bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing process-centered software engineering environments
Authors: Ambriola Vincenzo , Conradi Reidar , Fuggetta Alfonso
Published: July 2002

Process-centered software engineering environments (PSEEs) are the most recent generation of environments supporting software development activities. They exploit an representation of the process (called the
process model
that specifies how to carry out software development activities, the roles and tasks of software developers, and how to use and control software development tools. A process model is therefore a vehicle to better understand and communicate the process. If it is expressed in a formal notation, it can be used to support a variety of activities such as process analysis, process simulation, and process enactment. PSEEs provide automatic support for these activities. They exploit languages based on different paradigms, such as Petri nets and rule-based systems. They include facilities to edit and analyze process models. By enacting the process model, a PSEE provides a variety of services, such as assistance for software developers, automation of routine tasks, invocation and control of software development tools, and enforcement of mandatory rules and practices. Several PSEEs have been developed, both as research projects and as commercial products. The initial deployment and exploitation of this technology have made it possible to produce a significant amount of experiences, comments, evaluations, and feedback. We still lack, however, consistent and comprehensive assessment methods that can be used to collect and organize this information. This article aims at contributing to the definition of such methods, by providing a systematic comparison grid and by accomplishing an initial evaluation of the state of the art in the field. This evaluation takes into account the systems that have been developed by the authors in the past five years, as well as the main characteristics of other well-known environments
On automated message processing in electronic commerce and work support systems
Authors: Kimbrough Steven O. , Moore Scott A.
Published: July 2002

Electronic messaging, whether in an office environment or for electronic commerce, is normally carried out in natural language, even when supported by information systems. For a variety of reasons, it would be useful if electronic messaging systems could have semantic access to, that is, access to the meanings and contents of, the messages they process. Given that natural language understanding is not a practicable alternative, there remain three approaches to delivering systems with semantic access: electronic data interchange (EDI), tagged messages, and the development of a formal language for business communication (FLBC). We favor the latter approach. In this article we compare and contrast these three approaches, present a theoretical basis for an FLBC (using speech act theory), and describe a prototype implementation.
Software process validation
Authors: Cook Jonathan E. , Wolf Alexander L.
Published: July 2002

To a great extent, the usefulness of a formal model of a software process lies in its ability to accurately predict the behavior of the executing process. Similarly, the usefulness of an executing process lies largely in its ability to fulfill the requirements embodied in a formal model of the process. When process models and process executions diverge, something significant is happening. We have developed techniques for uncovering and measuring the discrepancies between models and executions, which we call
process validation
. Process validation takes a process execution and a process model, and measures the level of correspondence between the two. Our metrics are tailorable and give process engineers control over determining the severity of different types of discrepancies. The techniques provide detailed information once a high-level measurement indicates the presence of a problem. We have applied our processes validation methods in an industrial case study, of which a portion is described in this article.
Associative hardware and software techniques for integrity control
Authors: Hong Y. C. , Su Stanley Y. W.
Published: July 2002

This paper presents the integrity control mechanism of the associative processing system, CASSM. The mechanism takes advantage of the associative techniques, such as content and context addressing, tagging and marking data, parallel processing, automatic triggering of integrity control procedures, etc., for integrity control and as a result offers three significant advantages: (1) The problem of staging data in a main memory for integrity checking can be eliminated because database storage operations are verified at the place where the data are stored. (2) The backout or merging procedures are relatively easy and inexpensive in the associative system because modified copies can be substituted for the originals or may be discarded by merely changing their associated tags. (3) The database management system software is simplified because database integrity functions are handled by the associative processing system to which a mainframe computer is a front-end computer.
Performance of recovery architectures in parallel associative database processors
Authors: Cardenas Alfonso F. , Alavian Farid , Avizienis Algirdas
Published: July 2002

The need for robust recovery facilities in modern database management systems is quite well known. Various authors have addressed recovery facilities and specific techniques, but none have delved into the problem of recovery in database machines. In this paper, the types of undesirable events that occur in a database environment are classified and the necessary recovery information, with subsequent actions to recover the correct state of the database, is summarized. A model of the “processor-per-track” class of parallel associative database processor is presented. Three different types of recovery mechanisms that may be considered for parallel associative database processors are identified. For each architecture, both the workload imposed by the recovery mechanisms on the execution of database operations (i.e., retrieve, modify, delete, and insert) and the workload involved in the recovery actions (i.e., rollback, restart, restore, and reconstruct) are analyzed. The performance of the three architectures is quantitatively compared. This comparison is made in terms of the number of extra revolutions of the database area required to process a transaction versus the number of records affected by a transaction. A variety of different design parameters of the database processor, of the database, and of a mix of transaction types (modify, insert, and delete) are considered. A large number of combinations is selected and the effects of the parameters on the extra processing time are identified.
Construction of relations in relational databases
Authors: Lozinskii Eliezer L.
Published: July 2002

Using a nonprocedural language for query formulation requires certain automatization of a query answering process. Given a query for creation of a new relation, the problem is to find an efficient procedure which produces this relation from a given relational database. We concentrate upon sequences of join operations which losslessly produce a relation required by a query. A new property of such sequences is analyzed which provides a basis for the presented algorithms that construct an efficient join procedure. The algorithms have polynomial complexity. A modified AND/OR graph is used for the display of a given set of dependencies and a collection of relations representing a database.
One Man's View of Computer Science
Authors: Hamming R. W.
Published: July 2002

A number of observations and comments are directed toward suggesting that more than the usual engineering flavor be given to computer science. The engineering aspect is important because most present difficulties in this field do not involve the theoretical question of whether certain things can be done, but rather the practical question of how can they be accomplished well and simply.

The teaching of computer science could be made more effective by various alterations, for example, the inclusion of a laboratory course in programming, the requirement for a strong minor in something other than mathematics, and more practical coding and less abstract theory, as well as more seriousness and less game playing.
Some New Bounds on the Condition Numbers of Optimally Scaled Matrices
Authors: Fenner T. I. , Loizou G.
Published: July 2002

New lower bounds on the minimal condition numbers of a matrix with respect to both one-sided and two-sided scaling by diagonal matrices are obtained. These bounds improve certain results obtained by F. L. Bauer.
Proving Properties of Complex Data Structures
Authors: Wegbreit Ben , Spitzen Jay M.
Published: July 2002

This paper is concerned with proving properties of programs which use data structures. The goal is to be able to prove that all instances of a class (e.g. as defined in Simula) satisfy some property. A method of proof which achieves this goal,
generator induction
, is studied and compared to other proof rules and methods: inductive assertions, recursion induction, computation induction, and, in some detail, structural induction. The paper concludes by using generator induction to prove a characteristic property of an implementation of hashtables.
The Desert environment
Authors: Reiss Steven P.
Published: July 2002

The Desert software engineering environment is a suite of tools developed to enhance programmer productivity through increased tool integration. It introduces an inexpensive form of data integration to provide additional tool capabilities and information sharing among tools, uses a common editor to give high-quality semantic feedback and to integrate different types of software artifacts, and builds virtual files on demand to address specific tasks. All this is done in an open and extensible environment capable of handling large software systems.
The harmonic
k
-server algorithm is competitive
Authors: Bartal Yair , Grove Eddie
Published: July 2002

The
k
-server problem is a generalization of the paging problems, and is the most studied problem in the area of competive online problems. The Harmonic algorithm is a very natural and simple randomized algorithm for the
k
-server problem. We give a simple proof that the Harmonic
k
-server algorithm is competitive. The competitive ratio we prove is the best currently known fo the algorithm. The Harmonic algorithm is memoryless and time-efficient. This is the only such algorithm known to be competitive for the
k
-server problem.
Ethernet
Authors: Metcalfe Robert M. , Boggs David R.
Published: July 2002

Ethernet is a branching broadcast communication system for carrying digital data packets among locally distributed computing stations. The packet transport mechanism provided by Ethernet has been used to build systems which can be viewed as either local computer networks or loosely coupled multiprocessors. An Ethernet's shared communication facility, its Ether, is a passive broadcast medium with no central control. Coordination of access to the Ether for packet broadcasts is distributed among the contending transmitting stations using controlled statistical arbitration. Switching of packets to their destinations on the Ether is distributed among the receiving stations using packet address recognition. Design principles and implementation are described, based on experience with an operating Ethernet of 100 nodes along a kilometer of coaxial cable. A model for estimating performance under heavy loads and a packet protocol for error controlled communication are included for completeness.
The choice of reference points in best-match file searching
Authors: Shapiro Marvin
Published: July 2002

Improvements to the exhaustive search method of best-match file searching have previously been achieved by doing a preprocessing step involving the calculation of distances from a reference point. This paper discusses the proper choice of reference points and extends the previous algorithm to use more than one reference point. It is shown that reference points should be located outside of data clusters. The results of computer simulations are presented which show that large improvements can be achieved by the proper choice and location of multiple reference points.
A study of errors, error-proneness, and error diagnosis in Cobol
Authors: Litecky Charles R. , Davis Gordon B.
Published: July 2002

This paper provides data on Cobol error frequency for correction of errors in student-oriented compilers, improvement of teaching, and changes in programming language. Cobol was studied because of economic importance, widespread usage, possible error-inducing design, and lack of research. The types of errors were identified in a pilot study; then, using the 132 error types found, 1,777 errors were classified in 1,400 runs of 73 Cobol students. Error density was high: 20 percent of the types contained 80 percent of the total frequency, which implies high potential effectiveness for software-based correction of Cobol. Surprisingly, only four high-frequency errors were error-prone, which implies minimal error inducing design. 80 percent of Cobol misspellings were classifiable in the four error categories of previous researchers, which implies that Cobol misspellings are correctable by existent algorithms. Reserved word usage was not error-prone, which implies minimal interference with usage of reserved words. Over 80 percent of error diagnosis was found to be inaccurate. Such feedback is not optimal for users, particularly for the learning user of Cobol.
The treatment of data types in EL1
Authors: Wegbreit Ben
Published: July 2002

In constructing a general purpose programming language, a key issue is providing a sufficient set of data types and associated operations in a manner that permits both natural problem-oriented notation and efficient implementation. The EL1 language contains a number of features specifically designed to simultaneously satisfy both requirements. The resulting treatment of data types includes provision for programmer-defined data types and generaic routines, programmer control over type conversion, and very flexible data type behavior, in a context that allows efficient compiled code and compact data representation.
A view of computer architecture
Authors: Foster Caxton C.
Published: July 2002

An attempt is made to predict the developments of the next 25 years in the field of computer architecture. Standardized, inexpensive microcomputers on a single chip are predicted. These will be used extensively to provide logical functions for noncomputational devices and incidentally for the design of superscale computers.
Implementation of a high level language machine
Authors: Hassitt A. , Lageschulte J. W. , Lyon L. E.
Published: July 2002

Computing machines which directly execute the statements of a high level language have been proposed in the past. This report describes the actual implementation of such a machine: it is a computer whose “machine language” is APL. The machine is fully operational and correctly executes almost all of the APL operations on scalars, vectors, and arrays. The machine automatically allocates memory, executes statements, calls functions, converts numbers from one type to another, checks subscripts, and automatically detects many types of programmer errors.
Evaluation and selection of file organization—a model and system
Authors: Cardenas Alfonso F.
Published: July 2002

This work first discusses the factors that affect file (data base) organization performance, an elusive subject, and then presents a methodology, a model and a programmed system to estimate primarily total storage costs and average access time of several file organizations, given a specific data base, query characterization and device-related specifications. Based on these estimates, an appropriate file structure may be selected for the specific situation. The system is a convenient tool to study file structures and to facilitate as much as possible the process of data base structure design and evaluation.
A computer technique for displaying
n
-dimensional hyperobjects
Authors: Noll A. Michael
Published: July 2002

A digital computer and automatic plotter have been used to generate three-dimensional stereoscopic movies of the three-dimensional parallel and perspective projections of four-dimensional hyperobjects rotating in four-dimensional space. The observed projections and their motions were a direct extension of three-dimensional experience, but no profound "feeling" or insight into the fourth spatial dimension was obtained. The technique can be generalized to n-dimensions and applied to any n-dimensional hyperobject or hypersurface.
On the equivalent bandwidth of self-similar sources
Authors: Fonseca Nelson L. S. , Mayor Gilberto S. , Neto Cesar A. V.
Published: July 2002

This article presents a method for the computation of the equivalent bandwidth of an aggregate of heterogeneous self-similar sources, as well as the time scales of interest for queueing systems fed by a fractal Brownian motion (fBm) process. Moreover, the fractal leaky bucket, a novel policing mechanism capable of accurately monitoring self-similar sources, is introduced.
Cache investment
Authors: Kossmann Donald , Franklin Michael J. , Drasch Gerhard , Ag Wig
Published: July 2002

Emerging distributed query-processing systems support flexible execution strategies in which each query can be run using a combination of data shipping and query shipping. As in any distributed environment, these systems can obtain tremendous performance and availability benefits by employing dynamic data caching. When flexible execution and dynamic caching are combined, however, a circular dependency arises: Caching occurs as a by-product of query operator placement, but query operator placement decisions are based on (cached) data location. The practical impact of this dependency is that query optimization decisions that appear valid on a per-query basis can actually cause suboptimal performance for all queries in the long run.

To address this problem, we developed
Cache Investment
- a novel approach for integrating query optimization and data placement that looks beyond the performance of a single query. Cache Investment sometimes intentionally generates a “suboptimal” plan for a particular query in the interest of effecting a better data placement for subsequent queries. Cache Investment can be integrated into a distributed database system without changing the internals of the query optimizer. In this paper, we propose Cache Investment mechanisms and policies and analyze their performance. The analysis uses results from both an implementation on the SHORE storage manager and a detailed simulation model. Our results show that Cache Investment can significantly improve the overall performance of a system and demonstrate the trade-offs among various alternative policies.
The NTree: a two dimension partial order for protection groups
Authors: Sandhu Ravinderpal S.
Published: July 2002

The benefits of providing access control with groups of users rather than with individuals as the unit of granularity are well known. These benefits are enhanced if the groups are organized in a subgroup partial order. A class of such partial orders, called ntrees, is defined by using a forest of rooted trees or inverted rooted trees as basic partial orders and combining these by refinement. Refinement explodes an existing group into a partially ordered ntree of new groups while maintaining the same relationship between each new group and the nonexploded groups that the exploded group had. Examples are discussed to show the practical significance of ntrees and the refinement operation. It is shown that ntrees can be represented by assigning a pair of integers called
lr-values
to each group so that g is a subgroup of h if and only if l[g] ≤ l[h] and r[g] ≤ r[h]. Refinement allows a complex ntree to be developed incrementally in a top-down manner and is useful for the initial definition of an ntree as well as for subsequent modifications. To make the latter use of refinement practical, a method is presented for assigning lr-values to the new groups introduced by refinement so lr-values assigned to nonexploded groups need not be changed. It is also shown how to guarantee that the lr-values of the exploded group will get assigned to one of the new groups.
The schematic protection model
Authors: Sandhu Ravinderpal Singh
Published: July 2002

The protection state of a system is defined by the privileges possessed by subjects at a given moment. Operations that change this state are themselves authorized by the current state. This poses a design problem in constructing the initial state so that all derivable states conform to a particular policy. It also raises an analysis problem of characterizing the protection states derivable from a given initial state. A protection model provides a framework for both design and analysis. Design generality and tractable analysis are inherently conflicting goals. Analysis is particularly difficult if creation of subjects is permitted. The schematic protection model resolves this conflict by classifying subjects and objects into protection types. The privileges possessed by a subject consist of a type-determined part specified by a static protection scheme and a dynamic part consisting of tickets (capabilities). It is shown that analysis is tractable for this model provided certain restrictions are imposed on subject creation. A scheme authorizes creation of subjects via a binary relation on subject types. Our principal constraint is that this relation be acyclic, excepting loops that authorize a subject to create subjects of its own type. Our assumptions admit a variety of useful systems.
Solution of large, dense symmetric generalized eigenvalue problems using secondary storage
Authors: Grimes Roger G. , Simon Horst D.
Published: July 2002

This paper describes a new implementation of algorithms for solving large, dense symmetric eigen-problems
AX
=
BX
Λ, where the matrices
A
and
B
are too large to fit in the central memory of the computer. Here
A
is assumed to be symmetric, and
B
symmetric positive definite. A combination of block Cholesky and block Householder transformations are used to reduce the problem to a symmetric banded eigenproblem whose eigenvalues can be computed in central memory. Inverse iteration is applied to the banded matrix to compute selected eigenvectors, which are then transformed back to eigenvectors of the original problem. This method is especially suitable for the solution of large eigenproblems arising in quantum physics, using a vector supercomputer with fast secondary storage device such as the Cray X-MP with SSD. Some numerical results demonstrate the efficiency of the new implementation.
Computing on an anonymous ring
Authors: Attiya Hagit , Snir Marc , Warmuth Manfred K.
Published: July 2002

The computational capabilities of a system of
n
indistinguishable (anonymous) processors arranged on a ring in the synchronous and asynchronous models of distributed computation are analyzed. A precise characterization of the functions that can be computed in this setting is given. It is shown that any of these functions can be computed in
O
(
n
2
) messages in the asynchronous model. This is also proved to be a lower bound for such elementary functions as AND, SUM, and Orientation. In the synchronous model any computable function can be computed in
O
(
n
log
n
) messages. A ring can be oriented and start synchronized within the same bounds.

The main contribution of this paper is a new technique for proving lower bounds in the synchronous model. With this technique tight lower bounds of θ(
n
log
n
) (for particular
n
) are proved for XOR, SUM, Orientation, and Start Synchronization. The technique is based on a string-producing mechanism from formal language theory, first introduced by Thue to study square-free words. Two methods for generalizing the synchronous lower bounds to arbitrary ring sizes are presented.
Introduction
Authors: Anandarajan Murugan
Published: July 2002

The ubiquitous nature of the Internet is dramatically revolutionizing the manner in which organizations and individuals acquire and distribute information. Recent reports from the International Data Group indicate the number of people on the Internet will reach 320 million by 2002 [5]. Studies also indicate that in the U.S. alone, e-commerce will account for approximately $325 billion by 2002.
Ontological computing
Authors: Castel Felipe
Published: July 2002

Ontologies help us represent information in different ways, but we need to look much deeper for a sharper picture.
Algorithms 683: a portable FORTRAN subroutine for exponential integrals of a complex argument
Authors: Amos Donald E.
Published: July 2002

The algorithm computes exponential integrals

E
n

(
z
) for integer orders
n
≥ 1 and complex
z
in -π < arg
z
≤ π. Both single and double precision subroutines are provided. Exponential scaling and stable sequence generation are auxiliary options.
Highly available systems for database applications
Authors: Kim Won
Published: July 2002

As users entrust more and more of their applications to computer
systems, the need for systems that are continuously operational (24
hours per day) has become even greater. This paper presents a
survey and analysis of representative architectures and techniques
that have been developed for constructing highly available systems
for database applications. It then proposes a design of a
distributed software subsystem that can serve as a unified
framework for constructing database application systems that meet
various requirements for high availability.
LESSONS FROM SEQUENCING OF THE GENOME OF A UNICELLULAR CYANOBACTERIUM, SYNECHOCYSTIS SP. PCC6803
Authors: Kotani H. , Tabata S.
Published: July 2002

▪ Abstract  The nucleotide sequence of the entire genome of the unicellular cyanobacterium, Synechocystis sp. PCC6803, has been determined. The length of the circular genome was 3,573,480 bp, and a total of 3168 protein-coding genes were assigned to the genome by a computer-assisted analysis. The functions of approximately 45% of the genes were deduced based on sequence similarity to known genes. Here are distinctive features of genetic information carried by the cyanobacteria, which have a phylogenetic relationship to both bacteria and plants.
RNA LOCALIZATION IN DEVELOPMENT
Authors: Bashirullah Arash , Cooperstock Ramona L. , Lipshitz Howard D.
Published: July 2002

Cytoplasmic RNA localization is an evolutionarily ancient mechanism for producing cellular asymmetries. This review considers RNA localization in the context of animal development. Both mRNAs and non-protein-coding RNAs are localized in Drosophila, Xenopus, ascidian, zebrafish, and echinoderm oocytes and embryos, as well as in a variety of developing and differentiated polarized cells from yeast to mammals. Mechanisms used to transport and anchor RNAs in the cytoplasm include vectorial transport out of the nucleus, directed cytoplasmic transport in association with the cytoskeleton, and local entrapment at particular cytoplasmic sites. The majority of localized RNAs are targeted to particular cytoplasmic regions by cis-acting RNA elements; in mRNAs these are almost always in the 3′-untranslated region (UTR). A variety of trans-acting factors—many of them RNA-binding proteins—function in localization. Developmental functions of RNA localization have been defined in Xenopus, Drosophila, and Saccharomyces cerevisiae. In Drosophila, localized RNAs program the antero-posterior and dorso-ventral axes of the oocyte and embryo. In Xenopus, localized RNAs may function in mesoderm induction as well as in dorso-ventral axis specification. Localized RNAs also program asymmetric cell fates during Drosophila neurogenesis and yeast budding.
NANOSECOND TIME-RESOLVED SPECTROSCOPY OF BIOMOLECULAR PROCESSES
Authors: Chen Eefei , Goldbeck Robert A. , Kliger David S.
Published: July 2002

▪ Abstract  Over the past two decades, nanosecond absorption and vibrational spectroscopies have developed into powerful tools for monitoring the secondary, tertiary, and quaternary structural relaxations of biological macromolecules under near-physiological conditions of solvent and temperature. Observed through such methods, the dynamic response of a biomolecule to photoinitiated excursions from equilibrium can reveal valuable information about the structure-function relationship, information beyond that obtained from the static structures provided by X-ray crystallography, nuclear magnetic resonance spectroscopy, and other steady-state methods. Most recently, the development of ultra-sensitive polarization techniques for absorption spectroscopy has greatly enhanced the amount of time-resolved structural information that can be obtained from the broadened electronic spectra of biomolecules. This review examines nanosecond absorption, vibrational, and polarized absorption methods, and their applications to protein function and folding, emphasizing the complementary nature of information obtained from electronic and vibrational spectra measured on the nanosecond time scale.
Function and Morphology of the Antennal Lobe: New Developments
Authors: Hansson B. S. , Anton S.
Published: July 2002

▪ Abstract  The antennal lobe of insects has emerged as an excellent model for olfactory processing in the CNS. In the present review we compile data from areas where substantial progress has been made during recent years: structure-function relationships within the glomerular array, integration and blend specificity, time coding and the effects of neuroactive substances and hormones on antennal lobe processing.
COLLAPSE, SYMMETRY BREAKING, AND HYSTERESIS IN SWIRLING FLOWS
Authors: Shtern Vladimir , Hussain Fazle
Published: July 2002

▪ Abstract  The paper reviews striking features of swirling flows—collapse, swirl generation, vortex breakdown, hysteresis, and axisymmetry breaking—and the mechanisms involved with the help of conical similarity solutions of the Navier-Stokes equations. The strong accumulation of axial and angular momenta, observed in tornadoes and flows over delta wings, corresponds to collapse, i.e. the singularity development in these solutions. Bifurcation of swirl explains the threshold character of swirl development in capillary and electrovortex flows. Analytical solutions for fold catastrophes and hysteresis reveal why there are so few stable states and why the jump transitions between the states occur—features typical of tornadoes, of flows over delta wings, and in vortex devices. Finally, the divergent instability explains such effects as the splitting of a tornado and the development of spiral branches in tree and near-wall swirling flows.
Early Management of Prostate Cancer: How to Respond to an Elevated PSA?
Authors: Canto Eduardo I. , Slawin Kevin M.
Published: July 2002

▪ Abstract  Support for prostate cancer screening efforts is provided by observational studies reporting decreases in prostate cancer–specific mortality in areas where screening is performed with digital rectal exam (DRE) and measurement of serum prostate-specific antigen (PSA) levels. The combination of PSA and DRE is an excellent cancer-screening tool with sensitivity and positive predictive value superior to that of mammography and breast exam. Use of percent free PSA further improves the specificity of PSA testing, particularly in the range of 4–10 ng/ml, at which most false positive PSA tests occur. Men older than 50 with a >10-year life expectancy should be considered for prostate cancer screening. Those with an abnormal DRE or a PSA above 4 ng/ml should be referred to a urologist for further discussion of the risks and benefits of a prostate biopsy. Furthermore, those with a significant change in either DRE or PSA results, or those at higher risk for prostate cancer with a PSA level above 2.5 ng/ml, should also be referred for evaluation.
Clinical Trials of HIV Vaccines
Authors: Graham Barney S.
Published: July 2002

▪ Abstract  Development of a preventive vaccine for HIV is the best hope of controlling the AIDS pandemic. Evidence from natural history studies and experiments in animal models indicates that immunity against HIV is possible, suggesting that vaccine development is feasible. These studies have shown that sufficient levels of neutralizing antibody against HIV can prevent infection, although the effect is type-specific. In contrast, HIV-specific cytotoxic T lymphocyte (CTL) activity has broad cross-reactivity, and although CTL activity alone cannot prevent HIV infection, it can control the level of viremia at a low level. Evaluation of candidate vaccines in human trials has focused on approaches that can safely elicit HIV-specific antibody and T cell responses. Current strategies have been unable to induce antibody with broad neutralizing activity against primary HIV isolates. However, recombinant poxvirus and DNA vaccines have elicited CTL responses that are broadly cross-reactive against primary HIV isolates from diverse clades. Future advances will require the discovery of new immunogens that can induce neutralizing antibody, as well as efficacy trial evaluation of regimens optimized for CTL induction.
Potential New Therapies for the Treatment of HIV-1 Infection
Authors: Condra Jon H. , Miller Michael D. , Hazuda Daria J. , Emini Emilio A.
Published: July 2002

▪ Abstract  The development and clinical use of chemotherapeutic agents for the treatment of persistent HIV-1 infection over the past decade has profoundly and favorably affected the course of HIV-1 disease for many infected individuals. Unfortunately, the long-term use of these therapies is complicated by unwanted metabolic side effects, by issues of adherence, and by the selection of viral variants with reduced susceptibility. These complications have spurred the search for new anti-HIV-1 agents having improved pharmacological properties and expressing activity against viral variants resistant to the currently available agents. This brief review describes the current state of this search as well as potentially novel viral targets for chemotherapeutic intervention.
Guanylyl Cyclases as a Family of Putative Odorant Receptors
Authors: Gibson Angelia D. , Garbers David L.
Published: July 2002

Mammals can discriminate among a large number (>10,000) of unique odorants. The most highly supported explanation for this ability is that olfactory neurons express a large number of seven transmembrane receptors that are not spatially organized at the level of the olfactory epithelium, but whose axonal projections form a distinct pattern within the olfactory bulb. The odor-induced signaling pathway in olfactory neurons includes a Gs-like protein (Golf) that activates a specific adenylyl cyclase (type III) isoform, resulting in elevations of cyclic AMP and subsequent activation of a cyclic nucleotide-gated channel. The channel also can be regulated by cyclic GMP. Recently, an olfactory neuron-specific guanylyl cyclase was discovered in rodents, and subsequently a large family of sensory neuronal guanylyl cyclases was identified in nematodes. These guanylyl cyclases are concentrated in the plasma membrane of the dendritic cilia and contain extracellular domains that retain many of the primary sequence characteristics of guanylyl cyclases known to be receptors for various peptides. Thus, the guanylyl cyclases appear to represent a second family of odorant/pheromone receptors.
IN VIVO KINETICS OF FOLATE METABOLISM
Authors: Gregory III Jesse F. , Quinlivan Eoin P.
Published: July 2002

▪ Abstract  Investigation of the in vivo kinetics of folate metabolism provides information that contributes to a better understanding of the manner in which this vitamin is processed in vivo. Kinetic studies can yield insight into the requirements for folate, especially with respect to factors that may lead to increased requirements. This review considers the strengths and weaknesses of various approaches to the study of folate kinetics and resulting data, followed by a summary and interpretation of existing data.
POLYMERADSORPTION–DRIVENSELF-ASSEMBLY OFNANOSTRUCTURES
Authors: Chakraborty Arup K , Golumbfskie Aaron J
Published: July 2002

▪ Abstract  Driven by prospective applications, there is much interest in developing materials that can perform specific functions in response to external conditions. One way to design such materials is to create systems which, in response to external inputs, can self-assemble to form structures that are functionally useful. This review focuses on the principles that can be employed to design macromolecules that when presented with an appropriate two-dimensional surface, will self-assemble to form nanostructures that may be functionally useful. We discuss three specific examples: (a) biomimetic recognition between polymers and patterned surfaces. (b) control and manipulation of nanomechanical motion generated by biopolymer adsorption and binding, and (c) creation of patterned nanostructuctures by exposing molten diblock copolymers to patterned surfaces. The discussion serves to illustrate how polymer sequence can be manipulated to affect self-assembly characteristics near adsorbing surfaces. The focus of this review is on theoretical and computational work aimed toward elucidating the principles underlying the phenomena pertinent to the three topics noted above. However, synergistic experiments are also described in the appropriate context.
PATHOPHYSIOLOGY OF ENDOTHELIN IN THE CARDIOVASCULAR SYSTEM
Authors: Miyauchi Takashi , Masaki Tomoh
Published: July 2002

▪ Abstract  In this article, we review the basic pharmacological and biochemical features of endothelin and the pathophysiological roles of endothelin in cardiovascular diseases. Development of receptor antagonists has accelerated the pace of investigations into the pathophysiological roles of endogenous endothelin-1 in various diseases, e.g. chronic heart failure, renal diseases, hypertension, cerebral vasospasm, and pulmonary hypertension. In chronic heart failure, the expression of endothelin-1 and its receptors in cardiomyocytes is increased, and treatment with an endothelin receptor antagonist improves survival and cardiac function. Endothelin receptor antagonists also improve other cardiovascular diseases. These results suggest that the interference with endothelin pathway either by receptor blockade or by inhibition of endothelin converting enzyme may provide novel therapeutic drugs strategies for multiple disease states.
Mechanisms of Guanylin Action Via Cyclic GMP in the Kidney
Authors: Forte Leonard R. , London Roslyn M. , Krause William J. , Freeman Ronald H.
Published: July 2002

▪ Abstract  Guanylin, uroguanylin, and lymphoguanylin are small peptides that activate cell-surface guanylate cyclase receptors and influence cellular function via intracellular cGMP. Guanylins activate two receptors, GC-C and OK-GC, which are expressed in intestine and/or kidney. Elevation of cGMP in the intestine elicits an increase in electrolyte and water secretion. Activation of renal receptors by uroguanylin stimulates urine flow and excretion of sodium, chloride, and potassium. Intracellular cGMP pathways for guanylins include activation of PKG-II and/or indirect stimulation of PKA-II. The result is activation of CFTR and/or ClC-2 channel proteins to enhance the electrogenic secretion of chloride and bicarbonate. Similar cellular mechanisms may be involved in the renal responses to guanylin peptides. Uroguanylin serves as an intestinal natriuretic hormone in postprandial states, thus linking the digestive and renal organ systems in a novel endocrine axis. Therefore, uroguanylin participates in the complex physiological processes underlying the saliuresis that is elicited by a salty meal.
Conserved Synteny in Rat and Mouse for a Blood Pressure QTL on Human Chromosome 17
Authors: Zimdahl Heike , Kreitler Thomas , Gösele Claudia , Ganten Detlev , Hübner Norbert
Published: July 2002

Evidence for blood pressure quantitative trait loci (QTLs) on rat chromosome 10 has been found in multiple independent studies. Analysis of the homologous region on human chromosome 17 revealed significant linkage to blood pressure. The critical segment on human chromosome 17 spans a large interval containing the genes
Itga2b, Gfap
, and
Itgb3
. Therefore, findings in the rat may help to refine the position of blood pressure–regulating loci, assuming a common molecular cause across species. However, it has recently been suggested that the gene order in human, rat, and mouse is not conserved in this region, leaving uncertainty about the overlap of the blood pressure– regulating region between human chromosome 17 and rat chromosome 10. We have performed a detailed comparative analysis among human, mouse, and rat, defining the segment in question, by obtaining gene structure information in silico and by radiation hybrid mapping. It is of interest that this region also contains
Wnk4
, a gene previously identified to cause pseudohypoaldosteronism type II and human hypertension. Our results definitively show that the conserved synteny extends among human chromosome 17, rat chromosome 10, and mouse chromosome 11, demonstrating an overlap between previously localized blood pressure QTLs in humans and rats.
Origins of the Federal Reserve System: International Incentives and the Domestic Free-rider Problem
Authors: Broz J. Lawrence
Published: July 2002

The Federal Reserve System was established in 1913 to provide the public good of domestic financial system stability. Its main purpose was to safeguard the nation from banking panics and other economically costly financial disturbances. In this article, I explain the collective action behind the Federal Reserve Act by way of the joint products (selective incentives) model. The selective inducement that motivated lobbying for the Federal Reserve was the desire to internationalize usage of the U.S. dollar, a benefit restricted primarily to money-center bankers. Bankers internalized the costs of producing the Federal Reserve because the private gains associated with internationalizing the currency could not be disassociated from production of domestic financial stability. The article provides a road map of the joint products model and demonstrates empirically the supply technology that bound together the public and private goods of the Federal Reserve Act.
Artistic Environments of Telepresence on the World Wide Web
Authors: Donati Luisa Paraguai , Prado Gilbertto
Published: July 2002

The recent use of streaming video on the World Wide Web for the distribution of live images has enabled an interface that supports a new phenomenon of virtual, defered, remote presence, extending perception and expanding the possibilities of remote interaction. The purpose of this essay is to provide a brief survey of the use of these live images in artistic spaces specifically conceived for this medium. These environments will be presented in three different categories, which propose transformations in possibilities of participation, interference, and the participants' self-expression.
Coming Full Circle: Composing a Cathartic Experience with CD-ROM Technology
Authors: Hinkle-Turner Elizabeth
Published: July 2002

After introducing the general advantages of CD-ROM technology as an artistic medium, the author chronicles her initial experiences with the format. Describing the inspiration for the CD-ROM Full Circle, the author outlines the three principal sections of the piece and their significance to its overall message. The article concludes with a discussion of the advantages of the CD-ROM format in subverting the concert-performance space-time continuum and the importance of this to the impact of Full Circle during its presentation.
Virtual Cairo: An Urban Historian's View of Computer Simulation
Authors: AlSayyad Nezar
Published: July 2002

Recent advances in computer-visualization technology have brought urban historians new tools for analyzing the growth of historic cities. This paper examines both the prospects and problems involved in using this technology to map the development of urban form. Using a computer model of Cairo in two different periods of the Middle Ages, the author has attempted to reconstruct the physical reality of the city and to animate the city so that modernday observers may experience its principal streets. While the work has shown computer simulation to be a significant tool for helping urban historians understand the built environments of the past, it has also exposed possible pitfalls in the seductive potential of such simulations.
Cortical Potential Distributions and Information Processing
Authors: Tuckwell Henry C.
Published: July 2002

The use of sets of spatiotemporal cortical potential distributions (CPDs) as the basis for cognitive information processing results in a very large space of cognitive elements with natural metrics. Results obtained from current source density (CSD) analysis suggest that in the CPD picture, action potentials may make only a relatively minor contribution to the brain's code. In order to establish if two CPDs are close, we consider standard metrics in spaces of continuous functions, and these may be employed to ascertain if two stimuli will be identified as the same. The correspondence between the electrical activity within brain regions, including not only action potentials but all postsynaptic potentials (PSPs), and CPDs is considered. We examine the possibility of using the CSD approach to find potential distributions using the descriptive approach in which precise sets of times are ascribed to the occurrence of action potentials and PSPs. Using metrics in the multidimensional space of paths of collections of point processes, we show that closeness of CPDs is implied by closeness of sets of spike times and PSP times if a certain metric is used but not others. We also set forth a dynamical model consisting of a system of reaction-diffusion equations for ionic concentrations coupled with nerve membrane potential equations and active transport systems. Making the approximation of a descriptive approach, the correspondence between sets of spike times and PSP times and CPDs is obtained as with the CSD method. However, since it is not possible to ascribe precise times to the occurrence of PSPs and action potentials, the descriptive approach cannot be used to describe the configuration of electrical activity in cortical regions accurately. We also discuss how the CPD framework relates to the binding problem and submillisecond timing.
Blind Source Separation Using Temporal Predictability
Authors: Stone James V.
Published: July 2002

A measure of temporal predictability is defined and used to separate linear mixtures of signals. Given any set of statistically independent source signals, it is conjectured here that a linear mixture of those signals has the following property: the temporal predictability of any signal mixture is less than (or equal to) that of any of its component source signals. It is shown that this property can be used to recover source signals from a set of linear mixtures of those signals by finding an un-mixing matrix that maximizes a measure of temporal predictability for each recovered signal. This matrix is obtained as the solution to a generalized eigenvalue problem; such problems have scaling characteristics of O (N3), where N is the number of signal mixtures. In contrast to independent component analysis, the temporal predictability method requires minimal assumptions regarding the probability density functions of source signals. It is demonstrated that the method can separate signal mixtures in which each mixture is a linear combination of source signals with supergaussian, sub-gaussian, and gaussian probability density functions and on mixtures of voices and music.
Weight-Value Convergence of the SOM Algorithm for Discrete Input
Authors: Lin Siming , Si Jennie
Published: July 2002

Some insights on the convergence of the weight values of the self-organizing map (SOM) to a stationary state in the case of discrete input are provided. The convergence result is obtained by applying the Robbins-Monro algorithm and is applicable to input-output maps of any dimension.