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Search Results: 1 - 10 of 218 matches for " Elad Mezuman "
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Tighter Linear Program Relaxations for High Order Graphical Models
Elad Mezuman,Daniel Tarlow,Amir Globerson,Yair Weiss
Computer Science , 2013,
Abstract: Graphical models with High Order Potentials (HOPs) have received considerable interest in recent years. While there are a variety of approaches to inference in these models, nearly all of them amount to solving a linear program (LP) relaxation with unary consistency constraints between the HOP and the individual variables. In many cases, the resulting relaxations are loose, and in these cases the results of inference can be poor. It is thus desirable to look for more accurate ways of performing inference in these models. In this work, we study the LP relaxations that result from enforcing additional consistency constraints between the HOP and the rest of the model. We address theoretical questions about the strength of the resulting relaxations compared to the relaxations that arise in standard approaches, and we develop practical and efficient message passing algorithms for optimizing the LPs. Empirically, we show that the LPs with additional consistency constraints lead to more accurate inference on some challenging problems that include a combination of low order and high order terms.
Genetics of breast cancer: Applications to the Mexican population
Ziv,Elad;
Salud Pública de México , 2011, DOI: 10.1590/S0036-36342011000500009
Abstract: breast cancer research has yielded several important results including the strong susceptibility genes,brca1 and brca2 and more recently 19 genes and genetic loci that confer a more moderate risk.the pace of discovery is accelerating as genetic technology and computational methods improve. these discoveries will change the way that breast cancer risk is understood in mexico over the next few decades.
Mapping the International: Global and Local Salience and News-Links Between Countries in Popular News Sites Worldwide
Elad Segev
International Journal of Internet Science , 2010,
Abstract: What countries get more online news attention around the world? The following paper compares 35 popular news sites in 10 different languages in order to assess the salience of countries in different news topic, their level of self-occupation, their news-links with other countries and their network configuration during a period of six months between February and July 2009. Based on special text-mining tools developed by the author for this purposes, it offers new indices, measurements, and techniques to portray the world perceived by news sites in different countries. Supporting previous observations on newspapers and traditional media, findings indicate that there is a strong correlation between the economic power of a country and its online news salience. The U.S. is by far the most salient country in popular news sites around the world. Middle-Eastern countries receive particularly high attention in world news, Asian countries in business and technology news and European countries in cultural news. Countries with higher political, economic, or social instabilities tend to be more self-occupied in their news. The networks of news-links within different countries display three different structures: centralized networks presented by American and French news sites, two-hub networks presented by most European and Asian news sites, and decentralized networks presented by Middle-Eastern news sites. The implications of these findings are discussed.
Search Engines and Power: A Politics of Online (Mis-) Information
Elad Segev
Webology , 2008,
Abstract: Media and communications have always been employed by dominant actors and played a crucial role in framing our knowledge and constructing certain orders. This paper examines the politics of search engines, suggesting that they increasingly become "authoritative" and popular information agents used by individuals, groups and governments to attain their position and shape the information order. Following the short evolution of search engines from small companies to global media corporations that commodify online information and control advertising spaces, this study brings attention to some of their important political, social, cultural and economic implications. This is indicated through their expanding operation and control over private and public informational spaces as well as through the structural bias of the information they attempt to organize. In particular, it is indicated that search engines are highly biased toward commercial and popular US-based content, supporting US-centric priorities and agendas. Consequently, it is suggested that together with their important role in "organizing the world's information" search engines reinforce certain inequalities and understandings of the world.
Sparse Representations Are Most Likely to Be the Sparsest Possible
Elad Michael
EURASIP Journal on Advances in Signal Processing , 2006,
Abstract: Given a signal and a full-rank matrix with , we define the signal's overcomplete representations as all satisfying . Among all the possible solutions, we have special interest in the sparsest one—the one minimizing . Previous work has established that a representation is unique if it is sparse enough, requiring . The measure stands for the minimal number of columns from that are linearly dependent. This bound is tight—examples can be constructed to show that with or more nonzero entries, uniqueness is violated. In this paper we study the behavior of overcomplete representations beyond the above bound. While tight from a worst-case standpoint, a probabilistic point of view leads to uniqueness of representations satisfying . Furthermore, we show that even beyond this point, uniqueness can still be claimed with high confidence. This new result is important for the study of the average performance of pursuit algorithms—when trying to show an equivalence between the pursuit result and the ideal solution, one must also guarantee that the ideal result is indeed the sparsest.
Organization of the Bacterial Light-Harvesting Apparatus Rationalized by Exciton Transport Optimization
Elad Harel
Physics , 2011,
Abstract: Photosynthesis, the process by which energy from sunlight drives cellular metabolism, relies on a unique organization of light-harvesting and reaction center complexes. Recently, the organization of light-harvesting LH2 complexes and dimeric reaction center-light harvesting I-PufX (RC-LH1-PufX) core complexes in membranes of purple non-sulfur bacteria was revealed by atomic force microscopy (AFM)1. Here, we report that the structure of LH2 and its organization within the membrane can be largely rationalized by a simple physical model that relies primarily on exciton transfer optimization. The process through which the light-harvesting complexes transfer excitation energy has been recognized to incorporate both coherent and incoherent processes mediated by the surrounding protein environment. Using the Haken-Strobl model, we show that the organization of the complexes in the membrane can be almost entirely explained by simple electrostatic considerations and that quantum effects act primarily to enforce robustness with respect to spatial disorder between complexes. The implications of such an arrangement are discussed in the context of biomimetic photosynthetic analogs capable of transferring energy efficiently across tens to hundreds of nanometers
Indiscernible arrays and rational functions with algebraic constraint
Elad Levi
Mathematics , 2015,
Abstract: Let $k$ be an algebraically closed field of characteristic zero and $P(x,y)\in k[x,y]$ be a polynomial which depends on all its variables. $P$ has an algebraic constraint if the set $\{(P(a,b),(P(a',b'),P(a',b),P(a,b')\,|\,a,a',b,b'\in k\}$ does not have the maximal Zariski-dimension. Tao proved that if $P$ has an algebraic constraint then it can be decomposed: there exists $Q,F,G\in k[x]$ such that $P(x_{1},x_{2})=Q(F(x_{1})+G(x_{2}))$, or $P(x_{1},x_{2})=Q(F(x_{1})\cdot G(x_{2}))$. In this paper we give an answer to a question raised by Hrushovski and Zilber regarding 3-dimensional indiscernible arrays in stable theories. As an application of this result we find a decomposition of rational functions in three variables which has an algebraic constraint.
Approximate Convex Optimization by Online Game Playing
Elad Hazan
Computer Science , 2006,
Abstract: Lagrangian relaxation and approximate optimization algorithms have received much attention in the last two decades. Typically, the running time of these methods to obtain a $\epsilon$ approximate solution is proportional to $\frac{1}{\epsilon^2}$. Recently, Bienstock and Iyengar, following Nesterov, gave an algorithm for fractional packing linear programs which runs in $\frac{1}{\epsilon}$ iterations. The latter algorithm requires to solve a convex quadratic program every iteration - an optimization subroutine which dominates the theoretical running time. We give an algorithm for convex programs with strictly convex constraints which runs in time proportional to $\frac{1}{\epsilon}$. The algorithm does NOT require to solve any quadratic program, but uses gradient steps and elementary operations only. Problems which have strictly convex constraints include maximum entropy frequency estimation, portfolio optimization with loss risk constraints, and various computational problems in signal processing. As a side product, we also obtain a simpler version of Bienstock and Iyengar's result for general linear programming, with similar running time. We derive these algorithms using a new framework for deriving convex optimization algorithms from online game playing algorithms, which may be of independent interest.
Meta to the Rescue—Augmented Metamodels for Better Deployment of Pre-Packaged Applications  [PDF]
Joseph Gil, Elad Fein, Natalia Razinkov
Journal of Software Engineering and Applications (JSEA) , 2012, DOI: 10.4236/jsea.2012.58067
Abstract: Recent estimates indicate that more than half the software market belongs to enterprise applications. One of the greatest challenges in these is in conducting the complex process of adaptation of pre-packaged applications, such as Oracle or SAP, to the organization needs. Although very detailed, structured and well documented methods govern this process, the consulting team implementing the method must spend much manual effort in making sure that the guidelines of the method are followed as intended by the method author. The problem is exacerbated by the diversity of skills and roles of team members, and the many sorts of communications of collaboration that methods prescribe. By enhancing the metamodel in which the methods are defined, we automatically produce a CASE tool (so to speak) for the applications of these methods. Our results are successfully employed in a number of large, ongoing projects with demonstrable, non-meager saving.
Collective Dynamics of Gene Expression in Cell Populations
Elad Stolovicki,Erez Braun
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0020530
Abstract: The phenotypic state of the cell is commonly thought to be determined by the set of expressed genes. However, given the apparent complexity of genetic networks, it remains open what processes stabilize a particular phenotypic state. Moreover, it is not clear how unique is the mapping between the vector of expressed genes and the cell's phenotypic state. To gain insight on these issues, we study here the expression dynamics of metabolically essential genes in twin cell populations. We show that two yeast cell populations derived from a single steady-state mother population and exhibiting a similar growth phenotype in response to an environmental challenge, displayed diverse expression patterns of essential genes. The observed diversity in the mean expression between populations could not result from stochastic cell-to-cell variability, which would be averaged out in our large cell populations. Remarkably, within a population, sets of expressed genes exhibited coherent dynamics over many generations. Thus, the emerging gene expression patterns resulted from collective population dynamics. It suggests that in a wide range of biological contexts, gene expression reflects a self-organization process coupled to population-environment dynamics.
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