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Linear Transformations and Restricted Isometry Property. (arXiv:0901.0541v1 [cs.IT]) - The Restricted Isometry Property (RIP) introduced by Cand\'es and Tao is a fundamental property in compressed sensing theory. It says that if a sampling matrix satisfies the RIP of certain order proportional to the sparsity of the signal, then the original signal can be reconstructed even if the sampling matrix provides a sample vector which is much smaller in size than the original signal. This short note addresses the problem of how a linear transformation will affect the RIP. This problem arises from the consideration of extending the sensing matrix and the use of compressed sensing in different bases. As an application, the result is applied to the redundant dictionary setting in compressed sensing. ...
Feed Source: arxiv.org

Resolution-based Query Answering for Semantic Access to Relational Databases: A Research Note. (arXiv:0901.0339v1 [cs.LO]) - We address the problem of semantic access to relational databases in the form of answering queries modulo knowledge bases using very expressive knowledge representation formalisms, such as full first-order logic or its various fragments. We propose to use a first-order logic (FOL) reasoner for computing generic answers to deductive queries, with the subsequent instantiation of these generic answers using a conventional relational DBMS. In this research note, we outline the main idea of this technique -- using abstractions of databases and constrained clauses for deriving generic answers, and provide a formal basis by proving soundness and completeness of the method in the case of FOL without equality. ...
Feed Source: arxiv.org

Thoughts on an Unified Framework for Artificial Chemistries. (arXiv:0901.0318v1 [cs.AI]) - Artificial Chemistries (ACs) are symbolic chemical metaphors for the exploration of Artificial Life, with specific focus on the problem of biogenesis or the origin of life. This paper presents authors thoughts towards defining a unified framework to characterize and classify symbolic artificial chemistries by devising appropriate formalism to capture semantic and organizational information. We identify three basic high level abstractions in initial proposal for this framework viz., information, computation, and communication. We present an analysis of two important notions of information, namely, Shannon's Entropy and Algorithmic Information, and discuss inductive and deductive approaches for defining the framework. ...
Feed Source: arxiv.org

Design of a P System based Artificial Graph Chemistry. (arXiv:0901.0317v1 [cs.NE]) - Artificial Chemistries (ACs) are symbolic chemical metaphors for the exploration of Artificial Life, with specific focus on the origin of life. In this work we define a P system based artificial graph chemistry to understand the principles leading to the evolution of life-like structures in an AC set up and to develop a unified framework to characterize and classify symbolic artificial chemistries by devising appropriate formalism to capture semantic and organizational information. An extension of P system is considered by associating probabilities with the rules providing the topological framework for the evolution of a labeled undirected graph based molecular reaction semantics. ...
Feed Source: arxiv.org

Experience versus Talent Shapes the Structure of the Web. (arXiv:0901.0296v1 [cs.CY]) - We use sequential large-scale crawl data to empirically investigate and validate the dynamics that underlie the evolution of the structure of the web. We find that the overall structure of the web is defined by an intricate interplay between experience or entitlement of the pages (as measured by the number of inbound hyperlinks a page already has), inherent talent or fitness of the pages (as measured by the likelihood that someone visiting the page would give a hyperlink to it), and the continual high rates of birth and death of pages on the web. We find that the web is conservative in judging talent and the overall fitness distribution is exponential, showing low variability. The small variance in talent, however, is enough to lead to experience distributions with high variance: The preferential attachment mechanism amplifies these small biases and leads to heavy-tailed power-law (PL) inbound degree distributions over all pages, as well as over pages that are of the same age. The b...
Feed Source: arxiv.org

An Algorithm for File Transfer Scheduling in Grid Environments. (arXiv:0901.0291v1 [cs.NI]) - This paper addresses the data transfer scheduling problem for Grid environments, presenting a centralized scheduler developed with dynamic and adaptive features. The algorithm offers a reservation system for user transfer requests that allocates them transfer times and bandwidth, according to the network topology and the constraints the user specified for the requests. This paper presents the projects related to the data transfer field, the design of the framework for which the scheduler was built, the main features of the scheduler, the steps for transfer requests rescheduling and two tests that illustrate the system's behavior for different types of transfer requests. ...
Feed Source: arxiv.org

Offline Algorithmic Techniques for Several Content Delivery Problems in Some Restricted Types of Distributed Systems. (arXiv:0901.0290v1 [cs.DS]) - In this paper we consider several content delivery problems (broadcast and multicast, in particular) in some restricted types of distributed systems (e.g. optical Grids and wireless sensor networks with tree-like topologies). For each problem we provide efficient algorithmic techniques for computing optimal content delivery strategies. The techniques we present are offline, which means that they can be used only when full information is available and the problem parameters do not fluctuate too much. ...
Feed Source: arxiv.org

Protecting infrastructure networks from cost-based attacks. (arXiv:0901.0349v1 [cs.NI]) - It has been known that heterogeneous networks are vulnerable to the intentional removal of a small fraction of highly connected or loaded nodes, which implies that, to protect a network effectively, a few important nodes should be allocated with more defense resources than the others. However, if too many resources are allocated to the few important nodes, the numerous less-important nodes will be less protected, which, when attacked all together, still capable of causing a devastating damage. A natural question therefore is how to efficiently distribute the limited defense resources among the network nodes such that the network damage is minimized whatever attack strategy the attacker may take. In this paper, taking into account the factor of attack cost, we will revisit the problem of network security and search for efficient network defense against the cost-based attacks. The study shows that, for a general complex network, there will exist an optimal distribution of the defense ...
Feed Source: arxiv.org

Polarization Codes: Characterization of Exponent, Bounds, and Constructions. (arXiv:0901.0536v1 [cs.IT]) - Polarization codes were recently introduced by Ar\i kan. They achieve the capacity of arbitrary symmetric binary-input discrete memoryless channels (and even extensions thereof) under a low complexity successive decoding strategy. The original polar code construction is closely related to the recursive construction of Reed-Muller codes and is based on the $2 \times 2$ matrix $\bigl[ 1 &0 1& 1 \bigr]$. It was shown by Ar\i kan and Telatar that this construction achieves an error exponent of $\frac12$, i.e., that for sufficiently large blocklengths the error probability decays exponentially in the square root of the length. It was already mentioned by Ar\i kan that in principle larger matrices can be used to construct polar codes. A fundamental question then is to see whether there exist matrices with exponent exceeding $\frac12$. We first show that any $\ell \times \ell$ matrix none of whose column permutations is upper triangular polarizes symmetric channels. We then charact...
Feed Source: arxiv.org

Measures for classification and detection in steganalysis. (arXiv:0901.0529v1 [cs.OH]) - Still and multi-media images are subject to transformations for compression, steganographic embedding and digital watermarking. In a major program of activities we are engaged in the modeling, design and analysis of digital content. Statistical and pattern classification techniques should be combined with understanding of run length, transform coding techniques, and also encryption techniques. ...
Feed Source: arxiv.org

On Multipath Fading Channels at High SNR. (arXiv:0901.0521v1 [cs.IT]) - This work studies the capacity of multipath fading channels. A noncoherent channel model is considered, where neither the transmitter nor the receiver is cognizant of the realization of the path gains, but both are cognizant of their statistics. It is shown that if the delay spread is large in the sense that the variances of the path gains decay exponentially or slower, then capacity is bounded in the signal-to-noise ratio (SNR). For such channels, capacity does not tend to infinity as the SNR tends to infinity. In contrast, if the variances of the path gains decay faster than exponentially, then capacity is unbounded in the SNR. It is further demonstrated that if the number of paths is finite, then at high SNR capacity grows double-logarithmically with the SNR, and the capacity pre-loglog, defined as the limiting ratio of capacity to log(log(SNR)) as SNR tends to infinity, is 1 irrespective of the number of paths. ...
Feed Source: arxiv.org

Interprocedural Dataflow Analysis over Weight Domains with Infinite Descending Chains. (arXiv:0901.0501v1 [cs.DS]) - We study generalized fixed-point equations over idempotent semirings and provide an efficient algorithm for the detection whether a sequence of Kleene's iterations stabilizes after a finite number of steps. Previously known approaches considered only bounded semirings where there are no infinite descending chains. The main novelty of our work is that we deal with semirings without the boundedness restriction. Our study is motivated by several applications from interprocedural dataflow analysis. We demonstrate how the reachability problem for weighted pushdown automata can be reduced to solving equations in the framework mentioned above and we describe a few applications to demonstrate its usability. ...
Feed Source: arxiv.org

Towards the characterization of individual users through Web analytics. (arXiv:0901.0498v1 [cs.HC]) - We perform an analysis of the way individual users navigate in the Web. We focus primarily in the temporal patterns of they return to a given page. The return probability as a function of time as well as the distribution of time intervals between consecutive visits are measured and found to be independent of the level of activity of single users. The results indicate a rich variety of individual behaviors and seem to preclude the possibility of defining a characteristic frequency for each user in his/her visits to a single site. ...
Feed Source: arxiv.org

Transmission Capacities for Overlaid Wireless Ad Hoc Networks with Outage Constraints. (arXiv:0901.0492v1 [cs.IT]) - We study the transmission capacities of two coexisting wireless networks (a primary network vs. a secondary network) that operate in the same geographic region and share the same spectrum. We define transmission capacity as the product among the density of transmissions, the transmission rate, and the successful transmission probability (1 minus the outage probability). The primary (PR) network has a higher priority to access the spectrum without particular considerations for the secondary (SR) network, where the SR network limits its interference to the PR network by carefully controlling the density of its transmitters. Assuming that the nodes are distributed according to Poisson point processes and the two networks use different transmission ranges, we quantify the transmission capacities for both of these two networks and discuss their tradeoff based on asymptotic analyses. Our results show that if the PR network permits a small increase of its outage probability, the sum transm...
Feed Source: arxiv.org

Highly Undecidable Problems For Infinite Computations. (arXiv:0901.0373v1 [cs.LO]) - We show that many classical decision problems about 1-counter omega-languages, context free omega-languages, or infinitary rational relations, are $\Pi_2^1$-complete, hence located at the second level of the analytical hierarchy, and "highly undecidable". In particular, the universality problem, the inclusion problem, the equivalence problem, the determinizability problem, the complementability problem, and the unambiguity problem are all $\Pi_2^1$-complete for context-free omega-languages or for infinitary rational relations. Topological and arithmetical properties of 1-counter omega-languages, context free omega-languages, or infinitary rational relations, are also highly undecidable. These very surprising results provide the first examples of highly undecidable problems about the behaviour of very simple finite machines like 1-counter automata or 2-tape automata. ...
Feed Source: arxiv.org

Weighted Naive Bayes Model for Semi-Structured Document Categorization. (arXiv:0901.0358v1 [cs.IR]) - The aim of this paper is the supervised classification of semi-structured data. A formal model based on bayesian classification is developed while addressing the integration of the document structure into classification tasks. We define what we call the structural context of occurrence for unstructured data, and we derive a recursive formulation in which parameters are used to weight the contribution of structural element relatively to the others. A simplified version of this formal model is implemented to carry out textual documents classification experiments. First results show, for a adhoc weighting strategy, that the structural context of word occurrences has a significant impact on classification results comparing to the performance of a simple multinomial naive Bayes classifier. The proposed implementation competes on the Reuters-21578 data with the SVM classifier associated or not with the splitting of structural components. These results encourage exploring the learning of a...
Feed Source: arxiv.org

Forbidden Information. (arXiv:cs/0203029v11 [cs.CC] UPDATED) - There appears to be a loophole in Goedel Incompleteness Theorem, vaguely perceived for a long time but not clearly identified. Closing this loophole does not seem obvious and involves Kolmogorov complexity. (This is unrelated to, well studied before, complexity quantifications of the usual Goedel effects.) Similar problems and answers apply to other unsolvability results for tasks allowing non-unique solutions, e.g. non-recursive tilings. The technical result is a theorem that any extension of the universal p.r. predicate to all n-bit strings contains nearly all information about the n-bit prefix of any r.e. real r (which is n bits for some r.e. r). ...
Feed Source: arxiv.org

Graph Grammars on Galois Machines. (arXiv:0812.4009v7 [cs.CC] UPDATED) - This paper describes a computer architecture. This architecture is then proven to be Turing complete. The proposed machine has a algebraic data structure called a abstract adjacency matrix. An Eucledian space is extended using two automorphisms creating a Galois Field. The operation modes can emulate a set of NOR gates, a graph isomorphism tester, SKI Combinators, and a Blum Shub Smale machine. Keywords: Graph Theory, Turing machines, Automaton, Galois Theory ...
Feed Source: arxiv.org

Convergence and Monotonicity Problems in an Information-Theoretic Law of Small Numbers. (arXiv:0810.5203v2 [cs.IT] UPDATED) - A version of the law of small numbers is analyzed in information-theoretic terms. Specifically, let $f=\{f_i, i=0, 1, \}$ be a probability mass function (pmf) on nonnegative integers with mean $\lambda<\infty$. Denote the $n$th convolution of $f$ by $f^{*n}$ and denote the $\alpha$-thinning of $f$ by $T_\alpha(f)$. Then, as $n\to\infty$, the entropy $H(T_{1/n}(f^{*n}))$ tends to $H(po(\lambda))$, where $po(\lambda)$ denotes the pmf of the Poisson distribution with mean $\lambda$, and the relative entropy $D(T_{1/n (f^{*n})|po(\lambda))$ tends to zero, if it ever becomes finite. Moreover, $\alpha^{-1} D(T_\alpha(f)|po(\alpha\lambda))$ increases in $\alpha\in (0,1)$, and $n^{-1} D(f^{*n}|po(n\lambda))$ decreases in $n=1,2, $. It follows that $D(T_{1/n}(f^{*n})|po(\lambda))$ decreases monotonically in $n$. Furthermore, assuming that $f$ is ultra-log-concave (i.e., log-concave relative to the Poisson pmf), we show that $H(T_{1/n}(f^{*n}))$ increases monotonically in $n$. This is...
Feed Source: arxiv.org

Camera distortion self-calibration using the plumb-line constraint and minimal Hough entropy. (arXiv:0810.4426v2 [cs.CV] UPDATED) - In this paper we present a simple and robust method for self-correction of camera distortion using single images of scenes which contain straight lines. Since the most common distortion can be modelled as radial distortion, we illustrate the method using the Harris radial distortion model, but the method is applicable to any distortion model. The method is based on transforming the edgels of the distorted image to a 1-D angular Hough space, and optimizing the distortion correction parameters which minimize the entropy of the corresponding normalized histogram. Properly corrected imagery will have fewer curved lines, and therefore less spread in Hough space. Since the method does not rely on any image structure beyond the existence of edgels sharing some common orientations and does not use edge fitting, it is applicable to a wide variety of image types. For instance, it can be applied equally well to images of texture with weak but dominant orientations, or images with strong vanish...
Feed Source: arxiv.org

How to Fully Exploit the Degrees of Freedom in the Downlink of MISO Systems With Opportunistic Beamforming. (arXiv:0809.0536v2 [cs.IT] UPDATED) - The opportunistic beamforming in the downlink of multiple-input single-output (MISO) systems forms $N$ transmit beams, usually, no more than the number of transmit antennas $N_t$. However, the degrees of freedom in this downlink is as large as $N_t^2$. That is, at most $N_t^2$ rather than only $N_t$ users can be simultaneously transmitted and thus the scheduling latency can be significantly reduced. In this paper, we focus on the opportunistic beamforming schemes with $N_t<N\le N_t^2$ transmit beams in the downlink of MISO systems over Rayleigh fading channels. We first show how to design the beamforming matrices with maximum number of transmit beams as well as least correlation between any pair of them as possible, through Fourier, Grassmannian, and mutually unbiased bases (MUB) based constructions in practice. Then, we analyze their system throughput by exploiting the asymptotic theory of extreme order statistics. Finally, our simulation results show the Grassmannian-based beam...
Feed Source: arxiv.org

Authenticated Adversarial Routing. (arXiv:0808.0156v3 [cs.CR] UPDATED) - The aim of this paper is to demonstrate the feasibility of authenticated throughput-efficient routing in an unreliable and dynamically changing synchronous network in which the majority of malicious insiders try to destroy and alter messages or disrupt communication in any way. More specifically, in this paper we seek to answer the following question: Given a network in which the majority of nodes are controlled by a malicious adversary and whose topology is changing every round, is it possible to develop a protocol with polynomially-bounded memory per processor that guarantees throughput-efficient and correct end-to-end communication? We answer the question affirmatively for extremely general corruption patterns: we only request that the topology of the network and the corruption pattern of the adversary leaves at least one path each round connecting the sender and receiver through honest nodes (though this path may change at every round). Out construction works in the public-key s...
Feed Source: arxiv.org

Compound Node-Kayles on Paths. (arXiv:0806.3033v2 [cs.DM] UPDATED) - In his celebrated book "On Number and Games" (Academic Press, New-York, 1976), J.H. Conway introduced twelve versions of compound games. We analyze these twelve versions for the Node-Kayles game on paths. For usual disjunctive compound, Node-Kayles has been solved for a long time under normal play, while it is still unsolved under mis\`ere play. We thus focus on the ten remaining versions, leaving only one of them unsolved. ...
Feed Source: arxiv.org

Bounds on the Sum Capacity of Synchronous Binary CDMA Channels. (arXiv:0806.1659v2 [cs.IT] UPDATED) - In this paper, we obtain a family of lower bounds for the sum capacity of Code Division Multiple Access (CDMA) channels assuming binary inputs and binary signature codes in the presence of additive i.i.d. noise with an arbitrary distribution. The envelope of this family gives a relatively tight lower bound in terms of the number of users, spreading gain and the noise distribution. The derivation methods for the noiseless and the noisy channels are different but when the noise variance goes to zero, the noisy channel bound approaches the noiseless case. The behavior of the lower bound shows that for small noise power, the number of users can be much more than the spreading gain without any significant loss of information (overloaded CDMA). An upper bound is also derived under the usual assumption that the users send out equally likely binary bits in the presence of additive i.i.d. noise with an arbitrary distribution. As the noise level increases, and/or, the ratio of the number of u...
Feed Source: arxiv.org

Robust Cognitive Beamforming With Partial Channel State Information. (arXiv:0806.1372v2 [cs.IT] UPDATED) - This paper considers a spectrum sharing based cognitive radio (CR) communication system, which consists of a secondary user (SU) having multiple transmit antennas and a single receive antenna and a primary user (PU) having a single receive antenna. The channel state information (CSI) on the link of the SU is assumed to be perfectly known at the SU transmitter (SU-Tx). However, due to loose cooperation between the SU and the PU, only partial CSI of the link between the SU-Tx and the PU is available at the SU-Tx. With the partial CSI and a prescribed transmit power constraint, our design objective is to determine the transmit signal covariance matrix that maximizes the rate of the SU while keeping the interference power to the PU below a threshold for all the possible channel realization within an uncertainty set. This problem, termed the robust cognitive beamforming problem, can be naturally formulated as a semi-infinite programming (SIP) problem with infinitely many constraints. Thi...
Feed Source: arxiv.org

Algebraic characterization of logically defined tree languages. (arXiv:0709.2962v2 [cs.LO] UPDATED) - We give an algebraic characterization of the tree languages that are defined by logical formulas using certain Lindstr\"om quantifiers. An important instance of our result concerns first-order definable tree languages. Our characterization relies on the usage of preclones, an algebraic structure introduced by the authors in a previous paper, and of the block product operation on preclones. Our results generalize analogous results on finite word languages, but it must be noted that, as they stand, they do not yield an algorithm to decide whether a given regular tree language is first-order definable. ...
Feed Source: arxiv.org

Physical-Layer Security: Combining Error Control Coding and Cryptography. (arXiv:0901.0275v1 [cs.IT] CROSS LISTED) - In this paper we consider tandem error control coding and cryptography in the setting of the wiretap channel due to Wyner. In a typical communications system a cryptographic application is run at a layer above the physical layer and assumes the channel is error free. However, in any real application the channels for friendly users and passive eavesdroppers are not error free and Wyner's wiretap model addresses this scenario. Using this model, we show the security of a common cryptographic primitive, i.e. a keystream generator based on linear feedback shift registers (LFSR), can be strengthened by exploiting properties of the physical layer. A passive eavesdropper can be made to experience greater difficulty in cracking an LFSR-based cryptographic system insomuch that the computational complexity of discovering the secret key increases by orders of magnitude, or is altogether infeasible. This result is shown for two fast correlation attacks originally presented by Meier and Staffelba...
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This Week in Science - Gold Nanoparticles on a Roll | Keeping Fungal Invaders at Bay | Ultra Clean, Ultra Small | Adding Injury to Insult | A Warped Route to Cloaking | Right on Target | Bright Shiny Flowers | Life's Too Short | Chaperone to Neurodegeneration | Trading Toxins | Rare Air | Peer Support | Viewing the Action of DNA Polymerase...
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Editors' Choice - CELL BIOLOGY: Moving Toward Asymmetry | ASTROPHYSICS: A Star at Death's Door | IMMUNOLOGY: Finding Negatives Wherever | OCEAN SCIENCE: Winter Carbonate Collapse | CHEMISTRY: Diverse Scaffolds | CELL BIOLOGY: Follow the Leader | AGRICULTURE: Controlling Salt Intake...
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Random Samples - TO CATCH A CELL | NO FREE RIDE FOR BLUBBER | GETTING THERE...
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Newsmakers - PEOPLE TO WATCH IN 2009 | PEOPLE TO WATCH IN 2009...
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[RESEARCH ARTICLES] A Glucosinolate Metabolism Pathway in Living Plant Cells Mediates Broad-Spectrum Antifungal Defense - Plant cells defend against fungal attack through an innate immunity pathway in which infection triggers glucosinolate synthesis, stimulating formation of a protective callose. Authors: Pawe? Bednarek, Mariola Pi?lewska-Bednarek, Ale? Svato?, Bernd Schneider, Jan Doubský, Madina Mansurova, Matt Humphry, Chiara Consonni, Ralph Panstruga, Andrea Sanchez-Vallet, Antonio Molina, Paul Schulze-Lefert...
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[REPORTS] Mott Insulating State in Ultraclean Carbon Nanotubes - Both metallic and semiconducting carbon nanotubes exhibit a radius-dependent energy gap arising from correlated electrons in the tubes. Authors: Vikram V. Deshpande, Bhupesh Chandra, Robert Caldwell, Dmitry S. Novikov, James Hone, Marc Bockrath...
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[REPORTS] Broadband Invisibility by Non-Euclidean Cloaking - In theory, materials with a negative refractive index deployed in a curved, non-Euclidean space can provide a route to cloaking and invisibility across a range of wavelengths. Authors: Ulf Leonhardt, Tomá? Tyc...
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[REPORTS] Control of Self-Assembly of DNA Tubules Through Integration of Gold Nanoparticles - Gold particles incorporated into DNA strands drive the formation of a variety of three-dimensional spiral architectures. Authors: Jaswinder Sharma, Rahul Chhabra, Anchi Cheng, Jonathan Brownell, Yan Liu, Hao Yan...
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[REPORTS] Declining Coral Calcification on the Great Barrier Reef - Calcification by Great Barrier Reef corals decreased by about 14% since 1990, the largest decline in the past 400 years. Authors: Glenn De?ath, Janice M. Lough, Katharina E. Fabricius...
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[REPORTS] Stretching the Envelope of Past Surface Environments: Neoproterozoic Glacial Lakes from Svalbard - Unusual oxygen isotope compositions indicate that a Precambrian glacial period had an anomalous, perhaps extremely CO2-rich, atmosphere. Authors: Huiming Bao, Ian J. Fairchild, Peter M. Wynn, Christoph Spötl...
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[REPORTS] Why Peer Discussion Improves Student Performance on In-Class Concept Questions - In the classroom, discussion among students improves understanding and leads to more accurate answers to questions. Authors: M. K. Smith, W. B. Wood, W. K. Adams, C. Wieman, J. K. Knight, N. Guild, T. T. Su...
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[REPORTS] Regulation of Neuronal Survival Factor MEF2D by Chaperone-Mediated Autophagy - The degradation of a key neuronal survival factor by chaperone-mediated autophagy may contribute to Parkinson's disease. Authors: Qian Yang, Hua She, Marla Gearing, Emanuela Colla, Michael Lee, John J. Shacka, Zixu Mao...
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[REPORTS] Signal Sequences Activate the Catalytic Switch of SRP RNA - Authors: Niels Bradshaw, Saskia B. Neher, David S. Booth, Peter Walter...
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[REPORTS] Floral Iridescence, Produced by Diffractive Optics, Acts As a Cue for Animal Pollinators - The iridescence of tulip petals, as well as their pigmentation, affects foraging behavior by bumblebees. Authors: Heather M. Whitney, Mathias Kolle, Piers Andrew, Lars Chittka, Ullrich Steiner, Beverley J. Glover...
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[REPORTS] Real-Time DNA Sequencing from Single Polymerase Molecules - Arrays of narrow waveguides can record the action of a DNA polymerase stepping along a primer template, potentially providing a way to sequence DNA molecules. Authors: John Eid, Adrian Fehr, Jeremy Gray, Khai Luong, John Lyle, Geoff Otto, Paul Peluso, David Rank, Primo Baybayan, Brad Bettman, Arkadiusz Bibillo, Keith Bjornson, Bidhan Chaudhuri, Frederick Christians, Ronald Cicero, Sonya Clark, Ravindra Dalal, Alex deWinter, John Dixon, Mathieu Foquet, Alfred Gaertner, Paul Hardenbol, Cheryl Heiner, Kevin Hester, David Holden, Gregory Kearns, Xiangxu Kong, Ronald Kuse, Yves Lacroix, Steven Lin, Paul Lundquist, Congcong Ma, Patrick Marks, Mark Maxham, Devon Murphy, Insil Park, Thang Pham, Michael Phillips, Joy Roy, Robert Sebra, Gene Shen, Jon Sorenson, Austin Tomaney, Kevin Travers, Mark Trulson, John Vieceli, Jeffrey Wegener, Dawn Wu, Alicia Yang, Denis Zaccarin, Peter Zhao, Frank Zhong, Jonas Korlach, Stephen Turner...
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[REPORTS] Phage-Mediated Intergeneric Transfer of Toxin Genes - Viruses may transfer toxin genes among pathogenic bacteria in raw milk, complicating veterinary use of phage therapy as a bacteriacide. Authors: John Chen, Richard P. Novick...
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[REPORTS] Stable Introduction of a Life-Shortening Wolbachia Infection into the Mosquito Aedes aegypti - Infection of mosquitoes with a bacterium shortens their lives and reduces disease transmission, without development of resistance. Authors: Conor J. McMeniman, Roxanna V. Lane, Bodil N. Cass, Amy W.C. Fong, Manpreet Sidhu, Yu-Feng Wang, Scott L. O?Neill...
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[EDITORIAL] Making a Science of Education - Author: Bruce Alberts...
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[NEWS] THE TRANSITION: Holdren Named Science Adviser, Varmus, Lander to Co-Chair PCAST - Authors: Eli Kintisch, Jeffrey Mervis...
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[NEWS] SCIENTIFIC COLLABORATION: Tehran Incident Threatens U.S.-Iran Project - Author: Richard Stone...
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[NEWS] RESEARCH ASSESSMENT: U.K. University Research Ranked; Funding Impacts to Follow - Author: John Travis...
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[NEWS] RESEARCH FUNDING: For Many Scientists, the Madoff Scandal Suddenly Hits Home - Author: Jennifer Couzin...
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[NEWS] PLANETARY IMPACTS: Did the Mammoth Slayer Leave A Diamond Calling Card? - Author: Richard A. Kerr...
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[NEWS] CORAL REEFS: Calcification Rates Drop in Australian Reefs - Author: Elizabeth Pennisi...
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[NEWS FOCUS] SCIENCE ADVISERS: Bending the President's Ear - A science adviser is only as effective as the president wants him to be, say the men who have held the job since Sputnik.Author: Eli Kintisch...
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[NEWS FOCUS] BRAIN CANCER: A Viral Link to Glioblastoma? - Circumstantial evidence hints that cytomegalovirus, a common herpesvirus, may play a role in the aggressive brain cancer, but big questions remain.Author: Greg Miller...
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[NEWS FOCUS] POLAR SCIENCE: A Death in Antarctica - The death in 2000 of a young Australian astrophysicist at the U.S. South Pole station raised many troubling questions. Eight years later, there are few answers.Author: Jeffrey Mervis...
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[LETTERS] Literature Citations in the Internet Era - Authors: Yves Gingras, Vincent Larivičre, Éric Archambault...
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[LETTERS] Narrower Focus May Be More Efficient - Author: K. Brad Wray...
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[LETTERS] To Each Citation, a Purpose - Authors: Christopher S. Von Bartheld, Shaun P. Collin, Onur Güntürkün...
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[LETTERS] A Cycle of Tradition and Innovation - Authors: Hanne Andersen;, James A. Evans...
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[TECHNICAL COMMENT] Comment on ?Log or Linear? Distinct Intuitions of the Number Scale in Western and Amazonian Indigene Cultures? - Authors: Jessica F. Cantlon, Sara Cordes, Melissa E. Libertus, Elizabeth M. Brannon...
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[TECHNICAL RESPONSE] Response to Comment on ?Log or Linear? Distinct Intuitions of the Number Scale in Western and Amazonian Indigene Cultures? - Authors: Stanislas Dehaene, Véronique Izard, Pierre Pica, Elizabeth Spelke...
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[BOOKS ET AL.] EDUCATION: The Gamers' Advancement of Learning - Starting from the observation that video games captivate both players and programmers, Gee explores their implications for learning theory, motivation, and development of expertise.Author: John Willinsky...
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[BOOKS ET AL.] EDUCATION: Inside the Schooled Mind - Reif discusses how findings from cognitive science can help improve teaching and learning, especially science education (and, within that, physics education).Author: Elsbeth Stern...
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[BOOKS ET AL.] SCIENCE EDUCATION: A Handbook for Hands-On Learning - The contributors present perspectives on undergraduate research programs from participants, administrators, and external evaluators.Authors: Robert A. Lue, Richard Losick...
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[BOOKS ET AL.] EDUCATION: What's Wrong with Inferences from Test Scores? - In this account of the complexities of educational testing written for nonspecialists, Koretz discusses what such tests can and cannot reveal and how test scores can be misunderstood and misused.Author: Edward Haertel...
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[POLICY FORUM] ENVIRONMENT: "True" Conservation Progress - Conservation performance in securing biodiversity can be evaluated better with metrics based on the concept of a conservation balance sheet.Authors: Eve McDonald-Madden, Ascelin Gordon, Brendan A. Wintle, Susan Walker, Hedley Grantham, Silvia Carvalho, Madeleine Bottrill, Liana Joseph, Rocio Ponce, Romola Stewart, Hugh P. Possingham...
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[PERSPECTIVES] ASTRONOMY: How Old Is That Star? - Despite being fundamental in determining its physical state, a star's age cannot be measured directly, and estimation methods are imprecise.Author: David R. Soderblom...
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[PERSPECTIVES] PHYSICS: Cloaking with Curved Spaces - Designs based on the mathematics behind curved space-time may lead to invisibility cloaks.Authors: André Nicolet, Frédéric Zolla...
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[PERSPECTIVES] CHEMISTRY: Repair or Replacement--A Joint Perspective - Insights into the molecular origins of cartilage lubrication could lead to more efficient tissue repair and to longer-lasting prostheses for hip and knee joints.Author: Jacob Klein...
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[PERSPECTIVES] GEOCHEMISTRY: A Matter of Preservation - Differences in the preservation potential of crustal rocks may explain peaks in crustal ages previously attributed to enhanced crust formation.Authors: Chris Hawkesworth, Peter Cawood, Tony Kemp, Craig Storey, Bruno Dhuime...
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[PERSPECTIVES] EDUCATION: Farewell, Lecture? - A physics professor describes his evolution from lecturing to dynamically engaging students during class and improving how they learn.Author: Eric Mazur...
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[PERSPECTIVES] MICROBIOLOGY: Mosquitoes Cut Short - Can the life-shortening effect of a bacterium on mosquitoes control the transmission of dengue?Authors: Andrew F. Read, Matthew B. Thomas...
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[SPECIAL SECTION] Adding a T to the Three R's - Authors: Pamela J. Hines, Barbara R. Jasny, Jeffrey Mervis...
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[SPECIAL/MULTIMEDIA] Video: Education and Technology - A video introduction to Science's special issue on the promises, and challenges, that rapidly changing technology presents for the educational world.Author: ...
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[SPECIAL/NEWS] NSF Rethinks Its Digital Library - A $175 million investment by the U.S. National Science Foundation has fostered collaboration and created vast amounts of material. But the digital world is changing.Author: Jeffrey Mervis...
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[SPECIAL/NEWS] New Landscape for the Earth Sciences - A digital library for the earth sciences community and by the community is now also of the community.Author: Jeffrey Mervis...
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[SPECIAL/NEWS] A Nobelist's Passionate Pursuit of Excellence - Nobelist Harry Kroto argues that the best educational resources often come from "people who are passionate about what they are doing and want to share it"--even if those materials haven't first been put under the sort of disciplinary scrutiny typical of material included in the National Science Digital Library. Author: Jeffrey Mervis...
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[SPECIAL/NEWS] A Vision in Search of Funding - Last summer, the U.S. government created an awkwardly named entity to fund research on how the Internet can improve U.S. education. But so far, the National Center for Research in Advanced Information and Digital Technologies exists only on paper.Author: Jeffrey Mervis...
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[SPECIAL/NEWS] Computers As Writing Instructors - Software that helps students hone their writing skills is finding a niche in the classroom.Author: Greg Miller...
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[SPECIAL/NEWS] Glow Lights Up Scottish Classrooms - Schools across Scotland are flocking to link up with a national intranet that serves students, teachers, and parents.Author: Daniel Clery...
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[SPECIAL/NEWS] Korea Tries to Level the Field - A cyber home learning system seeks to raise achievement and reduce the huge cost of private tutors, a practice not available to every Korean family.Author: Dennis Normile...
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[SPECIAL/NEWS] A Personal Tutor for Algebra - Commercial software created in the lab anticipates wrong answers and reinforces needed skills for first-year algebra students.Author: Yudhijit Bhattacharjee...
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[SPECIAL ISSUE Perspective] Immersive Interfaces for Engagement and Learning - Author: Chris Dede...
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[SPECIAL ISSUE Perspective] Technology and Informal Education: What Is Taught, What Is Learned - Author: Patricia M. Greenfield...
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[SPECIAL ISSUE Perspective] Education and Training Technology in the Military - Author: J. D. Fletcher...
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[SPECIAL ISSUE Perspective] Technology and Testing - Authors: Edys S. Quellmalz, James W. Pellegrino...
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[SPECIAL ISSUE Perspective] Video Games: A Route to Large-Scale STEM Education? - Author: Merrilea J. Mayo...
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[SPECIAL ISSUE Perspective] Laptop Programs for Students - Authors: Andrew A. Zucker, Daniel Light...
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[SPECIAL ISSUE REVIEWS] Online Education Today - Authors: A. Frank Mayadas, John Bourne, Paul Bacsich...
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[SPECIAL ISSUE REVIEWS] Opening Education - Author: Marshall S. Smith...
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[BREVIA] Nanodiamonds in the Younger Dryas Boundary Sediment Layer - Nanodiamonds in sites across North America suggest that an asteroid impact coincided with cooling 12,900 years ago. Authors: D. J. Kennett, J. P. Kennett, A. West, C. Mercer, S. S. Que Hee, L. Bement, T. E. Bunch, M. Sellers, W. S. Wolbach...
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[RESEARCH ARTICLES] Glucosinolate Metabolites Required for an Arabidopsis Innate Immune Response - Authors: Nicole K. Clay, Adewale M. Adio, Carine Denoux, Georg Jander, Frederick M. Ausubel...
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