress in other areas of knowledge. This justifies the fact that lexicographical techniques have had to wait for the arrival of the IT era of the last decades of the 20th century in order to be able to create specialised electronic dictionaries which can house and systemise enormous amounts of information which can later be dealt with quickly and efficiently. This study proposes a practical-methodological model which aims to solve the grammatical treatment of adverbs in Ancient Latin. We have suggested a list of 5 types, in a decreasing order from a greater to lesser degree of specialisation; technical (T), semi-technical (S-T), instrumental-valued (I-V), instrumental- descriptive (I-D), instrumental-expository (I-E).

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The Floridan aquifer was found to be principal source of ground water in the area, containing artesian water in the northern part of Columbia County, and being recharged in the southern part of the county. A few wells in the northern part of the county tap water present in sediments that lie above the Floridan aquifer. These shallow waters are generally high in iron and tannic acid. The details on the geology and hydrology necessary to conserve and utilize the water available to the residents of Columbia County are presented in this study. (PDF contains 86 pages)

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We analyzed the relationships between the larval and juvenile abundances of selected estuarine-dependent fishes that spawn during the winter in continental shelf waters of the U.S. Atlantic coast. Six species were included in the analysis based on their ecological and economic importance and relative abundance in available surveys: spot Leiostomus xanthurus, pinfish Lagodon rhomboides, southern flounder Paralichthys lethostigma, summer flounder Paralichthys dentatus, Atlantic croaker Micropogonias undulatus, and Atlantic menhaden Brevoortia tyrannus. Cross-correlation analysis was used to examine the relationships between the larval and juvenile abundances within species. Tests of synchrony across species were used to find similarities in recruitment dynamics for species with similar winter shelf-spawning life-history strategies. Positive correlations were found between the larval and juvenile abundances for three of the six selected species (spot, pinfish, and southern flounder). These three species have similar geographic ranges that primarily lie south of Cape Hatteras. There were no significant correlations between the larval and juvenile abundances for the other three species (summer flounder, Atlantic croaker, and Atlantic menhaden); we suggest several factors that could account for the lack of a relationship. Synchrony was found among the three southern species within both the larval and juvenile abundance time series. These results provide support for using larval ingress measures as indices of abundance for these and other species with similar geographic ranges and winter shelf-spawning life-history strategies.

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The aim of this paper is to propose a new solution for the roommate problem with strict preferences. We introduce the solution of maximum irreversibility and consider almost stable matchings (Abraham et al. [2])and maximum stable matchings (Ta [30] [32]). We find that almost stable matchings are incompatible with the other two solutions. Hence, to solve the roommate problem we propose matchings that lie at the intersection of the maximum irreversible matchings and maximum stable matchings, which are called Q-stable matchings. These matchings are core consistent and we offer an effi cient algorithm for computing one of them. The outcome of the algorithm belongs to an absorbing set.

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The condensation of phenanthroline-5,6-dione (phendione) with polyamines is a versatile synthetic route to a wide variety of chelating ligands. Condensation with 2,3- napthalene diamine gives benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (bdppz) a ligand containing weakly-coupled orbitals of benzophenazine (bpz) and 2,2' -bipyridinde(bpy) character. The bpy character gives Re and Ru complexes excited-state redox properties; intramolecular electron transfer (ET) takes place to the bpz portion of the ligand. The charge-separated state so produced has an extraordinarily-long 50 µs lifetime. The slow rate of charge recombination arises from a combination of extremely weak coupling between the metal center and the bpz acceptor orbital and Marcus "inverted region" behavior. Molecular orbital calculations show that only 3% the electron density in the lowest unoccupied molecular orbital lies on the bpy atoms of bdppz, effectively trapping the transferred electron on the bpz portion. The rate of charge recombination decreases with increasing driving force, showing that these rates lie in the inverted region. Comparison of forward and back ET rates shows that donor-acceptor coupling is four orders of magnitude greater for photoinduced electron transfer than it is for thermal charge recombination.

Condensation of phendione with itself or tetramines gives a series of binucleating tetrapyridophenazine ligands of incrementally-varying coordination-site separation. When a photoredox-active metal center is attached, excited-state energy and electron transfer to an acceptor metal center at the other coordination site can be studied as a function of distance. A variety of monometallic and homo- and heterodimetallic tetrapyridophenazine complexes has been synthesized. Electro- and magnetochemistry show that no ground-state interaction exists between the metals in bimetallic complexes. Excited-state energy and electron transfer, however, takes place at rates which are invariant with increasing donor-acceptor separation, indicating that a very efficient coupling mechanism is at work. Theory and experiment have suggested that such behavior might exist in extended π-systems like those presented by these ligands.

Condensation of three equivalents of 4,5-dimethyl-1,2-phenylenediamine with hexaketocyclohexane gives the trinucleating ligand hexaazahexamethyltrinapthalene (hhtn). Attaching two photredox-active metal centers and a third catalytic center to hhtn provides means by which multielectron photocatalyzed reactions might be carried out. The coordination properties of hhtn have been examined; X-ray crystallographic structure determination shows that the ligand's constricted coordination pocket leads to distorted geometries in its mono- and dimetallic derivatives.