9,701 research outputs found
The space-clamped Hodgkin-Huxley system with random synaptic input: inhibition of spiking by weak noise and analysis with moment equations
We consider a classical space-clamped Hodgkin-Huxley model neuron stimulated
by synaptic excitation and inhibition with conductances represented by
Ornstein-Uhlenbeck processes. Using numerical solutions of the stochastic model
system obtained by an Euler method, it is found that with excitation only there
is a critical value of the steady state excitatory conductance for repetitive
spiking without noise and for values of the conductance near the critical value
small noise has a powerfully inhibitory effect. For a given level of inhibition
there is also a critical value of the steady state excitatory conductance for
repetitive firing and it is demonstrated that noise either in the excitatory or
inhibitory processes or both can powerfully inhibit spiking. Furthermore, near
the critical value, inverse stochastic resonance was observed when noise was
present only in the inhibitory input process.
The system of 27 coupled deterministic differential equations for the
approximate first and second order moments of the 6-dimensional model is
derived. The moment differential equations are solved using Runge-Kutta methods
and the solutions are compared with the results obtained by simulation for
various sets of parameters including some with conductances obtained by
experiment on pyramidal cells of rat prefrontal cortex. The mean and variance
obtained from simulation are in good agreement when there is spiking induced by
strong stimulation and relatively small noise or when the voltage is
fluctuating at subthreshold levels. In the occasional spike mode sometimes
exhibited by spinal motoneurons and cortical pyramidal cells the assunptions
underlying the moment equation approach are not satisfied
Virtual Enriching Operators
We construct bounded linear operators that map conforming Lagrange
finite element spaces to conforming virtual element spaces in two and
three dimensions. These operators are useful for the analysis of nonstandard
finite element methods
Virtual Element Methods on Meshes with Small Edges or Faces
We consider a model Poisson problem in () and establish error
estimates for virtual element methods on polygonal or polyhedral meshes that
can contain small edges () or small faces ().Comment: 36 page
Optical properties of carbon grains: Influence on dynamical models of AGB stars
For amorphous carbon several laboratory extinction data are available, which
show quite a wide range of differences due to the structural complexity of this
material. We have calculated self-consistent dynamic models of circumstellar
dust-shells around carbon-rich asymptotic giant branch stars, based on a number
of these data sets. The structure and the wind properties of the dynamical
models are directly influenced by the different types of amorphous carbon. In
our test models the mass loss is not severely dependent on the difference in
the optical properties of the dust, but the influence on the degree of
condensation and the final outflow velocity is considerable. Furthermore, the
spectral energy distributions and colours resulting from the different data
show a much wider spread than the variations within the models due to the
variability of the star. Silicon carbide was also considered in the radiative
transfer calculations to test its influence on the spectral energy
distribution.Comment: 12 pages, 6 figures. To appear in A&
Leveraging Employer Practices in Global Regulatory Frameworks to Improve Employment Outcomes for People with Disabilities
Work is an important part of life, providing both economic security and a forum to contribute one’s talents and skills to society, thereby anchoring the individual in a social role. However, access to work is not equally available to people with disabilities globally. Regulatory environments that prohibit discrimination and support vocational training and educational opportunities constitute a critical first step toward economic independence. However, they have not proven sufficient in themselves. In this article, we aim to infuse deeper consideration of employer practice and demand-side policy reforms into global policy discussions of the right to work for people with disabilities. We begin by documenting the employment and economic disparities existing for people with disabilities globally, followed by a description of the international, regional, and local regulatory contexts aiming to improve labor market outcomes for people with disabilities. Next, we examine how policies can leverage employer interests to further address inequalities. We discuss employer policies and practices demonstrated in the research to facilitate recruitment, hiring, career development, retention, and meaningful workplace inclusion. The goal of the article is to synthesize existing international literature on employment rights for people with disabilities with the employer perspective
A Robust Solver for a Second Order Mixed Finite Element Method for the Cahn-Hilliard Equation
We develop a robust solver for a second order mixed finite element splitting
scheme for the Cahn-Hilliard equation. This work is an extension of our
previous work in which we developed a robust solver for a first order mixed
finite element splitting scheme for the Cahn-Hilliard equaion. The key
ingredient of the solver is a preconditioned minimal residual algorithm (with a
multigrid preconditioner) whose performance is independent of the spacial mesh
size and the time step size for a given interfacial width parameter. The
dependence on the interfacial width parameter is also mild.Comment: 17 pages, 3 figures, 4 tables. arXiv admin note: substantial text
overlap with arXiv:1709.0400
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