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Search Results: 1 - 10 of 251 matches for " Abootaleb Seadatee-Shamir "
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Reading Performance and Academic Achievement in Early Childhood Bilingual and Monolinguals  [PDF]
Abootaleb Seadatee-Shamir, Zohreh Siavoshi
Open Journal of Applied Sciences (OJAppS) , 2014, DOI: 10.4236/ojapps.2014.46031
Abstract: Relationship between reading performance and academic achievement is theoretically predictable. However, this relationship could be higher among early childhood bilingual (ECBL) students than monolingual peers. For evaluating this claim, two groups of randomly selected female second graders (150 Farsi speaking and 150 Farsi and Turkish speaking) were tested and compared on these characteristics. The measures used were Kormi-Nouri and associates’ tests of reading performance. Moreover, academic achievement was defined to be the average of scores obtained by students at their final school exams in Math, Science and Farsi. Analysis of regression was then performed to determine which construct served as the best predictor of academic achievement in both groups. Based on the results, ECBL girls were superior to their monolingual (ML) counterparts in all three areas. Findings also show that reading performance was a strong predictor of school achievement for both groups.
The Temporal Winner-Take-All Readout
Maoz Shamir
PLOS Computational Biology , 2009, DOI: 10.1371/journal.pcbi.1000286
Abstract: How can the central nervous system make accurate decisions about external stimuli at short times on the basis of the noisy responses of nerve cell populations? It has been suggested that spike time latency is the source of fast decisions. Here, we propose a simple and fast readout mechanism, the temporal Winner-Take-All (tWTA), and undertake a study of its accuracy. The tWTA is studied in the framework of a statistical model for the dynamic response of a nerve cell population to an external stimulus. Each cell is characterized by a preferred stimulus, a unique value of the external stimulus for which it responds fastest. The tWTA estimate for the stimulus is the preferred stimulus of the cell that fired the first spike in the entire population. We then pose the questions: How accurate is the tWTA readout? What are the parameters that govern this accuracy? What are the effects of noise correlations and baseline firing? We find that tWTA sensitivity to the stimulus grows algebraically fast with the number of cells in the population, N, in contrast to the logarithmic slow scaling of the conventional rate-WTA sensitivity with N. Noise correlations in first-spike times of different cells can limit the accuracy of the tWTA readout, even in the limit of large N, similar to the effect that has been observed in population coding theory. We show that baseline firing also has a detrimental effect on tWTA accuracy. We suggest a generalization of the tWTA, the n-tWTA, which estimates the stimulus by the identity of the group of cells firing the first n spikes and show how this simple generalization can overcome the detrimental effect of baseline firing. Thus, the tWTA can provide fast and accurate responses discriminating between a small number of alternatives. High accuracy in estimation of a continuous stimulus can be obtained using the n-tWTA.
Unsupervised Detection of Outlier Images Using Multi-Order Image Transforms
Lior Shamir
Theory and Applications of Mathematics & Computer Science , 2013,
Abstract: The task of unsupervised detection of peculiar images has immediate applications to numerous scientific disciplines such as astronomy and biology. Here we describe a simple non-parametric method that uses multi-order image transforms for the purpose of automatic unsupervised detection of peculiar images in image datasets. The method is based on computing a large set of image features from the raw pixels and the first and second order of several combinations of image transforms. Then, the features are assigned weights based on their variance, and the peculiarity of each image is determined by its weighted Euclidean distance from the centroid such that the weights are computed from the variance. Experimental results show that features extracted from multi-order image transforms can be used to automatically detect peculiar images in an unsupervised fashion in different image datasets, including faces, paintings, microscopy images, and more, and can be used to find uncommon or peculiar images in large datasets in cases where the target image of interest is not known. The performance of the method is superior to general methods such as one-class SVM. Source code and data used in this paper are publicly available, and can be used as a benchmark to develop and compare the performance of algorithms for unsupervised detection of peculiar images.
Color Differences between Clockwise and Counterclockwise Spiral Galaxies
Lior Shamir
Galaxies , 2013, DOI: 10.3390/galaxies1030210
Abstract: While spiral galaxies observed from Earth clearly seem to spin in different directions, little is yet known about other differences between galaxies that spin clockwise and galaxies that spin counterclockwise. Here we compared the color of 64,399 spiral galaxies that spin clockwise to 63,215 spiral galaxies that spin counterclockwise. The results show that clockwise galaxies tend to be bluer than galaxies that spin counterclockwise. The probability that the color differences can be attributed to chance is ~0.019. g-r, r-i and i-z did not show significant differences between clockwise and counterclockwise galaxies.
Automatic morphological classification of galaxy images
Lior Shamir
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.15366.x
Abstract: We describe an image analysis supervised learning algorithm that can automatically classify galaxy images. The algorithm is first trained using a manually classified images of elliptical, spiral, and edge-on galaxies. A large set of image features is extracted from each image, and the most informative features are selected using Fisher scores. Test images can then be classified using a simple Weighted Nearest Neighbor rule such that the Fisher scores are used as the feature weights. Experimental results show that galaxy images from Galaxy Zoo can be classified automatically to spiral, elliptical and edge-on galaxies with accuracy of ~90% compared to classifications carried out by the author. Full compilable source code of the algorithm is available for free download, and its general-purpose nature makes it suitable for other uses that involve automatic image analysis of celestial objects.
Lattice Chiral Fermions
Yigal Shamir
Physics , 1995, DOI: 10.1016/0920-5632(96)00046-1
Abstract: I review the ongoing attempts to define chiral gauge theories using the lattice regularization.
Reducing Chiral Symmetry Violations in Lattice QCD with Domain-Wall Fermions
Yigal Shamir
Physics , 1998, DOI: 10.1103/PhysRevD.59.054506
Abstract: The inverse of the fermion matrix squared is used to define a transfer matrix for domain-wall fermions. When the domain-wall height $M$ is bigger than one, the transfer matrix is complex. Slowly suppressed chiral symmetry violations may then arise from all eigenvalues of the transfer matrix which are located near the unit circle. Using a variable lattice spacing for the fifth coordinate we enforce the strict positivity of the transfer matrix for any $M$. We furthermore propose a modified pseudo-fermion action, aimed to decrease the density of close-to-unity eigenvalues of the (positive) transfer matrix, at the price of a small renormalization of the coupling constant. We explain why these changes may reduce chiral symmetry violations in lattice QCD simulations.
The Standard Model from a New Phase Transition on the Lattice
Yigal Shamir
Physics , 1995, DOI: 10.1103/PhysRevD.57.132
Abstract: Several years ago it was conjectured in the so-called Roma Approach, that gauge fixing is an essential ingredient in the lattice formulation of chiral gauge theories. In this paper we discuss in detail how the gauge-fixing approach may be realized. As in the usual (gauge invariant) lattice formulation, the continuum limit corresponds to a gaussian fixed point, that now controls both the transversal and the longitudinal modes of the gauge field. A key role is played by a new phase transition separating a conventional Higgs or Higgs-confinement phase, from a phase with broken rotational invariance. In the continuum limit we expect to find a scaling region, where the lattice correlators reproduce the euclidean correlation functions of the target (chiral) gauge theory, in the corresponding continuum gauge.
Lattice Chiral Gauge Theories in a Renormalizable Gauge
Yigal Shamir
Physics , 1996, DOI: 10.1016/S0920-5632(96)00748-7
Abstract: The lattice formulation of gauge theories in a renormalizable gauge is discussed. The formulation invokes a new phase diagram, and it may allow for a lattice definition of Chiral Gauge Theories.
On the absence of chiral fermions in interacting lattice theories
Yigal Shamir
Physics , 1993, DOI: 10.1016/0920-5632(94)90454-5
Abstract: We consider interacting theories with a compact internal symmetry group on a regular lattice. We show that the spectrum is necessarily vector-like provided the following conditions are satisfied: (a)~weak form of locality, (b)~relativistic continuum limit without massless bosons, and (c)~pole-free effective vertex functions for conserved currents. The proof exploits the zero frequency inverse retarded propagator of an appropriate set of interpolating fields as an effective quadratic hamiltonian, to which the Nielsen-Ninomiya theorem is applied. The main results of this paper have been reported in WIS-93/56-JUNE-PH, hep-lat/9306023.
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