2,489 research outputs found
Two distinct desynchronization processes caused by lesions in globally coupled neurons
To accomplish a task, the brain works like a synchronized neuronal network
where all the involved neurons work together. When a lesion spreads in the
brain, depending on its evolution, it can reach a significant portion of
relevant area. As a consequence, a phase transition might occur: the neurons
desynchronize and cannot perform a certain task anymore. Lesions are
responsible for either disrupting the neuronal connections or, in some cases,
for killing the neuron. In this work, we will use a simplified model of
neuronal network to show that these two types of lesions cause different types
of desynchronization.Comment: 5 pages, 3 figure
Kinetic and Exchange Energy Densities near the Nucleus
We investigate the behavior of the kinetic and the exchange energy densities
near the nuclear cusp of atomic systems. Considering hydrogenic orbitals, we
derive analytical expressions near the nucleus, for single shells, as well as
in the semiclassical limit of large non-relativistic neutral atoms. We show
that a model based on the helium iso-electronic series is very accurate, as
also confirmed by numerical calculations on real atoms up to two thousands
electrons. Based on this model, we propose non-local density-dependent
ingredients that are suitable for the description of the kinetic and exchange
energy densities in the region close to the nucleus. These non-local
ingredients are invariant under the uniform scaling of the density, and they
can be used in the construction of non-local exchange-correlation and kinetic
functionals.Comment: 11 pages, 7 figure
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