40,853 research outputs found
Keyed Non-Parametric Hypothesis Tests
The recent popularity of machine learning calls for a deeper understanding of
AI security. Amongst the numerous AI threats published so far, poisoning
attacks currently attract considerable attention. In a poisoning attack the
opponent partially tampers the dataset used for learning to mislead the
classifier during the testing phase.
This paper proposes a new protection strategy against poisoning attacks. The
technique relies on a new primitive called keyed non-parametric hypothesis
tests allowing to evaluate under adversarial conditions the training input's
conformance with a previously learned distribution . To do so we
use a secret key unknown to the opponent.
Keyed non-parametric hypothesis tests differs from classical tests in that
the secrecy of prevents the opponent from misleading the keyed test
into concluding that a (significantly) tampered dataset belongs to
.Comment: Paper published in NSS 201
Cobalt-Porphyrin Catalyzed Electrochemical Reduction of Carbon Dioxide in Water II: Mechanism from First Principles
We apply first principles computational techniques to analyze the
two-electron, multi-step, electrochemical reduction of CO2 to CO in water using
cobalt porphyrin as a catalyst. Density Functional Theory calculations with
hybrid functionals and dielectric continuum solvation are used to determine the
steps at which electrons are added. This information is corroborated with ab
initio molecular dynamics simulations in an explicit aqueous environment which
reveal the critical role of water in stabilizing a key intermediate formed by
CO2 bound to cobalt. Using potential of mean force calculations, the
intermediate is found to spontaneously accept a proton to form a carboxylate
acid group at pH<9.0, and the subsequent cleavage of a C-OH bond to form CO is
exothermic and associated with a small free energy barrier. These predictions
suggest that the proposed reaction mechanism is viable if electron transfer to
the catalyst is sufficiently fast. The variation in cobalt ion charge and spin
states during bond breaking, DFT+U treatment of cobalt 3d orbitals, and the
need for computing electrochemical potentials are emphasized.Comment: 33 pages, 7 figure
A weighted reduced basis method for parabolic PDEs with random data
This work considers a weighted POD-greedy method to estimate statistical
outputs parabolic PDE problems with parametrized random data. The key idea of
weighted reduced basis methods is to weight the parameter-dependent error
estimate according to a probability measure in the set-up of the reduced space.
The error of stochastic finite element solutions is usually measured in a root
mean square sense regarding their dependence on the stochastic input
parameters. An orthogonal projection of a snapshot set onto a corresponding POD
basis defines an optimum reduced approximation in terms of a Monte Carlo
discretization of the root mean square error. The errors of a weighted
POD-greedy Galerkin solution are compared against an orthogonal projection of
the underlying snapshots onto a POD basis for a numerical example involving
thermal conduction. In particular, it is assessed whether a weighted POD-greedy
solutions is able to come significantly closer to the optimum than a
non-weighted equivalent. Additionally, the performance of a weighted POD-greedy
Galerkin solution is considered with respect to the mean absolute error of an
adjoint-corrected functional of the reduced solution.Comment: 15 pages, 4 figure
Palmatine inhibits TRIF-dependent NF-kB pathway against inflammation induced by LPS in goat endometrial epithelial cells
Improved harmonic approximation and the 2D Ising model at and
We propose a new method to determine the unknown parameter associated to a
self-consistent harmonic approximation. We check the validity of our technique
in the context of the sine-Gordon model. As a non trivial application we
consider the scaling regime of the 2D Ising model away from the critical point
and in the presence of a magnetic field . We derive an expression that
relates the approximate correlation length , and .Comment: 11 pages, Latex, 3 figures. Accepted for publication in Journal of
Physics
Prelude to the Anthropocene: Two new North American Land Mammal Ages (NALMAs)
Human impacts have left and are leaving distinctive imprints in the geological record. Here we show that in North America, the human-caused changes evident in the mammalian fossil record since c. 14,000 years ago are as pronounced as earlier faunal changes that subdivide Cenozoic epochs into the North American Land Mammal Ages (NALMAs). Accordingly, we define two new North American Land Mammal Ages, the Santarosean and the Saintagustinean, which subdivide Holocene time and complete a biochronologic system that has proven extremely useful in dating terrestrial deposits and in revealing major features of faunal change through the past 66 million years. The new NALMAs highlight human-induced changes to the Earth system, and inform the debate on whether or not defining an Anthropocene epoch is justified, and if so, when it began
The Omega Deformation, Branes, Integrability, and Liouville Theory
We reformulate the Omega-deformation of four-dimensional gauge theory in a
way that is valid away from fixed points of the associated group action. We use
this reformulation together with the theory of coisotropic A-branes to explain
recent results linking the Omega-deformation to integrable Hamiltonian systems
in one direction and Liouville theory of two-dimensional conformal field theory
in another direction.Comment: 96 p
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