Dewetting of solid films with substrate mediated evaporation

The dewetting dynamics of an ultrathin film is studied in the presence of evaporation - or reaction - of adatoms on the substrate. KMC simulations are in good agreement with an analytical model with diffusion, rim facetting, and substrate sublimation. As sublimation is increased, we find a transition from the usual dewetting regime where the front slows down with time, to a sublimation-controlled regime where the front velocity is approximately constant. The rim width exhibits an unexpected non-monotonous behavior, with a maximum in time.Comment: 6 pages, 6 figure

La ontología negativa en las filosofías socráticas y sus proyecciones interepocales

In this article we intend to analyze the ontology of different Socratic lines of thought, through an approach of Zones of dialogic tension. Antisthenes and the megarics Euclid and Stilpo develop ontologically negative conceptions that reject the affirmation of ontological principles capable of sustaining reality and its linguistic expression. This theoretical stance not only offers an alternative to the platonic-aristotelic approach towards ontology, but affects, by means of interaction and reciprocal influence, the constitution of those affirmative variants in classical Greek thought. Thereby, the inclusion of Socratic lines of thought allows us to question the heideggerian diagnosis of ancient Greek philosophy, inscribed solely in the paradigm of "metaphysics of presence". The recovery of the Socratic philosophers, usually obs­cured by the figures of Plato and Xenophon, offers an opportunity to redimension the period of classical antiquity through the study of its diverse ontological conceptions.En este trabajo nos proponemos analizar la ontología de distintas corrientes socráticas con un enfoque por Zonas de tensión dialógica. Antístenes y los megáricos Euclides y Estilpón despliegan modelos de negatividad que rechazan la afirmación de principios ontológicos capaces de sustentar lo real y su expresión en el lenguaje. Estas propuestas teóricas no solo ofrecen una perspectiva alternativa a la platónico-aristotélica, sino que influyen de manera decisiva, por medio de la interacción e influencia recíproca, en la construcción de las variantes afirmativas de la época clásica. De este modo, la inclusión de las líneas socráticas permite poner en cuestión el diagnóstico heideggeriano que ve en la filosofía griega la sede del paradigma de la “metafísica de la presencia”. La recuperación de las filosofías socráticas, habitualmente invisibilizadas bajo las figuras de Platón y Jenofonte, ofrece una oportunidad para redimensionar la Antigüedad clásica en función de propuestas ontológicas divergentes

Dewetting of a solid monolayer

We report on the dewetting of a monolayer on a solid substrate, where mass transport occurs via surface diffusion. For a wide range of parameters, a labyrinthine pattern of bilayer islands is formed. An irreversible regime and a thermodynamic regime are identified. In both regimes, the velocity of a dewetting front, the wavelength of the bilayer island pattern, and the rate of nucleation of dewetted zones are obtained. We also point out the existence of a scaling behavior, which is analyzed by means of a geometrical model.Comment: to be published in PhysRevLet

Nonlinear wavelength selection in surface faceting under electromigration

We report on the control of the faceting of crystal surfaces by means of surface electromigration. When electromigration reinforces the faceting instability, we find perpetual coarsening with a wavelength increasing as $t^{1/2}$. For strongly stabilizing electromigration, the surface is stable. For weakly stabilizing electromigration, a cellular pattern is obtained, with a nonlinearly selected wavelength. The selection mechanism is not caused by an instability of steady-states, as suggested by previous works in the literature. Instead, the dynamics is found to exhibit coarsening {\it before} reaching a continuous family of stable non-equilibrium steady-states.Comment: 5 pages, 4 figures, submitte

Fotografía: los creadores de verdad o de ficción

Photography proposes as an issue the essential problem of production-creation of real photographic images andreality itself. Photography and reality seem to be a tighten pair in the history of iconic reproduction as in the photographerswork itself. Speeches gathered through photography history show how the reality principle between image and its referentbelongs to photography itself from its beginning and is present all through its evolution. In the 19th century, the mechanicalaspect will stand out, turning out photography in a mirror of reality. In the 20th century, photography establishes its differencesfrom the real thing focusing on image interpretation. Photography as a treads, puts in evidence, its referential experience butonly like part of a greater process. A photography is the result of the encounter between photographer - photographed and thecontext of “doing”. To include a photography is to recover its meaning and a vision of the world.La fotografía problematiza, la cuestión esencial que gira en torno a la produccióncreación de imágenes reales-fotográficas y lo real mismo. Fotografía y realidad parecen ser una parejaindisociable, en la historia de la reproducción icónica y en el hacer mismo de los fotógrafos. Losdiscursos que se reúnen en la historia de la fotografía muestran como el principio de realidad entreimagen y referente es propio de la fotografía desde su inicio y está presente en toda su evolución.En el S.XIX, resaltará el aspecto mecánico, volviéndola un espejo mismo de la realidad. A partir ydurante todo el S.XX, la fotografía va a establecer sus diferencias con lo real haciendo hincapié en lainterpretación que una imagen ejerce. La fotografía como huella, pone en evidencia, su experienciareferencial pero sólo como parte de un proceso mayor.Una fotografía es el resultado del encuentro entre fotógrafo - fotografiado y el contexto del “hacer”.Comprender una fotografía es recuperar sus significados y una visión del mundo.A fotografia problematiza a cuestão essencial que gira em torno à procução – criação de imagens reáis fotográficase o real mesmo.Fotografia e realidade parecem ser uma dupla que não podem disociar-se, na história da reprodução icónica e no fazer mesmodos fotógrafos. Os discursos que se reúnem na história da fotografia mostram como o princípio de realidade entre imagem ereferente é próprio da fotografia desde seu início e está presente em toda sua evolução.No século XIX, resaltará o aspecto mecánico, voltándo-a um espelho mesmo da realidade. A partir e durante todo o século XX,a fotografia vai establecer suas diferenças com o real mostrando a interpretação que uma imagen excerse. A fotografia comoimpressão, põe em evidência sua experiência referencial mas somente como parte de um processo maior.Uma fotografia é o resultado do encontre entre fotógrafo – fotografado e o contexto do “fazer”. Compreender uma fotografia érecuperar seus significados e uma visão do mundo

El argumento de Metaphysica Θ 1 según el seminario de Londres: El uso del análisis focal y el problema de los enunciados programáticos

The London seminar’s famous notes on the central books of the Metaphysics constitute crucial bibliography for anyone working on Aristotle’s ontology. In this article, I provide an analysis of a representative passage of these notes, namely, the section devoted to Metaphysics Θ 1 (Burnyeat et al. 1984, pp. 46- 51). I will first reconstruct the main lines of interpretation put forward by the Londinenses. I will pay particular attention to Owen’s introductory analysis, which makes use of focal meaning analysis in order to explain the link between the various applications of the initial motion sense of δύναμις. I will also analyze the ensuing commentary on the so-called programmatic statements (Metaph. Θ 1.1045b37-1046a4). Second, I will make some considerations on the method of the notes. Finally, I will analyze the connection between Metaph. Θ 1 and Metaph. Δ 7.1017a35-b9. This will allow us to discuss in a different light the reading by the Londinenses of this important chapter.Fil: Chame, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Instituto de Filosofía "Dr. Alejandro Korn"; Argentina. Universita di Verona; Itali

Towards hybrid primary intersubjectivity: a neural robotics library for human science

Human-robot interaction is becoming an interesting area of research in cognitive science, notably, for the study of social cognition. Interaction theorists consider primary intersubjectivity a non-mentalist, pre-theoretical, non-conceptual sort of processes that ground a certain level of communication and understanding, and provide support to higher-level cognitive skills. We argue this sort of low level cognitive interaction, where control is shared in dyadic encounters, is susceptible of study with neural robots. Hence, in this work we pursue three main objectives. Firstly, from the concept of active inference we study primary intersubjectivity as a second person perspective experience characterized by predictive engagement, where perception, cognition, and action are accounted for an hermeneutic circle in dyadic interaction. Secondly, we propose an open-source methodology named \textit{neural robotics library} (NRL) for experimental human-robot interaction, and a demonstration program for interacting in real-time with a virtual Cartesian robot (VCBot). Lastly, through a study case, we discuss some ways human-robot (hybrid) intersubjectivity can contribute to human science research, such as to the fields of developmental psychology, educational technology, and cognitive rehabilitation

La creatividad a través del lenguaje fotográfico. La imagen fotográfica como medio expresivo, estético y comunicativo

Actualmente la fotografía se afirma como un modo de expresión, de comunicación y de información. Aparece en todas partes, en diarios, en revistas, en publicidades. También es una forma de registrar los recuerdos emotivos de acontecimientos íntimos, ilustrando la propia historia a través del álbum familiar

Produção de biodiesel catalisada por fosfatos metálicos básicos

O presente trabalho tem como principal objetivo sintetizar, caracterizar e avaliar as capacidades catalíticas de fosfatos metálicos básicos em reações de transesterificação para a produção de biodiesel. Em primeiro lugar, foram sintetizados os fosfatos de zircónio ácidos, α-ZrP e γ-ZrP a partir dos quais se sintetizaram os fosfatos de zircónio básicos, α-ZrPNa e γ-ZrPNa. Somente os fosfatos metálicos básicos foram avaliados como catalisadores nas reações de transesterificação com diferentes óleos (girassol, milho e azeite). Foram avaliadas as melhores condições de reação, otimizando-se o processo de produção, como forma de maximizar o rendimento das reações. Foi estudada a eficiência dos catalisadores nas reações de transesterificação e determinado o rendimento de biodiesel tendo em conta os métodos usados (micro-ondas e convencional com refluxo) para posterior comparação. Os catalisadores básicos α-ZrPNa e γ-ZrPNa apresentaram um bom desempenho catalítico na conversão de triglicerídeos em FAMEs (fatty acid methyl esters; biodiesel). Os testes catalíticos mostraram que as reações que deram maior rendimento em FAMEs foram as realizadas com o catalisador γ-ZrPNa. Com os catalisadores ácidos, α-ZrP e γ-ZrP, não se verificou qualquer formação de FAMEs. Todas as reações foram monitorizadas por GC e GC/MS o que possibilitou a análise quantitativa e a identificação dos produtos, respetivamente.The present work aims to synthesize, characterize and evaluate the catalytic performance of basic metal phosphates in transesterification reactions to produce biodiesel. First, the acid zirconium phosphates, α-ZrP and γ-ZrP were synthesized from which the basic zirconium phosphates α-ZrPNa and γ-ZrPNa were prepared. Only the basic metal phosphates were evaluated as catalysts in the transesterification reactions with different oils (sunflower, corn and olive oil). The best reaction conditions were evaluated, the production process was optimized in order to maximize the reactions yield. The efficiency of the catalysts in the transesterification reactions were studied and the biodiesel yield was determined considering the methods used (microwave and conventional with reflux) for later comparison. The basic catalysts α-ZrPNa and γ-ZrPNa showed good catalytic performance in the conversion of triglycerides to FAMEs (fatty acid methyl esters; biodiesel). The catalytic tests showed that the reactions that achieved the highest FAMEs yields were those performed with the γ-ZrPNa catalyst. With the acid catalysts, α-ZrP and γ-ZrP, no FAMEs were formed. All reactions were monitored by GC and GC/MS which allowed the quantitative analysis and the products identification, respectively.Mestrado em Químic