6,901 research outputs found
Transformation of stimulus correlations by the retina
Redundancies and correlations in the responses of sensory neurons seem to
waste neural resources but can carry cues about structured stimuli and may help
the brain to correct for response errors. To assess how the retina negotiates
this tradeoff, we measured simultaneous responses from populations of ganglion
cells presented with natural and artificial stimuli that varied greatly in
correlation structure. We found that pairwise correlations in the retinal
output remained similar across stimuli with widely different spatio-temporal
correlations including white noise and natural movies. Meanwhile, purely
spatial correlations tended to increase correlations in the retinal response.
Responding to more correlated stimuli, ganglion cells had faster temporal
kernels and tended to have stronger surrounds. These properties of individual
cells, along with gain changes that opposed changes in effective contrast at
the ganglion cell input, largely explained the similarity of pairwise
correlations across stimuli where receptive field measurements were possible.Comment: author list corrected in metadat
Application of Machine Learning in Malaysia Sign Language Translation
Sign language serves as a vital form of communication for individuals with hearing impairments, enabling seamless interaction among those who cannot hear. It is a widely used means of communication worldwide, facilitating communication within the deaf community. In Malaysia, Malaysian Sign Language (MySL) prevails as the primary sign language employed by the deaf community. However, sign languages possess unique grammatical rules and structures, making them unfamiliar to hearing individuals, leading to potential misunderstandings and communication barriers. This project aimed at developing a sign language translator capable of translating 24 alphabets based on hand gestures. The system employs a dataset of sign language alphabet images, gathered and trained using the Teachable Machine. To evaluate the translator's performance, response time is thoroughly analyzed. The results indicate that 18 out of the 24 alphabets can be recognized within 5 seconds, displaying promising accuracy. By bridging the communication gap between deaf and hearing individuals, the findings of this study hold substantial potential to enhance interactions and foster better understanding between these two communities. The sign language translator represents a significant step towards inclusive communication and improved accessibility for individuals with hearing impairment
Multiwavelength Mass Comparisons of the z~0.3 CNOC Cluster Sample
Results are presented from a detailed analysis of optical and X-ray
observations of moderate-redshift galaxy clusters from the Canadian Network for
Observational Cosmology (CNOC) subsample of the EMSS. The combination of
extensive optical and deep X-ray observations of these clusters make them ideal
candidates for multiwavelength mass comparison studies. X-ray surface
brightness profiles of 14 clusters with 0.17<z<0.55 are constructed from
Chandra observations and fit to single and double beta-models. Spatially
resolved temperature analysis is performed, indicating that five of the
clusters in this sample exhibit temperature gradients within their inner 60-200
kpc. Integrated spectra extracted within R_2500 provide temperature, abundance,
and luminosity information. Under assumptions of hydrostatic equilibrium and
spherical symmetry, we derive gas and total masses within R_2500 and R_200. We
find an average gas mass fraction within R_200 of 0.136 +/- 0.004, resulting in
Omega_m=0.28 +/- 0.01 (formal error). We also derive dynamical masses for these
clusters to R_200. We find no systematic bias between X-ray and dynamical
methods across the sample, with an average M(dyn)/M(X-ray) = 0.97 +/- 0.05. We
also compare X-ray masses to weak lensing mass estimates of a subset of our
sample, resulting in a weighted average of M(lens)/M(X-ray) of 0.99 +/- 0.07.
We investigate X-ray scaling relationships and find powerlaw slopes which are
slightly steeper than the predictions of self-similar models, with an E(z)^(-1)
Lx-Tx slope of 2.4 +/- 0.2 and an E(z) M_2500-Tx slope of 1.7 +/- 0.1.
Relationships between red-sequence optical richness (B_gc,red) and global
cluster X-ray properties (Tx, Lx and M_2500) are also examined and fitted.Comment: Astrophysical Journal, 48 pages, 11 figures, LaTeX. Added correction
to surface brightness normalization of MS1512.4+3647, corrections to sample
gas mass fractions and calculated value of Omega_m. Figure resolution has
been reduced to comply with astro-ph upload requirement
SCNet: Learning Semantic Correspondence
This paper addresses the problem of establishing semantic correspondences
between images depicting different instances of the same object or scene
category. Previous approaches focus on either combining a spatial regularizer
with hand-crafted features, or learning a correspondence model for appearance
only. We propose instead a convolutional neural network architecture, called
SCNet, for learning a geometrically plausible model for semantic
correspondence. SCNet uses region proposals as matching primitives, and
explicitly incorporates geometric consistency in its loss function. It is
trained on image pairs obtained from the PASCAL VOC 2007 keypoint dataset, and
a comparative evaluation on several standard benchmarks demonstrates that the
proposed approach substantially outperforms both recent deep learning
architectures and previous methods based on hand-crafted features.Comment: ICCV 201
Optical studies of carrier and phonon dynamics in Ga_{1-x}Mn_{x}As
We present a time-resolved optical study of the dynamics of carriers and
phonons in Ga_{1-x}Mn_{x}As layers for a series of Mn and hole concentrations.
While band filling is the dominant effect in transient optical absorption in
low-temperature-grown (LT) GaAs, band gap renormalization effects become
important with increasing Mn concentration in Ga_{1-x}Mn_{x}As, as inferred
from the sign of the absorption change. We also report direct observation on
lattice vibrations in Ga1-xMnxAs layers via reflective electro-optic sampling
technique. The data show increasingly fast dephasing of LO phonon oscillations
for samples with increasing Mn and hole concentration, which can be understood
in term of phonon scattering by the holes.Comment: 13 pages, 3 figures replaced Fig.1 after finding a mistake in
previous versio
Numerical study of 1.1 GeV electron acceleration over a-few-millimeter-long plasma with a tapered density
We present two-dimensional particle-in-cell simulations of laser wakefield electron acceleration up to 1.1 GeV over a-few-millimeter-long plasma with the help of density tapering. We observed that, in a uniform plasma, the electron beam reaches the dephasing state not only by the slow phase velocity of the wakefield but also by the relativistic prolonging of the plasma wavelength. Such a dephasing between the wakefield and beam can be mitigated by an upward density taper. By employing a parabolically increasing plasma density, we obtained a significant enhancement of the beam energy from 850 MeV (uniform) to 1.1 GeV (tapered). However, the similar relativistically promoted dephasing was observed again in the environment of tapered density. Over a few millimeters the driving laser pulse was well self-guided without any externally prepared channel. Thus, this parameter regime is suitable for the gas-jet laser wakefield electron acceleration experiments.open6
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