bluuebunny/crossref_metadata_2025 huggingface dataset:
Notes on the constructions of rational approximations for the error function and for similar functions
Authors: Clendenin W. W.
Published: July 2002

This note describes a rational approximation for the error function which has been found useful in a subroutine as an asymptotic expression of improved accuracy. While the method of the approximation is along well-established lines [1, 2, 3, 4] a brief description may be of interest since the feasibility of a simplified means of determining the basic coefficients is shown for the error function, and this technique may be useful in other cases.
An algorithm defining ALGOL assignment statements
Authors: Floyd Robert W.
Published: July 2002

It is not possible, by testing symbol pairs only [2], to determine whether a given symbol string is consistent with the formation rules of ALGOL [1]. For example, the formula
l
1:
l
2: x[i := 5j + 3.14.159; violates four distinct formation rules of ALGOL, yet each pair of adjacent characters may appear in permissible formulae. The algorithm described here will determine, with minor restrictions, whether a particular symbol string is a permissible ALGOL assignment statement. I believe that the same technique may be extended to determine whether a given symbol string is a permissible ALGOL program or not, where a program is defined as a sequence of permissible statements separated by semicolons. The algorithm scans the formula from left to right, replacing certain character pairs by single characters. If under the allowable transformations the symbol string may be reduced to the single character Σ, it is a well-formed formula in ALGOL; otherwise it violates the formation rules.
Survey of punched card codes
Authors: Smith H. J. , Williams F. A.
Published: July 2002

The “Survey of Coded Character Representation” by R. W. Bemer (p. 639) covers the representation of symbols in paper tape, magnetic tape and main storage of a number of different machine systems. Another method of mechanical storage is the punched card. The results of a similar survey for punched card codes are shown in the table on page 642.
Variable width stacks
Authors: Rotenberg Naomi , Opler Ascher
Published: July 2002

Character addressable, variable field computers permit ready establishment and manipulation of variable width stacks. Single machine commands may push variable field items down into such stacks or pop them up. The availability of a variety of field delimiters allows the machine to push down or pop up more than one variable width item with one command. Since these stacking operations can be made the basis of compiler decoding algorithms, the proper use of machines of this class for compilation has advantages over machines with fixed-length words.
Current status of IPL-V for the Philco 2000 computer (June 1962)
Authors: Shaffer Stuart S.
Published: July 2002

The initial version of IPL-V for the Philco 2000 has been completed and is now operating on the computer. This model, IPLT-1, contains the loader, interpreter, output, housekeeping functions, and some of the primitives of the 7090 version.

This system was written mainly in JOVIAL, a procedure-oriented language, and was compiled to produce a Philco TAC binary operating deck. Certain portions were written in Philco TAC language to speed up the operation of the system during execution and to facilitate handling of primitives which in JOVIAL would have been uneconomical. These assembly-language coded sections constitute less than 3 percent of the system.

The present model assembles IPL program cards at the rate of 500 per minute in the listing mode. This compares favorably with the 7090 model, since System Development Corporation's configuration of the Philco computer operates at approximately one-fifth the speed of the 7090. Interpretation time also compares favorably with the 7090 model taking into account the difference in speeds of the two computers. The package of J primitives produced by H. A. Simon is being used and assembled with the IPL program. With listing suppressed, assembly time of these routines is only a few seconds. Input to the Philco 2000 is by card, and the system operates as a program executed in phase three of the SL Philco operating system. The J165, J166 dump and reload features are working, and this technique can be used to save an assembled IPL program on tape for later use. Unused region assignments are not returned to available space; therefore additional routines may be added with new data for reload and run from a dump tape. However, card input is extremely fast (2000 cards per minute) and normal operating procedure at SDC is card input.
TALL—a list processor for the Philco 2000 computer
Authors: Feldman Julian
Published: July 2002

Several of the computer languages that are oriented toward problems in symbol manipulation use a list type of memory organization.
1
The advantages of such a memory organization have been discussed elsewhere and will not be repeated here. The purpose of this note is to describe the method used in realizing a list language on the Philco 2000.

Information Processing Language V (IPL-V) was chosen as the source language for the list processor for the 2000 because this language has been well documented and has been implemented on several computers.
2
Heretofore, IPL-V has been implemented as an interpretive system. The interpretive system has three major components: (1) a loader which translates card images into internal machine words; (2) an interpreter which decodes instructions; and (3) a set of primitive processes, the “J's,” which make up the bulk of the instruction vocabulary. The implementation of such an interpretive system has been a rather lengthy procedure usually estimated as taking six man-months.
Performance-constrained hierarchical pipelining for behaviors, loops, and operations
Authors: Bakshi Smita , Gajski Daniel D.
Published: July 2002

Behavioral specifications of DSP systems generally contain a number of nested loops. In order to obtain high date rates for such systems, it is necessary to pipeline the system within the behavior, within the loop bodies, and also within the operations. In order to hierarchically pipeline a performance-constrained system, an important step consists of distributing the performance constraint among the loops in such a manner that the constraint is satisfied and design cost is minimized. This paper presents an algorithm for propagating constraints and hierarchically pipelining a given throughput-constrained system. Along with pipelining, the algorithm schedules the operations within the loop bodies and selects components for them, with the aim of minimizing cost while satisfying the constraint propagated to the loop body. Results demonstrate the necessity of pipelining across the three granularity levels in order to obtain high performance designs. They also demonstrate the feasibility and quality of our approach, the indicate that it may be efficiently used for synthesizing or estimating within system-level design.
A variational method to model
G
1
surfaces over triangular meshes of arbitrary topology in
R
3
Authors: Sarraga Ramon F.
Published: July 2002

This article presents a method for constructing a
G
1
-smooth surface, composed of independently parametrized triangular polynomial Bézier patches, to fit scattered data points triangulated in
R
3
with arbitrary topology. The method includes a variational technique to optimize the shape of the surface. A systematic development of the method is given, presenting general equations provided by the theory of manifolds, explaining the heuristic assumptions made to simplify calculations, and analyzing the numerical results obtained from fitting two test configurations of scattered data points. The goal of this work is to explore an alternative
G
3
construction, inspired by the theory of manifolds, that is subject to fewer application constraints than approaches found in the technical literature; e.g., this approach imposes no artificial restrictions on the tangents of patch boundary curves at vertex points of a
G
1
surface. The constructed surface shapes fit all test data surprisingly well for for a noniterative method based on polynomial patches.
Editorial
Authors: Apt Krzysztof R. , Kakas Antonis C. , Sadri Fariba
Published: July 2002

This special issue of the ACM Transactions on Computational Logic (TOCL) is dedicated to Robert A. Kowalski, or as he is better known, to Bob Kowalski, on the occasion of his 60th birthday. Throughout his distinguished research career Bob has been interested in various forms of logic-based reasoning from the computer science point of view. This novel view of logic has had an impact on a number of areas, including programming languages, databases, artificial intelligence, natural language processing, and more recently machine learning.

In the late sixties and early seventies Bob contributed to the development of the theory of resolution by proposing a number of modifications to the original proposal of Alan Robinson. One of the notions that withstood the test of time is his and Hayes concept of semantic trees. This research eventually led him to the seminal 1974 paper Predicate Logic as a Programming Language which is at the roots of the logic programming paradigm.

His early work with Maarten van Emden provided a direction for the subsequent research on procedural and declarative semantics of programming languages within the specific field of logic programming. In turn, his influential dictum "Algorithm+Logic=Control" has shaped our views on the essence of declarative programming within the logic programming framework and has had a large impact on the design of new control mechanisms for this approach to programming. His subsequent research revealed the rich potential of the logic programming paradigm. He showed how legal, metalevel, and commonsense reasoning can naturally be formalized by means of logic programs.

His work with Marek Sergot on the event calculus had a long-standing impact on the research effort of representing temporal knowledge and formalizing commonsense reasoning. His research on verification of integrity constraints for database systems became highly relevant in deductive and temporal databases, while his work on abductive reasoning and argumentation was influential for mechanized legal and diagnostic reasoning. More recently, his work on multiagent systems has helped shape new approaches to building intelligent distributed systems.

Several of these themes can be found in the collection of papers that constitute this special issue. All of these papers were solicited directly by the guest editors but, conforming to the high standards of TOCL, went through the usual rigorous refereeing process.

We would like to thank the authors of the contributed papers for their willingness and interest in contributing to this issue. We also thank the referees for their precious time in providing helpful reviews of the submissions.

And to Bob we extend our best wishes and hope he will agree with us that
this special issue shows, at least partly, the long-term impact of his research.
Structuring computer-mediated communication systems to avoid information overload
Authors: Hiltz Starr R. , Turoff Murray
Published: July 2002

Unless computer-mediated communication systems are structured, users will be overloaded with information. But structure should be imposed by individuals and user groups according to their needs and abilities, rather than through general software features.
Report on the microelectronics and computer technology corporation conference
Authors: Frenkel Karen A.
Published: July 2002

MCC, the consortium of companies headed by Admiral B. R. Inman, that some consider America's reply to Japan's Fifth Generation initiative, invited members and nonmembers to brainstorm on software design. Also on the agenda was the announcement of LEONARDO, MCC's software research project.
Computing Poisson probabilities
Authors: Fox Bennett L. , Glynn Peter W.
Published: July 2002

We propose an algorithm to compute the set of individual (nonnegligible) Poisson probabilities, rigorously bound truncation error, and guarantee no overflow or underflow. Work and space requirements are modest, both proportional to the square root of the Poisson parameter. Our algorithm appears numerically stable. We know no other algorithm with all these (good) features. Our algorithm speeds generation of truncated Poisson variates and the computation of expected terminal reward in continuous-time, uniformizable Markov chains. More generally, our algorithm can be used to evaluate formulas involving Poisson probabilities.
Remarks on implementation of
O
(
n
1/2
τ) assignment algorithms
Authors: Duff Iain S. , Wiberg Torbjörn
Published: July 2002

We examine an implementation and a number of modifications of a 1973 algorithm of Hopcroft and Karp for permuting a sparse matrix so that there are no zeros on the diagonal. We describe our implementation of the original Hopcroft and Karp algorithm and compare this with modifications which we prove to have the same
O
(
n
1/2
τ) behavior, where the matrix is of order
n
with τ entries. We compare the best of these with an efficient implementation of an algorithm whose worst-case behavior is
O
(
nτ
).
Toward Virtual Marketplaces for E-Commerce Support
Authors: Maamar Zakaria , Dorion Eric , Daigle Catherine
Published: July 2002

Using advanced technologies to support both sellers and buyers.
Aligning internet usage with business priorities
Authors: Simmers Claire A.
Published: July 2002

Regulating Internet activities so that targeted outcomes remain within acceptable limits.
Metaphors and user interfaces in the 21st Century
Authors: Marcus Aaron
Published: July 2002

"Fast Forward" is a new column that the editors of
interactions
have kindly permitted me to write. It presents an opportunity for me to think about where our profession of user-interface design has been over the past three-and-a-half decades in which I have worked and about its future. I hope you will enjoy and benefit from joining me in this discussion. Your feedback is welcome.
AM+A
Authors: Chen Eugene
Published: July 2002

AM+A
provides user interface design, usability, and strategy services. With design offices on the East and West coasts, AM+A brings 20 years of experience in thorough analysis to provide tailored, flexible design solutions. Our clients' products range from information-rich applications for the professional to everyday innovations for the home, car, and handheld device.
SWIM
Authors: Salomon Gitta , Ward Jason , Liao Tzufen
Published: July 2002

Founded in 1996 and based in San Francisco,
Swim
is an interaction design consultancy. It assists clients with all phases of interactive product development, from product definition through final art. Swim projects include Web and client applications, interactive handheld devices, and medical products. Clients include startups and well-established companies, addressing both consumer and enterprise needs.
Teaching the Nintendo generation to program
Authors: Guzdial Mark , Soloway Elliot
Published: July 2002

Preparing a new strategy for teaching introductory computer programming.
The relationship between benchmark tests and microcomputer price
Authors: Sircar Sumit , Dave Dinesh
Published: July 2002

A highly accurate model predicts microcomputer price based on benchmark performance by analyzing the impact on predicted price of fluctuations in system configuration and benchmark results.
Toward the perfect workplace?
Authors: Bailyn L.
Published: July 2002

The experience of home-based systems developers is compared with their office-based counterparts in a UK computer firm. The analysis produced two major patterns: the home-based workers find intrinsic value in the job, whereas office-based employees view it more instrumentally and find it interferes with satisfaction on a personal level.
Computer hardware performance: production and cost function analyses
Authors: Kang Y. M.
Published: July 2002

Based on microeconomics, computer hardware performance is analyzed using two methods. For the cost function analysis, both purchase and lease prices are used. The results show no economies of scale for the mainframes and superminis during the 1981-1985 period.
The next generation of interactive technologies
Authors: Frenkel Karen A.
Published: July 2002

From home entertainment to cultural exhibits to educational methodologies to personal computing, interactive technologies could change observers in to participants.
Chain mulitplication of matrices of approximately or exactly the same size
Authors: Santoro Nicola
Published: July 2002

We present a different approach to finding an optimal computation order; it exploits both the difference between the size of the matrices and the difference between the number of nonzero elements in the matrices. Therefore, this technique can be usefully applied where the matrices are almost or exactly the same size. We show that using the proposed technique, an optimal computation order can be determined in time O
(
n
)
if the matrices have the same size, and in time O
(

n
3

)
otherwise.
Polychannel systems for mass digital communications
Authors: Gifford David K.
Published: July 2002

A new type of distributed computer system looks toward the time when computers will be used by everyone everywhere.
Polynomial evaluation with scaling
Authors: Hansen Eldon R. , Patrick Merrell L. , Wang Richard L. C.
Published: July 2002

To overcome difficulties in polynomial evaluation caused by overflow or unnecessary underflow, we introduce a simple scaling procedure into Horner's method.
A butterfly subdivision scheme for surface interpolation with tension control
Authors: Dyn Nira , Levine David , Gregory John A.
Published: July 2002

A new interpolatory subdivision scheme for surface design is presented. The new scheme is designed for a general triangulation of control points and has a tension parameter that provides design flexibility. The resulting limit surface is
C
1
for a specified range of the tension parameter, with a few exceptions. Application of the butterfly scheme and the role of the tension parameter are demonstrated by several examples.
Evaluation of safety-critical software
Authors: Parnas David L. , van Schouwen A. John , Kwan Shu Po
Published: July 2002

Methods and approaches for testing the reliability and trustworthiness of software remain among the most controversial issues facing this age of high technology. The authors present some of the crucial questions faced by software programmers and eventual users.
Distributed file systems: concepts and examples
Authors: Levy Eliezer , Silberschatz Abraham
Published: July 2002

The purpose of a distributed file system (DFS) is to allow users of physically distributed computers to share data and storage resources by using a common file system. A typical configuration for a DFS is a collection of workstations and mainframes connected by a local area network (LAN). A DFS is implemented as part of the operating system of each of the connected computers. This paper establishes a viewpoint that emphasizes the dispersed structure and decentralization of both data and control in the design of such systems. It defines the concepts of transparency, fault tolerance, and scalability and discusses them in the context of DFSs. The paper claims that the principle of distributed operation is fundamental for a fault tolerant and scalable DFS design. It also presents alternatives for the semantics of sharing and methods for providing access to remote files. A survey of contemporary UNIX-based systems, namely, UNIX United, Locus, Sprite, Sun's Network File System, and ITC's Andrew, illustrates the concepts and demonstrates various implementations and design alternatives. Based on the assessment of these systems, the paper makes the point that a departure from the extending centralized file systems over a communication network is necessary to accomplish sound distributed file system design.
PHYSIOLOGY AND ECOLOGY OF DISPERSAL POLYMORPHISM IN INSECTS
Authors: Zera Anthony J. , Denno Robert F.
Published: July 2002

▪ Abstract  Studies of dispersal polymorphism in insects have played a pivotal role in advancing our understanding of population dynamics, life history evolution, and the physiological basis of adaptation. Comparative data on wing-dimorphic insects provide the most definitive evidence to date that habitat persistence selects for reduced dispersal capability. The increased fecundity of flightless females documents that a fitness trade-off exists between flight capability and reproduction. However, only recently have studies of nutrient consumption and allocation provided unequivocal evidence that this fitness trade-off results from a trade-off of internal resources. Recent studies involving wing-dimorphic insects document that flight capability imposes reproductive penalties in males as well as females. Direct information on hormone titers and their regulation implicates juvenile hormone and ecdysone in the control of wing-morph determination. However, detailed information is available for only one species, and the physiological regulation of wing-morph production remains poorly understood. Establishing a link betweeen the ecological factors that influence dispersal and the proximate physiological mechanisms regulating dispersal ability in the same taxon remains as a key challenge for future research.
The French School of Genetics: From Physiological and Population Genetics to Regulatory Molecular Genetics
Authors: Burian RM , Gayon J
Published: July 2002

▪ Abstract  French genetics had unusual beginnings. There are clear indications that the French biological establishment resisted Mendelian genetics strenuously from about 1910 to 1940. From about 1930 to 1950 several unconventional research programs with a strongly physiological orientation paved the way for the full entrance of French biology into genetics after World War II. This review examines some salient features of this history to clarify the strengths, weaknesses, and distinctive features of French genetics until about 1965. We suggest that after that date French genetics slowly merged into the international mainstream as genetics has become a largely molecular discipline.
BCL-2 FAMILY: Regulators of Cell Death
Authors: Chao Debra T. , Korsmeyer Stanley J.
Published: July 2002

▪ Abstract  An expanding family of BCL-2 related proteins share homology, clustered within four conserved regions, namely BCL-2 homology (BH1-4) domains, which control the ability of these proteins to dimerize and function as regulators of apoptosis. Moreover, BCL-XL, BCL-2, and BAX can form ion-conductive pores in artificial membranes. The BCL-2 family, comprised of both pro-apoptotic and anti-apoptotic members, acts as a checkpoint upstream of CASPASES and mitochondrial dysfunction. BID and BAD possess the minimal death domain BH3, and the phosphorylation of BAD connects proximal survival signals to the BCL-2 family. BCL-2 and BCL-XLdisplay a reciprocal pattern of expression during lymphocyte development. Gain- and loss-of-function models revealed stage-specific roles for BCL-2 and BCL-XL. BCL-2 can rescue maturation at several points of lymphocyte development. The BCL-2 family also reveals evidence for a cell-autonomous coordination between the opposing pathways of proliferation and cell death.
LAYERED CERAMICS: Processing and Mechanical Behavior
Authors: Chan Helen M.
Published: July 2002

▪ Abstract  Recent progress in the field of mechanical behavior of layered ceramics is reviewed. Several processing techniques are described with reference to the fabrication of ceramic laminates. These include tape-casting, centrifugal casting, slip-casting, electrophoretic deposition (EPD), and the production of fibrous monolith materials. The review discusses various laminar design approaches for achieving improvements in strength, toughness, work of fracture, R-Curve behavior, and contact damage resistance. Examples of effective strategies include manipulation of residual stresses, the incorporation of weak interlayers to induce crack deflection, and promotion of synergistic effects between layer materials that exhibit intrinsically different responses.
THE CHANGING FACE OF TUBERCULOSIS
Authors: Huebner, Ph.D., M.P.H Robin E. , Castro, M.D Kenneth G.
Published: July 2002

▪ Abstract  Tuberculosis (TB) remains an important public health problem worldwide, resulting in an estimated 8 to 10 million new cases and 2 to 3 million deaths each year. Between 1953 and 1985, the number of TB cases in the US declined by an average of 6% per year. However, since 1985, TB has been increasing in the US. Approximately 64,000 additional cases of the disease have been reported beyond the number expected had the rate of decline observed from 1980 to 1984 continued from 1985 through 1993. Increases in the number of TB cases have been significant in racial and ethnic minorities, in persons born outside the US, and in children less than 15 years of age. Infection with the human immunodeficiency virus (HIV) has also been recognized as a major risk factor for the development of active TB in persons with latent Mycobacterium tuberculosis infection. The unusual radiographic findings and the increased likelihood of extrapulmonary TB in HIV-infected persons make diagnosis of the disease problematic. Lastly, concomitant with the resurgence of TB has been the emergence of drug resistance. All of these factors make successful control of TB in the US difficult.
AUTOIMMUNITY AND NEUROLOGICAL DISEASE: Antibody Modulation of Synaptic Transmission
Authors: Whitney K. D. , McNamara J. O.
Published: July 2002

▪ Abstract  Over the past three decades, compelling evidence has emerged that the immune system can attack the nervous system with devastating consequences for human health. Either cell-mediated or humoral (antibody-mediated) autoimmune mechanisms may predominate in effecting a given disease, and either glia or neurons may fall under immune attack. A subset of these diseases has been particularly useful for understanding fundamental neuroscience as well as mechanisms of human disease. This subset involves humoral autoimmune attack on cell surface molecules subserving transmembrane signaling of excitable cells; special emphasis is placed here on proteins involved in synaptic transmission. We begin by reviewing the prototypic humoral autoimmune disease of synaptic transmission, myasthenia gravis. This provides a context for insights obtained from the study of diseases targeting molecules that regulate synaptic transmission at the neuromuscular junction and in the central nervous system. We also explore a disease where autoimmunity produces agonist antibodies acting at two distinct G-protein-coupled receptors. We conclude with an exploration of the vital issue of access of antibodies to targets within the central nervous system and the implications that such access may have in the pathogenesis of poorly understood idiopathic central nervous system diseases.
NEURAL SELECTION AND CONTROL OF VISUALLY GUIDED EYE MOVEMENTS
Authors: Schall Jeffrey D. , Thompson Kirk G.
Published: July 2002

▪ Abstract  We review neural correlates of perceptual and motor decisions, examining whether the time they occupy explains the duration and variability of behavioral reaction times. The location of a salient target is identified through a spatiotemporal evolution of visually evoked activation throughout the visual system. Selection of the target leads to stochastic growth of movement-related activity toward a fixed threshold to generate the gaze shift. For a given image, the neural concomitants of perceptual processing occupy a relatively constant interval so that stochastic variability in response generation introduces additional variability in reaction times.
Problems for Judgment and Decision Making
Authors: Hastie R.
Published: July 2002

▪ Abstract  This review examines recent developments during the past 5 years in the field of judgment and decision making, written in the form of a list of 16 research problems. Many of the problems involve natural extensions of traditional, originally rational, theories of decision making. Others are derived from descriptive algebraic modeling approaches or from recent developments in cognitive psychology and cognitive neuroscience.

“Wir müssen wissen. Wir werden wissen.” (We must know. We will know.) David Hilbert, Mathematische Probleme ( 1900 )
A RETROSPECTIVE ON THE CIVIL RIGHTS MOVEMENT: Political and Intellectual Landmarks
Authors: Morris Aldon D.
Published: July 2002

▪ Abstract  This review provides an analysis of the political and intellectual contributions made by the modern civil rights movement. It argues that the civil rights movement was able to overthrow the Southern Jim Crow regime because of its successful use of mass nonviolent direct action. Because of its effectiveness and visibility, it served as a model that has been utilized by other movements both domestically and internationally. Prior to the civil rights movement social movement scholars formulated collective behavior and related theories to explain social movement phenomena. These theories argued that movements were spontaneous, non-rational, and unstructured. Resource mobilization and political process theories reconceptualized movements stressing their organized, rational, institutional and political features. The civil rights movement played a key role in generating this paradigmatic shift because of its rich empirical base that led scholars to rethink social movement phenomena.
Urban Poverty afterThe Truly Disadvantaged: The Rediscovery of the Family, the Neighborhood, and Culture
Authors: Small Mario Luis , Newman Katherine
Published: July 2002

▪ Abstract  In what follows we critically assess a selection of the works on urban poverty that followed the publication of WJ Wilson's The Truly Disadvantaged ( 1987 ), with a particular focus on the family, the neighborhood, and culture. We frame our discussion by assessing the broad explanations of the increased concentration of poverty in urban neighborhoods characteristic of the 1970s and 1980s. Then, in the section on the family, we address the rising out-of-wedlock and disproportionately high teenage birthrates of poor urban women. Next, we critique the literature on neighborhood effects. Finally, in the discussion of culture, we examine critically the new efforts at complementing structural explanations with cultural accounts. We conclude by calling for more comparative, cross-regional, and historical studies, broader conceptions of urban poverty, and a greater focus on Latinos and other ethnic groups.
Perverse Institutionalism: NATO and the Greco-Turkish Conflict
Authors: Krebs Ronald R.
Published: July 2002

Last year the U.S. Senate overwhelmingly approved the expansion of the Atlantic alliance. Whereas some advocates of enlarging NATO, particularly Eastern European leaders for whom the Soviets' iron grip is an all too recent memory, stress the extension of the alliance's traditional deterrent function, others acknowledge that Russia is in no position to reconquer its former empire. Rather, they argue that membership in NATO would stabilize the region by filling the power vacuum and eliminating the need for security competition. Traditionally a volatile area, East-Central Europe is rife with potential irredentist and ethnic conflicts, and NATO can help arbitrate and limit these disputes. Critics have denounced the move as unnecessarily provocative to Russia, and they have also decried its hefty cost. But they have not challenged the claim that alliances create zones of peace.
SBART 2.4: An IEC Tool for Creating Two-Dimensional Images, Movies and Collages
Authors: Unemi Tatsuo
Published: July 2002

In this article, the author gives an overview of SBART 2.4, an interactive system used to create abstract two-dimensional images, collages and movies. The system, one of the successors of Karl Sims's system, runs on a small computer that uses a function to calculate the color value of each pixel as a genotype. All of the ranges and domains are three-dimensional vectors. The system utilizes a multi-field user interface to enhance the diversity of production and has optional facilities that allow the creation of collages of external images or short movies.
Is One Eye Better Than Two When Viewing Pictorial Art?
Authors: Ciuffreda Kenneth J. , Engber Kimberly
Published: July 2002

During viewing of most objects in one's everyday environment, the binocular and monocular relative depth cues interact in a harmonious, concordant and reinforcing manner to provide perceptual stability. However, when one views pictorial art, these binocular and monocular cues are discordant, and thus a perceptual “cue conflict” arises. This acts to reduce the relative apparent perceived distance of objects in a painting, thus producing overall perceptual depth “flattening.” The theory and physiology underlying this phenomenon are discussed.
Automatic Verb Classification Based on Statistical Distributions of Argument Structure
Authors: Merlo Paola , Stevenson Suzanne
Published: July 2002

Automatic acquisition of lexical knowledge is critical to a wide range of natural language processing tasks. Especially important is knowledge about verbs, which are the primary source of relational information in a sentence-the predicate-argument structure that relates an action or state to its participants (i.e., who did what to whom). In this work, we report on supervised learning experiments to automatically classify three major types of English verbs, based on their argument structure-specifically, the thematic roles they assign to participants. We use linguistically-motivated statistical indicators extracted from large annotated corpora to train the classifier, achieving 69.8% accuracy for a task whose baseline is 34%, and whose expert-based upper bound we calculate at 86.5%. A detailed analysis of the performance of the algorithm and of its errors confirms that the proposed features capture properties related to the argument structure of the verbs. Our results validate our hypotheses that knowledge about thematic relations is crucial for verb classification, and that it can be gleaned from a corpus by automatic means. We thus demonstrate an effective combination of deeper linguistic knowledge with the robustness and scalability of statistical techniques.
Involuntary Motor Activity in Pianists Evoked by Music Perception
Authors: Haueisen Jens , Knösche Thomas R.
Published: July 2002

Pianists often report that pure listening to a well-trained piece of music can involuntarily trigger the respective finger movements. We designed a magnetoencephalography (MEG) experiment to compare the motor activation in pianists and nonpianists while listening to piano pieces. For pianists, we found a statistically significant increase of activity above the region of the contralateral motor cortex. Brain surface current density (BSCD) reconstructions revealed a spatial dissociation of this activity between notes preferably played by the thumb and the little finger according to the motor homunculus. Hence, we could demonstrate that pianists, when listening to well-trained piano music, exhibit involuntary motor activity involving the contralateral primary motor cortex (M1).
A Model of Saccade Initiation Based on the Competitive Integration of Exogenous and Endogenous Signals in the Superior Colliculus
Authors: Trappenberg Thomas P. , Dorris Michael C. , Munoz Douglas P. , Klein Raymond M.
Published: July 2002

Significant advances in cognitive neuroscience can be achieved by combining techniques used to measure behavior and brain activity with neural modeling. Here we apply this approach to the initiation of rapid eye movements (saccades), which are used to redirect the visual axis to targets of interest. It is well known that the superior colliculus (SC) in the midbrain plays a major role in generating saccadic eye movements, and physiological studies have provided important knowledge of the activity pattern of neurons in this structure. Based on the observation that the SC receives localized sensory (exogenous) and voluntary (endogenous) inputs, our model assumes that this information is integrated by dynamic competition across local collicular interactions. The model accounts well for the effects upon saccadic reaction time (SRT) due to removal of fixation, the presence of distractors, execution of pro-versus antisaccades, and variation in target probability, and suggests a possible mechanism for the generation of express saccades. In each of these cases, the activity patterns of “neurons” within the model closely resemble actual cell behavior in the intermediate layer of the SC. The interaction structure we employ is instrumental for producing a physiologically faithful model and results in new insights and hypotheses regarding the neural mechanisms underlying saccade initiation.
Selectively Impaired Associative Learning in Older People with Cognitive Decline
Authors: Collie Alexander , Myers Catherine , Schnirman Geoffrey , Wood Stephen , Maruff Paul
Published: July 2002

Older people with declining cognitive function typically display deficits in declarative memory processes, often most evident on tests of associative learning (AL). The hippocampal formation (HF) is thought to be critically involved in the encoding and retrieval of such associations, consistent with neuroimaging findings that the HF is damaged in early stages of neurodegenerative disease and in older people with AL impairments. In the clinic, older people with cognitive decline commonly report difficulties associating names with faces. However, we have observed that such people are particularly impaired on tests requiring the association of novel stimuli. In Experiment 1, a series of AL tasks were administered to older people with cognitive decline to determine whether they were impaired at simply making associations, or at making associations between novel stimuli. In Experiment 2, we measured HF function in these subjects by administering an AL task designed to differentiate between HF-damaged and HF-intact individuals. Our experimental protocols were guided by a computational model of HF function in AL described by Gluck and Myers (1997). Older people with cognitive decline displayed impaired performance on tasks designed to be highly dependent upon intact HF function, including a task in which novel patterns and spatial locations were to be associated. These results suggest that the AL impairments observed in older people with cognitive decline may be due to HF dysfunction.
Neural Mechanisms of Global and Local Processing: A Combined PET and ERP Study
Authors: Heinze H. J. , Hinrichs H. , Scholz M. , Burchert W. , Mangun G. R.
Published: July 2002

The neural mechanisms of hierarchical stimulus processing were investigated using a combined event-related potentials (ERPs) and positron emission tomography (PET) approach. Healthy subjects were tested under two conditions that involved selective or divided attention between local and global levels of hierarchical letter stimuli in order to determine whether and where hemispheric differences might exist in the processing of local versus global information. When attention was divided between global and local levels, the N2 component of the ERPs (260- to 360-msec latency) elicited by the target stimuli showed asymmetries in amplitude over the two hemispheres. The N2 to local targets was larger over the left hemisphere, but the N2 to global targets tended to be slightly larger over the right hemisphere. However, the shorter-latency, sensory-evoked P1 component (90- to 150-msec latency) was not different for global versus local targets under conditions of divided attention. In contrast, during selective attention to either global or local targets, asymmetries in the N2 component were not observed. But under selective attention conditions, the sensory-evoked P1 components in the extrastriate cortex were enlarged for global versus local attention. In- creased regional cerebral blood flow in the posterior fusiform gyrus bilaterally was observed in the PET data during selective attention to either global or local targets, but neither these nor the P1 component showed any tendency toward hemispheric difference for global versus local attention. Neither were there any activations observed in the parietal lobe during selective attention to global versus local targets. Together these data indicate that early sensory inputs are not modulated to gate global versus local information differentially into the two hemi- spheres. Rather, later stages of processing that may be asym- metrically organized in the left and right hemispheres operate in parallel to process global and local aspects of complex stimuli (i.e., the N2 effect of the ERPs). This pattern of results supports models proposing that spatial frequency analysis is only asymmetric at higher stages of perceptual processing and not at the earliest stages of visual cortical analysis.
Accessory Stimulus Effects on Response Selection: Does Arousal Speed Decision Making?
Authors: Hackley Steven A. , Valle-Inclán Fernando
Published: July 2002

When an intense but task-irrelevant “accessory” stimulus accompanies the imperative stimulus in a choice reaction task, reaction times (RTs) are facilitated. In a similar previous study (Hackley & Valle-Inclán, 1998), we showed that this effect is not due to a reduction of the interval from onset of the lateralized readiness potential (LRP) until movement onset. In the present study, the RT task was modified to move a portion of the response selection stage into this time interval. The interval remained invariant, indicating that this late phase of the response selection process is not speeded by accessory stimulation. However, we observed amplitude modulation of the LRP on no-go trials in a condition with three alternative responses. This finding suggests that an earlier phase of response selection is influenced by accessory stimulation. In addition, a novel dependent measure was introduced to event-related potential research—the latency of spontaneous, posttrial blinking.
Statistical Signs of Common Inhibitory Feedback with Delay
Authors: Pauluis Quentin
Published: July 2002

Cross-correlation histograms (CCHs) sometimes exhibit an isolated central peak flanked by two troughs. What can cause this pattern? The absence of CCH satellite peak makes an oscillatory common input doubtful. It is here shown using a simple counting model that a common inhibitory feedback with delay can account for this pattern.
A Computational Model of Lateralization and Asymmetries in Cortical Maps
Authors: Levitan Svetlana , Reggia James A.
Published: July 2002

While recent experimental work has defined asymmetries and lateralization in left and right cortical maps, the mechanisms underlying these phenomena are currently not established. In order to explore some possible mechanisms in theory, we studied a neural model consisting of paired cerebral hemispheric regions interacting via a simulated corpus callosum. Starting with random synaptic strengths, unsupervised (Hebbian) synaptic modifications led to the emergence of a topographic map in one or both hemispheric regions. Because of uncertainties concerning the nature of hemispheric interactions, both excitatory and inhibitory callosal influences were examined independently. A sharp transition in model behavior was observed depending on callosal strength. For excitatory or weakly inhibitory callosal interactions, complete and symmetric mirror-image maps generally appeared in both hemispheric regions. In contrast, with stronger inhibitory callosal interactions, partial to complete map lateralization tended to occur, and the maps in each hemispheric region often became complementary. Lateralization occurred readily toward the side having a larger cortical region or higher excitability. Asymmetric synaptic plasticity, however, had only a transitory effect on lateralization. These results support the hypotheses that interhemispheric competition occurs, that multiple underlying asymmetries may lead to function lateralization, and that the effects of asymmetric synaptic plasticity may vary depending on whether supervised or unsupervised learning is involved. To our knowledge, this is the first computational model to demonstrate the emergence of topographic map lateralization and asymmetries.
Dynamics of Strongly Coupled Spiking Neurons
Authors: Bressloff Paul C. , Coombes S.
Published: July 2002

We present a dynamical theory of integrate-and-fire neurons with strong synaptic coupling. We show how phase-locked states that are stable in the weak coupling regime can destabilize as the coupling is increased, leading to states characterized by spatiotemporal variations in the interspike intervals (ISIs). The dynamics is compared with that of a corresponding network of analog neurons in which the outputs of the neurons are taken to be mean firing rates. A fundamental result is that for slow interactions, there is good agreement between the two models (on an appropriately defined timescale). Various examples of desynchronization in the strong coupling regime are presented. First, a globally coupled network of identical neurons with strong inhibitory coupling is shown to exhibit oscillator death in which some of the neurons suppress the activity of others. However, the stability of the synchronous state persists for very large networks and fast synapses. Second, an asymmetric network with a mixture of excitation and inhibition is shown to exhibit periodic bursting patterns. Finally, a one-dimensional network of neurons with long-range interactions is shown to desynchronize to a state with a spatially periodic pattern of mean firing rates across the network. This is modulated by deterministic fluctuations of the instantaneous firing rate whose size is an increasing function of the speed of synaptic response.
On the Phase-Space Dynamics of Systems of Spiking Neurons. II: Formal Analysis
Authors: Banerjee Arunava
Published: July 2002

We begin with a brief review of the abstract dynamical system that models systems of biological neurons, introduced in the original article. We then analyze the dynamics of the system. Formal analysis of local properties of flows reveals contraction, expansion, and folding in different sections of the phase-space. The criterion for the system, set up to model a typical neocortical column, to be sensitive to initial conditions is identified. Based on physiological parameters, we then deduce that periodic orbits in the region of the phase-space corresponding to normal operational conditions in the neocortex are almost surely (with probability 1) unstable, those in the region corresponding to seizure-like conditions are almost surely stable, and trajectories in the region corresponding to normal operational conditions are almost surely sensitive to initial conditions. Next, we present a procedure that isolates all basic sets, complex sets, and attractors incrementally. Based on the two sets of results, we conclude that chaotic attractors that are potentially anisotropic play a central role in the dynamics of such systems. Finally, we examine the impact of this result on the computational nature of neocortical neuronal systems.