Pure strategy dominance with quasiconcave utility functions

By a result of Pearce (1984), in a finite strategic form game, the set of a player's serially undominated strategies coincides with her set of rationalizable strategies. In this note we consider an extension of this result that applies to games with continuous utility functions that are quasiconcave in own action. We prove that in such games, when the players are endowed with compact, metrizable, and convex action spaces, a strategy of some player is dominated by some other pure strategy if and only if it is not a best reply to any belief over the strategies adopted by her opponents. For own-quasiconcave games, this can be used to give a characterization of the set of rationalizable strategies, different from the one given by Pearce. Moreover, expected utility functions defined on the mixed extension of a game are always own-quasiconcave, and therefore the result in this note generalizes Pearce''s characterization to infinite games, by a simple shift of perspective.

Risk of cardiovascular disease in first and second generation Mexican-Americans.

This study examines the cardiovascular disease (CVD) risk profiles of first generation (FG) and second generation (SG) Mexican-Americans (MA) in two large national studies--the Hispanic Health and Nutrition Examination Study (HHANES) (1982-1984) and the National Health and Examination Study (NHANES) (1999-2004). The main outcome measures were five individual risk indicators of CVD (total cholesterol, HDL cholesterol, hypertension, diabetes, and smoking) and a composite measure (the Framingham Risk Score [FRS]). The analyses included cross-survey (pseudocohort) and within-survey (cross-sectional) comparisons. In multivariate analyses, SG men had higher rates of hypertension and lower rates of smoking than FG men; and SG women had lower total cholesterol levels, higher rates of hypertension, and lower rates of smoking than FG women. There was no generational difference in the FRS in men or women. The cross-survey comparisons detected generational differences in CVD risk factors not detected in within-survey comparisons, particularly among MA women. Future studies of generational differences in risk should consider using pseudocohort comparisons when possible

Improved proposal distribution with gradient measures for tracking

Particle filters have become a useful tool for the task of object tracking due to their applicability to a wide range of situations. To be able to obtain an accurate estimate from a particle filter a large number of particles is usually necessary. A crucial step in the design of a particle filter is the choice of the proposal distribution. A common choice for the proposal distribution is to use the transition distribution which models the dynamics of the system but takes no account of the current measurements. We present a particle filter for tracking rigid objects in video sequences that makes use of image gradients in the current frame to improve the proposal distribution. The gradient information is efficiently incorporated in the filter to minimise the computational cost. Results from synthetic and natural sequences show that the gradient information improves the accuracy and reduces the number of particles requiredParticle filters have become a useful tool for the task of object tracking due to their applicability to a wide range of situations. To be able to obtain an accurate estimate from a particle filter a large number of particles is usually necessary. A crucial step in the design of a particle filter is the choice of the proposal distribution. A common choice for the proposal distribution is to use the transition distribution which models the dynamics of the system but takes no account of the current measurements. We present a particle filter for tracking rigid objects in video sequences that makes use of image gradients in the current frame to improve the proposal distribution. The gradient information is efficiently incorporated in the filter to minimise the computational cost. Results from synthetic and natural sequences show that the gradient information improves the accuracy and reduces the number of particles require

The influence of joints and composite floor slabs on effective tying of steel structures in preventing progressive collapse

The event of the terrorist attack at 11th September 2001 in the USA has attracted increasing attention of researchers and engineers on progressive collapse of structures. It has gradually become a general practice for engineers to consider progressive collapse resistance in their design. In this paper, progressive collapse of steel frames with composite floor slabs is simulated by the finite element method. The numerical results are compared with test results. The influence of the joints and the concrete slabs on the effective tying of steel beams is investigated through parametric studies. From the analysis, methods of preventing progressive collapse that can be considered in design and when retrofitting existing structures are proposed. The results show that retrofitting a structure with pre-stressed steel cables and an increase of crack resistance in the concrete near joints can effectively improve effective tying of a structure, which results in an enhanced structural capacity in preventing progressive collapse

Soil microbial communities in restored and unrestored coastal dune ecosystems in California

Most restoration projects involving invasive plant eradication tend to focus on plant removal with little consideration given to how these invasives change soil microbial communities. However, soil microorganisms can determine invasibility of habitats and, in turn, be altered by invasives once established, potentially inhibiting native plant establishment. We studied soil microbial communities in coastal dunes with varying invasion intensity and different restoration approaches (herbicide, mechanical excavation) at Point Reyes National Seashore. Overall, we found evidence of a strong link between bacterial and fungal soil communities and the presence of invasives and restoration approach. Heavily invaded sites were characterized by a lower abundance of putatively identified nitrifiers, fermentative bacteria, fungal parasites, and fungal dung saprotrophs and a higher abundance of cellulolytic bacteria and a class of arbuscular mycorrhizal fungi (Archaeosporomycetes). Changes in soil microbiota did not fully dissipate following removal of invasives using herbicide, with exception of reductions in cellulolytic bacteria and Archaeosporomycetes abundance. Mechanical restoration effectively removed both invasives and soil legacy effects by inverting or “flipping” rhizome-contaminated surface soils with soils from below and may have inadvertently induced other adverse effects on soils that impeded reestablishment of native dune plants. Land managers should consider additional measures to counteract lingering legacy effects and/or focus restoration efforts in areas where legacy effects are less pronounced