4,541 research outputs found
Análisis bioquímico del micelio del hongo Hormoconis resinae en la corrosión de aleaciones aeronáuticas de aluminio
Las diferencias entre el comportamiento corrosivo y no corrosivo de una cepa del hongo Hormoconis resinae sobre aluminio y sus aleaciones aeronáuticas se explicarían a través de análisis bioquímicos del micelio. En trabajos previos, el comportamiento corrosivo se estudió mediante análisis de superficie SEM-EDX, técnicas electroquímicas y ensayos de inmersión. En este trabajo, se llevó a cabo la separación de proteínas del micelio producido por una cepa que perdió su corrosividad y su cultivo a través de tres generaciones. Cultivos en batch, en presencia y ausencia de aluminio y sus aleaciones AA 2024, AA 7005 y AA 7075, a través de tres generaciones del micelio crecido, fueron recuperando sus características, incluida su habitual corrosividad, en la tercera replicación. De las fracciones de biomoléculas separadas y analizadas durante este estudio preliminar, sólo, las fracciones proteicas revelaron cambios de una a otra generación. Cuando esta cepa del hongo se cultivó en presencia de probetas de los metales, las modificaciones en la electroforesis de las respectivas fracciones proteicas fueron correlativas del comportamiento del micelio frente a la corrosión del aluminio y sus aleaciones.Biochemical analyses of the Hormoconis resinae fungal mycelium would explain behaviour differences of corrosive and non-corrosive strains on Al and its aeronautical alloys. In previous works its aggressiveness had been studied through SEM-EDX surface analysis, electrochemical techniques and immersion testing. In this paper separation of the proteins of the mycelium produced by a non-corrosive strain and its culture along three generations was performed. Cultures were prepared in batch in the presence and absence of pure Al and AA 2024, AA 7005 and AA 7075 alloys. The mycelia grown throughout the three generations increasingly recovered usual characteristics at the third replication, included their corrosiveness on Al and its alloys previously shown by all our strains. Amongst the bio-molecule fractions isolated and analysed during this preliminary study only the proteins revealed changes with the generation grown. When this fungal strain was cultured in the presence of alloy metal sheets electrophoresis of the protean fraction was correlative wFil: Araya, R.. Pontificia Universidad Católica de Valparaíso; ChileFil: Bobadilla, C.. Pontificia Universidad Católica de Valparaíso; ChileFil: Vera, R.. Pontificia Universidad Católica de Valparaíso; ChileFil: Rosales, Blanca Margarita. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Tecnología de Pinturas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones en Tecnología de Pinturas; Argentin
Theory of weakly nonlinear self sustained detonations
We propose a theory of weakly nonlinear multi-dimensional self sustained
detonations based on asymptotic analysis of the reactive compressible
Navier-Stokes equations. We show that these equations can be reduced to a model
consisting of a forced, unsteady, small disturbance, transonic equation and a
rate equation for the heat release. In one spatial dimension, the model
simplifies to a forced Burgers equation. Through analysis, numerical
calculations and comparison with the reactive Euler equations, the model is
demonstrated to capture such essential dynamical characteristics of detonations
as the steady-state structure, the linear stability spectrum, the
period-doubling sequence of bifurcations and chaos in one-dimensional
detonations and cellular structures in multi- dimensional detonations
On "jamitons," self-sustained nonlinear traffic waves
"Phantom jams," traffic blockages that arise without apparent cause, have
long frustrated transportation scientists. Herein, we draw a novel homology
between phantom jams and a related class of self-sustained transonic waves,
namely detonations. Through this analogy, we describe the jam structure;
favorable agreement with reported measurements from congested highways is
observed. Complementary numerical simulations offer insights into the jams'
development. Our results identify conditions likely to result in a dangerous
concentration of vehicles and thereby lend guidance in traffic control and
roadway design.Comment: 6 pages, 4 figure
Unification of step bunching phenomena on vicinal surfaces
We unify step bunching (SB) instabilities occurring under various conditions on crystal surfaces below roughening. We show that when attachment-detachment of atoms at step edges is the rate-limiting process, the SB of interacting, concentric circular steps is equivalent to the commonly observed SB of interacting straight steps under deposition, desorption, or drift. We derive a continuum Lagrangian partial differential equation, which is used to study the onset of instabilities for circular steps. These findings place on a common ground SB instabilities from numerical simulations for circular steps and experimental observations of straight steps
Supergroup BF action for supergravity
General relativity can be formulated as a SU(2) BF-theory with constraints,
as has been shown, by Pleba\'nski. The cosmological constant term can be
obtained from the constraint term, following from the consistency of the
equations of motion, as recently shown by Krasnov. We consider an
invariant, supergravity extension of this theory, for which the consistency of
the equations of motion and the constraints contribute as well to the
cosmological constant terms of Townsend's supergravity. The Kalb-Ramond
invariance is shortly discussed.Comment: 14 page
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