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Showing papers by "IBM published in 2002"


Proceedings ArticleDOI
06 Jul 2002
TL;DR: This paper proposed a method of automatic machine translation evaluation that is quick, inexpensive, and language-independent, that correlates highly with human evaluation, and that has little marginal cost per run.
Abstract: Human evaluations of machine translation are extensive but expensive. Human evaluations can take months to finish and involve human labor that can not be reused. We propose a method of automatic machine translation evaluation that is quick, inexpensive, and language-independent, that correlates highly with human evaluation, and that has little marginal cost per run. We present this method as an automated understudy to skilled human judges which substitutes for them when there is need for quick or frequent evaluations.

21,126 citations


Proceedings ArticleDOI
06 Jul 2002
TL;DR: This work considers the problem of classifying documents not by topic, but by overall sentiment, e.g., determining whether a review is positive or negative, and concludes by examining factors that make the sentiment classification problem more challenging.
Abstract: We consider the problem of classifying documents not by topic, but by overall sentiment, e.g., determining whether a review is positive or negative. Using movie reviews as data, we find that standard machine learning techniques definitively outperform human-produced baselines. However, the three machine learning methods we employed (Naive Bayes, maximum entropy classification, and support vector machines) do not perform as well on sentiment classification as on traditional topic-based categorization. We conclude by examining factors that make the sentiment classification problem more challenging.

6,626 citations


Journal ArticleDOI
TL;DR: This work presents a simple and efficient implementation of Lloyd's k-means clustering algorithm, which it calls the filtering algorithm, and establishes the practical efficiency of the algorithm's running time.
Abstract: In k-means clustering, we are given a set of n data points in d-dimensional space R/sup d/ and an integer k and the problem is to determine a set of k points in Rd, called centers, so as to minimize the mean squared distance from each data point to its nearest center. A popular heuristic for k-means clustering is Lloyd's (1982) algorithm. We present a simple and efficient implementation of Lloyd's k-means clustering algorithm, which we call the filtering algorithm. This algorithm is easy to implement, requiring a kd-tree as the only major data structure. We establish the practical efficiency of the filtering algorithm in two ways. First, we present a data-sensitive analysis of the algorithm's running time, which shows that the algorithm runs faster as the separation between clusters increases. Second, we present a number of empirical studies both on synthetically generated data and on real data sets from applications in color quantization, data compression, and image segmentation.

5,288 citations


Journal ArticleDOI
TL;DR: In this article, the authors present new insight into conduction mechanisms and performance characteristics, as well as opportunities for modeling properties of organic thin-film transistors (OTFTs) and discuss progress in the growing field of n-type OTFTs.
Abstract: Organic thin-film transistors (OTFTs) have lived to see great improvements in recent years. This review presents new insight into conduction mechanisms and performance characteristics, as well as opportunities for modeling properties of OTFTs. The shifted focus in research from novel chemical structures to fabrication technologies that optimize morphology and structural order is underscored by chapters on vacuum-deposited and solution-processed organic semiconducting films. Finally, progress in the growing field of the n-type OTFTs is discussed in ample detail. The Figure, showing a pentacene film edge on SiO2, illustrates the morphology issue.

4,804 citations


Journal ArticleDOI
Shouheng Sun1, Hao Zeng1
TL;DR: The reported procedure can be used as a general approach to various ferrite nanoparticles and nanoparticle superlattices.
Abstract: Monodisperse magnetite nanoparticles have been synthesized by high-temperature solution-phase reaction of Fe(acac)3 in phenyl ether with alcohol, oleic acid, and oleylamine. Seed-mediated growth is used to control Fe3O4 nanoparticle size, and variously sized nanoparticles from 3 to 20 nm have been produced. The as-synthesized Fe3O4 nanoparticles have inverse spinel structure, and their assemblies can be transformed into γ-Fe2O3 or α-Fe nanoparticle assemblies, depending on the annealing conditions. The reported procedure can be used as a general approach to various ferrite nanoparticles and nanoparticle superlattices.

2,605 citations


Proceedings ArticleDOI
03 Jun 2002
TL;DR: This paper shows that XML's ordered data model can indeed be efficiently supported by a relational database system, and proposes three order encoding methods that can be used to represent XML order in the relational data model, and also proposes algorithms for translating ordered XPath expressions into SQL using these encoding methods.
Abstract: XML is quickly becoming the de facto standard for data exchange over the Internet. This is creating a new set of data management requirements involving XML, such as the need to store and query XML documents. Researchers have proposed using relational database systems to satisfy these requirements by devising ways to "shred" XML documents into relations, and translate XML queries into SQL queries over these relations. However, a key issue with such an approach, which has largely been ignored in the research literature, is how (and whether) the ordered XML data model can be efficiently supported by the unordered relational data model. This paper shows that XML's ordered data model can indeed be efficiently supported by a relational database system. This is accomplished by encoding order as a data value. We propose three order encoding methods that can be used to represent XML order in the relational data model, and also propose algorithms for translating ordered XPath expressions into SQL using these encoding methods. Finally, we report the results of an experimental study that investigates the performance of the proposed order encoding methods on a workload of ordered XML queries and updates.

2,402 citations


Journal ArticleDOI
24 Jan 2002-Nature
TL;DR: It is demonstrated that medulloblastomas are molecularly distinct from other brain tumours including primitive neuroectodermal tumours, atypical teratoid/rhabdoid tumours (AT/RTs) and malignant gliomas, and it is shown that the clinical outcome of children with medullOBlastomas is highly predictable on the basis of the gene expression profiles of their tumours at diagnosis.
Abstract: Embryonal tumours of the central nervous system (CNS) represent a heterogeneous group of tumours about which little is known biologically, and whose diagnosis, on the basis of morphologic appearance alone, is controversial. Medulloblastomas, for example, are the most common malignant brain tumour of childhood, but their pathogenesis is unknown, their relationship to other embryonal CNS tumours is debated, and patients' response to therapy is difficult to predict. We approached these problems by developing a classification system based on DNA microarray gene expression data derived from 99 patient samples. Here we demonstrate that medulloblastomas are molecularly distinct from other brain tumours including primitive neuroectodermal tumours (PNETs), atypical teratoid/rhabdoid tumours (AT/RTs) and malignant gliomas. Previously unrecognized evidence supporting the derivation of medulloblastomas from cerebellar granule cells through activation of the Sonic Hedgehog (SHH) pathway was also revealed. We show further that the clinical outcome of children with medulloblastomas is highly predictable on the basis of the gene expression profiles of their tumours at diagnosis.

2,365 citations


Journal ArticleDOI
Andrei Z. Broder1
01 Sep 2002
TL;DR: This taxonomy of web searches is explored and how global search engines evolved to deal with web-specific needs is discussed.
Abstract: Classic IR (information retrieval) is inherently predicated on users searching for information, the so-called "information need". But the need behind a web search is often not informational -- it might be navigational (give me the url of the site I want to reach) or transactional (show me sites where I can perform a certain transaction, e.g. shop, download a file, or find a map). We explore this taxonomy of web searches and discuss how global search engines evolved to deal with web-specific needs.

2,094 citations


Journal ArticleDOI
TL;DR: In this paper, the authors focus on the nature of the services that respond to protocol messages and propose a set of services that can be aggregated in various ways to meet the needs of virtual organizations, which themselves can be defined by the services they operate and share.
Abstract: Increasingly, computing addresses collaboration, data sharing, and interaction modes that involve distributed resources, resulting in an increased focus on the interconnection of systems both within and across enterprises. These evolutionary pressures have led to the development of Grid technologies. The authors' work focuses on the nature of the services that respond to protocol messages. Grid provides an extensible set of services that can be aggregated in various ways to meet the needs of virtual organizations, which themselves can be defined in part by the services they operate and share.

1,816 citations


Journal ArticleDOI
TL;DR: This survey covers rollback-recovery techniques that do not require special language constructs and distinguishes between checkpoint-based and log-based protocols, which rely solely on checkpointing for system state restoration.
Abstract: This survey covers rollback-recovery techniques that do not require special language constructs. In the first part of the survey we classify rollback-recovery protocols into checkpoint-based and log-based.Checkpoint-based protocols rely solely on checkpointing for system state restoration. Checkpointing can be coordinated, uncoordinated, or communication-induced. Log-based protocols combine checkpointing with logging of nondeterministic events, encoded in tuples called determinants. Depending on how determinants are logged, log-based protocols can be pessimistic, optimistic, or causal. Throughout the survey, we highlight the research issues that are at the core of rollback-recovery and present the solutions that currently address them. We also compare the performance of different rollback-recovery protocols with respect to a series of desirable properties and discuss the issues that arise in the practical implementations of these protocols.

1,772 citations


Journal ArticleDOI
Paramvir S. Dehal1, Yutaka Satou2, Robert K. Campbell3, Jarrod Chapman1, Bernard M. Degnan4, Anthony W. De Tomaso5, Brad Davidson6, Anna Di Gregorio6, Maarten D. Sollewijn Gelpke1, David Goodstein1, Naoe Harafuji6, Kenneth E. M. Hastings7, Isaac Ho1, Kohji Hotta8, Wayne Huang1, Takeshi Kawashima2, Patrick Lemaire9, Diego Martinez1, Ian A. Meinertzhagen10, Simona Necula1, Masaru Nonaka11, Nik Putnam1, Sam Rash1, Hidetoshi Saiga12, Masanobu Satake13, Astrid Terry1, Lixy Yamada2, Hong Gang Wang14, Satoko Awazu2, Kaoru Azumi15, Jeffrey L. Boore1, Margherita Branno16, Stephen T. Chin-Bow17, Rosaria DeSantis16, Sharon A. Doyle1, Pilar Francino1, David N. Keys6, David N. Keys1, Shinobu Haga8, Hiroko Hayashi8, Kyosuke Hino2, Kaoru S. Imai2, Kazuo Inaba13, Shungo Kano2, Shungo Kano16, Kenji Kobayashi2, Mari Kobayashi2, Byung In Lee1, Kazuhiro W. Makabe2, Chitra Manohar1, Giorgio Matassi16, Mónica Medina1, Yasuaki Mochizuki2, Steve Mount18, Tomomi Morishita8, Sachiko Miura8, Akie Nakayama2, Satoko Nishizaka8, Hisayo Nomoto8, Fumiko Ohta8, Kazuko Oishi8, Isidore Rigoutsos17, Masako Sano8, Akane Sasaki2, Yasunori Sasakura2, Eiichi Shoguchi2, Tadasu Shin-I8, Antoinetta Spagnuolo16, Didier Y.R. Stainier19, Miho Suzuki20, Olivier Tassy9, Naohito Takatori2, Miki Tokuoka2, Kasumi Yagi2, Fumiko Yoshizaki11, Shuichi Wada2, Cindy Zhang1, P. Douglas Hyatt21, Frank W. Larimer21, Chris Detter1, Norman A. Doggett22, Tijana Glavina1, Trevor Hawkins1, Paul G. Richardson1, Susan Lucas1, Yuji Kohara8, Michael Levine6, Nori Satoh2, Daniel S. Rokhsar6, Daniel S. Rokhsar1 
13 Dec 2002-Science
TL;DR: A draft of the protein-coding portion of the genome of the most studied ascidian, Ciona intestinalis, is generated, suggesting that ascidians contain the basic ancestral complement of genes involved in cell signaling and development.
Abstract: The first chordates appear in the fossil record at the time of the Cambrian explosion, nearly 550 million years ago. The modern ascidian tadpole represents a plausible approximation to these ancestral chordates. To illuminate the origins of chordate and vertebrates, we generated a draft of the protein-coding portion of the genome of the most studied ascidian, Ciona intestinalis. The Ciona genome contains approximately 16,000 protein-coding genes, similar to the number in other invertebrates, but only half that found in vertebrates. Vertebrate gene families are typically found in simplified form in Ciona, suggesting that ascidians contain the basic ancestral complement of genes involved in cell signaling and development. The ascidian genome has also acquired a number of lineage-specific innovations, including a group of genes engaged in cellulose metabolism that are related to those in bacteria and fungi.

Proceedings ArticleDOI
09 Jun 2002
TL;DR: It is shown that a network with CONFIDANT and up to 60% of misbehaving nodes behaves almost as well as a benign network, in sharp contrast to a defenseless network.
Abstract: Mobile ad-hoc networking works properly only if the participating nodes cooperate in routing and forwarding. However,it may be advantageous for individual nodes not to cooperate. We propose a protocol, called CONFIDANT, for making misbehavior unattractive; it is based on selective altruism and utilitarianism. It aims at detecting and isolating misbehaving nodes, thus making it unattractive to deny cooperation. Trust relationships and routing decisions are based on experienced, observed, or reported routing and forwarding behavior of other nodes. The detailed implementation of CONFIDANT in this paper assumes that the network layer is based on the Dynamic Source Routing (DSR) protocol. We present a performance analysis of DSR fortified by CONFIDANT and compare it to regular defenseless DSR. It shows that a network with CONFIDANT and up to 60% of misbehaving nodes behaves almost as well as a benign network, in sharp contrast to a defenseless network. All simulations have been implemented and performed in GloMoSim.

Journal ArticleDOI
28 Nov 2002-Nature
TL;DR: The fabrication of exchange-coupled nanocomposites using nanoparticle self-assembly with an energy product that exceeds the theoretical limit of 13 MG Oe for non-exchange- coupled isotropic FePt by over 50 per cent is reported.
Abstract: Exchange-spring magnets are nanocomposites that are composed of magnetically hard and soft phases that interact by magnetic exchange coupling. Such systems are promising for advanced permanent magnetic applications, as they have a large energy product--the combination of permanent magnet field and magnetization--compared to traditional, single-phase materials. Conventional techniques, including melt-spinning, mechanical milling and sputtering, have been explored to prepare exchange-spring magnets. However, the requirement that both the hard and soft phases are controlled at the nanometre scale, to ensure efficient exchange coupling, has posed significant preparation challenges. Here we report the fabrication of exchange-coupled nanocomposites using nanoparticle self-assembly. In this approach, both FePt and Fe3O4 particles are incorporated as nanometre-scale building blocks into binary assemblies. Subsequent annealing converts the assembly into FePt-Fe3Pt nanocomposites, where FePt is a magnetically hard phase and Fe3Pt a soft phase. An optimum exchange coupling, and therefore an optimum energy product, can be obtained by independently tuning the size and composition of the individual building blocks. We have produced exchange-coupled isotropic FePt-Fe3Pt nanocomposites with an energy product of 20.1 MG Oe, which exceeds the theoretical limit of 13 MG Oe for non-exchange-coupled isotropic FePt by over 50 per cent.

Journal ArticleDOI
TL;DR: This tutorial explores the most salient and stable specifications in each of the three major areas of the emerging Web services framework, which are the simple object access protocol, the Web Services Description Language and the Universal Description, Discovery, and Integration directory.
Abstract: This tutorial explores the most salient and stable specifications in each of the three major areas of the emerging Web services framework. They are the simple object access protocol, the Web Services Description Language and the Universal Description, Discovery, and Integration directory, which is a registry of Web services descriptions.

Proceedings Article
Frank B. Schmuck1, Roger L. Haskin1
28 Jan 2002
TL;DR: GPFS is IBM's parallel, shared-disk file system for cluster computers, available on the RS/6000 SP parallel supercomputer and on Linux clusters, and discusses how distributed locking and recovery techniques were extended to scale to large clusters.
Abstract: GPFS is IBM's parallel, shared-disk file system for cluster computers, available on the RS/6000 SP parallel supercomputer and on Linux clusters. GPFS is used on many of the largest supercomputers in the world. GPFS was built on many of the ideas that were developed in the academic community over the last several years, particularly distributed locking and recovery technology. To date it has been a matter of conjecture how well these ideas scale. We have had the opportunity to test those limits in the context of a product that runs on the largest systems in existence. While in many cases existing ideas scaled well, new approaches were necessary in many key areas. This paper describes GPFS, and discusses how distributed locking and recovery techniques were extended to scale to large clusters.

Proceedings ArticleDOI
03 Jun 2002
TL;DR: The paper explores an algebraic framework to split the query to minimize the computation at the client site, and explores techniques to execute SQL queries over encrypted data.
Abstract: Rapid advances in networking and Internet technologies have fueled the emergence of the "software as a service" model for enterprise computing. Successful examples of commercially viable software services include rent-a-spreadsheet, electronic mail services, general storage services, disaster protection services. "Database as a Service" model provides users power to create, store, modify, and retrieve data from anywhere in the world, as long as they have access to the Internet. It introduces several challenges, an important issue being data privacy. It is in this context that we specifically address the issue of data privacy.There are two main privacy issues. First, the owner of the data needs to be assured that the data stored on the service-provider site is protected against data thefts from outsiders. Second, data needs to be protected even from the service providers, if the providers themselves cannot be trusted. In this paper, we focus on the second challenge. Specifically, we explore techniques to execute SQL queries over encrypted data. Our strategy is to process as much of the query as possible at the service providers' site, without having to decrypt the data. Decryption and the remainder of the query processing are performed at the client site. The paper explores an algebraic framework to split the query to minimize the computation at the client site. Results of experiments validating our approach are also presented.

Book
E. F. Codd1
01 Jan 2002
TL;DR: In this article, a model based on n-ary relations, a normal form for data base relations, and the concept of a universal data sublanguage are introduced, and certain operations on relations are discussed and applied to the problems of redundancy and consistency in the user's model.
Abstract: Future users of large data banks must be protected from having to know how the data is organized in the machine (the internal representation). A prompting service which supplies such information is not a satisfactory solution. Activities of users at terminals and most application programs should remain unaffected when the internal representation of data is changed and even when some aspects of the external representation are changed. Changes in data representation will often be needed as a result of changes in query, update, and report traffic and natural growth in the types of stored information.Existing noninferential, formatted data systems provide users with tree-structured files or slightly more general network models of the data. In Section 1, inadequacies of these models are discussed. A model based on n-ary relations, a normal form for data base relations, and the concept of a universal data sublanguage are introduced. In Section 2, certain operations on relations (other than logical inference) are discussed and applied to the problems of redundancy and consistency in the user's model.

Journal ArticleDOI
Stefan Heinze1, Jerry Tersoff1, Richard Martel1, Vincent Derycke1, Joerg Appenzeller1, Ph. Avouris1 
TL;DR: In this paper, the authors show that carbon nanotube transistors operate as unconventional Schottky barrier transistors, in which transistor action occurs primarily by varying the contact resistance rather than the channel conductance.
Abstract: We show that carbon nanotube transistors operate as unconventional "Schottky barrier transistors," in which transistor action occurs primarily by varying the contact resistance rather than the channel conductance. Transistor characteristics are calculated for both idealized and realistic geometries, and scaling behavior is demonstrated. Our results explain a variety of experimental observations, including the quite different effects of doping and adsorbed gases. The electrode geometry is shown to be crucial for good device performance.

Proceedings Article
01 Jan 2002
TL;DR: It is shown that a network with CONFIDANT and up to 60% of misbehaving nodes behaves almost as well as a benign network, in sharp contrast to a defenseless network.
Abstract: Mobile ad-hoc networking works properly only if the participating nodes cooperate in routing and forwarding. However, it may be advantageous for individual nodes not to cooperate. We propose a protocol, called CONFIDANT, for making misbehavior unattractive; it is based on selective altruism and utilitarianism. It aims at detecting and isolating misbehaving nodes, thus making it unattractive to deny cooperation. Trust relationships and routing decisions are based on experienced, observed, or reported routing and forwarding behavior of other nodes. The detailed implementation of CONFIDANT in this paper assumes that the network layer is based on the Dynamic Source Routing (DSR) protocol. We present a performance analysis of DSR fortified by CONFIDANT and compare it to regular defenseless DSR. It shows that a network with CONFIDANT and up to 60% of misbehaving nodes behaves almost as well as a benign network, in sharp contrast to a defenseless network. All simulations have been implemented and performed in GloMoSim.

Journal ArticleDOI
Ricardo Vilalta1, Youssef Drissi1
TL;DR: This paper provides its own perspective view in which the goal is to build self-adaptive learners that improve their bias dynamically through experience by accumulating meta-knowledge, and provides a survey of meta-learning as reported by the machine-learning literature.
Abstract: Different researchers hold different views of what the term meta-learning exactly means. The first part of this paper provides our own perspective view in which the goal is to build self-adaptive learners (i.e. learning algorithms that improve their bias dynamically through experience by accumulating meta-knowledge). The second part provides a survey of meta-learning as reported by the machine-learning literature. We find that, despite different views and research lines, a question remains constant: how can we exploit knowledge about learning (i.e. meta-knowledge) to improve the performance of learning algorithms? Clearly the answer to this question is key to the advancement of the field and continues being the subject of intensive research.

Journal ArticleDOI
24 Jan 2002
TL;DR: Deep Blue as discussed by the authors is the chess machine that defeated then-reigning World Chess Champion Garry Kasparov in a six-game match in 1997 and won the first World Chess Championship.
Abstract: Deep Blue is the chess machine that defeated then-reigning World Chess Champion Garry Kasparov in a six-game match in 1997. There were a number of factors that contributed to this success, including: a single-chip chess search engine, a massively parallel system with multiple levels of parallelism, a strong emphasis on search extensions, a complex evaluation function, and effective use of a Grandmaster game database. This paper describes the Deep Blue system, and gives some of the rationale that went into the design decision behind Deep Blue. Copyright 2001 Elsevier B.V.

01 Jan 2002
TL;DR: The TESLA (Timed Efficient Stream Loss-tolerant Authentication) broadcast authentication protocol is presented, an efficient protocol with low communication and computation overhead, which scales to large numbers of receivers, and tolerates packet loss.
Abstract: One of the main challenges of securing broadcast communication is source authentication, or enabling receivers of broadcast data to verify that the received data really originates from the claimed source and was not modified en route. This problem is complicated by mutually untrusted receivers and unreliable communication environments where the sender does not retransmit lost packets. This article presents the TESLA (Timed Efficient Stream Loss-tolerant Authentication) broadcast authentication protocol, an efficient protocol with low communication and computation overhead, which scales to large numbers of receivers, and tolerates packet loss. TESLA is based on loose time synchronization between the sender and the receivers. Despite using purely symmetric cryptographic functions (MAC functions), TESLA achieves asymmetric properties. We discuss a PKI application based purely on TESLA, assuming that all network nodes are loosely time synchronized.

Journal ArticleDOI
Phaedon Avouris1
TL;DR: In this article, the authors review the electrical properties of carbon nanotubes, and then focus on carbon Nanotube field effect transistors (CNTFETs) and compare their electrical properties with those of Si MOSFETs.
Abstract: Carbon nanotubes have unique properties that make them a most promising system on which to base molecular electronics. We briefly review the electrical characteristics of carbon nanotubes, and then focus on carbon nanotube field-effect transistors (CNTFETs). Procedures by which hole-transport, electron-transport and ambipolar CNTFETs can be fabricated are presented, and their electrical characteristics are discussed and compared with those of Si MOSFETs. Ways to fabricate arrays of CNTFETs are also demonstrated, and electron and hole CNTFETs are integrated to form complementary logic circuits.

BookDOI
Michael Muller1
01 Jan 2002
TL;DR: In this paper, the authors propose to add users and stir participants in participatory design, which is based on the idea of Just Add Users and Stir (Just-Add-Users and Stir).
Abstract: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166Just Add Users and Stir? . . . . . . . . . . . . . . . . . . . . . . . . . .166Major Bibliographic Sources for Participatory Design . . .167

Proceedings ArticleDOI
23 Jul 2002
TL;DR: A class of randomization operators are proposed that are much more effective than uniform randomization in limiting the breaches of privacy breaches and derived formulae for an unbiased support estimator and its variance are derived.
Abstract: We present a framework for mining association rules from transactions consisting of categorical items where the data has been randomized to preserve privacy of individual transactions. While it is feasible to recover association rules and preserve privacy using a straightforward "uniform" randomization, the discovered rules can unfortunately be exploited to find privacy breaches. We analyze the nature of privacy breaches and propose a class of randomization operators that are much more effective than uniform randomization in limiting the breaches. We derive formulae for an unbiased support estimator and its variance, which allow us to recover itemset supports from randomized datasets, and show how to incorporate these formulae into mining algorithms. Finally, we present experimental results that validate the algorithm by applying it on real datasets.

Posted Content
TL;DR: This article used machine learning techniques such as Naive Bayes, maximum entropy classification, and support vector machines (SVM) for sentiment classification of movie reviews, and found that SVM outperformed human-produced baselines.
Abstract: We consider the problem of classifying documents not by topic, but by overall sentiment, e.g., determining whether a review is positive or negative. Using movie reviews as data, we find that standard machine learning techniques definitively outperform human-produced baselines. However, the three machine learning methods we employed (Naive Bayes, maximum entropy classification, and support vector machines) do not perform as well on sentiment classification as on traditional topic-based categorization. We conclude by examining factors that make the sentiment classification problem more challenging.

Journal ArticleDOI
08 Aug 2002-Nature
TL;DR: The implementation of a computer-controlled aberration correction system in a scanning transmission electron microscope, which is less sensitive to chromatic aberration, is reported here and allows dynamic imaging of single atoms, clusters of a few atoms, and single atomic layer ‘rafts' of atoms coexisting with Au islands on a carbon substrate.
Abstract: Following the invention of electron optics during the 1930s, lens aberrations have limited the achievable spatial resolution to about 50 times the wavelength of the imaging electrons. This situation is similar to that faced by Leeuwenhoek in the seventeenth century, whose work to improve the quality of glass lenses led directly to his discovery of the ubiquitous "animalcules" in canal water, the first hints of the cellular basis of life. The electron optical aberration problem was well understood from the start, but more than 60 years elapsed before a practical correction scheme for electron microscopy was demonstrated, and even then the remaining chromatic aberrations still limited the resolution. We report here the implementation of a computer-controlled aberration correction system in a scanning transmission electron microscope, which is less sensitive to chromatic aberration. Using this approach, we achieve an electron probe smaller than 1 A. This performance, about 20 times the electron wavelength at 120 keV energy, allows dynamic imaging of single atoms, clusters of a few atoms, and single atomic layer 'rafts' of atoms coexisting with Au islands on a carbon substrate. This technique should also allow atomic column imaging of semiconductors, for detection of single dopant atoms, using an electron beam with energy below the damage threshold for silicon.

Journal ArticleDOI
31 Oct 2002-Nature
TL;DR: It is shown that a single hydrogen molecule can form a stable bridge between platinum electrodes, and represents a simple test system in which to understand fundamental transport properties of single-molecule devices.
Abstract: Recent years have shown steady progress towards molecular electronics, in which molecules form basic components such as switches, diodes and electronic mixers. Often, a scanning tunnelling microscope is used to address an individual molecule, although this arrangement does not provide long-term stability. Therefore, metal-molecule-metal links using break-junction devices have also been explored; however, it is difficult to establish unambiguously that a single molecule forms the contact. Here we show that a single hydrogen molecule can form a stable bridge between platinum electrodes. In contrast to results for organic molecules, the bridge has a nearly perfect conductance of one quantum unit, carried by a single channel. The hydrogen bridge represents a simple test system in which to understand fundamental transport properties of single-molecule devices.

Journal ArticleDOI
TL;DR: In this paper, a new scanning-probe-based data-storage concept called the "millipede" is presented, which combines ultrahigh density, terabit capacity, small form factor, and high data rate.
Abstract: Present a new scanning-probe-based data-storage concept called the "millipede" that combines ultrahigh density, terabit capacity, small form factor, and high data rate. Ultrahigh storage density has been demonstrated by a new thermomechanical local-probe technique to store, read back, and erase data in very thin polymer films. With this new technique, nanometer-sized bit indentations and pitch sizes have been made by a single cantilever/tip into thin polymer layers, resulting in a data storage densities of up to 1 Tb/in/sup 2/. High data rates are achieved by parallel operation of large two-dimensional (2-D) atomic force microscope (AFM) arrays that have been batch-fabricated by silicon surface-micromachining techniques. The very large-scale integration (VLSI) of micro/nanomechanical devices (cantilevers/tips) on a single chip leads to the largest and densest 2-D array of 32/spl times/32 (1024) AFM cantilevers with integrated write/read/erase storage functionality ever built. Time-multiplexed electronics control the functional storage cycles for parallel operation of the millipede array chip. Initial areal densities of 100-200 Gb/in/sup 2/ have been achieved with the 32/spl times/32 array chip.

Patent
Stephane H. Maes1
21 Mar 2002
TL;DR: In this article, a system and method for implementing conversational protocols for distributed conversational networking architectures and/or distributed conversations, as well as real-time conversational computing between network-connected pervasive computing devices and servers over a computer network is described.
Abstract: A system and method for implementing conversational protocols for distributed conversational networking architectures and/or distributed conversational applications, as well as real-time conversational computing between network-connected pervasive computing devices and/or servers over a computer network. The implementation of distributed conversational systems/applications according to the present invention is based, in part, on a suitably defined conversational coding, transport and control protocols. The control protocols include session control protocols, protocols for exchanging of speech meta-information, and speech engine remote control protocols.