13,838 research outputs found
The OpenPicoAmp : an open-source planar lipid bilayer amplifier for hands-on learning of neuroscience
Neuroscience education can be promoted by the availability of low cost and
engaging teaching materials. To address this issue, we developed an open-source
lipid bilayer amplifier, the OpenPicoAmp, which is appropriate for use in
introductory courses in biophysics or neurosciences dealing with the electrical
properties of the cell membrane. The amplifier is designed using the common
lithographic printed circuit board fabrication process and off-the-shelf
electronic components. In addition, we propose a specific design for
experimental chambers allowing the insertion of a commercially available
polytetrafluoroethylene film. This experimental setup can be used in simple
experiments in which students monitor the bilayer formation by capacitance
measurement and record unitary currents produced by ionic channels like
gramicidin A. Used in combination with a low-cost data acquisition board this
system provides a complete solution for hands-on lessons, therefore improving
the effectiveness in teaching basic neurosciences or biophysics.Comment: 13 pages, 6 figures and supplementary information (9 files including
one movie). Added references, added figure, corrected typos, corrected board
components list, more detailled implementation documen
Event-Driven Contrastive Divergence for Spiking Neuromorphic Systems
Restricted Boltzmann Machines (RBMs) and Deep Belief Networks have been
demonstrated to perform efficiently in a variety of applications, such as
dimensionality reduction, feature learning, and classification. Their
implementation on neuromorphic hardware platforms emulating large-scale
networks of spiking neurons can have significant advantages from the
perspectives of scalability, power dissipation and real-time interfacing with
the environment. However the traditional RBM architecture and the commonly used
training algorithm known as Contrastive Divergence (CD) are based on discrete
updates and exact arithmetics which do not directly map onto a dynamical neural
substrate. Here, we present an event-driven variation of CD to train a RBM
constructed with Integrate & Fire (I&F) neurons, that is constrained by the
limitations of existing and near future neuromorphic hardware platforms. Our
strategy is based on neural sampling, which allows us to synthesize a spiking
neural network that samples from a target Boltzmann distribution. The recurrent
activity of the network replaces the discrete steps of the CD algorithm, while
Spike Time Dependent Plasticity (STDP) carries out the weight updates in an
online, asynchronous fashion. We demonstrate our approach by training an RBM
composed of leaky I&F neurons with STDP synapses to learn a generative model of
the MNIST hand-written digit dataset, and by testing it in recognition,
generation and cue integration tasks. Our results contribute to a machine
learning-driven approach for synthesizing networks of spiking neurons capable
of carrying out practical, high-level functionality.Comment: (Under review
I Am The Passenger: How Visual Motion Cues Can Influence Sickness For In-Car VR
This paper explores the use of VR Head Mounted Displays
(HMDs) in-car and in-motion for the first time. Immersive
HMDs are becoming everyday consumer items and, as they
offer new possibilities for entertainment and productivity, people
will want to use them during travel in, for example, autonomous
cars. However, their use is confounded by motion
sickness caused in-part by the restricted visual perception
of motion conflicting with physically perceived vehicle motion
(accelerations/rotations detected by the vestibular system).
Whilst VR HMDs restrict visual perception of motion, they
could also render it virtually, potentially alleviating sensory
conflict. To study this problem, we conducted the first on-road
and in motion study to systematically investigate the effects
of various visual presentations of the real-world motion of
a car on the sickness and immersion of VR HMD wearing
passengers. We established new baselines for VR in-car motion
sickness, and found that there is no one best presentation
with respect to balancing sickness and immersion. Instead,
user preferences suggest different solutions are required for
differently susceptible users to provide usable VR in-car. This
work provides formative insights for VR designers and an entry
point for further research into enabling use of VR HMDs,
and the rich experiences they offer, when travelling
A Critical Commentary on Block 2011: "David Friedman and Libertarianism: a Critique" and a Comparison with Lester [2000] 2012's Responses to Friedman
David Friedman posed a number of libertarian philosophical problems (Friedman 1989). This essay criticizes Walter Block’s Rothbardian responses (Block 2011) and compares them with J C Lester’s critical-rationalist, libertarian-theory responses (Lester [2000] 2012). The main issues are as follows. 1. Critical rationalism and how it applies to libertarianism. 2.1. How libertarianism is not inherently about law and is inherently about morals. 2.2. How liberty relates to property and can be maximized: carbon dioxide and radio waves. 2.3. Applying the theory to flashlights. 2.4. Applying the theory to the probability of imposed risks. 2.5. “Homesteading” or initial acquisition. 2.6 What is “essential” for a “true libertarian.” 2.7. Crime and punishment. 2.8. Extent of punishment. 2.9. The libertarian response to a madman with a gun. 2.10. How contradictions in rights are possible. 2.11. The draft. 3.1. Utilitarian libertarianism and “nose counting”. 3.2. How interpersonal comparisons of utility are possible and utility monsters are not a threat. 3.3. Why it is not utilitarian in practice to kill an innocent prisoner to prevent a riot. 3.4. Why David Friedman should not be forced to give up one of his eyes. 3.5. How utilitarians can be libertarians. Conclusion: a proper theory of liberty combined with critical rationalism offers superior solutions to Friedman’s problems. Appendix: replies to two commentators
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