Evaluation of dynamic causal modelling and Bayesian model selection using simulations of networks of spiking neurons

Inferring the mechanisms underlying physiological and pathological processes in the brain from recorded electrical activity is challenging. Bayesian model selection and dynamic causal modelling aim to identify likely biophysical models to explain data and to fit the model parameters. Here, we use data generated by simulations to investigate the effectiveness of Bayesian model selection and dynamic causal modelling when applied at steady state in the frequency domain to identify and fit Jansen-Rit models. We first investigate the impact of the necessary assumption of linearity on the dynamics of the Jansen-Rit model. We then apply dynamic causal modelling and Bayesian model selection to data generated from simulations of linear neural mass models, non-linear neural mass models, and networks of discrete spiking neurons. Action potentials are a characteristic feature of neuronal dynamics but have not previously been explicitly included in simulations used to test Bayesian model selection or dynamic causal modelling. We find that the assumption of linearity abolishes the qualitative transitions seen as a function of the connectivity parameter in the original Jansen-Rit model. As with previous work, we find that the recovery procedures are effective when applied to data from linear Jansen-Rit neural mass models, however, when applying them to non-linear neural mass models and networks of discrete spiking neurons we find that their effectiveness is significantly reduced, suggesting caution is required when applying these methods.Comment: 18 pages, 15 figure

Statistical Observations of Positioning, Navigation, and Timing in a Combat Simulation

The Global Positioning System (GPS) has become an important asset in the lives of civilians and defense organizations. GPS uses include positioning, navigation, timing, as well as many other daily applications. With such dependence, protection against attacks on the system is paramount to continue its effectiveness. Attacks on its signal is the easiest way for enemies to degrade and harm not only everyday functioning for civilians, but a nation\u27s defense as well. Jamming interference and spoofing are the two most frequent attacks on GPS signals. Could these two attacks cause significant effect on military operations? We use a System Effectiveness Analysis Simulation (SEAS) model to emulate a special operation force (SOF) using GPS recovering a weapon of mass destruction (WMD) against an opposing military in an urban canyon environment. Simulating jamming (modeled as availability and accuracy) and spoofing (modeled as timeliness) of the GPS satellites\u27 signal produces a greater understanding of its impact on this type of operation. Statistical analysis determined the significance of these types of attacks on several responses for this simulation. Our results include a designed experiment capturing how individual model factors representing spoofing and jamming can degrade GPS performance, and the subsequent impact on mission operations through selected MOEs for the scenario modeled

Beliefs about development versus environmental tradeoffs in the Puget Sound region

Using data from a phone survey of 1,980 Puget Sound residents conducted in 2012, this fact sheet outlines residents’ views about the importance of environmental protection as well as their opinions about energy development, protection of wild salmon, and land use regulation. Seventy-four percent of Puget Sound residents believe that protecting the environment should be a priority even if it means limiting economic growth. The majority of residents favor both increased use of renewable energy (82 percent) and protecting wild salmon (75 percent). Residents are more divided about curbing development, with those from rural areas being more apt to prioritize protecting private property rights over regulating land use. Read more about Communities and Coastal Restoration in the Puget Sound Region

Urban-rural differences in concern about the environment and jobs in the Puget Sound region

Using data from a phone survey of 1,980 Puget Sound residents conducted in 2012, this fact sheet examines the severity of different environmental problems and compares the strength of concern about the lack of jobs and beliefs about the environment. Too few jobs and the loss of wildlife habitat were the two community issues most likely to be ranked as important problems among residents of Puget Sound. Environmental concern is higher among urban than rural residents, while those in rural areas are more likely than urbanites to believe the lack of jobs is a threat to their community. Read more about Communities and Coastal Restoration in the Puget Sound Region

Public perceptions of environmental management in the Puget Sound region

Using data from a phone survey of 1,980 Puget Sound residents conducted in 2012, this fact sheet describes public perceptions of different environmental interventions. Puget Sound residents widely support a range of proposed interventions designed to protect and restore the marine environment. These proposals include restricting boating and shipping activities to protect marine mammals such as killer whales and sea lions; more strongly enforcing existing environmental rules and regulations; spending government money to restore the environment for fish and wildlife; and providing tax credits to businesses that voluntarily reduce their environmental impact. Residents are divided about whether existing environmental regulations have benefited their community. Read more about Communities and Coastal Restoration in the Puget Sound Region

More Energy, More Searches, but the pMSSM Lives On

We further examine the capability of the 7 and 8 TeV LHC to explore the parameter space of the p(henomenological)MSSM with neutralino LSPs. Here we present an updated study employing all of the relevant ATLAS SUSY analyses, as well as all relevant LHC non-MET searches, whose data were publically available as of mid-September 2012. We find that roughly 1/3 of our pMSSM model points are excluded at present with an important role being played by both the heavy flavor and multi-lepton searches, as well as those for heavy stable charged particles. Nonetheless, we find that light gluinos, 1st/2nd generation squarks, and stop/sbottoms (\lsim 400-700 GeV), as well as models with 1% fine-tuning or better, are still viable in the pMSSM. In addition, we see that increased luminosity at 8 TeV is unlikely to significantly improve the reach of the "vanilla" searches. The impact of these null searches on the SUSY sparticle spectrum is discussed in detail and the implications of these results for models with low fine-tuning, a future lepton collider and dark matter searches are examined.Comment: 33 pages, 9 figure

The Changing Financial Structure of the U.S. Farm Sector

Agricultural Finance,

Sparse Bayesian mass-mapping with uncertainties: hypothesis testing of structure

A crucial aspect of mass-mapping, via weak lensing, is quantification of the uncertainty introduced during the reconstruction process. Properly accounting for these errors has been largely ignored to date. We present results from a new method that reconstructs maximum a posteriori (MAP) convergence maps by formulating an unconstrained Bayesian inference problem with Laplace-type $\ell_1$-norm sparsity-promoting priors, which we solve via convex optimization. Approaching mass-mapping in this manner allows us to exploit recent developments in probability concentration theory to infer theoretically conservative uncertainties for our MAP reconstructions, without relying on assumptions of Gaussianity. For the first time these methods allow us to perform hypothesis testing of structure, from which it is possible to distinguish between physical objects and artifacts of the reconstruction. Here we present this new formalism, demonstrate the method on illustrative examples, before applying the developed formalism to two observational datasets of the Abel-520 cluster. In our Bayesian framework it is found that neither Abel-520 dataset can conclusively determine the physicality of individual local massive substructure at significant confidence. However, in both cases the recovered MAP estimators are consistent with both sets of data

pMSSM Benchmark Models for Snowmass 2013

We present several benchmark points in the phenomenological Minimal Supersymmetric Standard Model (pMSSM). We select these models as experimentally well-motivated examples of the MSSM which predict the observed Higgs mass and dark matter relic density while evading the current LHC searches. We also use benchmarks to generate spokes in parameter space by scaling the mass parameters in a manner which keeps the Higgs mass and relic density approximately constant.Comment: 10 pages, 6 figure