bluuebunny/crossref_metadata_2025 huggingface dataset:
Life in the fast lane: actin-based motility of plant peroxisomes
Authors: Collings David A , Harper John DI , Marc Jan , Overall Robyn L , Mullen Robert T
Published: July 2002

Peroxisomal shape, distribution, motility, and interactions with cytoskeletal elements were examined during interphase in living leek (Allium porrum L.) epidermal cells transiently transformed with a construct encoding the green fluorescent protein bearing a carboxy-terminal type 1 peroxisomal targeting signal. Confocal laser scanning microscopy and time-course analysis revealed that labeled peroxisomes were either spherical or rod-shaped and possessed several types of motility including random oscillations, slow and fast directional and bidirectional movements, and stop-and-go movements. Co-localization studies indicated that most peroxisomes were in close association with actin filaments, while treatment of cells with the actin-disrupting drug cytochalasin D blocked all types of peroxisomal movements. In contrast, the overall spatial organization of peroxisomes and the microtubule cytoskeleton were different, and the microtubule-destabilizing agent oryzalin had no obvious effect on peroxisomal motility. These data indicate that the peroxisome in plant cells is a highly dynamic compartment that is dependent upon the actin cytoskeleton, not microtubules, for its subcellular distribution and movements.Key words: actin filaments, cytoskeleton, green fluorescent protein, leek, microtubules, peroxisomes.
The influence of hydrological and biotic processes on brown trout (Salmo trutta) population dynamics
Authors: Cattanéo Franck , Lamouroux Nicolas , Breil Pascal , Capra Hervé
Published: July 2002

Hydrological and biotic forces constrain brown trout (Salmo trutta) population dynamics, but tests of their role across numerous streams are uncommon. In 30 French stream reaches, using 58 samples (1 per year) each, we investigated whether the year-to-year seasonal hydrology influenced annual trout densities within reaches, and whether the relationships were shared by all reaches. We also searched for intraspecific interactions between and within cohorts. Trout data were age class (0+, 1+, and adults) densities. For each year, hydrology was described using 13 variables, each computed for a reproduction, emergence, and growth period related to the biological cycle of trout. We used analyses of covariance (ANCOVA) to test how trout densities at year n  1 and hydrology at year n influenced trout densities at year n. High flows during emergence significantly reduced the 0+ densities, consistently across the 30 reaches. Then, 1+ and adult densities were linked, respectively, to 0+ and 1+ densities from the previous year. Analyses also revealed density-dependent survival mechanisms for the 0+ cohort, suggesting intracohort competition. Therefore, hydrology constrains trout dynamics only during the critical emergence period, after which intracohort interactions regulate the 0+ density. Such mechanisms, validated across 30 environmentally different reaches, seem to be fundamental to trout population dynamics.
Transferability of habitat suitability criteria of juvenile Atlantic salmon (Salmo salar)
Authors: Mäki-Petäys Aki , Huusko Ari , Erkinaro Jaakko , Muotka Timo
Published: July 2002

We constructed generalized habitat criteria for juvenile Atlantic salmon (Salmo salar) based on four river-specific suitability indices for depth, water velocity, and substrate to assess whether habitat criteria for juvenile Atlantic salmon are transferable across rivers. We first tested whether salmon are more likely to occupy higher-quality habitats than generally available in a stream reach based on these composite criteria. We then repeated the same procedure using the river-specific criteria of this study and the generalized habitat suitability criteria of Heggenes. As expected, the river-specific criteria were generally the most effective ones in predicting fish habitat use. However, both of the two generalized criteria also transferred fairly well to the test sites. Viewed across salmon size-classes (<9 cm and >9 cm), the river-specific criteria passed the test in ten of eleven cases (91%), and the two generalized criteria passed in nine (82%) of eleven. Thus, it appears that with respect to summertime habitat criteria for juvenile Atlantic salmon, criteria transference is conceivable at least on a regional scale, and perhaps even on a more "universal" scale.
Identification and characterization of RAPD markers inferring genetic relationships among Pine species
Authors: Nkongolo K K , Michael P , Gratton W S
Published: July 2002

Total genomic DNAs were extracted from several populations of pine species and amplified using oligonucleotides of random sequences. Polymorphism in random amplified polymorphic DNA (RAPD) markers was high and sufficient in distinguishing each of the species. Genetic relationships among eight pine species (Pinus sylvestris, Pinus strobus, Pinus rigida, Pinus resinosa, Pinus nigra, Pinus contorta, Pinus monticola, and Pinus banksiana) from different provenances were analyzed. The degree of band sharing was used to evaluate genetic distance between species and to construct a phylogenetic tree. In general, the dendrogram corroborated the description of relationships based on morphological characteristics and crossability, but also provided new insights into pine taxonomy. RAPD markers specific to some pine species were cloned and sequenced. PCR amplifications using pairs of designed specific primers revealed that all the cloned sequences were likely genus specific because they were not found in spruce or larch. True species-specific sequences were identified using designed primers flanking cloned RAPD fragments. The analysis of RAPD fragment sequences confirmed the genetic relationships among species. A 2281-bp RAPD band called PI-Mt-Stb-23 from P. strobus was used as a probe in restriction fragment length polymorphism (RFLP) analysis and produced distinct banding patterns for each species examined, consistent with the highly polymorphic character of DNA-fingerprinting probes.Key words: Pine, RAPD, RFLP, cloning, species-specific sequences.
A microsatellite sequence from the rice blast fungus (Magnaporthe grisea) distinguishes between the centromeres ofHordeum vulgareandH. bulbosumin hybrid plants
Authors: Kim N -S , Armstrong K C , Fedak G , Ho K , Park N -I
Published: July 2002

A TC/AG-repeat microsatellite sequence derived from the rice blast fungus (Magnaporthe grisea) hybridized to all of the centromeres of Hordeum vulgare chromosomes, but hybridized faintly or not at all to the chromosomes of Hordeum bulbosum. Using this H. vulgare centromere-specific probe, the chromosomes of four F1hybrids between H. vulgare and H. bulbosum were analyzed. The chromosome constitution in the root tips of the hybrids was mosaic, i.e., 7 (7v, H. vulgare) and 14 (7v + 7b H. bulbosum), or 14 (7v + 7b) and 27 (14v + 13b), or 7 (7v), 14 (7v + 7b), and 27 (14v + 13b). The 27-chromosome tetraploid hybrid cells were revealed to have the NOR (nucleolus organizer region) bearing chromosome of H. bulbosum in a hemizygous state, which might indicate some role for this chromosome in the chromosome instability of the hybrid condition. The chromosomal distribution showed that the chromosomes of H. vulgare were concentric and chromosomes of H. bulbosum were peripheral in the mitotic squash. This non-random chromosome distribution and the centromere-specific repeated DNA differences in the two species were discussed in relation to H. bulbosum chromosome elimination. Meiotic chromosome analyses revealed a high frequency of homoeologous chromosome pairing in early prophase. However, this chromosome pairing did not persist until later meiotic stages and many univalents and chromosome fragments resulted. These were revealed to be H. bulbosum by fluorescence in situ hybridization (FISH) analysis with the H. vulgare centromere-specific probe. Because the chromosome segregation of H. vulgare and H. bulbosum chromosomes at anaphase I of meiosis was random, the possibility for obtaining chromosome substitution lines in diploid barley from the diploid hybrid was discussed.Key words: Hordeum vulgare, Hordeum bulbosum, centromere-specific repeated DNA, FISH, chromosome instability.
PROLOG'S CONTROL CONSTRUCTS IN A FUNCTIONAL SETTING — AXIOMS AND IMPLEMENTATION
Authors: HINZE RALF
Published: July 2002

The purpose of this article is twofold. First, we show that Prolog's control constructs can be smoothly integrated into a functional language like Haskell. The resulting 'language', termed embedded Prolog, incorporates many of the features prescribed by the Prolog ISO standard: control constructs including the cut, all solution collecting functions, and error handling facilities. Embedded Prolog lacks some concepts such as logical variables but it inherits all of Haskell's strengths, eg static polymorphic typing, higher order functions etc. Technically, the integration is achieved using monads and monad transformers. One of the main innovations is the definition of a backtracking monad transformer, which allows us to combine backtracking with exception handling and interaction. Second, we work towards an axiomatization of the operations, through which the computational features are accessed. Equations are used to lay down the meaning of the various operations and their interrelations enabling the programmer to reason about programs in a simple calculational style. The axiomatization is applied to show that each finite computation has a simple canonical form.
THE EXPONENTIAL LOCALIZATION AND STRUCTURE OF THE SPECTRUM FOR 1D QUASI-PERIODIC DISCRETE SCHRÖDINGER OPERATORS
Authors: CHULAEVSKY V. A. , SINAI YA. G.
Published: July 2002

We discuss main mechanisms of the exponential localization of the eigenfunctions for one-dimensional quasi-periodic Schrödinger operators with the potential of the form V(α + nω), where V(α) is a non-degenerate C2-function on the d-dimensional torus, and ω ∈ ℝd is a typical vector with rationally incommensurate components. The exponential localization is proved so far for d ≤ 2. We emphasize the different nature of the support of the spectral measure for d = 1 and for d > 1.
GRAVITATIONAL WAVES AND CAUSALITY
Authors: EHRLICH PAUL E. , EMCH GERARD G.
Published: July 2002

A strictly ordered hierarchy of eight causal properties encountered in General Relativity is reviewed for the explicit case of the gravitational plane waves. Illustrative proofs are given to the effect that the place of these space-times is precisely known in the hierarchy: they are causally continuous, but not causally simple. The other conditions of the hierarchy are also discussed separately, as are some causality conditions that belong outside the hierarchy. The investigation relies on the following tools: (1) the symplectic structure appearing in certain matrix differential equations of the Riccati type; and (2) the global properties that can be derived from the isometry group generated by the Killing vector fields of the metric. Connections to some of the techniques of singularity theory are also pointed out.
A NONSTANDARD SUPERSYMMETRIC KP HIERARCHY
Authors: BRUNELLI J.C. , DAS A.
Published: July 2002

We show that the supersymmetric nonlinear Schrödinger equation can be written as a constrained super KP flow in a nonstandard representation of the Lax equation. We construct the conserved charges and show that this system reduces to the super mKdV equation with appropriate identifications. We construct various flows generated by the general nonstandard super Lax equation and show that they contain both the KP and mKP flows in the bosonic limits. This nonstandard supersymmetric KP hierarchy allows us to construct a new super KP equation which is nonlocal.
HYPERSURFACE EXCEPTIONAL SINGULARITIES
Authors: ISHII SHIHOKO , PROKHOROV YURI
Published: July 2002

This paper studies hypersurface exceptional singularities in [Formula: see text] defined by non-degenerate function. For each canonical hypersurface singularity, there exists a weighted homogeneous singularity such that the former is exceptional if and only if the latter is exceptional. So we study the weighted homogeneous case and prove that the number of weights of weighted homogeneous exceptional singularities are finite. Then we determine all exceptional singularities of the Brieskorn type of dimension 3.
THE TWO-PARTICLE TIME-ASYMMETRIC RELATIVISTIC MODEL WITH CONFINEMENT INTERACTION AND QUANTIZATION
Authors: DUVIRYAK A.
Published: July 2002

The relativistic two-particle system with confinement interaction is considered. The quantum-mechanical description of the system is built on the base of classical time-asymmetric model presented in Ref. 1. The mass spectrum and the Regge trajectories are analyzed with the use of continued fraction technique.
CLASSIFICATION OF CONSTRAINTS USING THE CHAIN-BY-CHAIN METHOD
Authors: LORAN F. , SHIRZAD A.
Published: July 2002

We introduce the "chain-by-chain" method for constructing the constraint structure of a system possessing both first- and second-class constraints. We show that the whole constraint can be classified into completely irreducible first- or second-class chains. We found an appropriate redefinition of second-class constraints to obtain a symplectic algebra among them.
PHASE DIAGRAMS FOR FILMS OF TWO-COMPONENT MAGNETIC ALLOYS
Authors: ZHOU YUNSONG , LIN D. L.
Published: July 2002

Phase diagrams for diluted bulk magnetic alloys and two-component magnetic films are investigated. On the basis of the Ising model for layered structures, we calculate the transition temperature as a function of the relative concentration x by means of the variational cumulant expansion. Both the ferromagnetic and antiferromagnetic interactions are considered and the exchange coupling constants between different atoms are treated as adjustable parameters. Experimental phase diagrams in the Tc-x plane for both La 2 Cu 1-x Zn x O 4 and Sm 2 Fe 14-x Co x Si 2 are qualitatively accounted for, and phase diagrams for a randomly mixed two-component thin film of magnetic alloys are predicted.
ELECTRONS ON SOLID HYDROGEN AND SOLID NEON SURFACES
Authors: SMOLYANINOV IGOR I.
Published: July 2002

Two-dimensional gases of electrons levitating on the surfaces of solid hydrogen and solid neon may find novel applications in such diverse areas as quantum computing and supercooling of molecular hydrogen down through the superfluid transition.
LIMITATIONS ON QUANTUM CONTROL
Authors: SOLOMON ALLAN I. , SCHIRMER SONIA G.
Published: July 2002

In this note we give an introduction to the topic of Quantum Control, explaining what its objectives are, and describing some of its limitations.
Two Types of Mechanism of Electrorheological Effect in Polymer Blends
Authors: Orihara H. , Doi M. , Ishibashi Y.
Published: July 2002

We have found two different types of mechanism of electrorheological (ER) effect observed in polymer blends of side-chain type liquid crystalline polymers and a dimethylsiloxane, and clarified the relationship between the ER effect and the structure. On the basis of their mechanisms we discuss the electrorheological properties of these two blends.
Effect of Structures on Rheology in a Model Magnetorheological Fluid
Authors: Zhu Yun , McNeary Michael , Breslin Neal , Liu Jing
Published: July 2002

The structure dependence of rheology on a model magnetorheological fluid is investigated experimentally. We find that the column-dominated structure formed under slow ramping of the magnetic field has higher dynamic yield stress than the "bent-wall" dominated structure formed under the fast ramping field. The measurement of the shear rate loop under fast ramping shows an abnormal rheological hysteresis. It indicates a shear assisted structural transition from the "bent-wall" dominated structure to a more stable structure. A possible shear-induced structure with circular stripes is suggested.
PSEUDO-GAP FEATURES OF INTRINSIC TUNNELING IN (HgBr2)-Bi2212 SINGLE CRYSTALS
Authors: YURGENS AUGUST , WINKLER DAG , CLAESON TORD , HWANG SEONG-JU , CHOY JIN-HO
Published: July 2002

The c-axis tunneling properties of both pristine Bi2212 and its HgBr 2 intercalate have been measured in the temperature range 4.2-250 K. Lithographically patterned 7-10 unit-cell heigh mesa structures on the surfaces of these single crystals were investigated. Clear SIS-like tunneling curves for current applied in the c-axis direction have been observed. The dynamic conductance d I/ d V(V) shows both sharp peaks corresponding to a superconducting gap edge and a dip feature beyond the gap, followed by a wide maximum, which persists up to a room temperature. Shape of the temperature dependence of the c-axis resistance does not change after the intercalation suggesting that a coupling between CuO 2-bilayers has little effect on the pseudogap.
NORMALLY ORDERED EXPANSION OF ENTANGLING OPERATORS AND THEIR SQUEEZING TRANSFORMATION
Authors: FAN HONG-YI
Published: July 2002

We extract two-kinds of entangling operators from the Schmidt decomposition of the EPR-pair eigenstate |η> and |ξ> of continuum variables (see Ref. 10) and study their properties. We derive their normally ordering form and analyze the squeezing effect caused by the entangling operators. The extension to multi-mode entangling operators is also discussed.
SELF-TRAPPING ON A GENERALIZED NONLINEAR TETRAHEDRON
Authors: MOLINA M. I.
Published: July 2002

We analyze the dynamical self-trapping of an excitation propagating on a generalized n-sites tetrahedron, characterized by having every site at equal distance from each other. The evolution equation is given by the Discrete Nonlinear Schrödinger (DNLS) equation. For completely localized initial conditions, we find an exact solution for the critical nonlinearity strength (χ/V) c as a function of the number of sites n of the generalized tetrahedron. This critical nonlinearity, that marks the onset of the self-trapping transition, is always negative for n ≥ 3 and its magnitude increases monotonically with n, always remaining inside the sector delimited by (|χ|/V) = n and (|χ|/V) = 2n.
A TABU SEARCH APPROACH TO POLYGONAL APPROXIMATION OF DIGITAL CURVES
Authors: YIN PENG-YENG
Published: July 2002

Most of the previous polygonal approximation methods are sub-optimal and their compression ratio with respect to a given error tolerance is not good enough for some applications. Recently, a genetic-based approach which can provide near-optimal solutions is presented, but the demands on computation and memory are too high. In this paper, a new polygonal approximation method using the tabu search technique is presented. The proposed method produces a higher compression ratio than the suboptimal approach and the genetic-based approach, and the computation cost and the memory store are more efficient.
COMPLEXITY IN SOME PHYSICAL SYSTEMS
Authors: LÓPEZ-RUIZ R.
Published: July 2002

The LMC-complexity introduced by López-Ruiz et al. [1995] is calculated for different physical situations: one instance of classical statistical mechanics, normal and exponential distributions, and a simplified laser model. We focus on the specific value of the population inversion for which the laser presents maximum complexity.
MELNIKOV'S METHOD AND STICK–SLIP CHAOTIC OSCILLATIONS IN VERY WEAKLY FORCED MECHANICAL SYSTEMS
Authors: AWREJCEWICZ J. , HOLICKE M. M.
Published: July 2002

In this paper we predict stick–slip chaotic dynamics in a one-degree-of-freedom very weakly forced (quasiautonomous) oscillator using the Melnikov's technique. Numerical simulation confirms the validity of our approach.
DETERMINISTIC CHAOS SEEN IN TERMS OF FEEDBACK CIRCUITS: ANALYSIS, SYNTHESIS, "LABYRINTH CHAOS"
Authors: THOMAS R.
Published: July 2002

This paper aims to show how complex nonlinear dynamic systems can be classified, analyzed and synthesized in terms of feedback circuits. The Rössler equations for deterministic chaos are revisited and generalized in this perspective. It is shown that once a proper set of feedback circuits is present in the Jacobian matrix of the system, the chaotic character of trajectories is remarkably robust versus changes in the nature of the nonlinearities. "Labyrinth chaos", whereby simple differential systems generate large lattices of many unstable steady states embedded in a chaotic attractor, is constructed using this technique. In the limit case of a single three-element circuit without diagonal elements, one finds systems possessing an infinite lattice of unstable steady states between which trajectories percolate in a deterministic chaotic way.
DESIGN OF A HYPERCHAOTIC CRYPTOSYSTEM BASED ON IDENTICAL AND GENERALIZED SYNCHRONIZATION
Authors: BRUCOLI MICHELE , CAFAGNA DONATO , CARNIMEO LEONARDA , GRASSI GIUSEPPE
Published: July 2002

In this paper identical and generalized synchronization and the complex dynamics of hyperchaotic circuits are exploited for designing reliable cryptosystems. Since chaotic additive masking, chaotic switching and chaotic parameter modulation methods can have a low degree of security, an attempt to overcome this drawback is made by utilizing hyperchaotic circuits which make available several chaotic signals. Some of these signals are used to properly synchronize the encrypter and the decrypter in an identical and generalized way. Other chaotic signals are considered for encrypting and decrypting the information messages by means of a multishift cipher scheme. The approach is applied to a communication system constituted by an encrypter and a decrypter each consisting of two coupled Chua's circuits, unidirectionally coupled with two coupled Chua's oscillators. Simulation results are reported to show the performance of the suggested cryptosystem.
CALCULATION OF THE SMOOTHING SPLINE WITH WEIGHTED ROUGHNESS MEASURE
Authors: de BOOR CARL
Published: July 2002

A self-contained mathematical derivation of the smoothing spline with weighted roughness measure is offered, along with a discussion of the computational details required for its implementation. The introduction of a weighted roughness measure, even if only piecewise constant, provides additional flexibility in the shaping of the smoothing spline, while not materially increasing the computational cost of its construction or use.
A MATHEMATICAL MODEL FOR FUNGAL POPULATION GROWTH AND THE FUNGICIDE RESISTANCE PROBLEM
Authors: VENDITE LAÉRCIO L. , GHINI RAQUEL
Published: July 2002

A deterministic mathematical model which includes impulses occurring at fixed time periods is proposed in the study of the effects of different dosages on the population dynamics of resistant fungi. The model includes the following parameters which characterize the phenomenon: rS and rR (the apparent infection rates in the sense of Vanderplank for susceptible and resistant fungi), α (change rate from susceptible to resistant populations) and F (the rate by which the population is reduced by fungicide application). As a preliminary step, the model is solved in the absence of fungicide, in order to establish the resistance frequency in the initial population. Numerical simulations have been carried out considering low dosages and high dosages and varying the parameters α, rS, rR. According to the simulations, smaller dosages result in a lower reduced efficacy and delay the instant for total population resistance.
GENERALIZATIONS OF NEWTON'S METHOD
Authors: GILBERT WILLIAM J.
Published: July 2002

We give a survey of the complex dynamics of various generalizations of Newton's method for finding a complex root of a polynomial of a single variable.
MULTIFRACTALITY OF ITERATED PULSE PROCESSES WITH PULSE AMPLITUDES GENERATED BY A RANDOM CASCADE
Authors: VENEZIANO DANIELE , FURCOLO PIERLUIGI , IACOBELLIS VITO
Published: July 2002

A previous paper1 has introduced a class of random functions in Rn called iterated random pulse (IRP) processes. IRP processes are sums of pulses whose locations form an iterated clustered point process and whose deterministic shapes, sizes and amplitudes satisfy affine scaling relations. In the simplest case, at each finer scale the pulse support is isotropically contracted by a factor r>1 and the amplitude is multiplied by r-γ, where γ>-n is a given constant and n is the space dimension. We consider extensions in which the pulse amplitudes are random variables with a multiplicative cascade structure. This means that, if a parent pulse at a certain level has amplitude A, its offspring pulses at the next level have amplitudes Ai=Ar-γ ηi, where the ηi are positive iid variables with mean value 1. Interest is in the generalized field X(h)= lim j→∞Xj(h) where h(t) is a test function, Xj(h)=∫ h(t)Xj(t)dt, and Xj(t) is the pulse field at resolution level j. We show that X(h) is multifractal at small scales. We also derive its scaling properties and the fractal dimension of the support. In the case of non=isotropic contraction of the pulse support from level j to level j+1, X(h) has a more general form of multifractality known as generalized scale invariance (gsi). This seems to be the first known construction of gsi random fields.
THE Ge(001) SURFACE RECONSTRUCTION: DFT AND MCS
Authors: YOSHIMOTO YOSHIHIDE , NAKAMURA YOSHIMICHI , KAWAI HIROSHI , TSUKADA MASARU , NAKAYAMA MASATOSHI
Published: July 2002

The problem of relative energetic stabilities of the high order reconstructions of the Ge(001) surface is revisited by a more refined first-principles calculation based on density functional theory. Using this result, we performed a Monte Carlo simulation of the phase transition, and obtained 315 K as the transition temperature of p(2× 1) → c(4× 2). This reproduces fairly well the transient temperature (250–350 K) observed by an X-ray diffraction experiment. The obtained geometry of the c(4× 2) structure compares well with an X-ray diffraction experiment. The potential energy curves of flip-flop motions of both single dimer and dimer in type-P defect are also obtained.
THE CHARACTERIZATION OF CONTINUOUS QUERIES
Authors: BARBARÁ DANIEL
Published: July 2002

In a world where the amount of electronic information available is constantly growing, techniques to select and filter information efficiently become increasingly important. Continuous queries are a tool that allows users to monitor one or more information sources, by giving the impression that the queries are being run continually over them. In this paper, we formalize the notion of continuous queries for a wide spectrum of environments. We consider both append-only data sources and systems that allow more general data manipulation. We examine the case where the database management software may be modified as well as where we must treat it as a black box. We study the classes of queries that can be supported in each case and present efficient implementation techniques for them.
MINIMAL COST INDEX TRACKING UNDER NONLINEAR TRANSACTION COSTS AND MINIMAL TRANSACTION UNIT CONSTRAINTS
Authors: KONNO HIROSHI , WIJAYANAYAKE ANNISTA
Published: July 2002

Index tracking is a very common and popular approach in portfolio management. When there is neither (nonconvex) transaction costs nor minimal transaction unit constraints, the problem can be formulated as a convex least square problem, so that it can be solved by standard methods. However, when the transaction cost is nonconvex and not negligible, or if there is a minimal unit constraint on the amount of transaction, the problem becomes a nonconvex minimization problem with discrete variables. In this paper, we will propose a branch and bound algorithm for solving this class of problems and show that it can solve an index tracking problem of practical size in a reasonable amount of computation time.
ON THE ASYMPTOTIC BEHAVIOUR OF THE SOLUTION OF ELLIPTIC PROBLEMS IN CYLINDRICAL DOMAINS BECOMING UNBOUNDED
Authors: CHIPOT M. , ROUGIREL A.
Published: July 2002

We study the asymptotic behavior of the solution of linear and nonlinear elliptic problems in cylindrical domains becoming unbounded in one or several directions. In particular we show that this solution converges in H1norm toward the solution of problems set on the cross section of the domains.
INTERTWINING OPERATOR SUPERALGEBRAS AND VERTEX TENSOR CATEGORIES FOR SUPERCONFORMAL ALGEBRAS, I
Authors: HUANG YI-ZHI , MILAS ANTUN
Published: July 2002

We apply the general theory of tensor products of modules for a vertex operator algebra (developed by Lepowsky and the first author) and the general theory of intertwining operator algebras (developed by the first author) to the case of the N=1 superconformal minimal models and related models in superconformal field theory. We show that for the category of modules for a vertex operator algebra containing a subalgebra isomorphic to a tensor product of rational vertex operator superalgebras associated to the N =1 Neveu–Schwarz Lie superalgebra, the intertwining operators among the modules have the associativity property, the category has a natural structure of vertex tensor category, and a number of related results hold. We obtain, as a corollary and special case, a construction of a braided tensor category structure on the category of finite direct sums of minimal modules of central charge [Formula: see text] for the N = 1 Neveu–Schwarz Lie superalgebra for any fixed integers p, q larger than 1 such that p - q ∈ 2ℤ and (p - q)/2 and q relatively prime to each other.
TRANSIENT AND STEADY-STATE DYNAMICS OF GRANULAR SHEAR FLOWS
Authors: LOSERT W. , KWON G.
Published: July 2002

The initiation and steady-state dynamics of granular shear flow are investigated experimentally in a Couette geometry with independently moveable outer and inner cylinders. The motion of particles on the top surface is analyzed using fast imaging. During steady state rotation of both cylinders at different rates, a shear band develops close to the inner cylinder for all combinations of speeds of each cylinder we investigated. Experiments on flow initiation were carried out with one of the cylinders fixed. When the inner cylinder is stopped and restarted after a lag time of seconds to minutes in the same direction, a shear band develops immediately. When the inner cylinder is restarted in the opposite direction, shear initially spans the whole material, i.e. particles far from the shear surface are moving significantly more than in steady state.
BETTER BEING THIRD THAN SECOND IN A SEARCH FOR A MAJORITY OPINION
Authors: STAUFFER DIETRICH
Published: July 2002

Monte Carlo simulations of a Sznajd model show that if a near-consensus is formed out of four initially equally widespread opinions, the one which at intermediate times is second in the number of adherents usually loses out against the third-placed opinion.
IMMUNE AND NEURAL NETWORK MODELS: THEORETICAL AND EMPIRICAL COMPARISONS
Authors: DE CASTRO LEANDRO N. , VON ZUBEN FERNANDO J.
Published: July 2002

This paper brings a detailed mathematical description of an artificial immune network model, named aiNet. The model is implemented in association with graph concepts and hierarchical clustering techniques, and is proposed to perform machine learning, data compression and cluster analysis. Pictorial representations for the aiNet basic units and typical architectures are introduced. The proposed immune network was primarily compared on a theoretical basis with well-known artificial neural networks. Then, the aiNet was applied to a non-linearly separable benchmark and a real-world problem, and the results were compared with that of the self-organizing feature map and with others already presented in the literature.
CLIM
Authors: McKay Scott
Published: July 2002

The essence of an application is a set of objects and a set of operations on those objects. The essence of the behavior of an application's user interface is similar to Lisp's
read-eval-print
loop: the user specifies what he or she wants to do (perhaps via a menu or a dialog or a direct manipulation), the application performs the operation, and then the result of that operation is displayed. The Common Lisp Interface Manager (CLIM) is a system for constructing portable users interfaces in a way that directly connects the objects and operations of an application to the objects of its user interface.
Bounds and approximations for self-initiating distributed simulation without lookahead
Authors: Felderman Robert E. , Kleinrock Leonard
Published: July 2002

We provide upper and lower bounds and an approximation for speedup of an optimistic self-initiated distributed simulation using a very simple model. We assume an arbitrary number of processors and a uniform connection topology. By showing that the lower bound increases essentially linearly with
P
, the number of processors, we find that the optimistic approach scales well as
P
increases. The model tracks the progress of Global Virtual Time (GVT) and eliminates the need to know the virtual time positions of all processors, thus making the analysis quite straightforward.
Providing high availability using lazy replication
Authors: Ladin Rivka , Liskov Barbara , Shrira Liuba , Ghemawat Sanjay
Published: July 2002

To provide high availability for services such as mail or bulletin boards, data must be replicated. One way to guarantee consistency of replicated data is to force service operations to occur in the same order at all sites, but this approach is expensive. For some applications a weaker causal operation order can preserve consistency while providing better performance. This paper describes a new way of implementing causal operations. Our technique also supports two other kinds of operations: operations that are totally ordered with respect to one another and operations that are totally ordered with respect to all other operations. The method performs well in terms of response time, operation-processing capacity, amount of stored state, and number and size of messages; it does better than replication methods based on reliable multicast techniques.
Processing time-constrained aggregate queries in CASE-DB
Authors: Hou Wen-Chi , Ozsoyoglu Gultekin
Published: July 2002

In this paper, we present an algorithm to strictly control the time to process an estimator for an aggregate relational query. The algorithm implemented in a prototype database management system, called CASE-DB, iteratively samples from input relations, and evaluates the associated estimator until the time quota expires.

In order to estimate the time cost of a query, CASE-DB uses adaptive time cost formulas. The formulas are adaptive in that the parameters of the formulas can be adjusted at runtime to better fit the characteristics of a query. To control the use of time quota, CASE-DB adopts the one-at-a-time-interval time control strategy to make a tradeoff between the risks of overspending and the overhead, finally, experimental evaluation of the methodology is presented.
Retrieving reusable software by sampling behavior
Authors: Podgurski Andy , Pierce Lynn
Published: July 2002

A new method, called
behavior sampling
, is proposed for automated retrieval of reusable components from software libraries. Behavior sampling exploits the property of software that distinguished it from other forms of test: executability. Basic behavior sampling identifies relevant routines by executing candidates on a searcher-supplied sample of operational inputs and by comparing their output to output provided by the searcher. The probabilistic basis for behavior sampling is described, and experimental results are reported that suggest that basic behavior sampling exhibits high precision when used with small samples. Extensions to basic behavior sampling are proposed to improve its recall and to make it applicable to the retrieval of abstract data types and object classes.
Information systems security design methods
Authors: Baskerville Richard
Published: July 2002

The security of information systems is a serious issue because computer abuse is increasing. It is important, therefore, that systems analysts and designers develop expertise in methods for specifying information systems security. The characteristics found in three generations of general information system design methods provide a framework for comparing and understanding current security design methods. These methods include approaches that use checklists of controls, divide functional requirements into engineering partitions, and create abstract models of both the problem and the solution. Comparisons and contrasts reveal that advances in security methods lag behind advances in general systems development methods. This analysis also reveals that more general methods fail to consider security specifications rigorously.
On the expressive power of query languages
Authors: Schäuble Peter , Wüthrich Beat
Published: July 2002

Two main topics are addressed. First, an algebraic approach is presented to define a general notion of expressive power. Heterogeneous algebras represent information systems and morphisms represent the correspondences between the instances of databases, the correspondences between answers, and the correspondences between queries. An important feature of this new notion of expressive power is that query languages of different types can be compared with respect to their expressive power. In the case of relational query languages, the new notion of expressive power is shown to be equivalent to the notion used by Chandra and Harel. In the case of nonrelational query languages, the versatility of the new notion of expressive power is demonstrated by comparing the fixpoint query languages with an object-oriented query language called FQL. The expressive power of the Functional Query Language FQL is the second main topic of this paper. The specifications of FQL functions can be recursive or even mutually recursive, FQL has a fixpoint semantics based on a complete lattice consisting of bag functions. The query language FQL is shown to be more expressive than the fixpoint query languages. This result implies that FQL is also more expressive than Datalog with stratified negation. Examples of recursive FQL functions are given that determine the ancestors of persons and the bill of materials.
A coherent distributed file cache with directory write-behind
Authors: Mann Timothy , Birrell Andrew , Hisgen Andy , Jerian Charles , Swart Garret
Published: July 2002

Extensive caching is a key feature of the Echo distributed file system. Echo client machines maintain coherent caches of file and directory data and properties, with write-behind (delayed write-back) ofallcached information. Echo specifies ordering constraints on this write-behind, enabling applications to store and maintain consistent data structures in the file system even when crashes or network faults prevent some writes from being completed. In this paper we describe the Echo cache's coherence and ordering semantics, show how they can improve the performance and consistency of applications, explain how they are implemented. We also discuss the general problem of reliably notifying applications and users when write-behind is lost; we addressed this problem as part of the Echo design, but did not find a fully satisfactory solution.
Design tradeoffs for software-managed TLBs
Authors: Uhlig Richard , Nagle David , Stanley Tim , Mudge Trevor , Sechrest Stuart , Brown Richard
Published: July 2002

An increasing number of architectures provide virtual memory support through software-managed TLBs. However, software management can impose considerable penalties that are highly dependent on the operating system's structure and its use of virtual memory. This work explores software-managed TLB design tradeoffs and their interaction with a range of monolithic and microkernel operating systems. Through hardware monitoring and simulation, we explore TLB performance for benchmarks running on a MIPS R2000-based workstation running Ultrix, OSF/1, and three versions of Mach 3.0.
Toward a logical/physical theory of spreadsheet modeling
Authors: Isakowitz Tomás , Schocken Shimon , Lucas Henry C.
Published: July 2002

In spite of the increasing sophistication and power of commercial spreadsheet packages, we still lack a formal theory or a methodology to support the construction and maintenance of spreadsheet models. Using a dual logical/physical perspective, we identify four principal components that characterize any spread sheet model:
schema, data, editorial,
and
binding
. We present a
factoring
algorithm for identifying and extracting these components from conventional spreadsheets with minimal user intervention, and a
synthesis
algorithm that assists users in the construction of executable spreadsheets from reusable model components. This approach opens new possibilities for applying object-oriented and model management techniques to support the construction, sharing, and reuse of spreadsheet models in organizations. Importantly, our approach to model management and the Windows-based prototype that we have developed are designed to
coexist
with, rather than
replace
, traditional spreadsheet programs. In other words, the users are not required to learn a new modeling language; instead, their logical models and data sets are extracted from their spreadsheets transparently, as a side-effect of using standard spreadsheet programs.
A security architecture for fault-tolerant systems
Authors: Reiter Michael K. , Birman Kenneth P. , van Renesse Robbert
Published: July 2002

Process groups are a common abstraction for fault-tolerant computing in distributed systems. We present a security architecture that extends the process group into a security abstraction. Integral parts of this architecture are services that securely and fault tolerantly support cryptographic key distribution. Using replication only when necessary, and introducing novel replication techniques when it was necessary, we have constructed these services both to be easily defensible against attack and to permit key distribution despite the transient unavailability of a substantial number of servers. We detail the design and implementation of these services and the secure process group abstraction they support. We also give preliminary performance figures for some common group operations.
Application and experimental evaluation of state space reduction methods for deadlock analysis in Ada
Authors: Duri S. , Buy U. , Devarapalli R. , Shatz S. M.
Published: July 2002

An emerging challenge for software engineering is the development of the methods and tools to aid design and analysis of concurrent and distributed software. Over the past few years, a number of analysis methods that focus on Ada tasking have been developed. Many of these methods are based on some form of reachability analysis, which has the advantage of being conceptually simple, but the disadvantage of being computationally expensive. We explore the effectiveness of various Petri net-based techniques for the automated deadlock analysis of Ada programs. Our experiments consider a variety of state space reduction methods both individually and in various combinations. The experiments are applied to a number of classical concurrent programs as well as a set of “real-world” programs. The results indicate that Petri net reduction and reduced state space generation are mutually beneficial techniques, and that combined approaches based on Petri net models are quite effective, compared to alternative analysis approaches.
Discovering the way programmers think about new programming environments
Authors: Dumas Joseph , Parsons Paige
Published: July 2002

An interesting usability study of a prototype development environment for the Dylan programming language is presented here. This study's purpose is to determine just how close the prototype is to developers. New approaches to source code organization and to the relationship between the environment and the application being developed are introduced. An asessment of how effectively the prototype conveys these innovations to Dylan developers is also given, followed by some proposed improvements.
Race differences in job performance and career success
Authors: Igbaria Magid , Wormley Wayne M.
Published: July 2002

Although blacks have gained entry to the information systems (IS) field and various managerial positions, they continue to experience more restricted career advancement prospects than whites. They have found it difficult to advance professionally and managerially within their organizations. Perhaps, as the management literature suggests, this is because minorities may experience considerable discrimination in their jobs that lowers their performance and ultimately impedes their career advancement [10].
Techniques for reducing consistency-related communication in distributed shared-memory systems
Authors: Carter John B. , Bennett John K. , Zwaenepoel Willy
Published: July 2002

Distributed shared memory (DSM) is an abstraction of shared memory on a distributed-memory machine. Hardware DSM systems support this abstraction at the architecture level; software DSM systems support the abstraction within the runtime system. One of the key problems in building an efficient software DSM system is to reduce the amount of communication needed to keep the distributed memories consistent. In this article we present four techniques for doing so: software release consistency; multiple consistency protocols; write-shared protocols; and an update-with-timeout mechanism. These techniques have been implemented in the Munin DSM system. We compare the performance of seven Munin application programs: first to their performance when implemented using message passing, and then to their performance when running on a conventional software DSM system that does not embody the preceding techniques. On a 16-processor cluster of workstations, Munin's performance is within 5% of message passing for four out of the seven applications. For the other three, performance is within 29 to 33%. Detailed analysis of two of these three applications indicates that the addition of a function-shipping capability would bring their performance to within 7% of the message-passing performance. Compared to a conventional DSM system, Munin achieves performance improvements ranging from a few to several hundred percent, depending on the application.
Memory system performance of programs with intensive heap allocation
Authors: Diwan Amer , Tarditi David , Moss Eliot
Published: July 2002

Heap allocation with copying garbage collection is a general storage management technique for programming languages. It is believed to have poor memory system performance. To investigate this, we conducted an in-depth study of the memory system performance of heap allocation for memory systems found on many machines. We studied the performance of mostly functional Standard ML programs which made heavy use of heap allocation. We found that most machines support heap allocation poorly. However, with the appropriate memory system organization, heap allocation can have good performance. The memory system property crucial for achieving good performance was the ability to allocate and initialize a new object into the cache without a penalty. This can be achieved by having subblock by placement with a subblock size of one word with a write-allocate policy, along with fast page-mode writes or a write buffer. For caches with subblock placement, the data cache overhead was under 9% for a 64K or larger data cache; without subblock placement the overhead was often higher than 50%.
Aspect
Authors: Jackson Daniel
Published: July 2002

Aspect is a static analysis technique for detecting bugs in imperative programs, consisting of an annotation language and a checking tool. Like a type declaration, an Aspect annotation of a procedure is a kind of declarative, partial specification that can be checked efficiently in a modular fashion. But instead of constraining the types of arguments and results, Aspect specifications assert dependences that should hold between inputs and outputs. The checker uses a simple dependence analysis to check code against annotations and can find bugs automatically that are not detectable by other static means, especially errors of omission, which are common, but resistant to type checking. This article explains the basic scheme and shows how it is elaborated to handle data abstraction and aliasing.