Stressed Web Environments as Strategic Games: Risk Profiles and Weltanschauung

We consider the behaviour of a set of services in a stressed web environment where performance patterns may be difficult to predict. In stressed environments the performances of some providers may degrade while the performances of others, with elastic resources, may improve. The allocation of web-based providers to users (brokering) is modelled by a strategic non-cooperative angel-daemon game with risk profiles. A risk profile specifies a bound on the number of unreliable service providers within an environment without identifying the names of these providers. Risk profiles offer a means of analysing the behaviour of broker agents which allocate service providers to users. A Nash equilibrium is a fixed point of such a game in which no user can locally improve their choice of provider – thus, a Nash equilibrium is a viable solution to the provider/user allocation problem. Angel daemon games provide a means of reasoning about stressed environments and offer the possibility of designing brokers using risk profiles and Nash equilibria.

High-order harmonic generation from controlled plasma mirrors

Ultrashort, high contrast laser pulses when focused to high intensity and reflected from a steep solid density 'plasma mirror (PM)' contain coherent XUV radiation in the form of high-order harmonics. The emission can either be due to the relativistically driven oscillating PM (ROM) [1] or due to Coherent wake emission (CWE) [2]. Selective control over the mechanisms and the characteristics of these harmonics and understanding the physics is crucial for the development of intense attosecond light sources. © 2013 IEEE.

Characterizing Aquifer Heterogeneity Using Bacterial and Bacteriophage Tracers

Gravel aquifers act as important potable water sources in central western Europe yet they are subject to numerous contamination pressures. Compositional and textural heterogeneity makes protection zone delineation around groundwater supplies in these units challenging; artificial tracer testing aids characterization. This paper reappraises previous tracer test results in light of new geological and microbiological data. Comparative passive gradient testing, using a fluorescent solute (Uranine), virus (H40/1 bacteriophage), and comparably sized bacterial tracers Escherichia coli and Pseudomonas putida, was used to investigate a calcareous gravel aquifer’s ability to remove microbiological contaminants at a test site near Munich, Germany. Test results revealed E. coli relative recoveries could exceed those of H40/1 at monitoring wells 10 m and 20 m from an injection well by almost four times; P. putida recoveries varied by a factor of up to three between wells. Application of filtration theory suggested greater attenuation of H40/1 relative to similarly charged E. coli occurred due to differences in microorganism size, while estimated collision efficiencies appeared comparable. By contrast, more positively charged P. putida experienced greater attenuation at one monitoring point, while lower attenuation rates at the second location indicated the influence of geochemical heterogeneity. Test findings proved consistent with observations from nearby fresh outcrops that suggested thin open framework gravel beds dominated mass transport in the aquifer, while discrete intervals containing stained clasts reflect localized geochemical heterogeneity. Study results highlight the utility of reconciling outcrop observations with artificial tracer test responses, using microbiological tracers with well-defined properties, to characterize aquifer heterogeneity.

Acceleration-as-a-Service: Exploiting Virtualised GPUs for a Financial Application

How can GPU acceleration be obtained as a service in a cluster? This question has become increasingly significant due to the inefficiency of installing GPUs on all nodes of a cluster. The research reported in this paper is motivated to address the above question by employing rCUDA (remote CUDA), a framework that facilitates Acceleration-as-a-Service (AaaS), such that the nodes of a cluster can request the acceleration of a set of remote GPUs on demand. The rCUDA framework exploits virtualisation and ensures that multiple nodes can share the same GPU. In this paper we test the feasibility of the rCUDA framework on a real-world application employed in the financial risk industry that can benefit from AaaS in the production setting. The results confirm the feasibility of rCUDA and highlight that rCUDA achieves similar performance compared to CUDA, provides consistent results, and more importantly, allows for a single application to benefit from all the GPUs available in the cluster without loosing efficiency.

Effective-fourth-order resonator based MASH bandpass sigma-delta modulators

Two novel effective-fourth-order (eighth-order) resonator based MASH (MultistAge noise SHaping) bandpass Σ-Δ modulators are introduced at the behavioural level and subsequently examined by simulations utilising the ALTA SPW environment. The considered bandpass configurations have in their loop filter a cascade of standard second-order resonator structures in order to achieve appropriate noise shaping. The quantisation noise in each stage is suppressed by feeding the error of each section into the input of the following stage. It is demonstrated in this paper that the quadruple effective-first-order cascade configuration has significantly better performance as well as conforming more closely with theory in comparison with the effective-second-order effective-second-order cascade. The superior performance of the former can be attributed to the cumulative effect of the multi-bit outputs as well as the presence of more notch filters.

Uma dramaturgia da viagem: registos de uma experiência [TheaterSpielhaus]: relatório de estágio

Mestrado Teatro, especialização em artes performativas, interpretação

A protocol guided by transpulmonary thermodilution and lactate levels for resuscitation of patients with severe burns.

Over-resuscitation is deleterious in many critically ill conditions, including major burns. For more than 15 years, several strategies to reduce fluid administration in burns during the initial resuscitation phase have been proposed, but no single or simple parameter has shown superiority. Fluid administration guided by invasive hemodynamic parameters usually resulted in over-resuscitation. As reported in the previous issue of Critical Care, Sánchez-Sánchez and colleagues analyzed the performance of a 'permissive hypovolemia' protocol guided by invasive hemodynamic parameters (PiCCO, Pulsion Medical Systems, Munich, Germany) and vital signs in a prospective cohort over a 3-year period. The authors' results confirm that resuscitation can be achieved with below-normal levels of preload but at the price of a fluid administration greater than predicted by the Parkland formula (2 to 4 mL/kg per% burn). The classic approach based on an adapted Parkland equation may still be the simplest until further studies identify the optimal bundle of resuscitation goals.

Análisis de la viabilidad de Bogotá como sede principal para el Mundial de Fútbol 2026

El pasado Mundial de Fútbol Categoría Sub-20 fue una gran oportunidad que tuvo Colombia para seguir mostrándose a nivel internacional y para mejorar su imagen negativa de ser un país violento. Debido al éxito de este evento, y que estuvo a la altura de los de su tipo, ya que también superó en record de asistencia a los que se habían realizado anteriormente (FIFA.COM, 2011), y sumado a las declaraciones del presidente de la FIFA: "Colombia está preparada para la gran Copa Mundial de FIFA, pero de momento deberá esperar hasta el año 2026, porque las sedes de los años 2014 (Brasil), 2018 (Rusia) y 2022 (Qatar) ya están asignadas" (Semana, 2011); este trabajo pretende analizar con base en los principales indicadores (infraestructuras, movilidad, vías, ciudades, seguridad), si Bogotá podría ser sede principal del mundial de fútbol del 2026. Para lograr el objetivo se tomaron como referencia los diferentes mundiales anteriormente realizados. Se hizo un análisis comparativo entre Johannesburgo (sede principal del Mundial realizado en Suráfrica en el 2010) y Bogotá, en 5 factores que permiten visualizar las fortalezas y debilidades de la capital colombiana para poder ser sede principal de un Mundial. Se presentan conclusiones.

Cambios en el régimen de pensiones en Colombia y su efecto en el margen intensivo de la oferta laboral

En Colombia, como en muchos países de América Latina, en los años 80 y 90 se hicieron cambios importantes en los regímenes de pensiones. Este trabajo hace un análisis de uno de esos cambios en Colombia. El cambio consistió en aumentar el tiempo de cotización necesario para reclamar los beneficios pensionales y la inclusión del salario dentro de la fórmula del monto de pensiones. Para este propósito se estudia el impacto sobre la oferta laboral de un cambio exógeno en estas condiciones usando un diseño de regresión discontinua. Se encuentra un efecto positivo sobre las horas promedio trabajadas en la semana.

Parametric pension reform and the intensive margin of labor supply, evidence from Colombia

We analyze the effect of a parametric reform of the fully-funded pension regime in Colombia on the intensive margin of the labor supply. We take advantage of a threshold defined by law in order to identify the causal effect using a regression discontinuity design. We find that a pension system that increases retirement age and the minimum weeks during which workers must contribute to claim pension benefits causes an increase of around 2 hours on the number of weekly worked hours; this corresponds to 4% of the average number of weekly worked hours or around 14% of a standard deviation of weekly worked hours. The effect is robust to different specifications, polynomial orders and sample sizes.