63,890 research outputs found
Towards Theory of Massive-Parallel Proofs. Cellular Automata Approach
In the paper I sketch a theory of massively parallel proofs using cellular
automata presentation of deduction. In this presentation inference rules play
the role of cellular-automatic local transition functions. In this approach we
completely avoid axioms as necessary notion of deduction theory and therefore
we can use cyclic proofs without additional problems. As a result, a theory of
massive-parallel proofs within unconventional computing is proposed for the
first time.Comment: 13 page
Spatial moment analysis of transport of nonlinearly absorbing pesticides using analytical approximations
Analytical approximations were derived for solute transport of pesticides subject to Freundlich sorption, and first-order degradation restricted to the liquid phase. Solute transport was based on the convection-dispersion equation (CDE) assuming steady flow. The center of mass (first spatial moment) was approximated both for a non-degraded solute pulse and for a pulse degraded in the liquid phase. The remaining mass (zeroth spatial moment) of a linearly sorbing solute degraded in the liquid phase was found to be a function of only the center of mass (first spatial moment) and the Damköhler number (i.e., the product of degradation rate coefficient and dispersivity divided by flow velocity). This relationship between the zeroth and first spatial moments was shown to apply to nonlinearly sorbing pulses as well. The mass fraction leached of a pesticide subject to Freundlich sorption and first-order degradation in the solution phase only was found to be a function of the Damköhler number and of the dispersivity, so independent of sorption. Hence perceptions of the effects of sorption on pesticide leaching should be reconsidered. These conclusions equally hold for other micropollutants that degrade in the solution phase onl
A Nonparametric Bayesian Approach to Uncovering Rat Hippocampal Population Codes During Spatial Navigation
Rodent hippocampal population codes represent important spatial information
about the environment during navigation. Several computational methods have
been developed to uncover the neural representation of spatial topology
embedded in rodent hippocampal ensemble spike activity. Here we extend our
previous work and propose a nonparametric Bayesian approach to infer rat
hippocampal population codes during spatial navigation. To tackle the model
selection problem, we leverage a nonparametric Bayesian model. Specifically, to
analyze rat hippocampal ensemble spiking activity, we apply a hierarchical
Dirichlet process-hidden Markov model (HDP-HMM) using two Bayesian inference
methods, one based on Markov chain Monte Carlo (MCMC) and the other based on
variational Bayes (VB). We demonstrate the effectiveness of our Bayesian
approaches on recordings from a freely-behaving rat navigating in an open field
environment. We find that MCMC-based inference with Hamiltonian Monte Carlo
(HMC) hyperparameter sampling is flexible and efficient, and outperforms VB and
MCMC approaches with hyperparameters set by empirical Bayes
The Random-Diluted Triangular Plaquette Model: study of phase transitions in a Kinetically Constrained Model
We study how the thermodynamic properties of the Triangular Plaquette Model
(TPM) are influenced by the addition of extra interactions. The thermodynamics
of the original TPM is trivial, while its dynamics is glassy, as usual in
Kinetically Constrained Models. As soon as we generalize the model to include
additional interactions, a thermodynamic phase transition appears in the
system. The additional interactions we consider are either short ranged,
forming a regular lattice in the plane, or long ranged of the small-world kind.
In the case of long-range interactions we call the new model Random-Diluted
TPM. We provide arguments that the model so modified should undergo a
thermodynamic phase transition, and that in the long-range case this is a glass
transition of the "Random First-Order" kind. Finally, we give support to our
conjectures studying the finite temperature phase diagram of the Random-Diluted
TPM in the Bethe approximation. This corresponds to the exact calculation on
the random regular graph, where free-energy and configurational entropy can be
computed by means of the cavity equations.Comment: 20 pages, 7 figures; final version to appear on PR
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