3,019 research outputs found
Monte Carlo Planning method estimates planning horizons during interactive social exchange
Reciprocating interactions represent a central feature of all human exchanges. They have been the target of various recent experiments, with healthy participants and psychiatric populations engaging as dyads in multi-round exchanges such as a repeated trust task. Behaviour in such exchanges involves complexities related to each agent's preference for equity with their partner, beliefs about the partner's appetite for equity, beliefs about the partner's model of their partner, and so on. Agents may also plan different numbers of steps into the future. Providing a computationally precise account of the behaviour is an essential step towards understanding what underlies choices. A natural framework for this is that of an interactive partially observable Markov decision process (IPOMDP). However, the various complexities make IPOMDPs inordinately computationally challenging. Here, we show how to approximate the solution for the multi-round trust task using a variant of the Monte-Carlo tree search algorithm. We demonstrate that the algorithm is efficient and effective, and therefore can be used to invert observations of behavioural choices. We use generated behaviour to elucidate the richness and sophistication of interactive inference
Electromechanical Simulation of Actively Controlled Rotordynamic Systems with Piezoelectric Actuators
Theories and tests for incorporating piezoelectric pushers as actuator devices for active vibration control are discussed. It started from a simple model with the assumption of ideal pusher characteristics and progressed to electromechanical models with nonideal pushers. Effects on system stability due to the nonideal characteristics of piezoelectric pushers and other elements in the control loop were investigated
Conceptual model of salt marsh management on Merritt Island National Wildlife Refuge, Florida: final report
Diking and holding water on salt marshes ("impounding" the marsh) is a
management technique used on Merritt Island National Wildlife Refuge
(MINWR) and elsewhere in the Southeast to: a) prevent the reproduction of
saltmarsh mosquitos, and b) attract wintertering waterfowl and other marsh,
shore, and wading birds. Because of concern that diking and holding water
may interfere with the production of estuarine fish and shellfish,
impoundment managers are being asked to consider altering management
protocol to reduce or eliminate any such negative influence. How to change
protocol and preserve effective mosquito control and wildlife management is
a decision of great complexity because: a) the relationships between
estuarine organisms and the fringing salt marshes at the land-water interface
are complex, and b) impounded marshes are currently good habitat for a
variety of species of fish and wildlife. Most data collection by scientists
and managers in the area has not been focused on this particular
problem. Furthermore, collection of needed data may not be possible before
changes in protocol are demanded. Therefore, the purpose of this document
is two-fold: 1) to suggest management alternatives, given existing information,
and 2) to help identify research needs that have a high probability
of leading to improved simultaneous management of mosquitos, waterfowl,
other wildlife, freshwater fish, and estuarine fish and shellfish on the
marshland of the Merritt Island National Wildlife Refuge. (92 page document
Categorized bibliography for a conceptual model of salt marsh management on Merritt Island, Florida
Enclosed is a bibliography of 556 published articles,
technical reports, theses, dissertations, and books that form the
basis for a conceptual model of salt marsh management on Merritt
Island, Florida (Section 1). A copy of each item is available on
file at the Florida Cooperative Fish and Wildlife Research Unit,
Gainesville. Some relevant proprietary items and unpublished
drafts have not been included pending permission of the authors.
We will continue to add pertinent references to our bibliography
and files. Currently, some topics are represented by very few
items. As our synthesis develops, we will be able to indicate a
subset of papers most pertinent to an understanding of the
ecology and management of Merritt Island salt marshes.
(98 page document
FGF/heparin differentially regulates Schwann cell and olfactory ensheathing cell interactions with astrocytes: a role in astrocytosis
After injury, the CNS undergoes an astrocyte stress response characterized by reactive astrocytosis/proliferation, boundary formation, and increased glial fibrillary acidic protein (GFAP) and chondroitin sulfate proteoglycan (CSPG) expression. Previously, we showed that in vitro astrocytes exhibit this stress response when in contact with Schwann cells but not olfactory ensheathing cells (OECs). In this study, we confirm this finding in vivo by demonstrating that astrocytes mingle with OECs but not Schwann cells after injection into normal spinal cord. We show that Schwann cell-conditioned media (SCM) induces proliferation in monocultures of astrocytes and increases CSPG expression in a fibroblast growth factor receptor 1 (FGFR1)-independent manner. However, SCM added to OEC/astrocyte cocultures induces reactive astrocytosis and boundary formation, which, although sensitive to FGFR1 inhibition, was not induced by FGF2 alone. Addition of heparin to OEC/astrocyte cultures induces boundary formation, whereas heparinase or chlorate treatment of Schwann cell/astrocyte cultures reduces it, suggesting that heparan sulfate proteoglycans (HSPGs) are modulating this activity. In vivo, FGF2 and FGFR1 immunoreactivity was increased over grafted OECs and Schwann cells compared with the surrounding tissue, and HSPG immunoreactivity is increased over reactive astrocytes bordering the Schwann cell graft. These data suggest that components of the astrocyte stress response, including boundary formation, astrocyte hypertrophy, and GFAP expression, are mediated by an FGF family member, whereas proliferation and CSPG expression are not. Furthermore, after cell transplantation, HSPGs may be important for mediating the stress response in astrocytes via FGF2. Identification of factors secreted by Schwann cells that induce this negative response in astrocytes would further our ability to manipulate the inhibitory environment induced after injury to promote regeneration
Simulating future value in intertemporal choice
The laboratory study of how humans and other animals trade-off value and time has a long and storied history, and is the subject of a vast literature. However, despite a long history of study, there is no agreed upon mechanistic explanation of how intertemporal choice preferences arise. Several theorists have recently proposed model-based reinforcement learning as a candidate framework. This framework describes a suite of algorithms by which a model of the environment, in the form of a state transition function and reward function, can be converted on-line into a decision. The state transition function allows the model-based system to make decisions based on projected future states, while the reward function assigns value to each state, together capturing the necessary components for successful intertemporal choice. Empirical work has also pointed to a possible relationship between increased prospection and reduced discounting. In the current paper, we look for direct evidence of a relationship between temporal discounting and model-based control in a large new data set (n = 168). However, testing the relationship under several different modeling formulations revealed no indication that the two quantities are related
On Representations of Conformal Field Theories and the Construction of Orbifolds
We consider representations of meromorphic bosonic chiral conformal field
theories, and demonstrate that such a representation is completely specified by
a state within the theory. The necessary and sufficient conditions upon this
state are derived, and, because of their form, we show that we may extend the
representation to a representation of a suitable larger conformal field theory.
In particular, we apply this procedure to the lattice (FKS) conformal field
theories, and deduce that Dong's proof of the uniqueness of the twisted
representation for the reflection-twisted projection of the Leech lattice
conformal field theory generalises to an arbitrary even (self-dual) lattice. As
a consequence, we see that the reflection-twisted lattice theories of Dolan et
al are truly self-dual, extending the analogies with the theories of lattices
and codes which were being pursued. Some comments are also made on the general
concept of the definition of an orbifold of a conformal field theory in
relation to this point of view.Comment: 11 pages, LaTeX. Updated references and added preprint n
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