A decomposition procedure based on approximate newton directions

The efficient solution of large-scale linear and nonlinear optimization problems may require exploiting any special structure in them in an efficient manner. We describe and analyze some cases in which this special structure can be used with very little cost to obtain search directions from decomposed subproblems. We also study how to correct these directions using (decomposable) preconditioned conjugate gradient methods to ensure local convergence in all cases. The choice of appropriate preconditioners results in a natural manner from the structure in the problem. Finally, we conduct computational experiments to compare the resulting procedures with direct methods, as well as to study the impact of different preconditioner choices

COMPUTING ROBUST STYLIZED FACTS ON COMOVEMENT

We propose an alternative method of obtaining stylized facts on comovement, based on the cross-correlation function of the prewhitened time series, which only depends on the purely stochastic components of the series and the cross efects between them. This approach has the property of being robust to the filtering procedure and hence to the cicle definition. The usual approach consists of obtaining the cross-correlation function of filtered variables, which reflect a mixture of both the existing cross-correlation between the variables and the autocorrelation structure of each of them. The autocorrelation structure, in turn, crucially depends on the filtering procedure. The relevance of such an approach is tested by revisiting some of the facts reported by Kydland and Prescott (1990).Prewhitening, Business Cycle, Stylized Facts, Comovement.

Fragmento y mirada en los ciclos de cuentos autobiográficos de Norah Lange y Nellie Campobello

En el presente trabajo me referiré a la relación, en un plano temático y estructural que puede establecerse entre Cuadernos de infancia (1937) de la argentina Lange con los de otra escritora preterida y recuperada para el canon de la literatura mexicana: Nellie Campobello, quien compuso en la misma época dos libros memorialísticos: Cartucho (1931) y Las manos de Mamá (1937). En particular, se trata de mostrar la concepción fragmentaria del relato autobiográfico en las dos escritoras y el valor de la mirada como focalización de la experiencia.------------This paper deals with the thematic and structural relations between, on the one hand, Cuadernos de infancia (1937) by the Argentinian woman writer Norah Lange, and, on the other, Cartucho and Las manos de Mamá by Nellie Campobello, a forgotten Mexican writer, shortly reinstallated inside the canon of Mexican literature. The target of the comparison consists in pointing out the fragmentary outlook of the autobiographical discourse in both Lange and Campobello, and the importance of the act of looking as the focal point of experience

Información, conocimiento, sabiduría: a propósito de Borges y de Sófocles

Se analizan los conceptos de información, conocimiento y sabiduría, de acuerdo con sus alcances y limitaciones a partir de los textos literarios de Borges y Sófocles. La noción de información, base necesaria para todo prograso intelectual, puede encerrar el peligro de dispersión del conocimiento, sobre todo en la era de Internet. Mediante la interpretación de las tragedias clásicas, se propone la experiencia vital, la superación del dolor y la adversidad como fuentes de sabiduría, complementarias de la información

Jesucristo en la literatura española e hispanoamericana del siglo XX. [Reseña]

Reseña de: José Antonio CARRO CELADA, Jesucristo en la literatura española e hispanoamericana del siglo XX, La Editorial Católica (BAC), Madrid, 1997, 142 pp

Understanding the impact of line-of-sight in the ergodic spectral efficiency of cellular networks

In this paper we investigate the impact of lineof-sight (LoS) condition in the ergodic spectral efficiency of cellular networks. To achieve this goal, we have considered the kappa-mu shadowed model, which is a general model that provides an excellent fit to a wide set of propagation conditions. To overcome the mathematical complexity of the analysis, we have split the analysis between large and small-scale effects. Building on the proposed framework, we study a number of scenarios that range from heavily-fluctuating LoS to deterministic-LoS. Finally, we shed light on the interplay between fading severity and spectral efficiency by means of the amount of fading.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Los arrecifes messinienses de Almería (S.E. de España)

En las cuencas neógenas de la provincia de Almería (sureste de España) afloran depósitos arrecifales muy bien desarrollados, de edad Messiniense. Del estudio de algunos de los arrecifes más conocidos se han deducido sus principales rasgos estratigráficos y su significado paleogeográfico. Los arrecifes se desarrollaron sobre las áreas marginales de las plataformas al tiempo que en las cuencas adyacentes más profundas se producía una sedimentación margosa. Por esta causa, las series estratigráficas acumuladas en cada uno de estos lugares difieren notablemente. Dentro del arrecife se distinguen varias facies relacionadas con los distintos subambientes de este último. Las facies de armazón está constituida por colonias de Porites en tubos verticales de hasta varios metros de altura, cementadas tempranamente en el ambiente submarino donde crecían, y muy resistentes a la erosión. La facies de talud, que presenta un buzamiento original de 10·25", está constituida por calcirruditas y calcarenitas que presentan cambios notables en el tipo de elementos esqueletales constituyentes conforme nos desplazamos hacia la cuenca. Las facies de transición talud distal-cuenca consiste en calcilutitas laminadas. La recons1rucción paleogeográfica del área estudiada muestra un archipiélago constituido por islas dispersas, la mayor parte de las cuales corresponden a las actuales sierras, las cuales, por aquel entonces, estaban ya parcialmente emergidas. Los arrecifes se desarrollaron como orlas que progradaron hacia la cuenca desde las islas. Por esta razón, los buzamientos de los taludes divergen en todas las direcciones y tienen una disposición radial. Posteriormente en estas zonas marginales se desarrollaron plataformas carbonatadas, no arrecifales, que en las áreas del sureste son típicamente oolíticas e intercalan estromatolitos. Los depósitos arrecifales han sido dolomitizados en la diagénesis. La disolución, posiblemente concomitante a la dolomitización, de los componentes esqueletales riginalmente aragoníticos confiere a los arrecifes una elevada porosidad intragranular, lo que los hace interesantes desde el punto de vista petrolífero como posibles roca de almacén. Finalmente se resaltan los rasgos principales de los arrecifes messinienses y se comparan con los de los arrecifes tortonienses que afloran en la misma área. [ABSTRACT] Well-developed Messinian coral reef deposits outcrop in the neogene hasins of Almería (Southeastem Spain). The study of some of the best known reefs leads to the establishement of their main stratigraphic features and of their paleogeographic meaning. Reefs grew on shelf marginal areas while, at the same time, marly sedimentation was taking place on adjacent deeper basins. Because of that, completely different stratigraphic sections accumulated in each place. Several sedimentary facies related to reef subenvironments can be distinguished. Reef framework facies is built up by Porytes. Vertical tube-like colonies, up to several meters high, were cemented early in the submarine environment and became highly resistant to erosion. Fore-reef facies (reef talus facies) dipping originally 10-25° are mainly composed by calcirudites and calcarenites showing changes in the type of skeletal constituents as we move toward the basin. Distal talus/basin transition facies consist of laminated calcilutites. The paleogeographical reconstruction shows an archipielago with scattered islands most of them corresponding to the present sierras which, at that time, were partly emerged. The reefs developed as fringes which prograded basinward from the islands. Thus radial pattems of talus originated. Later on broad shallow carbonate platforns, without reefs, developed on these reliefs, in the Southeastem outcrops the sediments tipically consisting of oolites and some interlayered stromatolite beds. Reef deposits were laler dolomitized during diagenesis. Intragranular porosity due to dissolution of primary aragonitic skeletal remains (and possibly accompanying dolomitation) is very high. That is why they are thought to be good potential oil reservoir. Major features of Messinian reefs have been finally outlined and compared with those who present the reefs of Tortonian age occurring in the same area

Characterization of the iron-regulated desA promoter of Streptomyces pilosus as a system for controlled gene expression in actinomycetes

BACKGROUND: The bioavailability of iron is quite low since it is usually present as insoluble complexes. To solve the bioavailability problem microorganisms have developed highly efficient iron-scavenging systems based on the synthesis of siderophores that have high iron affinity. The systems of iron assimilation in microorganisms are strictly regulated to control the intracellular iron levels since at high concentrations iron is toxic for cells. Streptomyces pilosus synthesizes the siderofore desferrioxamine B. The first step in desferrioxamine biosynthesis is decarboxylation of L-lysine to form cadaverine, a desferrioxamine B precursor. This reaction is catalyzed by the lysine decarboxylase, an enzyme encoded by the desA gene that is repressed by iron. RESULTS: The binding of the DmdR (acronym for divalent metal dependent repressor) to the desA promoter in presence of Fe(2+ )or other divalent ions has been characterized. A 51 bp DNA fragment of the desA promoter containing the 9 bp inverted repeat was sufficient for binding of the DmdR repressor, as observed by the electrophoretic mobility shift assay. The desA mobility shift was prevented by neutralizing DmdR with anti-DmdR antibodies or by chelating the divalent metal in the binding reaction with 2,2'-dipyridyl. Binding to the desA promoter was observed with purified DmdR repressors of Streptomyces coelicolor or Rhodococcus fascians suggesting that there is a common mechanism of iron-regulation in actinomycetes. The complete desA promoter region was coupled using transcriptional fusions to the amy reporter gene (encoding α-amylase) in low copy or multicopy Streptomyces vectors. The iron-regulated desA promoter was induced by addition of the iron chelating agent 2,2'-dipyridyl resulting in a strong expression of the reporter gene. CONCLUSIONS: The iron-regulated desA promoter can be used for inducible expression of genes in Streptomyces species, as shown by de-repression of the promoter when coupled to a reporter gene