52,546 research outputs found
The iso-response method
Throughout the nervous system, neurons integrate high-dimensional input streams and transform them into an output of their own. This integration of incoming signals involves filtering processes and complex non-linear operations. The shapes of these filters and non-linearities determine the computational features of single neurons and their functional roles within larger networks. A detailed characterization of signal integration is thus a central ingredient to understanding information processing in neural circuits. Conventional methods for measuring single-neuron response properties, such as reverse correlation, however, are often limited by the implicit assumption that stimulus integration occurs in a linear fashion. Here, we review a conceptual and experimental alternative that is based on exploring the space of those sensory stimuli that result in the same neural output. As demonstrated by recent results in the auditory and visual system, such iso-response stimuli can be used to identify the non-linearities relevant for stimulus integration, disentangle consecutive neural processing steps, and determine their characteristics with unprecedented precision. Automated closed-loop experiments are crucial for this advance, allowing rapid search strategies for identifying iso-response stimuli during experiments. Prime targets for the method are feed-forward neural signaling chains in sensory systems, but the method has also been successfully applied to feedback systems. Depending on the specific question, “iso-response” may refer to a predefined firing rate, single-spike probability, first-spike latency, or other output measures. Examples from different studies show that substantial progress in understanding neural dynamics and coding can be achieved once rapid online data analysis and stimulus generation, adaptive sampling, and computational modeling are tightly integrated into experiments
Signal Processing during Developmental Multicellular Patterning
Developing design strategies for tissue engineering and regenerative medicine is limited by our nascent understanding of how cell populations self-organize into multicellular structures on synthetic scaffolds. Mechanistic insights can be gleaned from the quantitative analysis of biomolecular signals that drive multicellular patterning during the natural processes of embryonic and adult development. This review describes three critical layers of signal processing that govern multicellular patterning: spatiotemporal presentation of extracellular cues, intracellular signaling networks that mediate crosstalk among extracellular cues, and finally, intranuclear signal integration at the level of transcriptional regulation. At every level in this hierarchy, the quantitative attributes of signals have a profound impact on patterning. We discuss how experiments and mathematical models are being used to uncover these quantitative features and their impact on multicellular phenotype
Speaker-following Video Subtitles
We propose a new method for improving the presentation of subtitles in video
(e.g. TV and movies). With conventional subtitles, the viewer has to constantly
look away from the main viewing area to read the subtitles at the bottom of the
screen, which disrupts the viewing experience and causes unnecessary eyestrain.
Our method places on-screen subtitles next to the respective speakers to allow
the viewer to follow the visual content while simultaneously reading the
subtitles. We use novel identification algorithms to detect the speakers based
on audio and visual information. Then the placement of the subtitles is
determined using global optimization. A comprehensive usability study indicated
that our subtitle placement method outperformed both conventional
fixed-position subtitling and another previous dynamic subtitling method in
terms of enhancing the overall viewing experience and reducing eyestrain
UHE neutrino searches using a Lunar target: First Results from the RESUN search
During the past decade there have been several attempts to detect cosmogenic
ultra high energy (UHE) neutrinos by searching for radio Cerenkov bursts
resulting from charged impact showers in terrestrial ice or the lunar regolith.
So far these radio searches have yielded no detections, but the inferred flux
upper limits have started to constrain physical models for UHE neutrino
generation. For searches which use the Moon as a target, we summarize the
physics of the interaction, properties of the resulting Cerenkov radio pulse,
detection statistics, effective aperture scaling laws, and derivation of upper
limits for isotropic and point source models. We report on initial results from
the RESUN search, which uses the Expanded Very Large Array configured in
multiple sub-arrays of four antennas at 1.45 GHz pointing along the lunar limb.
We detected no pulses of lunar origin during 45 observing hours. This implies
upper limits to the differential neutrino flux E^2 dN/dE < 0.003 EeV km^{-2}
s^{-1} sr^{-1} and < 0.0003 EeV km$^{-2} s^{-1} at 90% confidence level for
isotropic and sampled point sources respectively, in the neutrino energy range
10^{21.6} < E(eV) < 10^{22.6}. The isotropic flux limit is comparable to the
lowest published upper limits for lunar searches. The full RESUN search, with
an additional 200 hours observing time and an improved data acquisition scheme,
will be be an order of magnitude more sensitive in the energy range 10^{21} <
E(eV) < 10^{22} than previous lunar-target searches, and will test Z burst
models of neutrino generation.Comment: 26 pages, 14 figure
Particle Physics Instrumentation
This report summarizes a series of three lectures aimed at giving an overview
of basic particle detection principles, the interaction of particles with
matter, the application of these principles in modern detector systems, as well
techniques to read out detector signals in high-rate experiments.Comment: 11 pages, contribution to the 1st Asia-Europe-Pacific School of
High-Energy Physics, Fukuoka, Japan, 14 - 27 Oct 201
An improved adaptive sidelobe blanker
We propose a two-stage detector consisting of a subspace
detector followed by the whitened adaptive beamformer orthogonal rejection test. The performance analysis shows that it possesses the constant false alarm rate property with respect to the unknown covariance matrix of the noise and that it can guarantee a wider range of directivity values with respect to previously proposed two-stage detectors. The probability of false alarm and the probability of detection (for both matched and mismatched signals) have been evaluated by means of numerical integration techniques
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