Showing papers by "Technion – Israel Institute of Technology published in 2005"
TL;DR: This tutorial presents the CE methodology, the basic algorithm and its modifications, and discusses applications in combinatorial optimization and machine learning.
Abstract: The cross-entropy (CE) method is a new generic approach to combinatorial and multi-extremal optimization and rare event simulation. The purpose of this tutorial is to give a gentle introduction to the CE method. We present the CE methodology, the basic algorithm and its modifications, and discuss applications in combinatorial optimization and machine learning.
2,367 citations
TL;DR: The induction of endothelial vessel networks in engineered skeletal muscle tissue constructs using a three-dimensional multiculture system consisting of myoblasts, embryonic fibroblasts and endothelial cells coseeded on highly porous, biodegradable polymer scaffolds is described.
Abstract: One of the major obstacles in engineering thick, complex tissues such as muscle is the need to vascularize the tissue in vitro. Vascularization in vitro could maintain cell viability during tissue growth, induce structural organization and promote vascularization upon implantation. Here we describe the induction of endothelial vessel networks in engineered skeletal muscle tissue constructs using a three-dimensional multiculture system consisting of myoblasts, embryonic fibroblasts and endothelial cells coseeded on highly porous, biodegradable polymer scaffolds. Analysis of the conditions for induction and stabilization of the vessels in vitro showed that addition of embryonic fibroblasts increased the levels of vascular endothelial growth factor expression in the construct and promoted formation and stabilization of the endothelial vessels. We studied the survival and vascularization of the engineered muscle implants in vivo in three different models. Prevascularization improved the vascularization, blood perfusion and survival of the muscle tissue constructs after transplantation.
1,227 citations
TL;DR: Results indicate that organization-level and group- level climates are globally aligned, and the effect of organization climate on safety behavior is fully mediated by group climate level, but the data also revealed meaningful group-level variation in a single organization, attributable to supervisory discretion in implementing formal procedures.
Abstract: Organizational climates have been investigated separately at organization and subunit levels. This article tests a multilevel model of safety climate, covering both levels of analysis. Results indicate that organization-level and group-level climates are globally aligned, and the effect of organization climate on safety behavior is fully mediated by group climate level. However, the data also revealed meaningful group-level variation in a single organization, attributable to supervisory discretion in implementing formal procedures associated with competing demands like safety versus productivity. Variables that limit supervisory discretion (i.e., organization climate strength and procedural formalization) reduce both between-groups climate variation and within-group variability (i.e., increased group climate strength), although effect sizes were smaller than those associated with cross-level climate relationships. Implications for climate theory are discussed.
1,221 citations
TL;DR: The available literature on the crystal structure of the metastable alumina polymorphs and their associated transitions is critically reviewed and summarized in this article, where possible mechanisms for the phase transitions between the different alumina morphological polymorphs also discussed.
Abstract: The available literature on the crystal structure of the metastable alumina polymorphs and their associated transitions is critically reviewed and summarized. All the metastable alumina structures have been identified as ordered or partially ordered cation arrays on the interstitial sites of an approximately close-packed oxygen sublattice (either face-centered cubic or hexagonal close packed). The analysis of the symmetry relations between reported alumina polymorphs having an approximately face-centered cubic packing of the oxygen anions allows for an exact interpretation of all the complex domain structures that have been observed experimentally. Possible mechanisms for the phase transitions between the different alumina polymorphs also are discussed.
1,188 citations
TL;DR: In this article, the authors showed that the mutual information with respect to the signal-to-noise ratio (SNR) is equal to half the MMSE, regardless of the input statistics.
Abstract: This paper deals with arbitrarily distributed finite-power input signals observed through an additive Gaussian noise channel. It shows a new formula that connects the input-output mutual information and the minimum mean-square error (MMSE) achievable by optimal estimation of the input given the output. That is, the derivative of the mutual information (nats) with respect to the signal-to-noise ratio (SNR) is equal to half the MMSE, regardless of the input statistics. This relationship holds for both scalar and vector signals, as well as for discrete-time and continuous-time noncausal MMSE estimation. This fundamental information-theoretic result has an unexpected consequence in continuous-time nonlinear estimation: For any input signal with finite power, the causal filtering MMSE achieved at SNR is equal to the average value of the noncausal smoothing MMSE achieved with a channel whose SNR is chosen uniformly distributed between 0 and SNR.
1,129 citations
TL;DR: In this paper, the authors present the state of the art in LST and the potential of this technology in various lubricated applications like mechanical seals, piston rings and thrust bearings.
Abstract: Surface texturing has emerged in the last decade as a viable option of surface engineering resulting in significant improvement in load capacity, wear resistance, friction coefficient etc. of tribological mechanical components. Various techniques can be employed for surface texturing but Laser Surface Texturing (LST) is probably the most advanced so far. LST produces a very large number of micro-dimples on the surface and each of these micro-dimples can serve either as a micro-hydrodynamic bearing in cases of full or mixed lubrication, a micro-reservoir for lubricant in cases of starved lubrication conditions, or a micro-trap for wear debris in either lubricated or dry sliding. The present paper reviews the current effort being made world wide on surface texturing in general and on laser surface texturing in particular. It presents the state of the art in LST and the potential of this technology in various lubricated applications like mechanical seals, piston rings and thrust bearings. The paper also describes some fundamental on going research around the world with LST.
1,123 citations
TL;DR: A review of several innovative advances in culture and international business to stimulate new avenues for future research is provided in this paper, where the issues surrounding cultural convergence and divergence, and the processes underlying cultural changes are discussed.
Abstract: The paper provides a state-of-the-art review of several innovative advances in culture and international business (IB) to stimulate new avenues for future research. We first review the issues surrounding cultural convergence and divergence, and the processes underlying cultural changes. We then examine novel constructs for characterizing cultures, and how to enhance the precision of cultural models by pinpointing when cultural effects are important. Finally, we examine the usefulness of experimental methods, which are rarely used by IB researchers. Implications of these path-breaking approaches for future research on culture and IB are discussed.
1,116 citations
TL;DR: A novel method for separating images into texture and piecewise smooth (cartoon) parts, exploiting both the variational and the sparsity mechanisms is presented, combining the basis pursuit denoising (BPDN) algorithm and the total-variation (TV) regularization scheme.
Abstract: The separation of image content into semantic parts plays a vital role in applications such as compression, enhancement, restoration, and more. In recent years, several pioneering works suggested such a separation be based on variational formulation and others using independent component analysis and sparsity. This paper presents a novel method for separating images into texture and piecewise smooth (cartoon) parts, exploiting both the variational and the sparsity mechanisms. The method combines the basis pursuit denoising (BPDN) algorithm and the total-variation (TV) regularization scheme. The basic idea presented in this paper is the use of two appropriate dictionaries, one for the representation of textures and the other for the natural scene parts assumed to be piecewise smooth. Both dictionaries are chosen such that they lead to sparse representations over one type of image-content (either texture or piecewise smooth). The use of the BPDN with the two amalgamed dictionaries leads to the desired separation, along with noise removal as a by-product. As the need to choose proper dictionaries is generally hard, a TV regularization is employed to better direct the separation process and reduce ringing artifacts. We present a highly efficient numerical scheme to solve the combined optimization problem posed by our model and to show several experimental results that validate the algorithm's performance.
1,032 citations
TL;DR: In this paper, the ubiquitin-proteasome system resolved the enigma of how cellular proteins are degraded in the lysosome and showed that non-lysosomal pathways have an important role in intracellular proteolysis, although their identity and mechanisms of action remained obscure.
Abstract: How the genetic code is translated into proteins was a key focus of biological research before the 1980s, but how these proteins are degraded remained a neglected area With the discovery of the lysosome, it was suggested that cellular proteins are degraded in this organelle However, several independent lines of experimental evidence strongly indicated that non-lysosomal pathways have an important role in intracellular proteolysis, although their identity and mechanisms of action remained obscure The discovery of the ubiquitin–proteasome system resolved this enigma
1,009 citations
TL;DR: A novel inpainting algorithm that is capable of filling in holes in overlapping texture and cartoon image layers using a direct extension of a recently developed sparse-representation-based image decomposition method called MCA (morphological component analysis).
974 citations
TL;DR: In this article, the authors investigated the relationship between the characteristic broad-line region size (RBLR) and the Balmer emission-line, X-ray, UV, and optical continuum luminosities.
Abstract: We reinvestigate the relationship between the characteristic broad-line region size (RBLR) and the Balmer emission-line, X-ray, UV, and optical continuum luminosities. Our study makes use of the best available determinations of RBLR for a large number of active galactic nuclei (AGNs) from Peterson et al. Using their determinations of RBLR for a large sample of AGNs and two different regression methods, we investigate the robustness of our correlation results as a function of data subsample and regression technique. Although small systematic differences were found depending on the method of analysis, our results are generally consistent. Assuming a power-law relation RBLR ∝ Lα, we find that the mean best-fitting α is about 0.67 ± 0.05 for the optical continuum and the broad Hβ luminosity, about 0.56 ± 0.05 for the UV continuum luminosity, and about 0.70 ± 0.14 for the X-ray luminosity. We also find an intrinsic scatter of ~40% in these relations. The disagreement of our results with the theoretical expected slope of 0.5 indicates that the simple assumption of all AGNs having on average the same ionization parameter, BLR density, column density, and ionizing spectral energy distribution is not valid and there is likely some evolution of a few of these characteristics along the luminosity scale.
TL;DR: An analysis of a unique record of call center operations that comprises a complete operational history of a small banking call center, call by call, over a full year is summarized.
Abstract: A call center is a service network in which agents provide telephone-based services. Customers who seek these services are delayed in tele-queues. This article summarizes an analysis of a unique record of call center operations. The data comprise a complete operational history of a small banking call center, call by call, over a full year. Taking the perspective of queueing theory, we decompose the service process into three fundamental components: arrivals, customer patience, and service durations. Each component involves different basic mathematical structures and requires a different style of statistical analysis. Some of the key empirical results are sketched, along with descriptions of the varied techniques required. Several statistical techniques are developed for analysis of the basic components. One of these techniques is a test that a point process is a Poisson process. Another involves estimation of the mean function in a nonparametric regression with lognormal errors. A new graphical technique ...
University of Michigan1, Van Andel Institute2, Royal Melbourne Hospital3, Johns Hopkins University4, Technion – Israel Institute of Technology5, Institute for Systems Biology6, ETH Zurich7, Northeastern University8, Bristol-Myers Squibb9, Ruhr University Bochum10, Yonsei University11, University of California, Los Angeles12, Pacific Northwest National Laboratory13, Icahn School of Medicine at Mount Sinai14, University of New South Wales15, Peking Union Medical College16, Russian Academy17, NEC18, IBM19, Wistar Institute20, Fred Hutchinson Cancer Research Center21
TL;DR: Reverse protein to DNA matching identified proteins for 118 previously unidentified ORFs in the PPP database, and the database permits examination of many other subsets, such as 1274 proteins identified with three or more peptides.
Abstract: HUPO initiated the Plasma Proteome Project (PPP) in 2002. Its pilot phase has (1) evaluated advantages and limitations of many depletion, fractionation, and MS technology platforms; (2) compared PPP reference specimens of human serum and EDTA, heparin, and citrate-anti-coagulated plasma; and (3) created a publicly-available knowledge base (www.bioinformatics.med.umich.edu/hupo/ppp; www.ebi.ac.uk/pride). Thirty-five participating laboratories in 13 countries submitted datasets. Working groups addressed (a) specimen stability and protein concentrations; (b) protein identifications from 18 MS/MS datasets; (c) independent analyses from raw MS-MS spectra; (d) search engine performance, subproteome analyses, and biological insights; (e) antibody arrays; and (f) direct MS/SELDI analyses. MS-MS datasets had 15 710 different International Protein Index (IPI) protein IDs; our integration algorithm applied to multiple matches of peptide sequences yielded 9504 IPI proteins identified with one or more peptides and 3020 proteins identified with two or more peptides (the Core Dataset). These proteins have been characterized with Gene Ontology, InterPro, Novartis Atlas, OMIM, and immunoassay-based concentration determinations. The database permits examination of many other subsets, such as 1274 proteins identified with three or more peptides. Reverse protein to DNA matching identified proteins for 118 previously unidentified ORFs. We recommend use of plasma instead of serum, with EDTA (or citrate) for anticoagulation. To improve resolution, sensitivity and reproducibility of peptide identifications and protein matches, we recommend combinations of depletion, fractionation, and MS/MS technologies, with explicit criteria for evaluation of spectra, use of search algorithms, and integration of homologous protein matches. This Special Issue of PROTEOMICS presents papers integral to the collaborative analysis plus many reports of supplementary work on various aspects of the PPP workplan. These PPP results on complexity, dynamic range, incomplete sampling, false-positive matches, and integration of diverse datasets for plasma and serum proteins lay a foundation for development and validation of circulating protein biomarkers in health and disease.
TL;DR: To improve motor-imagery-based BCI control, user training should emphasize kinesthetic experiences instead of visual representations of actions.
TL;DR: In insights into the molecular pathogenesis of AML have led to the development of more specific targeted agents and have ushered in an exciting new era of antileukemia therapy.
TL;DR: The term intelligent packaging is defined based on a proposed model of packaging functions, which is consistent with the historical development of food packaging, and a conceptual framework is developed to provide more precise meaning to the definition.
Abstract: Intelligent packaging is an emerging technology that uses the communication function of the package to facilitate decision making to achieve the benefits of enhanced food quality and safety. In this paper, the term intelligent packaging is defined based on a proposed model of packaging functions, which is consistent with the historical development of food packaging. A conceptual framework is also developed to provide more precise meaning to the definition and to elucidate the anatomy of the intelligent packaging system. The latest advances in smart package devices including barcode labels, radio frequency identification tags, time-temperature indicators, gas indicators, and biosensors are reviewed. The applications of the conceptual framework to Hazard Analysis Critical Control Points and microwave ovens are illustrated. A research roadmap for intelligent packaging is also suggested.
TL;DR: In this article, a highly oxidized graphite oxide was synthesized from natural graphite powder by oxidation with KMnO4 in concentrated H2SO4 followed by hydrolysis, washing and centrifugation.
TL;DR: The international acute lymphoblastic leukemia (ALL) study was designed to prospectively define the optimal therapy for adults 60 years of age or younger with newly diagnosed ALL, and 91% achieved complete remission (CR) as discussed by the authors.
TL;DR: The result is an efficient and accurate face recognition algorithm, robust to facial expressions, that can distinguish between identical twins and compare its performance to classical face recognition methods.
Abstract: An expression-invariant 3D face recognition approach is presented. Our basic assumption is that facial expressions can be modelled as isometries of the facial surface. This allows to construct expression-invariant representations of faces using the bending-invariant canonical forms approach. The result is an efficient and accurate face recognition algorithm, robust to facial expressions, that can distinguish between identical twins (the first two authors). We demonstrate a prototype system based on the proposed algorithm and compare its performance to classical face recognition methods.
The numerical methods employed by our approach do not require the facial surface explicitly. The surface gradients field, or the surface metric, are sufficient for constructing the expression-invariant representation of any given face. It allows us to perform the 3D face recognition task while avoiding the surface reconstruction stage.
TL;DR: In this article, the impact of laser surface texturing on friction transition was investigated with a pin-on-disk apparatus at sliding speeds in the range of 0.015-0.75m/s and nominal contact pressures that ranged from 0.16 to 1.6m/a.
TL;DR: The results suggest that parkin is a dual-function ubiquitin ligase and that K63-linked ubiquitination of synphilin-1 by parkin may be involved in the formation of Lewy body inclusions associated with PD.
Abstract: It is widely accepted that the familial Parkinson's disease (PD)-linked gene product, parkin, functions as a ubiquitin ligase involved in protein turnover via the ubiquitin-proteasome system. Substrates ubiquitinated by parkin are hence thought to be destined for proteasomal degradation. Because we demonstrated previously that parkin interacts with and ubiquitinates synphilin-1, we initially expected synphilin-1 degradation to be enhanced in the presence of parkin. Contrary to our expectation, we found that synphilin-1 is normally ubiquitinated by parkin in a nonclassical, proteasomal-independent manner that involves lysine 63 (K63)-linked polyubiquitin chain formation. Parkin-mediated degradation of synphilin-1 occurs appreciably only at an unusually high parkin to synphilin-1 expression ratio or when primed for lysine 48 (K48)-linked ubiquitination. In addition we found that parkin-mediated ubiquitination of proteins within Lewy-body-like inclusions formed by the coexpression of synphilin-1, α-synuclein, and parkin occurs predominantly via K63 linkages and that the formation of these inclusions is enhanced by K63-linked ubiquitination. Our results suggest that parkin is a dual-function ubiquitin ligase and that K63-linked ubiquitination of synphilin-1 by parkin may be involved in the formation of Lewy body inclusions associated with PD.
TL;DR: A biosynthetic hybrid scaffold comprised of a fibrinogen backbone and crosslinked with difunctional polyethylene glycol (PEG) side chains that provides attachment motifs for endothelial cell and smooth muscle cell adhesion as well as proteolytic sensitivity for biodegradation is described.
TL;DR: The results provide an information-theoretic framework for the study of common communication problems such as precoding for intersymbol interference (ISI) channels and broadcast channels.
Abstract: We consider the generalized dirty-paper channel Y=X+S+N,E{X/sup 2/}/spl les/P/sub X/, where N is not necessarily Gaussian, and the interference S is known causally or noncausally to the transmitter. We derive worst case capacity formulas and strategies for "strong" or arbitrarily varying interference. In the causal side information (SI) case, we develop a capacity formula based on minimum noise entropy strategies. We then show that strategies associated with entropy-constrained quantizers provide lower and upper bounds on the capacity. At high signal-to-noise ratio (SNR) conditions, i.e., if N is weak relative to the power constraint P/sub X/, these bounds coincide, the optimum strategies take the form of scalar lattice quantizers, and the capacity loss due to not having S at the receiver is shown to be exactly the "shaping gain" 1/2log(2/spl pi/e/12)/spl ap/ 0.254 bit. We extend the schemes to obtain achievable rates at any SNR and to noncausal SI, by incorporating minimum mean-squared error (MMSE) scaling, and by using k-dimensional lattices. For Gaussian N, the capacity loss of this scheme is upper-bounded by 1/2log2/spl pi/eG(/spl Lambda/), where G(/spl Lambda/) is the normalized second moment of the lattice. With a proper choice of lattice, the loss goes to zero as the dimension k goes to infinity, in agreement with the results of Costa. These results provide an information-theoretic framework for the study of common communication problems such as precoding for intersymbol interference (ISI) channels and broadcast channels.
TL;DR: A computer vision approach that removes degradation effects in underwater vision is presented, which inverts the image formation process for recovering good visibility in images of scenes and analyzes the noise sensitivity of the recovery.
Abstract: Underwater imaging is important for scientific research and technology as well as for popular activities, yet it is plagued by poor visibility conditions. In this paper, we present a computer vision approach that removes degradation effects in underwater vision. We analyze the physical effects of visibility degradation. It is shown that the main degradation effects can be associated with partial polarization of light. Then, an algorithm is presented, which inverts the image formation process for recovering good visibility in images of scenes. The algorithm is based on a couple of images taken through a polarizer at different orientations. As a by-product, a distance map of the scene is also derived. In addition, this paper analyzes the noise sensitivity of the recovery. We successfully demonstrated our approach in experiments conducted in the sea. Great improvements of scene contrast and color correction were obtained, nearly doubling the underwater visibility range.
TL;DR: The effects of the unique learning environment of the TEAL project on students' cognitive and affective outcomes are analyzed and TEAL students improved their conceptual understanding of the subject matter to a significantly higher extent than their control group peers.
Abstract: Educational technology supports meaningful learning and enables the presentation of spatial and dynamic images, which portray relationships among complex concepts. The Technology-Enabled Active Learning (TEAL) Project at the Massachusetts Institute of Technology (MIT) involves media-rich software for simulation and visualization in freshman physics carried out in a specially redesigned classroom to facilitate group interaction. These technology-based learning materials are especially useful in electromagnetism to help students conceptualize phenomena and processes. This study analyzes the effects of the unique learning environment of the TEAL project on students' cognitive and affective outcomes. The assessment of the project included examining students' conceptual understanding before and after studying electromagnetism in a media-rich environment. We also investigated the effect of this environment on students' preferences regarding the various teaching methods. As part of the project, we developed pre-...
TL;DR: In this paper, the authors present an experimental study on wave propagation in highly nonlocal optically nonlinear media, for which far-away boundary conditions significantly affect the evolution of localized beams.
Abstract: We present an experimental study on wave propagation in highly nonlocal optically nonlinear media, for which far-away boundary conditions significantly affect the evolution of localized beams. As an example, we set the boundary conditions to be anisotropic and demonstrate the first experimental observation of coherent elliptic solitons. Furthermore, exploiting the natural ability of such nonlinearities to eliminate azimuthal instabilities, we perform the first observation of stable vortex-ring solitons. These features of highly nonlocal nonlinearities affected by far-away boundary conditions open new directions in nonlinear science by facilitating remote control over soliton propagation.
TL;DR: The mechanical and structural properties of individual PAN-derived carbon nanofibers are presented in this article, where the Weibull fracture stress fit to this statistical distribution was 0.64 GPa with a failure probability of 63%.
TL;DR: In this paper, the authors describe the results of the experimental investigation and modeling of multiple jets during the electrospinning of polymer solutions, and demonstrate how the external electric fields and mutual electric interaction of multiple charged jets influence their path and evolution during electro-spinning.
TL;DR: The discovery of the ubiquitin–proteasome system resolved the enigma and it is recognized that degradation of intracellular proteins is involved in regulation of a broad array of cellular processes, such as cell cycle and division, regulation of transcription factors and assurance of the cellular quality control.
Abstract: Between the 1950s and 1980s, scientists were focusing mostly on how the genetic code is transcribed to RNA and translated to proteins, but how proteins are degraded has remained a neglected research area. With the discovery of the lysosome by Christian de Duve, it was assumed that cellular proteins are degraded within this organelle. Yet, several independent lines of experimental evidence strongly suggested that intracellular proteolysis is largely nonlysosomal, but the mechanisms involved remained obscure. The discovery of the ubiquitin-proteasome system resolved the enigma. We now recognize that degradation of intracellular proteins is involved in regulation of a broad array of cellular processes, such as cell cycle and division, regulation of transcription factors, and assurance of the cellular quality control. Not surprisingly, aberrations in the system have been implicated in the pathogenesis of human disease, such as malignancies and neurodegenerative disorders, which led subsequently to an increasing effort to develop mechanism-based drugs.
10 Feb 2005
TL;DR: This work investigates the problem of privacy-preserving access to a database, where records in the database are accessed according to their associated keywords and gives efficient solutions for various settings of KS.
Abstract: We study the problem of privacy-preserving access to a database. Particularly, we consider the problem of privacy-preserving keyword search (KS), where records in the database are accessed according to their associated keywords and where we care for the privacy of both the client and the server. We provide efficient solutions for various settings of KS, based either on specific assumptions or on general primitives (mainly oblivious transfer). Our general solutions rely on a new connection between KS and the oblivious evaluation of pseudorandom functions (OPRFs). We therefore study both the definition and construction of OPRFs and, as a corollary, give improved constructions of OPRFs that may be of independent interest.