310 research outputs found
Signal acquisition via polarization modulation in single photon sources
A simple model system is introduced for demonstrating how a single photon
source might be used to transduce classical analog information. The theoretical
scheme results in measurements of analog source samples that are (i) quantized
in the sense of analog-to-digital conversion and (ii) corrupted by random noise
that is solely due to the quantum uncertainty in detecting the polarization
state of each photon. This noise is unavoidable if more than one bit per sample
is to be transmitted, and we show how it may be exploited in a manner inspired
by suprathreshold stochastic resonance. The system is analyzed information
theoretically, as it can be modeled as a noisy optical communication channel,
although unlike classical Poisson channels, the detector's photon statistics
are binomial. Previous results on binomial channels are adapted to demonstrate
numerically that the classical information capacity, and thus the accuracy of
the transduction, increases logarithmically with the square root of the number
of photons, N. Although the capacity is shown to be reduced when an additional
detector nonideality is present, the logarithmic increase with N remains.Comment: 7 pages, 2 figures, accepted by Physical Review E. This version adds
a referenc
Channel noise induced stochastic facilitation in an auditory brainstem neuron model
Neuronal membrane potentials fluctuate stochastically due to conductance
changes caused by random transitions between the open and close states of ion
channels. Although it has previously been shown that channel noise can
nontrivially affect neuronal dynamics, it is unknown whether ion-channel noise
is strong enough to act as a noise source for hypothesised noise-enhanced
information processing in real neuronal systems, i.e. 'stochastic
facilitation.' Here, we demonstrate that biophysical models of channel noise
can give rise to two kinds of recently discovered stochastic facilitation
effects in a Hodgkin-Huxley-like model of auditory brainstem neurons. The
first, known as slope-based stochastic resonance (SBSR), enables phasic neurons
to emit action potentials that can encode the slope of inputs that vary slowly
relative to key time-constants in the model. The second, known as inverse
stochastic resonance (ISR), occurs in tonically firing neurons when small
levels of noise inhibit tonic firing and replace it with burst-like dynamics.
Consistent with previous work, we conclude that channel noise can provide
significant variability in firing dynamics, even for large numbers of channels.
Moreover, our results show that possible associated computational benefits may
occur due to channel noise in neurons of the auditory brainstem. This holds
whether the firing dynamics in the model are phasic (SBSR can occur due to
channel noise) or tonic (ISR can occur due to channel noise).Comment: Published by Physical Review E, November 2013 (this version 17 pages
total - 10 text, 1 refs, 6 figures/tables); Associated matlab code is
available online in the ModelDB repository at
http://senselab.med.yale.edu/ModelDB/ShowModel.asp?model=15148
Distance Distributions for Real Cellular Networks
This paper presents the general distribution for the distance between a
mobile user and any base station (BS). We show that a random variable
proportional to the distance squared is Gamma distributed. In the case of the
nearest BS, it can be reduced to the well established result of the distance
being Rayleigh distributed. We validate our results using a random node
simulation and real Vodafone 3G network data, and go on to show how the
distribution is tractable by deriving the average aggregate interference power.Comment: 2 pages, 1 figure, IEEE Conference on Computer Communications
(INFOCOM
New political actors in Europe: Beppe Grillo and the M5S
New social and political movements from radically different political positions are emerging across Europe using social media, posing a new challenge to existing political parties and structures. The Pirate Party in Germany and the Occupy movement are examples of movements that have employed social media to grow rapidly and create a significant political and social impact – all in the last three years.
Beppe Grillo, the Italian comedian and blogger, is one of the first political figures to have embraced this change. He has used social media to communicate, recruit and organise, growing the Moviment 5 Stelle from practically nothing to a major political force in Italy in the space of three years, with it expected to play a crucial role in the 2013 Italian elections. His anti-establishment message has resonated with many against a backdrop of declining trust in political institutions, falling political party membership and ever-lower voter turnout.
This report presents the results of a survey of 1,865 Facebook fans of Beppe Grillo and the Movimento 5 Stelle. It includes data on who they are, what they think, and what motivates them to shift from virtual to real-world activism. It also compares them with other similar parties in Western Europe and their attitudes to those of the Italian population. This report is the seventh in a series of country specific briefings about the online support of populist parties across Europe
Phase changes in neuronal postsynaptic spiking due to short term plasticity
In the brain, the postsynaptic response of a neuron to time-varying inputs is determined by the interaction of presynaptic spike times with the short-term dynamics of each synapse. For a neuron driven by stochastic synapses, synaptic depression results in a quite different postsynaptic response to a large population input depending on how correlated in time the spikes across individual synapses are. Here we show using both simulations and mathematical analysis that not only the rate but the phase of the postsynaptic response to a rhythmic population input varies as a function of synaptic dynamics and synaptic configuration. Resultant phase leads may compensate for transmission delays and be predictive of rhythmic changes. This could be particularly important for sensory processing and motor rhythm generation in the nervous system. © 2017 McDonnell, Graham
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