Social Learning and Coordination Conventions in Inter-Generational Games: An Experimental Study

This is a paper on the creation and evolution of conventions of behavior in "inter-generational games". In these games a sequence of nonoverlapping "generations" of players play a stage game for a finite number of periods and are then replaced by other agents who continue the game in their role for an identical length of time. Players in generation t are allowed to see the history of the game played by all (or some subset) of the generations who played it before them and can communicate with their successors in generation t+1 and advise them on how they should behave. What we find is that word-of-mouth social learning (in the form of advice from laboratory "parents" to laboratory "children") can be a strong force in the creation of social conventions, far stronger than the type of learning subjects seem capable of doing simply by learning the lessons of history without the guidance o¥ered by such advice.

Advice and Behavior in Intergenerational Ultimatum Games: An Experimental Approach

In the real world, when people play games, they often receive advice from those that have played it before them. Such advice can facilitate the creation of a convention of behavior. This paper studies the impact of advice on the behavior subjects who engage in a non-overlapping generational Ultimatum game where after a subject plays he is replaced by another subject to whom he can offer advice. Our results document the fact that allowing advice has a dramatic impact on the behavior of subjects. It diminishes the variance of offers made over time, lowers their mean, and causes Receivers to reject low offers with higher probability. In addition, by reading the advice offered we conclude that arguments of fairness are rarely used to justify the offers of Senders but are relied upon to justify rejections by Receivers.

Creating Culture in the Lab: Equilibrium Conventions in Inter-Generational Ultimatum Games

The Ultimatum Game and the experiments surrounding it, have presented economists with a puzzle that they have struggled to explain. But as Robert Aumann has pointed out, while there may be only one sub-game perfect equilibrium to the Ultimatum Game, there are an infinite number of Nash equilibria. All that is needed to maintain a non-sub-game perfect equilibrium is a set of Sender beliefs that the offer contemplated is the minimum that would be accepted and behavior on the part of the Receivers that confirms these beliefs. The only puzzle is how such a set of mutually consistent beliefs developed in the first place and how they are passed on from one generation of player to the next. Using an inter-generational game experimental setting, this paper investigates how "culture" serves as the selection mechanism which solves this puzzle. Culture is then simply a system of beliefs and self-confirming actions which support any one of these non-sub-game perfect Nash equilibria as the accepted solution to the game being played. The outcome is, as Robert Aumann has called it a "perfectly good" Nash equilibrium convention which is just not perfect.

The influence of muscle pennation angle and cross-sectional area on contact forces in the ankle joint

Data about a muscle’s fibre pennation angle and physiological cross-sectional area are used in musculoskeletal modelling to estimate muscle forces, which are used to calculate joint contact forces. For the leg, muscle architecture data are derived from studies that measured pennation angle at the muscle surface, but not deep within it. Musculoskeletal models developed to estimate joint contact loads have usually been based on the mean values of pennation angle and physiological cross-sectional area. Therefore, the first aim of this study was to investigate differences between superficial and deep pennation angles within each muscle acting over the ankle and predict how differences may influence muscle forces calculated in musculoskeletal modelling. The second aim was to investigate how inter-subject variability in physiological cross-sectional area and pennation angle affects calculated ankle contact forces. Eight cadaveric legs were dissected to excise the muscles acting over the ankle. The mean surface and deep pennation angles, fibre length and physiological cross-sectional area were measured. Cluster analysis was applied to group the muscles according to their architectural characteristics. A previously validated OpenSim model was used to estimate ankle muscle forces and contact loads using architecture data from all eight limbs. The mean surface pennation angle for soleus was significantly greater (54%) than the mean deep pennation angle. Cluster analysis revealed three groups of muscles with similar architecture and function: deep plantarflexors and peroneals, superficial plantarflexors and dorsiflexors. Peak ankle contact force was predicted to occur before toe-off, with magnitude greater than five times bodyweight. Inter-specimen variability in contact force was smallest at peak force. These findings will help improve the development of experimental and computational musculoskeletal models by providing data to estimate force based on both surface and deep pennation angles. Inter-subject variability in muscle architecture affected ankle muscle and contact loads only slightly. The link between muscle architecture and function contributes to the understanding of the relationship between muscle structure and function

Total ankle replacement design and positioning affect implant-bone micromotion and bone strains

Implant loosening - commonly linked with elevated initial micromotion - is the primary indication for total ankle replacement (TAR) revision. Finite element modelling (FEM) has not been used to assess micromotion of TAR implants; additionally, the biomech anical consequences of TAR malpositioning - previously linked with higher failure rates - remain unexplored. The aim of this study was to estimate implant - bone micromotion and peri - implant bone strains for optimally positioned and malpositioned TAR prosthe ses, and thereby identify fixation features and malpositioning scenarios increasing the risk of loosening. Computational models simulating three of the most commonly used TAR devices (BOX®, Mobility® and Salto®) implanted into the tibia/talus and subjected to physiological loads were developed. Mobility and Salto demonstrated the largest micromotion of all tibial and talar components, respectively. Any malpositioning of the implant creating a gap between it and the bone resulted in a considerable increase i n micromotion and bone strains. It was concluded that better primary stability can be achieved through fixation nearer to the joint line and/or while relying on more than a single peg. Incomplete seating on the bone may result in considerably elevated impl ant - bone micromotion and bone strains, thereby increasing the risk for TAR failure

Polyglutamine-expanded androgen receptor interferes with TFEB to elicit autophagy defects in SBMA.

Macroautophagy (hereafter autophagy) is a key pathway in neurodegeneration. Despite protective actions, autophagy may contribute to neuron demise when dysregulated. Here we consider X-linked spinal and bulbar muscular atrophy (SBMA), a repeat disorder caused by polyglutamine-expanded androgen receptor (polyQ-AR). We found that polyQ-AR reduced long-term protein turnover and impaired autophagic flux in motor neuron-like cells. Ultrastructural analysis of SBMA mice revealed a block in autophagy pathway progression. We examined the transcriptional regulation of autophagy and observed a functionally significant physical interaction between transcription factor EB (TFEB) and AR. Normal AR promoted, but polyQ-AR interfered with, TFEB transactivation. To evaluate physiological relevance, we reprogrammed patient fibroblasts to induced pluripotent stem cells and then to neuronal precursor cells (NPCs). We compared multiple SBMA NPC lines and documented the metabolic and autophagic flux defects that could be rescued by TFEB. Our results indicate that polyQ-AR diminishes TFEB function to impair autophagy and promote SBMA pathogenesis

3-D reflection seismic imaging of the Hontomín structure in the Basque–Cantabrian Basin (Spain)

The Basque–Cantabrian Basin of the northern Iberia Peninsula constitutes a unique example of a major deformation system, featuring a dome structure developed by extensional tectonics followed by compressional reactivation. The occurrence of natural resources in the area and the possibility of establishing a geological storage site for carbon dioxide motivated the acquisition of a 3-D seismic reflection survey in 2010, centered on the Jurassic Hontomín dome. The objectives of this survey were to obtain a geological model of the overall structure and to establish a baseline model for a possible geological CO2 storage site. The 36 km 2 survey included approximately 5000 mixed (Vibroseis and explosives) source points recorded with a 25 m inline source and receiver spacing. The target reservoir is a saline aquifer, at approximately 1450 m depth, encased and sealed by carbonate formations. Acquisition and processing parameters were influenced by the rough topography and relatively complex geology. A strong near-surface velocity inversion is evident in the data, affecting the quality of the data. The resulting 3-D image provides constraints on the key features of the geologic model. The Hontomín structure is interpreted to consist of an approximately 107 m2 large elongated dome with two major (W–E and NW–SE) striking faults bounding it. Preliminary capacity estimates indicate that about 1.2 Gt of CO2 can be stored in the target reservoirFunding for this Project has been partially provided by the Spanish Ministry of Industry, Tourism and Trade, through the CIUDEN-CSIC-Inst. Jaume Almera agreement (Characterization, Development and Validation of Seismic Techniques applied to CO2 Geological Storage Sites) and by the European Union through the Technology Demonstration Plant of Compostilla OXYCFB300 project (European Energy Programme for 534 Recovery). Additional support has been provided by Spanish Ministry of Education Science (CSD2006-00041), Generalitat de Catalunya (2009SGR006) and CSIC JAE-Doc postdoctoral research contract (E.S.).Peer Reviewe