29,987 research outputs found
Two-photon imaging and analysis of neural network dynamics
The glow of a starry night sky, the smell of a freshly brewed cup of coffee
or the sound of ocean waves breaking on the beach are representations of the
physical world that have been created by the dynamic interactions of thousands
of neurons in our brains. How the brain mediates perceptions, creates thoughts,
stores memories and initiates actions remains one of the most profound puzzles
in biology, if not all of science. A key to a mechanistic understanding of how
the nervous system works is the ability to analyze the dynamics of neuronal
networks in the living organism in the context of sensory stimulation and
behaviour. Dynamic brain properties have been fairly well characterized on the
microscopic level of individual neurons and on the macroscopic level of whole
brain areas largely with the help of various electrophysiological techniques.
However, our understanding of the mesoscopic level comprising local populations
of hundreds to thousands of neurons (so called 'microcircuits') remains
comparably poor. In large parts, this has been due to the technical
difficulties involved in recording from large networks of neurons with
single-cell spatial resolution and near- millisecond temporal resolution in the
brain of living animals. In recent years, two-photon microscopy has emerged as
a technique which meets many of these requirements and thus has become the
method of choice for the interrogation of local neural circuits. Here, we
review the state-of-research in the field of two-photon imaging of neuronal
populations, covering the topics of microscope technology, suitable fluorescent
indicator dyes, staining techniques, and in particular analysis techniques for
extracting relevant information from the fluorescence data. We expect that
functional analysis of neural networks using two-photon imaging will help to
decipher fundamental operational principles of neural microcircuits.Comment: 36 pages, 4 figures, accepted for publication in Reports on Progress
in Physic
Transport-Based Neural Style Transfer for Smoke Simulations
Artistically controlling fluids has always been a challenging task.
Optimization techniques rely on approximating simulation states towards target
velocity or density field configurations, which are often handcrafted by
artists to indirectly control smoke dynamics. Patch synthesis techniques
transfer image textures or simulation features to a target flow field. However,
these are either limited to adding structural patterns or augmenting coarse
flows with turbulent structures, and hence cannot capture the full spectrum of
different styles and semantically complex structures. In this paper, we propose
the first Transport-based Neural Style Transfer (TNST) algorithm for volumetric
smoke data. Our method is able to transfer features from natural images to
smoke simulations, enabling general content-aware manipulations ranging from
simple patterns to intricate motifs. The proposed algorithm is physically
inspired, since it computes the density transport from a source input smoke to
a desired target configuration. Our transport-based approach allows direct
control over the divergence of the stylization velocity field by optimizing
incompressible and irrotational potentials that transport smoke towards
stylization. Temporal consistency is ensured by transporting and aligning
subsequent stylized velocities, and 3D reconstructions are computed by
seamlessly merging stylizations from different camera viewpoints.Comment: ACM Transaction on Graphics (SIGGRAPH ASIA 2019), additional
materials: http://www.byungsoo.me/project/neural-flow-styl
High-speed high-resolution plasma spectroscopy using spatial-multiplex coherence imaging techniques
We have recently obtained simultaneous two-dimensional (2D) plasmaDoppler spectroscopic images of plasma brightness, temperature, and flow fields. Using compact polarization optical methods, quadrature images of the optical coherence of an isolated spectral line are multiplexed to four quadrants of a fast charge-coupled device camera. The simultaneously captured, but distinct, images can be simply processed to unfold the plasma brightness, temperature, and flow fields. This static system, which is a spatial-multiplex variant of previously reported electro-optically modulated, temporal-multiplex coherence imaging systems, is based on a high-throughput imagingpolarizationinterferometer that employs crossed Wollaston prisms and appropriate image plane masks. Because the images are captured simultaneously, it is well suited to high-spectral-resolution, high-throughput 2D imaging of transient or rapidly changing spectroscopic scenes. To illustrate instrument performance we present recent results using a static 4-quadrant Dopplercoherence imaging on the H-1 heliac at the ANU.This work has been, in part, supported by the Australian
Government Department of Education, Science and Training under the International Science Linkages program, Grant No.
CG050061
Probing the cosmic web: inter-cluster filament detection using gravitational lensing
The problem of detecting dark matter filaments in the cosmic web is
considered. Weak lensing is an ideal probe of dark matter, and therefore forms
the basis of particularly promising detection methods. We consider and develop
a number of weak lensing techniques that could be used to detect filaments in
individual or stacked cluster fields, and apply them to synthetic lensing data
sets in the fields of clusters from the Millennium Simulation. These techniques
are multipole moments of the shear and convergence, mass reconstruction, and
parameterized fits to filament mass profiles using a Markov Chain Monte Carlo
approach. In particular, two new filament detection techniques are explored
(multipole shear filters and Markov Chain Monte Carlo mass profile fits), and
we outline the quality of data required to be able to identify and quantify
filament profiles. We also consider the effects of large scale structure on
filament detection. We conclude that using these techniques, there will be
realistic prospects of detecting filaments in data from future space-based
missions. The methods presented in this paper will be of great use in the
identification of dark matter filaments in future surveys.Comment: 12 pages, 4 figures, MNRAS accepted, (replacement due to corrupted
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