Criticality of the "critical state" of granular media: Dilatancy angle in the tetris model

The dilatancy angle describes the propensity of a granular medium to dilate under an applied shear. Using a simple spin model (the ``tetris'' model) which accounts for geometrical ``frustration'' effects, we study such a dilatancy angle as a function of density. An exact mapping can be drawn with a directed percolation process which proves that there exists a critical density $\rho_c$ above which the system expands and below which it contracts under shear. When applied to packings constructed by a random deposition under gravity, the dilatancy angle is shown to be strongly anisotropic, and it constitutes an efficient tool to characterize the texture of the medium.Comment: 7 pages RevTex, 8eps figure, to appear in Phys. Rev.

Feedback linearization control for a distributed solar collector field

This article describes the application of a feedback linearization technique for control of a distributed solar collector field using the energy from solar radiation to heat a fluid. The control target is to track an outlet temperature reference by manipulating the fluid flow rate through the solar field, while attenuating the effect of disturbances (mainly radiation and inlet temperature). The proposed control scheme is very easy to implement, as it uses a numerical approximation of the transport delay and a modification of the classical control scheme to improve startup in such a way that results compared with other control structures under similar conditions are improved while preserving short commissioning times. Experiments in the real plant are also described, demonstrating how operation can be started up efficiently.Ministerio de Ciencia y Tecnología DPI2004-07444-C04-04Ministerio de Ciencia y Tecnología DPI2005-0286

La herencia del expresionismo. Sobre la discusión en Das Wort, Moscú, 1937/38

The issue of September 1937 of Das Wort, edited by the German intellectuals in exile in Moscow, initiates a debate on the legacy of expressionism marked by the political context before World War II. The discussion is declared closed in the issue of July 1938 anathematizing expressionism and advocating, more than an aesthetic concept, a model of realism subjugated to the official communist doctrine. The contributions of Ernst Bloch and Georg Lukács are analysed and contrasted in this paper, as well as those of expressionist authors like Rudolf Leonhard or Herwarth Walden and members of the League of Proletarian-Revolutionary Writers such as Werner Ilberg or Franz Leschnitzer among others. The immediate reactions of Anna Seghers and Bertolt Brecht, not published in Das Wort, will finally be discussed.En el número de septiembre de 1937 de la revista Das Wort, editada por los intelectuales alemanes exiliados en Moscú, se abre un debate sobre la herencia del expresionismo marcado por el contexto político previo a la II Guerra Mundial. La discusión se da por concluida en el número de julio de 1938, anatematizando el expresionismo y propugnando, más que un concepto estético, un modelo de realismo subyugado a la doctrina comunista oficial. En el artículo se analizan y contrastan las contribuciones de Ernst Bloch y Georg Lukács, y también las de autores expresionistas como Rudolf Leonhard o Herwarth Walden y miembros de la Liga de Escritores Proletarios Revolucionarios como Werner Ilberg o Franz Leschnitzer, entre otros. Se apuntan asimismo las inmediatas reacciones de Anna Seghers y Bertolt Brecht, que no tuvieron cabida en las páginas de Das Wort

TRAIL, DR5 and Caspase 3-dependent Apoptosis in Vessels of Diseased Human Temporomandibular Joint Disc. An Immunohistochemical Study

To evaluate the apoptosis involvement in the angiogenesis as a self-limiting process in patients with temporomandibular joint (TMJ) degenerated disc vessels, we assessed, by immunohistochemistry, the detection of TRAIL, its death receptor DR5 and caspase 3. TRAIL, its death receptor DR5 and caspase 3 expression were studied by immunohistochemistry in 15 TMJ discs displaced without reduction and in 4 unaffected discs. These apoptosis molecules were detected in the intima and media layers of newly formed vessels affected discs. In conclusion, vessels apoptosis activation in TMJ disc with ID could be regarded as a self-limiting process that try to leads to vessel regression; in this way an inhibition of angiogenic vessels may prove a key strategy in limiting pathological angiogenesis, by cutting off blood supply to tumors, or by reducing harmful inflammation

Internal avalanches in models of granular media

We study the phenomenon of internal avalanching within the context of recently introduced lattice models of granular media. The avalanche is produced by pulling out a grain at the base of the packing and studying how many grains have to rearrange before the packing is once more stable. We find that the avalanches are long-ranged, decaying as a power-law. We study the distriution of avalanches as a function of the density of the packing and find that the avalanche distribution is a very sensitive structural probe of the system.Comment: 12 pages including 9 eps figures, LaTeX. To appear in Fractal

Distance Education: Exploring Trends and Issues in the Global Context

With the end goal of informing school management practices, this paper presents a comprehensive review of literature and studies on the trends and issues of Distance Education (DE) in the global context. Due to the development of communication technologies, the change in the modes of Distance Education is very abrupt. Internationalization, cost-effectiveness, access, infrastructure, and quality are some of the trends being faced by our contemporary education system. However, the literature and research findings also revealed that there are some emerging issues in the field such as dropout rates, assessment of students, student concerns, cost-effectiveness, issues related to technology use, and infrastructure. Keywords: Distance Education, trends, issues, e-learning, education, Open University DOI: 10.7176/JEP/11-4-15 Publication date: February 29th 202

Business Economics in Postmodern Literature: Kathrin Röggla

El proceso deshumanizante que la New Economy finisecular comporta para los profesionales de alto nivel se perfila como una temática muy atractiva para los autores de la llamada Generación pop. En el contexto Kathrin Röggla presenta Wir schlafen nicht (2004) simultáneamente como novela y obra de teatro. Partiendo de su propuesta, en el artículo se apuntarán los parámetros artísticos de que se sirve la literatura postmoderna para tematizar la agresión del capitalismo más salvaje, precisamente para los cuerpos y las psiches de quienes lo sustentan y representan. Después de exponer brevemente el punto de partida argumental de Wir schlafen nicht y las peculiaridades léxicoformales que requiere la ficción narrativa de transcripción, se analizará el carácter más relevante, los consultants. En lo esperpéntico de su entorno profesional, aquejado de alergias, tics nerviosos y disonancias cognitivas, síntomas patológicos propios de la adicción al trabajo, Röggla consigue desenmascarar literariamente, y valiéndose de lo que ella describe como “hibridación de géneros y medios”, la vulnerabilidad del infalible homo oeconomicus.The dehumanising process that the turn of the century New Economy entailed for high level professionals turned out to be a very attractive theme for authors of the so-called Pop Generation. In this context, Kathrin Röggla presents Wir schlafen nicht (2004) as both a novel and a theatre play. Taking her work as starting point, this article outlines the artistic parameters used by postmodern literature to portray the aggression of the most savage capitalism, precisely on the bodies and psyches of those who sustain and represent it. After briefly describing the plot of Wir schlafen nicht and the lexical and formal peculiarities involved in the transcription of narrative fiction, the leading character of the consultants will be analysed. In their grotesque professional environment, riddled with allergies, nervous tics and cognitive dissonances, pathological symptoms of their workaholic habits, Röggla manages to unmask in a literary sense, employing what she describes as «a hybridisation of genres and media», the vulnerability of the infallible homo oeconomicus