bluuebunny/crossref_metadata_2025 huggingface dataset:
SYSTOLIC GENERATION OF k-ARY TREES
Authors: VAJNOVSZKI VINCENT , PHILLIPS CHRIS
Published: February 2003

The only parallel generating algorithms for k-ary trees are those of Akl and Stojmenović in 1996 and of Vajnovszki and Phillips in 1997. In the first of them, trees are represented by an inversion table and the processor model is a linear aray multicomputer. In the second, trees are represented by bitstrings and the algorithm executes on a shared memory multiprocessor. In this paper we give a parallel generating algorithm for k-ary trees represented by generalized P–sequences for execution on a linear array multicomputer.
DECODING AND DRAWING ON BSR FOR A BINARY TREE FROM ITS i-p SEQUENCE
Authors: XIANG Limin , USHIJIMA Kazuo
Published: February 2003

The i-p sequence is one of the most common encodings for a binary tree. This paper gives constant time BSR parallel algorithms for the decoding and drawing of a binary tree from its i-p sequence respectively.
AN EREW PARM ALGORITHM FOR UPDATING MINIMUM SPANNING TREES
Authors: DAS SAJAL K. , FERRAGINA PAOLO
Published: February 2003

We propose a parallel algorithm for the EREW PRAW model that maintains a minimum spanning tree (MST) of an undirected graph under single edge insertions and deletions. For a graph of n nodes and m edges, each update requires O( log n) time and O(m 2/3 log n) work. This is a substantial improvement over the known bounds on the work complexity. Our algorithm uses a partition of the MST, similar to the sequential approach due to Frederickson [6], and also employs a novel data structure for efficiently managing edge insertions in parallel.
Normality: A CONSISTENCY CONDITION FOR CONCURRENT OBJECTS
Authors: GARG VIJAY K. , RAYNAL MICHEL
Published: February 2003

This paper is focused on concurrent objects (objects shared by concurrent processes). It introduces a consistency condition called Normality whose definition is based only on local orders of operations as perceived by processes and by objects. First we consider the model in which each operation is on exactly one object. In this model we show that a history is linearizable iff it is normal. However, the definition of Normality is less constraining in the sense that there are strictly more legal sequential histories which are considered equivalent to the given history when Normality is used. We next consider a more general model where operations can span multiple objects. In this model we show that Normality is strictly weaker than Linearizability, i.e., history may be normal but not linearizable. As Normality refers only to local orders (process order and object order) it appears to be well-suited to objects supported by asynchronous distributed systems and accessed by RPC-like mechanisms.
DATA DISTRIBUTION ANALYSIS FOR IRREGULAR AND ADAPTIVE CODES
Authors: AGRAWAL GAGAN
Published: February 2003

An important component in compiling for distributed memory machines is data partitioning. While a number of automatic analysis techniques have been proposed for this phase, none of them is applicable for irregular problems. In this paper, we present compile-time analysis for determining data partitioning for such applications. We have developed a set of cost functions for determining communication and redistribution costs in irregular codes. We first determine the appropriate distributions for a single data parallel statement, and then use the cost functions with a greedy algorithm for computing distributions for the full program. Initial performance results on a 16 processor IBM SP-2 are also presented.
SHARED MEMORY VERSUS MESSAGE PASSING FOR ITERATIVE SOLUTION OF SPARSE, IRREGULAR PROBLEMS
Authors: CHONG FREDERIC T. , AGARWAL ANANT
Published: February 2003

The benefits of hardware support for shared memory versus those for message passing are difficult to evaluate without an in-depth study of real applications on a common platform. We evaluate the communication mechanisms of the MIT Alewife machine, a multiprocessor which provides integrated cache-coherent shared memory, massage passing, and DMA. We perform this evaluation with "best-effort" implementations which solve several sparse, irregular benchmark problems with a preconditioned conjugate gradient sparse matrix solver (ICCG).

We find that machines with fast global memory operations do not need message passing or bulk transfer to suport our irregular problems. This is primarily due to three reasons. First, a 5-to-1 ratio between global and local cache misses makes memory copies in bulk communication expensive relati to communication via shared memory. Second, although message passing has synchronization semantics superior to shared memory for data-driven computation, efficient shared memory can overcome this handicap by using global read-modify-writes to change from the traditional owner-computers model to a producer-computes model. Third, bulk transfers can result in high processor idle times in irregular applications.
OBJECT-RELATIONAL QUERIES INTO MULTIDIMENSIONAL DATABASES WITH THE ACTIVE DATA REPOSITORY
Authors: FERREIRA RENATO , KURC TAHSIN , BEYNON MICHAEL , CHANG CHIALIN , SUSSMAN ALAN , SALTZ JOEL
Published: February 2003

As computational power and storage capacity increase, processing and analyzing large volumes of multi-dimensional datasets play an increasingly important role in many domains of scientific research. Scientific applications that make use of very large scientific datasets have several important characteristics: datasets consist of complex data and are usually multi-dimensional; applications usually retrieve a subset of all the data available in the dataset; various application-specific operations are performed on the data items retrieved. Such applications can be supported by object-relational database management systems (OR-DBMSs). In addition to providing functionality to define new complex datatypes and user-defined functions, an OR-DBMS for scientific datasets should contain runtime support that will provide optimized storage for very large datasets and an execution environment for user-defined functions involving expensive operations. In this paper we describe an infrastructure, the Active Data Repository (ADR), which provides framework for building databases that enables integration of storage, retrieval and processing of multi-dimensional datasets on a parallel machine. The system architecture of ADR provides the functionality required from runtime support for an OR-DBMS that stores and processes scientific multi-dimensional datasets. We present the system architecture of the ADR, and experimental performance results for three applications implemented using ADR.
ALGORITHMIC ISSUES ON HETEROGENEOUS COMPUTING PLATFORMS
Authors: BOULET PIERRE , DONGARRA JACK , RASTELLO FABRICE , ROBERT YVES , VIVIEN FRÉDÉRIC
Published: February 2003

This paper discusses algorithmic issues when computing with a heterogeneous network of work-stations (the typical poor man's parallel computer). Dealing with processors of different speeds requires to use more involved strategies than block-cyclic data distributions. Dynamic data distribution is a first possibility but may prove impractical and not scalable due to communication and control overhead. Static data distributions tuned to balance execution times constitute another possibility but may prove ineffcient due to variations in the processor speeds (e.g. because of different workloads during the computation). We introduce a static distribution strategy that can be refined on the fly, and we show that it is well-suited to parallelizing scientific computing applications such as finite-difference stencils or LU decomposition.
BINARY VERSION MANAGEMENT FOR COMPUTATIONAL GRIDS
Authors: HOLLINGSWORTH JEFFREY K. , MILLER ETHAN L. , AKALA KENNEDY
Published: February 2003

Applications are no longer monolithic files, but rather a collection of dynamically linked libraries, images, fonts, etc. For such applications to function correctly, all of the required files must be available and be the correct version. Missing files preclude application execution, and incorrect versions lead to mysterious and frustrating failures. This paper describes a simple scheme to address this problem: Content-Derived Names (CDNs). CDNs use digital signatures to automatically and uniquely name specific versions of files. Because Content-Derived Names are computed using a cryptographically strong hash over the text of a package, this process is safe from spoofing and other attacks based on providing the wrong library. We explain how CDNs ease the management of application distribution for clusters and grids. We also describe a prototype implementation of CDNs for the Tel programming language.
PREDICTING CPU AVAILABILITY ON THE COMPUTATIONAL GRID USING THE NETWORK WEATHER SERVICE
Authors: WOLSKI RICH
Published: February 2003

In this paper, we focus on the problem of predicting CPU availability for Computational Grid settings in which individual machines may be either time-shared or batch-controlled. We use the Network Weather Service — a distributed system that monitors and forecasts resource performance in Computational Grid environments — to measure and predict CPU availability. We examine the accurancy with which CPU availability can be predicted in an interactive cluster computing environment under production load conditions, and compare these results with a similar study of a production batch system. Our work shows that in the environments we have studied, the availability of clusted interactive resources is significantly more predictable that of the batch system.
SOME METACOMPUTING EXPERIENCES FOR SCIENTIFIC APPLICATIONS
Authors: LARSSON O. , FEIG M. , JOHNSSON L.
Published: February 2003

We demonstrate good metacomputing efficiency and portability for three typical large-scale parallel applications; one molecular dynamics code and two electromagnetics codes. The codes were developed for distributed memory parallel platforms using Fortran77 or Fortran90 with MPI. The performance measurements were made for a testbed of two IBM SPs connected through the vBNS. No change of the application codes were required for correct execution of the codes on the testbed using the Globus Toolkit for the required metacomputing services. However, we observe that for good performance, it may be necessary for MPI codes to make use of overlapped computation and communication. For such MPI codes, a communications library designed for hierarchical or clustered communication can yield very good metacomputing efficiencies when high-performance networks, such as the vBNS or the Abilene networks, such as the vBNS or the Abilene networks, are used for platform connectivity. We demonstrate this by inserting a thin layer between the MPI application and the MPI libraries, providing some clustering of communications between platforms.
HARNESS: ADAPTABLE VIRTUAL MACHINE ENVIRONMENT FOR HETEROGENEOUS CLUSTER
Authors: GEIST G. A. , ARTHUR KOHL JAMES , SCOTT STEPHEN , PAPADOPOULOS PHILIP M.
Published: February 2003

This paper describes ongoing work on the Harness system for next-generation hetergeneous distributed computing. Harness is an adaptable, reliable virtual machine environment being built as a follow-on to PVM. The three fundamental concepts presented here are parallel plugins, fault-tolerant distributed control, and dynamically merging and splitting virtual machines. The distributed control mechanisms provide the support framework necessary for coordinating and applying parallel plugins that allow applications to customize or tune their operating environment on-the-fly. In the spirit of CUMULVS, Harness applications can plug into each other to couple for collaborative computing. Virtual machines that merge and split can assist applications in dynamically utilizing different computing resources to suit changing computational needs.
OPUS: HETEROGENEOUS COMPUTING WITH DATA PARALLEL TASKS
Authors: LAURE ERWIN , MEHROTRA PIYUSH , ZIMA HANS
Published: February 2003

The coordination language Opus is an object-based extension of High Performance Fortran (HPF) that supports the integration of coarse-grain task parallelism with HPF-style data parallelism. In this paper we discuss Opus in the Context of multidisciplinary applications (MDAs) which execute in a heterogencous environment. After outlining the major properties of such applications and a number of different approaches towards providing language and tool support for MDAs we describe the salientfeatures of Opus and its implementation, emphasizing the issues related to the coordination of data-parallel HPF programs in a heterogencous environment.
USING REFLECTION FOR INCORPORATING FAULT-TOLERANCE TECHNIQUES INTO DISTRIBUTED APPLICATIONS
Authors: NGUYEN-TUONG ANH , GRIMSHAW ANDREW S.
Published: February 2003

As part of the Legion metacomputing project, we have developed a reflective model, the Reflective Graph & Event (RGE) model, for incorporating functionality into applications. In this paper we apply the RGE model to the problem of making applications more robust to failures. RGE encourages system developers to express fault-tolerance algorithms in terms of transformations on the data structures that represent computations — messages and methods — hence enabling the construction of generic and reusable fault-tolerance components. We illustrate the expressive power of RGE by encapsulating the following fault-tolerance techniques into RGE components: two-phase commit distributed checkpointing, passive replication, pessimistic method logging, and forward recovery.
OPTIMALITY AND SELF-STABILIZATION IN ROOTED TREE NETWORKS
Authors: PETIT FRANCK , VILLAIN VINCENT
Published: February 2003

In this paper, we consider arbitrary tree networks where every processor, except one, called the root, executes the same program. We show that, to design a depth-first token circulation protocol in such networks, it is necessary to have at least [Formula: see text] configurations, where n is the number of processors in the network and Δi is the degree of processor pi.

We then propose a depth-first token circulation algorithm which matches the above minimal number of configurations. We show that the proposed algorithm is self-stabilizing, i.e., the system eventually recovers itself to a legitimate state after any perturbation modifying the state of the processors. Hence, the proposed algorithm is optimal in terms of the number of configurations and no extra cost is involved in making it stabilizing.
CALCULATING AN OPTIMAL HOMOMORPHIC ALGORITHM FOR BRACKET MATCHING
Authors: HU ZHENJIANG , TAKEICHI MASATO
Published: February 2003

It is widely recognized that a key problem of parallel computation is in the development of both efficient and correct parallel software. Although many advanced language features and compilation techniques have been proposed to alleviate the complexity of parallel programming, much effort is still required to develop parallelism in a formal and systematic way. In this paper, we intend to clarify this point by demonstrating a formal derivation of a correct but efficient homomorphic parallel algorithm for a simple language recognition problem known as bracket matching. To the best of our knowledge, our formal derivation leads to a novel divide-and-conquer parallel algorithm for bracket matching.
MEMORY HIERARCHY PERFORMANCE PREDICTION FOR BLOCKED SPARSE ALGORITHMS
Authors: FRAGUELA BASILIO B. , DOALLO RAMÓN , ZAPATA EMILIO L.
Published: February 2003

Nowadays the performance gap between processors and main memory makes an efficient usage of the memory hierarchy necessary for good program performance. Several techniques have been proposed for this purpose. Nevertheless most of them consider only regular access patterns, while many scientific and numerical applications give place to irregular patterns. A typical case is that of indirect accesses due to the use of compressed storage formats for sparse matrices. This paper describes an analytic approach to model both regular and irregular access patterns. The application modeled is an optimized sparse matrix-dense matrix product algorithm with several levels of blocking. Our model can be directly applied to any memory hierarchy consisting of K-way associative caches. Results are shown for several current microprocessor architectures.
SORTING AND SELECTION ON A LINEAR ARRAY WITH OPTICAL BUS SYSTEM
Authors: ELGINDY HOSSAM , RAJASEKARAN SANGUTHEVAR
Published: February 2003

In this paper we present randomized algorithms for selection and sorting on linear arrays with optical bus communication systems. We show that sorting n given numbers can be performed in O( log n) time with high probability on a linear array, of n processors, with a reconfigurable optical bus system (Linear-AROB). We also show that selection can be performed in O(1) time with high probability on the same parallel machine model.
PROVABLY FASTEST PARALLEL ALGORITHMS FOR BIPARTITE PERMUTATION GRAPHS
Authors: CHEN LIN , JIANG JULIUS Y. , NYEU MAUNG T.
Published: February 2003

Provably fastest parallel algorithms for a number of problems on bipartite permutation graphs are presented here. These problems include, among others, connectivity, recognition, isomorphism detection, Hamiltonian path, and shortest path. The algorithms here all run in logarithmic time on CREW PRAM. The processor bound is the same as that for multiplying two matrices in logarithmic time on the model and is subcubic.
A NOTE ON THE IMPLEMENTATION OF REPLICATION-BASED GARBAGE COLLECTION FOR MULTITHREADED APPLICATIONS AND MULTIPROCESSOR ENVIRONMENTS
Authors: AZAGURY ALAIN , KOLODNER ELLIOT K. , PETRANK EREZ
Published: February 2003

Replication-based incremental garbage collection is one of the more appealing concurrent garbage collection algorithms known today. It allows continuous operation of the application (the mutator) with very short pauses for garbage collection. There is a growing need for such garbage collectors suitable for a multithreaded environments such as the Java Virtual Machine. Furthermore, it is desirable to construct collectors that also work on multiprocessor computers.

We begin by pointing out an important, yet subtle point, which arises when implementing the replication-based garbage collector for a multithreaded environment. We first show that a simple and natural implementation of the algorithm may lead to an incorrect behavior of multithreaded applications. We then show that another simple and natural implementation eliminates the problem completely. Thus, the contribution of this part is in stressing this warning to future implementors.

Next, we address the effects of the memory coherence model on this algorithm. We show that even when the algorithm is properly implemented with respect to our first observation, a problem might still arise when a multiprocessor system is used. Adopting a naive solution to this problem results in very frequent (and expensive) synchronization. We offer a slight modification to the algorithm which eliminates the problem and requires little synchronization.
PERFORMANCE EVALUATION OF JPVM
Authors: LEE BU-SUNG , GU YAN , CAI WENTONG , HENG ALFRED
Published: February 2003

PVM for Java (JPVM) is a parallel programming environment that provides a set of Parallel Virtual Machine (PVM)-like class libraries developed using Java. JPVM inherits the attributes of Java, especially Java support of heterogeneous system. However, it also has the disadvantage of poor performance when compared to native codes. Java performance has been considerably improved with the recent introduction of Just in Time (JIT) compilers. This paper evaluates JPVM, with and without JIT compilation, using some well-known parallel processing benchmarks. It will also highlight some of the areas that limit the use of Java in parallel processing on distributed systems. The objective of the paper is to provide some performance indications of using Java in network-based parallel computing environments.
AN AIDED GENETIC ALGORITHM FOR MULTIPROCESSOR SCHEDULING
Authors: VAIDEHI V. , KRISHNAN C. N. , SWAMINATHAN P.
Published: February 2003

Genetic algorithms have been used for solving the problem of scheduling the tasks represented by a task graph onto parallel computing architectures to minimize the schedule length of the task graph. Due to the random nature of the initial population they however face the local extrema problem which could make the resulting schedules sub-optimal. To minimize this problem, an Aided Genetic Algorithm(AGA) is proposed in this paper, in which a member of the initial population of the Genetic algorithm is obtained from a heuristic pre-scheduler. It is found that the AGA achieves the required convergence in (a) lesser number of iterations, and (b) lesser number of trials in obtaining the near-optimal solution compared to the conventional genetic algorithm. The proposed AGA also takes the inter-task communication into account while scheduling. The method is then applied to the problem of optimally scheduling the Kalman filtering algorithm onto a multi-transputer network. The results are experimentally on a network of T-805 transputers.
THE OBSERVATION: AN ABSTRACT COMMUNICATION MECHANISM
Authors: CHARPENTIER MICHEL , FILALI MAMOUN , MAURAN PHILIPPE , PADIOU GÉRARD , QUÉINNEC PHILIPPE
Published: February 2003

In this paper, we introduce an observation relation as an abstraction of point-to-point communication in distributed architectures. After showing how its semantics and syntax can be embedded within the UNITY approach, we state general observation properties. Finally, we consider the description and the validation of a distributed mutual exclusion algorithm. The relevant aspect of such a validation is the exclusive use of refinements and observations properties for the proof of these refinements.
PROBABILISTIC ANALYSIS FOR DISCRETE ATTRIBUTES OF MOVING POINTS
Authors: BASCH JULIEN , DEVARAJAN HARISH , INDYK PIOTR , ZHANG LI
Published: February 2003

We perform a probabilistic study of discrete attributes of moving points. In our probabilistic model, an item is given an initial position and a velocity drawn independently at random from the same distribution. We study the expected number of changes that happen to the closest pair, the Voronoi diagram, and the convex hull of a set of such moving items.
NUCLEON-NUCLEON PARITY VIOLATION EXPERIMENTS
Authors: VAN OERS WILLEM T. H.
Published: February 2003

Measurements of parity-violating longitudinal analyzing powers Az (normalized asymmetries) in polarized proton-proton scattering and in polarized neutron capture on the proton (n-p→d - γ) provide a unique window on the interplay between the weak and strong interactions between and within hadrons. Several new proton-proton parity violation experiments are presently either being performed or are being prepared for execution in the near future: at TRIUMF at 221 MeV and 450 MeV and at COSY (Forschungszentrum Jülich) in the multi-GeV range. A new measurement of the parity-violating γ ray asymmetry with a ten-fold improvement in the accuracy over previous measurements is being developed at LANSCE. These experiments are intended to provide stringent constraints on the set of six effective weak meson-nucleon coupling constants, which characterize the weak interaction between hadrons in the energy domain where meson exchange models provide an appropriate description. The 221 MeV p - p experiment is unique in that it selects a single transition amplitude (3P2-1D2) and consequently constrains the weak meson-nucleon coupling constant [Formula: see text]. The n-p→d-γ experiment is mainly sensitive to the weak pion-nucleon coupling constant fπ. Together with the existing p-p parity violation experimental results one may be able to delineate the various weak meson-nucleon coupling constants. The TRIUMF 221 MeV p-p parity violation experiment will be described in some detail. Other parity violation nucleon-nucleon and nucleon-very-light-nucleus experiments are commented on. The anomalous result obtained at 6 GeV/c on a water target requires that a new multi-GeV p-p parity violation experiment be performed.
ELASTIC SCATTERING OF INTERMEDIATE ENERGY PARTICLES ON 20Ne NUCLEI
Authors: BEREZHNOY YU. A. , MIKHAILYUK V. P.
Published: February 2003

The differential cross-sections and polarization observables of 800 MeV proton and 1.37 GeV α-particle elastic scattering on 20 Ne nuclei are calculated on the basis of multiple diffraction scattering theory and α-cluster model with dispersion. It is shown that α-cluster structure is strongly manifested in 20 Ne nuclei and the assumption about that allows us to agree with the calculated and measured observables in the elastic 800 MeV proton scattering on these nuclei.
MODELLING UNCERTAINTY IN MULTIMEDIA DATABASE SYSTEMS: AN EXTENDED POSSIBILISTIC APPROACH
Authors: DE TRÉ GUY , DE CALUWE RITA
Published: February 2003

In database systems one often has to deal with constraints in order to compel the semantics of the stored data or to express some querying criteria. This is especially the case for multimedia database systems where information of different media types, as e.g. sound, video, images and texts, needs to be managed. A problem with the modelling of (the uncertainty about) the degree of satisfaction of a constraint, is the handling of missing information. In this paper, it is shown how extended possibilistic truth values can be employed to cope with this problem. The notion of an extended possibilistic truth value has been obtained from the assumption that the truth value, which expresses the degree of satisfaction of a constraint, can be undefined. This is for example the case if the constraint cannot be evaluated due to the non-applicability of (some of) its elements. An illustrative database definition and database querying example is presented and discussed.
A FUZZY OBJECT-BASED DATA MODEL FOR IMPERFECT SPATIAL INFORMATION INTEGRATING EXACT OBJECTS AND FIELDS
Authors: BORDOGNA GLORIA , CHIESA SERGIO
Published: February 2003

In this contribution a fuzzy object-based data model for imperfect spatial information is proposed within the formal framework of fuzzy set theory and possibility theory. The proposal integrates the two opposite views of geographic entities seen as either exact objects or continuous fields in current Geographic Information Systems. By assuming a Fuzzy Object-Oriented Data modelling approach new data types for representing geographic entities characterized by either unsharp boundaries or indeterminate boundaries and relationships are defined.

Linguistic qualifiers are adopted both to express the extent by which an element of the spatial domain satisfies a gradual property, and to identify regions with indeterminate boundaries.
FLEXIBILITY AND FUZZY CASE-BASED EVALUATION IN QUERYING: AN ILLUSTRATION IN AN EXPERIMENTAL SETTING
Authors: DE CALMÈS MARTINE , DUBOIS DIDIER , HULLERMEIER EYKE , PRADE HENRI , SEDES FLORENCE
Published: February 2003

Queries to a database can be made more powerful by allowing flexibility in the specification of what has to be retrieved, and by referring to cases either for expressing the request, or for computing the answer. In this paper, we present an implemented information system (applied to a database describing houses to let), based on an approach developed in the fuzzy set and possibility theory setting. This provides a unified framework for expressing users' preferences about what they are looking for, for weighting the importance of requirements, for referring to examples that they like and/or counter-examples that they dislike, and for making case-based predictions. Thus information querying goes beyond the retrieving of items from a database, and involves associated tools which help the user to figure out the actual contents of the database.
FOUR-VALUED KNOWLEDGE AUGMENTATION FOR STRUCTURED DOCUMENT RETRIEVAL
Authors: LALMAS M. , ROLLEKE T.
Published: February 2003

Structured documents are composed of objects with a content and a logical structure. The effective retrieval of structured documents requires models that provide for a content-based retrieval of objects that takes into account their logical structure, so that the relevance of an object is not solely based on its content, but also on the logical structure among objects. This paper proposes a formal model for representing structured documents where the content of an object is viewed as the knowledge contained in that object, and the logical structure among objects is capture by a process of knowledge augmentation: the knowledge contained in an object is augmented with that of its structurally related objects. The knowledge augmentation process takes into account the fact that knowledge can be incomplete and become inconsistent.
LEARNING RETRIEVAL EXPERT COMBINATIONS WITH GENETIC ALGORITHMS
Authors: BILLHARDT HOLGER , BORRAJO DANIEL , MAOJO VICTOR
Published: February 2003

The goal of information retrieval (IR) is to provide models and systems that help users to identify the relevant documents to their information needs. Extensive research has been carried out to develop retrieval methods that solve this goal. These IR techniques range from purely syntax-based, considering only frequencies of words, to more semantics-aware approaches. However, it seems clear that there is no single method that works equally well on all collections and for all queries. Prior work suggests that combining the evidence from multiple retrieval experts can achieve significant improvements in retrieval effectiveness. A common problem of expert combination approaches is the selection of both the experts to be combined and the combination function. In most studies the experts are selected from a rather small set of candidates using some heuristics. Thus, only a reduced number of possible combinations is considered and other possibly better solutions are left out. In this paper we propose the use of genetic algorithms to find a suboptimal combination of experts for a document collection at hand. Our approach automatically determines both the experts to be combined and the parameters of the combination function. Because we learn this combination for each specific document collection, this approach allows us to automatically adjust the IR system to specific user needs. To learn retrieval strategies that generalize well on new queries we propose a fitness function that is based on the statistical significance of the average precision obtained on a set of training queries. We test and evaluate the approach on four classical text collections. The results show that the learned combination strategies perform better than any of the individual methods and that genetic algorithms provide a viable method to learn expert combinations. The experiments also evaluate the use of a semantic indexing approach, the context vector model, in combination with classical word matching techniques.
UNCERTAINTY AND TERM SELECTION IN TEXT CATEGORIZATION
Authors: PETERS CHARLES M. E. E. , KOSTER CORNELIS H. A.
Published: February 2003

This paper discusses the notion of Uncertainty, which has a prominent place in the theory and experimental practice of modern Physics. It argues that the awareness of Uncertainty may also be of tremendous importance to the field of Information Retrieval, and in particular Text Categorization.

As an application of Uncertainty in Text Categorization, a new criterion for Term Selection is described, which is based on the Uncertainty in Term Frequency across categories. This criterion allows to distinguish between low-quality (or "noisy") and high-quality ("stiff") terms.

We describe an experiment investigating the effect of eliminating noisy and stiff terms in the context of text classification. In the experiment we applied the Rocchio and Winnow classification algorithms to a collection of newspaper items, a mono-classified subset of the well-known Reuters 21578 corpus.

This investigation shows that both the local elimination of noisy terms and the global elimination of stiff terms can be used for Term Selection in Text Categorization.
LONG MEMORY IN FINANCIAL TIME SERIES DATA WITH NON-GAUSSIAN DISTURBANCES
Authors: GIL-ALANA LUIS A.
Published: March 2003

In this article we propose the use of a version of the tests of Robinson [32] for testing unit and fractional roots in financial time series data. The tests have a standard null limit distribution and they are the most efficient ones in the context of Gaussian disturbances. We compute finite sample critical values based on non-Gaussian disturbances and the power properties of the tests are compared when using both, the asymptotic and the finite-sample (Gaussian and non-Gaussian) critical values. The tests are applied to the monthly structure of several stock market indexes and the results show that the if the underlying I(0) disturbances are white noise, the confidence intervals include the unit root; however, if they are autocorrelated, the unit root is rejected in favour of smaller degrees of integration. Using t-distributed critical values, the confidence intervals for the non-rejection values are generally narrower than with the asymptotic or than with the Gaussian finite-sample ones, suggesting that they may better describe the time series behaviour of the data examined.
Fates of Orphans: Poor Children in Antebellum Charleston
Authors: Murray John E.
Published: February 2003

The circumstances of children upon leaving the Charleston Orphan House were strongly influenced by their circumstances upon arriving. Most of these children were bound out as apprentices after a few years; a large, and growing, minority of them returned to their families; and others died or ran away from the institution. Those with widowed mothers who maintained close ties with them—as evidenced by the children's literacy—were most likely to resume family life after their mothers remarried. Those who had been delivered to the orphanage by other family members or by public officials tended not to be so fortunate.
Rich in the Wisdom of Hindsight
Authors: Henige David
Published: February 2003

The modern historiography of Africa has been so accelerated that many of its earliest practitioners still ply their trade. The fact that these pioneering scholars have changed their minds and practices considerably over time, often without any discussion of their reasons for doing so, suggests, among other things, that the evaluation of their contributions to the field cannot take place on a small scale; it must take into account their entire corpora, both substantively and methodologically.
Gorillas in Our Midst: Rulers in the Twentieth Century
Authors: Rotberg Robert I.
Published: February 2003

The twentieth century saw its share of autocrats and tyrants. The question of how to understand each group, as well as the differences between them, is certainly a fit subject for the interdisciplinary study of history. Hard evidence from psychology and biology stand ready to make a valuable contribution to it. Yet, at this juncture, political and sociological explanations for the bizarre behavior of ruthless leaders have more to offer than taxonomical imperatives derived from anecdotal data about personality traits of rulers and sociobiological speculations based on the impulses of dominant male primates.
Docosahexaenoic acid enhances arsenic trioxide–mediated apoptosis in arsenic trioxide–resistant HL-60 cells
Authors: Sturlan Sanda , Baumgartner Melanie , Roth Erich , Bachleitner-Hofmann Thomas
Published: March 2003

Recent reports indicate a broad spectrum of antileukemic activity for arsenic trioxide (As2O3) due to its ability to induce apoptosis via intracellular production of reactive oxygen species (ROS). Despite its potent apoptotic mechanism, As2O3 is not equally effective in all leukemic cells, which has prompted a search for agents enhancing As2O3 efficacy. Recently, evidence has been gathered that the polyunsaturated fatty acid docosahexaenoic acid (DHA) may sensitize tumor cells to ROS-inducing anticancer agents. The aim of our investigation was to evaluate whether DHA enhances As2O3-mediated apoptosis in As2O3-resistant HL-60 cells. While 1 μM As2O3 or 25 μM DHA reduced cell viability to 85.8% ± 2.9% and 69.2% ± 3.6%, combined treatment with As2O3 and DHA reduced viability to 13.0% ± 9.9% with a concomitant increase of apoptosis. Apoptotic cell death was preceded by collapse of the mitochondrial membrane potential, increased expression of proapoptotic B-cell lymphoma protein-2–associated X protein (Bax), and caspase-3 activation. Importantly, the combined effect of As2O3 and DHA was associated with increased production of intracellular ROS and toxic lipid peroxidation products and was abolished by the antioxidant vitamin E or when oleic acid (a nonperoxidizable fatty acid) was used in place of DHA. Intracellular ROS and toxic lipid peroxidation products most likely constitute the key mediators contributing to the combined effect of As2O3 and DHA. Our data provide the first evidence that DHA may help to extend the therapeutic spectrum of As2O3 and suggest that the combination of As2O3 and DHA could be more broadly applied in leukemia therapy.
Major mutations in calf-1 and calf-2 domains of glycoprotein IIb in patients with Glanzmann thrombasthenia enable GPIIb/IIIa complex formation, but impair its transport from the endoplasmic reticulum to the Golgi apparatus
Authors: Rosenberg Nurit , Yatuv Rivka , Sobolev Vladimir , Peretz Hava , Zivelin Ariella , Seligsohn Uri
Published: March 2003

The crystal structure of integrin αvβ3 comprises 3 regions of contact between αv and β3. The main contact on αv is located in the β-propeller while calf-1 and calf-2 domains contribute minor interfaces. Whether or not contacts between calf-1 and calf-2 domains of glycoprotein (GP) IIb (αIIb) and GPIIIa (β3) play a role in GPIIb/IIIa complex formation has not been established. In this study we analyzed the effects of 2 naturally occurring mutations in calf-1 and calf-2 domains on GPIIb/IIIa complex formation, its processing, and transport to the cell membrane. The mutations investigated were a deletion-insertion in exon 25 located in calf-2 and an in-frame skipping of exon 20 located in calf-1. Mutated GPIIb cDNAs were cotransfected in baby hamster kidney cells with normal GPIIIa (β3) cDNA. Analysis by flow cytometry failed to demonstrate detectable amounts of GPIIb or GPIIb/IIIa complex on the surface of cells transfected with each mutation, but immunohistochemical staining revealed their intracellular presence. GPIIb was mainly demonstrable as pro-GPIIb by immunoprecipitation of cell lysates expressing each mutation. Differential immunofluorescence staining of GPIIb and cellular organelles suggested that most altered complexes were located in the endoplasmic reticulum. Homology modeling of normal GPIIb based on the αvβ3 crystal structure revealed similar contacts between αv and β3 and between αIIb and β3. Introduction of the mutations into the model yielded partial disruption of the normal contacts in the corresponding domains. These data suggest that despite partial disruption of calf-1 or calf-2 domain, GPIIb/IIIa complex is formed but its transport from the endoplasmic reticulum is impaired.
Phosphatidylserine externalization in sickle red blood cells: associations with cell age, density, and hemoglobin F
Authors: Yasin Zahida , Witting Scott , Palascak Mary B. , Joiner Clinton H. , Rucknagel Donald L. , Franco Robert S.
Published: March 2003

Phosphatidylserine (PS) is normally confined to the cytoplasmic leaflet of the red blood cell (RBC) membrane, but some sickle RBCs expose PS in the outer leaflet (PS+ cells). This study examined the relationships among PS externalization, fetal hemoglobin content, hydration state, and cell age. Sickle RBCs exhibit a wide range of PS externalization. Those with low-level exposure (type 1 PS+) include many young transferrin-receptor-positive (TfR+) cells. This is not specific for sickle cell disease because many nonsickle TfR+ cells are also PS+. RBCs with higher PS exposure (type 2 PS+) appear to be more specific for sickle cell disease. Their formation is most likely sickling dependent because type 2 PS+ dense sickle cells have a lower percentage of fetal hemoglobin (HbF) than PS- cells in the same density fraction (1.7 vs 2.9; n = 8; P < .01). In vivo experiments using biotin-labeled sickle cells showed a sharp decrease in the percentage of circulating, labeled PS+ cells in the first 24 hours after reinfusion. This decrease was confined to type 1 PS+ cells and was thus consistent with the reversal of PS exposure in very young cells. As the labeled cells aged in the circulation, the percentages of type 1 and type 2 PS+ cells increased. These studies indicate that PS externalization in sickle cells may be low level, as observed in many immature cells, or high level, which is associated with dehydration and appears to be more specific for sickle RBCs. (Blood. 2003;102: 365-370)
Telomerase and telomere length in multiple myeloma: correlations with disease heterogeneity, cytogenetic status, and overall survival
Authors: Wu Kai-Da , Orme Lisa M. , Shaughnessy John , Jacobson Joth , Barlogie Bart , Moore Malcolm A. S.
Published: March 2003

We have investigated the significance of telomerase activity (TA) and telomere length (TL) in multiple myeloma (MM). The analyses were undertaken on CD138+ MM cells isolated from the marrow of 183 patients either at diagnosis or in relapse. There was heterogeneity in telomerase expression; 36% of the patients had TA levels comparable to those detected in normal plasma cells, and 13% of patients had levels 1- to 4-fold greater than in a neuroblastoma cell line control. The TL of MM cells was significantly shorter than that of the patients' own leukocytes; in 25% of patients, the TL measured less than 4.0 kbp. Analysis of TL distribution indicated selective TA-mediated stabilization of shorter telomeres when mean TL fell below 5.5 kbp. Unusually long (10.8-15.0 kbp) telomeres were observed in 7 patients, and low TA was observed in 5 of 7 patients, suggesting the operation of a TA-independent pathway of telomere stabilization. A strong negative correlation existed between TA and TL or platelet count. TL negatively correlated with age and with interleukin-6 (IL-6) and β2-microglobulin levels. Various cytogenetic abnormalities, including those associated with poor prognosis, strongly correlated with TA and, to a lesser extent, with short TL. High TA and short TL defined a subgroup of patients with poor prognosis. At 1 year the survival rate in patients with TA levels lower than 25% of neuroblastoma control and TL greater than 5.5 kbp was 82%, whereas in patients with higher TA and shorter TL the survival rate was 63% (P = .004). The 2-year survival rate for patients with TA levels lower than 25% was 81%, and it was 52% in those with higher TA levels (P <.0001).
Involvement of a CD47-dependent pathway in platelet adhesion on inflamed vascular endothelium under flow
Authors: Lagadec Patricia , Dejoux Olivier , Ticchioni Michel , Cottrez Françoise , Johansen Mette , Brown Eric J. , Bernard Alain
Published: March 2003

Resting platelet adhesion to inflammatory vascular endothelium is thought to play a causal role in secondary thrombus formation or microcirculatory disturbance after vessel occlusion. However, though adhesion receptors involved in platelet-matrix interactions have been extensively studied, the molecular mechanisms involved in platelet-endothelium interactions are incompletely characterized and have been mainly studied under static conditions. Using human platelets or platelets from wild-type and CD47–/– mice in whole blood, we demonstrated that at low shear rate, CD47 expressed on human and mouse platelets significantly contributes to platelet adhesion on tumor necrosis factor-α (TNF-α)–stimulated vascular endothelial cells. Using the CD47 agonist peptide 4N1K and blocking monoclonal antibodies (mAbs), we showed that CD47 binds the cell-binding domain (CBD) of endothelial thrombospondin-1 (TSP-1), inducing activation of the platelet αIIbβ3 integrin that in turn becomes able to link the endothelial receptors intercellular adhesion molecule 1 (ICAM-1) and αvβ3. Platelet CD36 and GPIbα are also involved because platelet incubation with blocking mAbs directed against each of these 2 receptors significantly decreased platelet arrest. Given that anti-CD47 treatment of platelets did not further decrease the adhesion of anti-CD36–treated platelets and CD36 is a TSP-1 receptor, it appears that CD36/TSP-1 interaction could trigger the CD47-dependent pathway. Overall, CD47 antagonists may be potentially useful to inhibit platelet adhesion on inflamed endothelium.
Selective T-cell ablation with bismuth-213–labeled anti-TCRαβ as nonmyeloablative conditioning for allogeneic canine marrow transplantation
Authors: Bethge Wolfgang A. , Wilbur D. Scott , Storb Rainer , Hamlin Donald K. , Santos Erlinda B. , Brechbiel Martin W. , Fisher Darrell R. , Sandmaier Brenda M.
Published: March 2003

Two major immunologic barriers, the host-versus-graft (HVG) and graft-versus-host (GVH) reactions, have to be overcome for successful allogeneic hematopoietic cell transplantation. T cells were shown to be primarily involved in these barriers in the major histocompatibility complex identical setting. We hypothesized that selective ablation of T cells using radioimmunotherapy together with postgrafting immunosuppression would suffice to ensure stable allogeneic engraftment. We had described a canine model of nonmyeloablative marrow transplantation in which host immune reactions were impaired by a single dose of 200 cGy total body irradiation (TBI), and both GVH and residual HVG reactions were controlled by postgrafting immunosuppression with mycophenolate mofetil (MMF) and cyclosporine (CSP). Here, we substituted the α-emitter bismuth-213 (213Bi) linked to a monoclonal antibody (mAb) against T-cell receptor (TCR) αβ, using the metal-binding chelate diethylenetriaminepentaacetic acid (DTPA) derivative cyclohexyl–(CHX)-A″, for 200 cGy TBI. Biodistribution studies using a γ-emitting indium-111–labeled anti-TCRαβ mAb showed uptake primarily in blood, marrow, lymph nodes, spleen, and liver. Four dogs were treated with 0.13 to 0.46 mg/kg TCRαβ mAb labeled with 3.7 to 5.6 mCi/kg (137-207 MBq/kg) 213Bi. The treatment was administered in 6 injections on days –3 and –2 followed by transplantation of dog leukocyte antigen-identical marrow on day 0 and postgrafting immunosuppression with MMF/CSP. The therapy was well tolerated except for elevations of transaminases that were transient in all but one of the dogs. No other organ toxicities or signs of graft-versus-host disease were noted. The dogs had prompt allogeneic hematopoietic engraftment and achieved stable mixed donor-host hematopoietic chimerism with donor contributions ranging from 5% to 55% after more than 30 weeks of follow up.