Métodos de representación en la pintura figurativa

El conocido secretismo de los talleres y el desinterés de los pintores en dejar constancia escrita de su trabajo dificultan el estudio de la representación en la pintura. Esta situación obliga al pintor a recorrer personalmente paso a paso el mismo camino que sus antecesores. No existe más guía que las obras de los maestros y las máximas que, de taller en taller, se han transmitido hasta nosotros; es cierto que algunas son curiosas y con visos de verdad, pero en el fondo, poco aportan al pintor actual. Nos falta el conocimiento contrastado de lo que los pintores llamamos "el concepto", que es la suma de ideas en las que se sustenta nuestro trabajo. En este artículo expongo dos procedimientos que he podido identificar y en los que principalmente he basado mi obra.

El juego de aprender

Hemos concedido unos valores casi épicos a la función de aprender: el esfuerzo, el tesón, la ambición o la absurda competición, son cualidades que marcan el transcurrir de nuestro periodo de aprendizaje: cuanto más cuesta, más valor tiene y se llega a premiar el esfuerzo por encima del resultado. Aprender debería ser un juego, un juego muy serio, es verdad, pero juego al fin y al cabo, en el que el conocimiento se adquiere a través del grado de satisfacción que se obtiene de la acción.

Archaoegastropoda del Plioceno del Empordà (Girona). Descriptiva y Sistemática

En el presente trabajo se describen y figuran siete especies diferentes de Archaeogastropoda (Gastropoda) procedentes de los yacimientos del Empordà, Girona (España).

Algunos datos paleoecológicos y tafonómicos de un yacimiento pliocénico del Ampurdán

The fossiliferous beds of the 'Cementerio de Ciurana (Gerona) ', have been studied from Taphonomy and Paleoeco.. logy viewpoints. The mode of formation of the fossil assem.. blages hardly implicates transport and the vertical successiori seems to represent a regressive sequence from former normal marine conditions.

Repartición geográfica y estratigráfica de los Gastrópoda del Plioceno de l'Empordà (Girona, Catalunya)

En el presente trabajo se da un cuadro de distribución geográfica y estratigráfica de las 115 especies de Gasterpodos conocidos hasta la actualidad en el Plioceno de Empordà, Girona.

Volutácea del Plioceno del Empordà (Girona)

En el presente trabajo se describen y figuran las diferentes especies de VOLUTACEA (NEOGASTROPODA, GASTROPODA) rocedeiites de los yacimientos pliocénicos del Empordà, Girona España).

Design and construction of precision heat fluxmeters

The possibility of local elastic instabilities is considered in a first¿order structural phase transition, typically a thermoelastic martensitic transformation, with associated interfacial and volumic strain energy. They appear, for instance, as the result of shape change accommodation by simultaneous growth of different crystallographic variants. The treatment is phenomenological and deals with growth in both thermoelastic equilibrium and in nonequilibrium conditions produced by the elastic instability. Scaling of the transformed fraction curves against temperature is predicted only in the case of purely thermoelastic growth. The role of the transformation latent heat on the relaxation kinetics is also considered, and it is shown that it tends to increase the characteristic relaxation times as adiabatic conditions are approached, by keeping the system closer to a constant temperature. The analysis also reveals that the energy dissipated in the relaxation process has a double origin: release of elastic energy Wi and entropy production Si. The latter is shown to depend on both temperature rate and thermal conduction in the system.

Preisach modeling of hysteresis for a pseudoelastic Cu-Zn-Al single crystal

Stress-strain trajectories associated with pseudoelastic behavior of a Cu¿19.4 Zn¿13.1 Al (at.%) single crystal at room temperature have been determined experimentally. For a constant cross-head speed the trajectories and the associated hysteresis behavior are perfectly reproducible; the trajectories exhibit memory properties, dependent only on the values of return points, where transformation direction is reverted. An adapted version of the Preisach model for hysteresis has been implemented to predict the observed trajectories, using a set of experimental first¿order reversal curves as input data. Explicit formulas have been derived giving all trajectories in terms of this data set, with no adjustable parameters. Comparison between experimental and calculated trajectories shows a much better agreement for descending than for ascending paths, an indication of a dissymmetry between the dissipation mechanisms operative in forward and reverse directions of martensitic transformation.

Radial displacement of a fluid annulus in a rotating Hele¿Shaw cell

The radial displacement of a fluid annulus in a rotating circular Hele-Shaw cell has been investigated experimentally. It has been found that the flow depends sensitively on the wetting conditions at the outer interface. Displacements in a prewet cell are well described by Darcy's law in a wide range of experimental parameters, with little influence of capillary effects. In a dry cell, however, a more careful analysis of the interface motion is required; the interplay between a gradual loss of fluid at the inner interface, and the dependence of capillary forces at the outer interface on interfacial velocity and dynamic contact angle, result in a constant velocity for the interfaces. The experimental results in this case correlate in the form of an empirical scaling relation between the capillary number Ca and a dimensionless group, related to the ratio of centrifugal to capillary forces, which spans about three orders of magnitude in both quantities. Finally, the relative thickness of the coating film left by the inner interface, alpha i, is obtained as a function of Ca.

Interfacial instabilities of a fluid annulus in a rotating Hele-Shaw cell

We have studied the interfacial instabilities experienced by a liquid annulus as it moves radially in a circular Hele-Shaw cell rotating with angular velocity Omega. The instability of the leading interface (oil displacing air) is driven by the density difference in the presence of centrifugal forcing, while the instability of the trailing interface (air displacing oil) is driven by the large viscosity contrast. A linear stability analysis shows that the stability of the two interfaces is coupled through the pressure field already at a linear level. We have performed experiments in a dry cell and in a cell coated with a thin fluid layer on each plate, and found that the stability depends substantially on the wetting conditions at the leading interface. Our experimental results of the number of fingers resulting from the instability compare well with the predictions obtained through a numerical integration of the coupled equations derived from a linear stability analysis. Deep in the nonlinear regime we observe the emission of liquid droplets through the formation of thin filaments at the tip of outgrowing fingers.

Cooperativisme i associacionisme agraris a Catalunya: els propietaris rurals i l'organització dels interessos agraris al primer terç del segle XX

Aquesta tesi doctoral centra l'atenció en la participació dels propietaris en el cooperativisme i l'associacionisme agraris del primer terç del segle XX, com una de les expressions de la reorganització dels interessos agraris després de la crisi del final del segle XIX. S'estructura en dues parts diferenciades segons l'àmbit d'anàlisi. La primera aborda la participació dels propietaris en l'associacionisme agrari a Catalunya, se centra fonamentalment en el model associatiu de les cambres agrícoles i destaca el protagonisme de l'Institut Agrícola Català de Sant Isidre en l'organització dels interessos agraris. La segona utilitza la comarca del Vallès Oriental com a banc de proves de la primera, i com que és un àmbit més reduït, permet ser més exhaustius en la descripció del moviment associatiu, identificar els seus protagonistes i analitzar la seva resposta als canvis econòmics i socials que es van produir durant el primer terç del segle XX.

Comparative effects of oleoyl-estrone and a specific b3-adrenergic agonist (CL316, 243) on the expression of genes involved in energy metabolism of rat white adipose tissue

Background: The combination of oleoyl-estrone (OE) and a selective b3-adrenergic agonist (B3A; CL316,243) treatment in rats results in a profound and rapid wasting of body reserves (lipid). Methods: In the present study we investigated the effect of OE (oral gavage) and/or B3A (subcutaneous constant infusion) administration for 10 days to overweight male rats, compared with controls, on three distinct white adipose tissue (WAT) sites: subcutaneous inguinal, retroperitoneal and epididymal. Tissue weight, DNA (and, from these values cellularity), cAMP content and the expression of several key energy handling metabolism and control genes were analyzed and computed in relation to the whole site mass. Results: Both OE and B3A significantly decreased WAT mass, with no loss of DNA (cell numbers). OE decreased and B3A increased cAMP. Gene expression patterns were markedly different for OE and B3A. OE tended to decrease expression of most genes studied, with no changes (versus controls) of lipolytic but decrease of lipogenic enzyme genes. The effects of B3A were widely different, with a generalized increase in the expression of most genes, including the adrenergic receptors, and, especially the uncoupling protein UCP1. Discussion: OE and B3A, elicit widely different responses in WAT gene expression, end producing similar effects, such as shrinking of WAT, loss of fat, maintenance of cell numbers. OE acted essentially on the balance of lipolysislipogenesis and the blocking of the uptake of substrates; its decrease of synthesis favouring lipolysis. B3A induced a shotgun increase in the expression of most regulatory systems in the adipocyte, an effect that in the end favoured again the loss of lipid; this barely selective increase probably produces inefficiency, which coupled with the increase in UCP1 expression may help WAT to waste energy through thermogenesis. Conclusions: There were considerable differences in the responses of the three WAT sites. OE in general lowered gene expression and stealthily induced a substrate imbalance. B3A increasing the expression of most genes enhanced energy waste through inefficiency rather than through specific pathway activation. There was not a synergistic effect between OE and B3A in WAT, but their combined action increased WAT energy waste.

Whole-rat protein content estimation: applicability of the Nx6.25 factor

The amino acid composition of the protein from three strains of rat (Wistar, Zucker lean and Zucker obese), subjected to reference and high-fat diets has been used to determine the mean empirical formula, molecular weight and N content of whole-rat protein. The combined whole protein of the rat was uniform for the six experimental groups, containing an estimate of 17.3% N and a mean aminoacyl residue molecular weight of 103.7. This suggests that the appropriate protein factor for the calculation of rat protein from its N content should be 5.77 instead of the classical 6.25. In addition, an estimate of the size of the non-protein N mass in the whole rat gave a figure in the range of 5.5 % of all N. The combination of the two calculations gives a protein factor of 5.5 for the conversion of total N into rat protein.