Adaptive structured parallelism for computational grids

Algorithmic skeletons abstract commonly-used patterns of parallel computation, communication, and interaction. They provide top-down design composition and control inheritance throughout the whole structure. Parallel programs are expressed by interweaving parameterised skeletons analogously to the way sequential structured programs are constructed. This design paradigm, known as structured parallelism, provides a high-level parallel programming method which allows the abstract description of programs and fosters portability. That is to say, structured parallelism requires the description of the algorithm rather than its implementation, providing a clear and consistent meaning across platforms while their associated structure depends on the particular implementation. By decoupling the structure from the meaning of a parallel program, it benefits entirely from any performance improvements in the systems infrastructure

Variaciones del ser nacional : entre la ilusión de "persona colectiva" o el concepto de una "generalización inviable"

Fil: González, Horacio. Universidad de Buenos Aires. Facultad de Ciencias Sociales; Argentina.Plantea que la idea del ?ser nacional? fue especialmente dejada de lado por las modernas ciencias sociales, bajo el comprensible argumento de que ninguna fórmula sospechada de tener raíces ahistóricas o fijada a esencias inmutables, podía hacerse cargo de la complejidad, diversidad y variedad de las experiencias de vida que surgen de estructuras sociales que se reproducen sobre la base de su desigualdad y heterogeneidad. No obstante, ciertos cuadros vivenciales que provienen tanto de la literatura social ensayística como del periodismo cultural o de las nuevas sociologías culturales -en cualquiera de sus innumerables estilos-, retoman el viejo y fantasmal tema del carácter nacional con distintos acercamientos y encuadramientos argumentales

La llegada de Ánforas Hispanas a Germania durante los últimos siglos de la dominación romana. Una cuestión para el futuro.

Este artículo supone un intento para empezar a sentar bases, donde se apoyen futuras investigaciones referentes al estudio de las relaciones interprovinciales entre el área Hispana y las provincias del noroeste del Imperio romano, a lo largo del mal conocido periodo de la Antigüedad tardía. El objeto principal de estudio son aquellas ánforas, que fabricadas en la Península Ibérica llegaron a las provincias fronterizas de Germania. Partiendo de un análisis de la situación existente y de los contextos arqueológicos más significativos, se pretende calibrar el alcance de la demanda de estos contenedores cerámicos y valorar su aportación al conocimiento de las relaciones comerciales y culturales entre estas dos áreas distantes, así como plantear cuestiones referentes al carácter de los consumidores de las mercancías que en ellos iban envasados.This paper attempts at setting the groundwork for new studies on the relations between the Hispanic and the Northwestern provinces of the Roman Empire in Late Antiquity. The main subject are the Spanish amphorae that reached the German border territories. An analysis of both, the historical background and of the main archeological contexts, allows us to estimate real significance of the demand and to appreciate the value of these items to understand the commercial and cultural relations between these remote areas. This is also an opportunity to answer several questions about the consumption in North Europe of the Mediterranean products transported in the amphorae

POLÍTICAS DE INGRESO Y RETENCIÓN EN LA UNIVERSIDAD

La planificación estratégica de las políticas de ingreso y admisión de los estudiantes a las universidades publicas constituye un capitulo importante en las acciones de gestión académica de estas instituciones. La deserción, el desgranamiento y la lentificación de los alumnos de nivel universitario, se han convertido en problemáticas relevantes de la dimensión educativa de los estudios superiores. Investigar las causas de estos fenómenos, que se ha incrementado en las últimas décadas, surge de la necesidad de dar respuestas y encontrar soluciones que contribuyan a mejorar las condiciones y la calidad de los procesos educativos de la enseñanza de grado en las universidades públicas. Resulta importante estudiar las condiciones y características de los Ingresantes al sistema, ya que es en los primeros años de las carreras donde se producen con mayor intensidad los fenómenos aludidos. Estimamos que las condiciones del ingreso y seguimiento académico y personal de los estudiantes constituyen un espacio fundamental en la planificación de las políticas de la universidad. En el marco del Proyecto de Investigación que dirijo, investigamos desde hace mas de cinco años, las características psicológicas y sociológicas de la elección de las Carreras de Grado y los conflictos emergentes de esta situación, analizando la incidencia de diversos factores en el desarrollo de los estudios, rendimiento académico y deserción de los jóvenes ingresantes, en el ámbito de la Universidad Nacional de Río Cuarto

Diffusion-viscosity decoupling in supercooled glycerol aqueous solutions

The diffusion of ferrocene methanol in supercooled glycerol-water mixtures has been measured over a wide viscosity range, which allowed analyzing the composition dependence of the Stokes-Einstein breakdown (diffusion-viscosity decoupling). The observed decoupling exhibits a common behavior for all studied compositions (glycerol mass fractions between 0.7 and 0.9), determined by the reduced temperature (T/Tg) of the mixtures. This result differs from that reported previously for the diffusion of glycerol in its aqueous solutions, where the reduced temperature for the decoupling decreases with increasing water content. We conclude that the contradictory results are only apparent, and they can be explained by the use of inconsistent extrapolated values of the viscosity of the glycerol-water mixtures in the supercooled region. (Figure Presented).Fil: Trejo González, José Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Longinotti, María Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Corti, Horacio Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin

To which extend is the "neural code" a metric ?

Here is proposed a review of the different choices to structure spike trains, using deterministic metrics. Temporal constraints observed in biological or computational spike trains are first taken into account. The relation with existing neural codes (rate coding, rank coding, phase coding, ..) is then discussed. To which extend the "neural code" contained in spike trains is related to a metric appears to be a key point, a generalization of the Victor-Purpura metric family being proposed for temporal constrained causal spike trainsComment: 5 pages 5 figures Proceeding of the conference NeuroComp200

Structural and dynamical studies on human epidermal-type fatty acid binding protein using high-resolution NMR spectroscopy

Human epidermal-type fatty acid binding protein (E-FABP) belongs to a family of intracellular non-enzymatic 14-15 kDa lipid binding proteins (LBP) that specifically bind and facilitate the transport of fatty acids, bile acids or retinoids. Their functions have also been associated with fatty acid signalling, cell growth, regulation and differentiation. As a contribution to better understand the structure-function relationship of this protein, the features of its solution structure determined by NMR spectroscopy are reported here. Both unlabeled and 15N-enriched samples of recombinant human E-FABP were used for multidimensional high-resolution NMR. The sequential backbone as well as side-chain resonance assignments have been completed. They are reported here and are also available at the BioMagResBank under the accession number BMRB-5083. The presence of six cysteines in the amino acid sequence of human E-FABP is highly unusual for LBPs. Four of the six cysteines are unique to the E-FABPs: C43, C47, C67 and C87. In the three-dimensional structure of E-FABP, two cysteine pairs (C67/C87 and C120/C127) were identified by X-ray analysis to be close enough to allow disulfide bridge formation, but a S-S bond was actually found only between C120 and C127 [Hohoff et al., 1999]. Since the exclusion of a disulfide bridge between C67 and C87 improved the Rfree factor of the crystallographic model, the existence of a covalent bond between these two side- chains was considered unlikely. This agrees with the NMR data, where SCH resonances have been observed for the cysteine residues C43, C67 (tentative assignment) and C87, thus excluding the possibility of a second disulfide bridge in solution. Based on the NOE and hydrogen exchange data, an ensemble of 20 energy-minimized conformers representing the solution structure of human E-FABP complexed with stearic acid has been obtained. The analysis of homonuclear 2D NOESY and 15N-edited 3D NOESY spectra led to a total of 2926 NOE-derived distance constraints. Furthermore, 37 slow- exchanging backbone amide protons were identified to be part of the hydrogen-bonding network in the >-sheet and subsequently converted into 74 additional distance constraints. Finally, the disulfide bridge between C120 and C127 was defined by 3 upper and 3 lower distance bounds. The structure calculation program DYANA regarded 998 of these constraints as irrelevant, i.e., they did not restrict the distance between two protons. Out of the remaining 2008 non-trivial distance constraints, 371 were intraresidual (i = j), 508 sequential (|i - j| = 1), 233 medium-range (1 4) NOEs. The protein mainly consists of 10 antiparallel -strands forming a >-barrel structure with a large internal cavity. The three-dimensional solution structure of human E-FABP has been determined with a root-mean-square deviation of 0.92 ± 0.11 Å and 1.46 ± 0.10 Å for the backbone and heavy atoms, respectively, excluding the terminal residues. Without the portal region (i.e., for residues 4-26, 40-56, 63-75 and 83-134; the portal region apparently represents the only opening in the protein surface through which the fatty acid ligand can enter and exit the internal binding cavity), an average backbone RMSD of 0.85 ± 0.10 Å was obtained, thus reflecting the higher conformational dispersion in the portal region. Superposition with the X-ray structure of human E-FABP (excluding the terminal residues) yielded average backbone RMSD values of 1.00 ± 0.07 Å for the entire residue range and 0.98 ± 0.06 Å without the portal region. This indicates a close similarity of the crystallographic and the solution structures. The structure coordinates have been deposited at the RCSB data bank under PDB ID code 1JJJ. The measurement of 15N relaxation experiments (T1, T2 and heteronuclear NOE) at three different fields (500, 600 and 800 MHz) provided information on the internal dynamics of the protein backbone. Nearly all non-terminal backbone amide groups showed order parameters S2 > 0.8, with an average value of 0.88 ± 0.04, suggesting a uniformly low backbone mobility in the nanosecond-to-picosecond time range throughout the entire protein sequence. Moreover, hydrogen/deuterium exchange experiments indicated a direct correlation between the stability of the hydrogen-bonding network in the >-sheet structure and the conformational exchange (Rex) in the millisecond-to-microsecond time range. The features of E-FABP backbone dynamics elaborated here differ from those of the phylogenetically closely related heart-type FABP and the more distantly related ileal lipid binding protein. The results on protein dynamics obtained in this work allow to conclude that the different LBP family members E-FABP, H-FABP and ILBP are characterized by varying stabilities in the protein backbone structures. Hydrogen/deuterium exchange experiments displayed significant differences in the chemical exchange with the solvent for the backbone amide protons belonging to the hydrogen-bonding network in the >-sheets. The >-barrel structure of H- FABP appears to be the most rigid, with exchange processes presumably slower than the millisecond-to-microsecond time range. ILBP, on the other hand, shows the fastest hydrogen exchange as well as a significant number of exchange parameters (Rex), implying a decreased stability in the >-sheet structure. E-FABP, finally, appears to rank between these two proteins based on the hydrogen/deuterium exchange, with Rex terms in the >-strands indicating millisecond-to-microsecond exchange processes like in ILBP