Improved routing strategies for Internet traffic delivery

We analyze different strategies aimed at optimizing routing policies in the Internet. We first show that for a simple deterministic algorithm the local properties of the network deeply influence the time needed for packet delivery between two arbitrarily chosen nodes. We next rely on a real Internet map at the autonomous system level and introduce a score function that allows us to examine different routing protocols and their efficiency in traffic handling and packet delivery. Our results suggest that actual mechanisms are not the most efficient and that they can be integrated in a more general, though not too complex, scheme.Comment: Final versio

Evolución de la relación entre atención primaria y especializada 1992-2001: estudio Delphi

ObjetivoValorar la tendencia en la relación de atención primaria (AP) y especializada (hospital) en 2 momentos diferentes de la reforma sanitaria, al inicio (1992) y tras una fase de consolidación (2001).DiseñoEstudio cualitativo basado en la técnica Delphi modificada.EmplazamientoComunidad Valenciana.ParticipantesSe seleccionó a un total de 196 profesionales de la Comunidad Valenciana (103 coordinadores de AP, 43 directores médicos hospitalarios y de AP, y 50 jefes de servicio de medicina interna/urgencias).ResultadosSe enviaron 196 cuestionarios, con una tasa de respuesta del 38%. Desde AP los problemas se mantienen, con un empeoramiento en la desmotivación del personal sanitario (+1,34), la falta de visión integral del paciente (+1,10) y la masificación asistencial (+1,06), y un mejoría en la presencia de especialistas de ambulatorio no integrados (–1,32). Desde el ámbito hospitalario empeora la falta de visión integral del paciente (+0,51), pero destaca la mejoría generalizada de los problemas, sobre todo la falta de comunicación y diálogo (–1,14). Las soluciones que aumentan su demanda desde AP son una historia clínica única informatizada (+1,50), la elaboración de protocolos comunes (+0,86) y las rotaciones periódicas de los médicos de AP (MAP) por servicios hospitalarios (+0,85), con una disminución de las derivaciones burocráticas a AP (–0,60) y la necesidad de especialistas en AP como consultores (–0,36). Desde el ámbito hospitalario, todas las soluciones disminuyen su valoración y entre ellas destaca facilitar el acceso de MAP para el seguimiento de los pacientes ingresados (–2,44) y la realización de guardias hospitalarias por MAP (–2,30).ConclusionesLos problemas y las soluciones siguen siendo los mismos que en 1992, pero en AP se observa una tendencia a empeorar y en el ámbito hospitalario se detecta una visión más positiva.AimTo evaluate the trends in the inter-professional relationship between primary health care (PHC) and secondary care (hospital) at 2 different moments of the health reform, at its start in 1992 and after a phase of consolidation (2001).DesignObservational study based on modified Delphi technique.SettingValencia Community, Spain.ParticipantsOne hundred and ninety six professionals from Valencia Community were selected (103 PH centre administrators, 43 hospital and PC medical directors, and 50 heads of internal medicine or emergency services).ResultsOne hundred and ninety six questionnaires were sent out, with a response rate of 38%. In PHC problems remained the same, but the following got worse: “lack of motivation” (+1.34), “lack of overall vision of patients” (+1.10), and “overuse of medical services” (+1.06). The existence of non-integrated out-patient specialists got better (–1.32). In hospitals, “lack of overall vision of patients” got worse (+0.51), but in general problems got better, especially in “lack of communication and dialogue” (–1.14). PC increased its demand for “a single computerized clinical record” (+1.50), drawing up of common protocols (+0.86), and periodic rotations of PC doctors through hospitals (+0.85), but bureaucratic referrals to PC (–0.60) and the need for specialists in PC as consultants (-0.36) diminished. In hospitals all solutions showed lower scores, particularly access of PC doctors to monitoring of admitted patients (–2.44) and PC doctors doing hospital cover (–2.30).ConclusionsProblems and solutions from PHC and hospitals remain the same, but there is a trend to the worse in PHC, whereas in hospitals the trend is more positive

On Limitations of the Ultrasonic Characterization of Pieces Manufactured with Highly Attenuating Materials

Some technical aspects of two Spanish cooperation projects, funded by DPI and Innpacto Programs of the R&D National Plan, are discussed. The objective is to analyze the common belief about than the ultrasonic testing in MHz range is not a tool utilizable to detect internal flaws in highly attenuating pieces made of coarse-grained steel. In fact high-strength steels, used in some safe industrial infrastructures of energy & transport sectors, are difficult to be inspected using the conventional “state of the art” in ultrasonic technology, due to their internal microstructures are very attenuating and coarse-grained. It is studied if this inspection difficulty could be overcome by finding intense interrogating pulses and advanced signal processing of the acquired echoes. A possible solution would depend on drastically improving signal-to-noise-ratios, by applying new advances on: ultrasonic transduction, HV electronics for intense pulsed driving of the testing probes, and an “ad-hoc” digital processing or focusing of the received noisy signals, in function of each material to be inspected. To attain this challenging aim on robust steel pieces would open the possibility of obtaining improvements in inspecting critical industrial components made of highly attenuating & dispersive materials, as new composites in aeronautic and motorway bridges, or new metallic alloys in nuclear area, where additional testing limitations often appear.The Spanish I+D National Plan (MINECO), by funding the Projects: Fundamental Research / DPI2011 – 22438, and INNPACTO Program / IMAAD - IPT-020000-2010-0004

Instability of scale-free networks under node-breaking avalanches

The instability introduced in a large scale-free network by the triggering of node-breaking avalanches is analyzed using the fiber-bundle model as conceptual framework. We found, by measuring the size of the giant component, the avalanche size distribution and other quantities, the existence of an abrupt transition. This test of strength for complex networks like Internet is more stringent than others recently considered like the random removal of nodes, analyzed within the framework of percolation theory. Finally, we discuss the possible implications of our results and their relevance in forecasting cascading failures in scale-free networks.Comment: 4 pages, 4 figures, final version to be published in Europhys. Let

Robustness of Cooperation in the Evolutionary Prisoner's Dilemma on Complex Networks

Recent studies on the evolutionary dynamics of the Prisoner's Dilemma game in scale-free networks have demonstrated that the heterogeneity of the network interconnections enhances the evolutionary success of cooperation. In this paper we address the issue of how the characterization of the asymptotic states of the evolutionary dynamics depends on the initial concentration of cooperators. We find that the measure and the connectedness properties of the set of nodes where cooperation reaches fixation is largely independent of initial conditions, in contrast with the behavior of both the set of nodes where defection is fixed, and the fluctuating nodes. We also check for the robustness of these results when varying the degree heterogeneity along a one-parametric family of networks interpolating between the class of Erdos-Renyi graphs and the Barabasi-Albert networks.Comment: 18 pages, 6 figures, revised version accepted for publication in New Journal of Physics (2007

Psicoterapia contemporánea: dilemas y perspectivas

Hablar de una psicoterapia contemporánea nos conduce necesariamente a abordajes en clave de complejidad que favorezcan miradas más abiertas, con más posibilidades, en su constitución, su ámbito de conocimiento, el ejercicio profesional y la formación de psicoterapeutas. Y pensarla desde una perspectiva interdisciplinar es fundamental para la comprensión, el análisis y las posibilidades de tratamiento de los problemas psicológicos que aquejan a las sociedades contemporáneas. Este es el planteamiento central que se desarrolla en esta obra conformada por ocho ensayos, en los cuales se abordan temas como la formación de los psicoterapeutas, la historia de este campo profesional, la influencia del entorno y de la familia en el consultante, así como la importancia del diálogo con otras disciplinas para el perfeccionamiento de este campo de generación e innovación en psicoterapia. Por ello, se recomienda la lectura de este volumen, el primero de la colección Psicoterapia y Diálogo Interdisciplinario, a estudiantes, docentes y profesionales en el campo de la psicoterapia y la salud mental, ya que este ejercicio profesional cobra cada día mayor relevancia para el entendimiento y abordaje de la complejidad de la vida humana hacia la promoción del bienestar.ITESO. A.C

Comparative study of PCR-sexing procedures using bovine embryos fertilized with sex-sorted spermatozoa

Sex determination in bovine embryos is a useful tool in reproductive biotechnology. This work compares two techniques of embryo sexing by polymerase chain reaction (PCR. Embryos were produced in vitro with sex-sorted sperm and two techniques of DNA lysis were tested (proteinase K versus heat shock). Subsequently, halves of each lysed sample was amplified both by amelogenin and BRY4a/SAT1 primers. Male embryos treated by both digestion methods and amplified by BRY4a/SAT1 gave higher rates of false negatives. Amelogenin amplification failed with embryos previously digested by proteinase K. In contrast, the lysis method allowed obtaining the best accuracy in terms of sex verification when using amelogenin amplification

Transmission of light through periodic arrays of square holes: From a metallic wire mesh to an array of tiny holes

J. Bravo-Abad, L. Martín-Moreno, F. J. García-Vidal, Euan Hendry, and J. Gómez Rivas, Physical Review B, Vol. 76, article 241102(R) (2007). "Copyright © 2007 by the American Physical Society."A complete landscape is presented of the electromagnetic coupling between square holes forming a two-dimensional periodic array in a metallic film. By combining both experimental and theoretical results along with a first-principles Fano model, we study the crossover between the physics of metallic wire meshes (when holes occupy most of the unit cell) and the phenomenon of extraordinary optical transmission, which appears when the size of the holes is very small in comparison with the period of the array

Introduction to protein folding for physicists

The prediction of the three-dimensional native structure of proteins from the knowledge of their amino acid sequence, known as the protein folding problem, is one of the most important yet unsolved issues of modern science. Since the conformational behaviour of flexible molecules is nothing more than a complex physical problem, increasingly more physicists are moving into the study of protein systems, bringing with them powerful mathematical and computational tools, as well as the sharp intuition and deep images inherent to the physics discipline. This work attempts to facilitate the first steps of such a transition. In order to achieve this goal, we provide an exhaustive account of the reasons underlying the protein folding problem enormous relevance and summarize the present-day status of the methods aimed to solving it. We also provide an introduction to the particular structure of these biological heteropolymers, and we physically define the problem stating the assumptions behind this (commonly implicit) definition. Finally, we review the 'special flavor' of statistical mechanics that is typically used to study the astronomically large phase spaces of macromolecules. Throughout the whole work, much material that is found scattered in the literature has been put together here to improve comprehension and to serve as a handy reference.Comment: 53 pages, 18 figures, the figures are at a low resolution due to arXiv restrictions, for high-res figures, go to http://www.pabloechenique.co