bluuebunny/crossref_metadata_2025 huggingface dataset:
Conditioning factors of iron ochre biofilm formation on geotextile filters
Authors: Mendonca Marcos Barreto de , Ehrlich Maurício , Cammarota Magali Christe
Published: December 2003

This paper presents a study of ochre formation on geotextile filters. Ochre is a substance found sticking to solid surfaces of drainage systems and may cause clogging. Ochre formation is discussed based on the new concepts of biofilm development. Ochre formation is the result of microbial colonization and its affinity to iron compounds naturally found in seepage water. The aerobicnonaerobic interface in drainage systems is a very favourable locale for optimum development of iron bacteria. Laboratory studies were done to verify the influence of intrinsic characteristics of the geotextiles and environment on ochre formation. Because flow condition was not considered in the tests, however, these results may not represent real field performance of geotextile filters. Tests of biofilm formation were conducted in Erlenmeyer flasks containing culture mediums for iron bacteria and geotextile samples. Nonwoven polyester, nonwoven polypropylene, and woven polypropylene geotextiles were used in the tests. The study was performed considering different levels of iron concentration, available dissolved oxygen, and pH. Laboratory tests have shown the fundamental importance of iron bacteria activity, type of geotextile, and environmental conditions on ochre formation.Key words: ochre, clogging, filtration, biofilm, geosynthetics.
2-Acetoxy-2-methoxy-5,5-dimethyl-Δ3-1,3,4-oxadiazoline and acetoxy(methoxy)carbene
Authors: Czardybon Wojciech , Klys Arkadiusz , Warkentin John , Werstiuk Nick Henry
Published: December 2003

2-Acetoxy-2-methoxy-5,5-dimethyl-Δ3-1,3,4-oxadiazoline undergoes two competitive 1,3-dipolar cycloreversions at 110 °C. It loses N2, presumably to afford a short-lived carbonyl ylide that fragments to acetone and acetoxy(methoxy)carbene. It also forms 2-diazopropane and the appropriate mixed anhydride. It is the only currently known source of acetoxy(methoxy)carbene. Key words: acetoxy(methoxy)carbene, 2-diazopropane, 1,3-dipolar cycloreversion.
Vanadium and niobium diamidophosphine complexes and their reactivity
Authors: Shaver Michael P , Thomson Robert K , Patrick Brian O , Fryzuk Michael D
Published: December 2003

The tridentate ligand precursors R′P(CH2SiMe2NR′′)2(R′R′′[NPN]: R′ = Cy, Ph; R′′ = Ph, Mes, Me) were prepared from metathesis reactions of a lithiated amine, chloro(chloromethyl)dimethylsilane, the appropriate 1° phosphine, and n-butyl lithium and were isolated as solvent adducts. Metathesis betweenCyPh[NPN]Li2(OEt2), 2, and VCl3(THF)3afforded (CyPh[NPN]VCl)2, 7, whose solid-state structure was established by X-ray crystallography. Reduction attempts of the (R′R′′[NPN]VCl)2species with KC8incorporated molecular nitrogen but were complicated by imide formation and ligand decomposition. Metathesis of 2 with NbCl2Me3afforded the highly unstable complexCyPh[NPN]NbMe3, 15. Attempts to hydrogenate this species were unsuccessful.Key words: vanadium, niobium, metathesis, coordination chemistry, reduction, hydrogenation.
Determination of the second stoichiometric dissociation constants of glycine in aqueous sodium or potassium chloride solutions at 298.15 K
Authors: Partanen Jaakko I , Juusola Pekka M , Minkkinen Pentti O , Verraes Virginie
Published: December 2003

Equations were determined for the calculation of the second stoichiometric (molality scale) dissociation constant, Km2, of glycine, in aqueous NaCl and KCl solutions at 298.15 K, from the thermodynamic dissociation constant, Ka2, of this acid and the ionic strength, Im, of the solution. The ionic strength of the solutions considered in this study is determined mostly by the salt alone, and the equations for Km2 were based on the single-ion activity coefficient equations of the Hückel type. New data measured by potentiometric titrations in a glass electrode cell were used in the estimation of the parameters for the Hückel equations of glycine species. By means of the calculation method suggested in this study, Km2 can be obtained almost within experimental error up to an Im of about 1.0 mol kg1 for glycine in NaCl and KCl solutions. The Km2 values obtained by these methods were also compared with the values suggested in the literature for this quantity.Key words: ionic strength dependence, stoichiometric dissociation constant, Debye–Hückel equation, potentiometry, glycine.
The gas-phase reaction of the CF3radical with thiophene
Authors: Herrera Olga S , Nieto Jorge D , Lane Silvia I , Oexler Elena V
Published: December 2003

The reaction of CF3radicals, generated by photolysis of CF3I or hexafluoroacetone with thiophene, was studied in the gas phase at 25 °C. At conversion of thiophene less than 20%, monosubstituted CF3-thiophenes were found as the main reaction products, in addition to CF3H, C2F6, and monosubstituted dihydro-CF3-thiophene, the latter in very low proportion. An isomeric mixture of 2- and 3-CF3-thiophene was obtained in a ratio of about 16, independent of the radical source used (CF3I or hexafluoroacetone) to produce the CF3radicals. A plausible mechanism that accounts for the observed products is proposed, and the reactivity of thiophene toward the CF3radical at 25 °C was determined as kadd/kc1/2= 106 ± 4 cm3/2mol–1/2s–1/2.Key words: thiophene, trifluoromethyl radical, reaction mechanism, reactivity.
Aqueous nonelectrolyte solutions  Part XX: Formula of structure I methane hydrate, congruent dissociation melting point, and formula of the metastable hydrate
Authors: Glew David N
Published: December 2003

Sixteen new measurements of high precision for structure I methane hydrate with water between 31.93 and 47.39 °C are shown to be metastable and exhibit higher methane pressures than found by earlier workers. Comparison of earlier measurements between 26.7 and 47.2 °C permit positive identification of the structure II and the structure I hydrates. Forty-nine equilibrium constants Kp(h1[Formula: see text]l1g) for dissociation of structure I methane hydrate into water and methane, 32 between 0.29 and 26.7 °C for the stable hydrate and 17 between 31.93 and 47.39 °C for the metastable hydrate, are best represented by a three-parameter thermodynamic equation, which indicates a standard error (SE) of 0.63% on a single Kp(h1[Formula: see text]l1g) determination. The congruent dissociation melting point C(h1l1gxm) of metastable structure I methane hydrate is at 47.41 °C with SE 0.02 °C and at pressure 505 MPa. The congruent equilibrium constant Kp(h1[Formula: see text]l1g) is 102.3 MPa with SE 0.2 MPa. ΔH°t(h1[Formula: see text]l1g) is 62 281 J mol1 with SE 184 J mol1, and the congruent formula is CH4·5.750H2O with SE 0.059H2O. At the congruent point, ΔV(h1[Formula: see text]l1g) is zero within experimental precision, and its estimate is 1.3 with SE 1.6 cm3 mol1. The stability range of structure I methane hydrate with water extends from quadruple point Q(s1h1l1g) at 0.29 °C up to quadruple point Q(h1h2l1g) at 26.7 °C, and its metastability range with water extends from 26.7 °C up to the congruent dissociation melting point C(h1l1gxm) at 47.41 °C. Key words: methane hydrate, clathrate structure I, metastability range, dissociation equilibrium constant, formula, congruent melting point, metastability of structure I hydrate.
Thermodynamics of binary mixtures containing a very strongly polar compound — Part 3: DISQUAC characterization of NMP + organic solvent mixtures
Authors: González J A , Domanska U , Lachwa J
Published: December 2003

Binary mixtures of 1-methyl pyrrolidin-2-one (NMP) with alkanes, benzene, toluene, 1-alkanol, or 1-alkyne have been investigated in the framework of the DISQUAC model. The reported interaction parameters change regularly with the molecular structure of the mixture components. The model consistently describes a set of thermodynamic properties, including liquid–liquid equilibria, vapor–liquid equilibria, solid–liquid equilibria, and molar excess enthalpies. A brief comparison of the DISQUAC results and those obtained from the UNIFAC and ERAS models is presented. The experimental excess enthalpies are better represented by DISQUAC than by UNIFAC because this quantity strongly depends on molecular structure. For NMP + alkane mixtures, the liquid–liquid equilibria data are also better represented by DISQUAC, while UNIFAC more accurately describes the vapor–liquid equilibria measurements at temperatures close to the critical point. This result suggests that a mean field theory is not able to represent simultaneously, with the same set of interaction parameters, liquid–liquid and vapor–liquid equilibria at the mentioned temperatures. ERAS fails when treating mixtures with 1-alkanols. This has been attributed to the strong dipole–dipole interactions between NMP molecules, characteristic of the investigated systems. Mixture structure is briefly studied in terms of the concentration–concentration structure factor.Key words: thermodynamics, NMP, organic solvent, self-association, dipole–dipole interactions.
The syntheses and structures of lithium phosphinimide and phosphinimine complexes
Authors: Courtenay Silke , Wei Pingrong , Stephan Douglas W
Published: December 2003

The preparation and structures of [Li(µ-NPt-Bu3)]4 1, [Li(µ-Cl)(HNPt-Bu3)]4 2, and [Li(µ-Cl)(HNPPh3)]4 3 are described. The structure of 1 stands in contrast to that of the only other known Li-phosphinimide derivative, [Li(µ-NPPh3)]6. The impact of the steric bulk on the aggregation and the geometries of the Li4N4 and Li4Cl4 cores are considered and discussed.Key words: lithium compounds, phosphinimine, phosphinimide, P-N ligands.
Oxazoline chemistry — Part IV: Synthesis and characterization of oxazoline complexes of the zinc halides
Authors: Barclay Tosha M , del Río Ignacio , Gossage Robert A , Jackson Sarah M
Published: December 2003

The synthesis and characterization of 11 zinc halide derivatives that contain monodentate oxazoline ligands is described. The treatment of ether solutions of [ZnX2] (X = Cl, Br, I) with 2-aryl- or 2-methyl-2-oxazolines results in the formation of mildly hygroscopic complexes of the general formulae [ZnX2(ox)2] (ox = 2-methyl-2-oxazoline (1), 2,4,4-trimethyl-2-oxazoline (2), 2-phenyl-2-oxazoline (3), or 4,4-dimethyl-2-phenyl-2-oxazoline (4)), except in the case of ZnI2, which does not form an isolable complex — likely for steric reasons — with oxazoline 4. Treatment of [ZnBr2(4)2] with 1 reveals (1H NMR) that 1 only sluggishly displaces coordinated 4 at temperatures below 50 °C. The structural characterization, via single crystal X-ray diffraction, of six of the complexes, viz. [ZnI2(1)2], [ZnI2(2)2], [ZnX2(3)2] (X = Cl, Br, or I), and [ZnBr2(4)2], is also reported. All of these structurally characterized complexes are mononuclear zinc compounds with an overall distorted tetrahedral arrangement of the two halide and two oxazoline ligands around the zinc metal centre. The oxazoline series of complexes reported herein show little structural diversity, a facet which is in contrast to their substituted pyridine analogues.Key words: oxazoline, zinc, X-ray crystal structure, coordination complex, NMR spectroscopy, Zn(II).
Thermochemical behavior of dissolved carboxylic acid solutes: Solubilities of 3-methylbenzoic acid and 4-chlorobenzoic acid in organic solvents
Authors: Daniels Charlisa R , Charlton Amanda K , Wold Rhiannon M , Acree, Jr. William E , Abraham Michael H
Published: December 2003

The Abraham general solvation model is used to correlate the solubility behavior of 3-methylbenzoic acid and 4-chlorobenzoic acid in alcohol and ether solvents. The mathematical correlations take the form of

[Formula: see text]

[Formula: see text]

where CS and CW refer to the solute solubility in the organic solvent and water, respectively; CG is a gas-phase concentration; R2 is the solute excess molar refraction; Vx is the McGowan volume of the solute; ΣαH2 and ΣβH2 are measures of the solute hydrogen-bond acidity and hydrogen-bond basicity; πH2 denotes the solute dipolaritypolarizability descriptor; and L(16) is the solute gas-phase dimensionless Ostwald partition coefficient into hexadecane at 298 K. The remaining symbols in the above expressions are known solvent coefficients, which have been determined previously for a large number of gassolvent and watersolvent systems. The Abraham general solvation model was found to describe the experimental solubility data and published literature partitioning data of 3-methylbenzoic acid and 4-chlorobenzoic acid to within overall standard deviations of 0.079 log units and 0.085 log units, respectively. Key words: 3-methylbenzoic acid solubilities, 4-chlorobenzoic acid solubilities, alcohol solvents, partition coefficients, molecular solute descriptors, solubility predictions.
PIPELINING A SKEW-INSENSITIVE PARALLEL JOIN ALGORITHM
Authors: BAMHA M. , EXBRAYAT M.
Published: November 2003

Most standard parallel join algorithms try to overcome data skews with a relatively static approach. The way they distribute data (and then computation) over nodes depends on a data re-distribution algorithm (hashing or range partitioning) that is determined before the actual join begins. On the contrary, our approach consists in pre-scanning data in order to choose an efficient join method for each given value of the join attribute. This approach has already proved to be efficient both theoretically and practically in our previous papers. In this paper we introduce a new pipelined version of our frequency adaptive join algorithm. The use of pipelining offers flexible strategies for resource allocation while avoiding unnecessary disk input/output of intermediate join results when computing multi-join queries. We present a detailed version of the algorithm and a cost analysis based on the BSP (Bulk Synchronous Parallel) model, showing that our pipelined algorithm achieves noticeable improvements compared to the sequential parallel version for multi-join queries while guaranteeing perfect balancing properties.
BSPGRID: VARIABLE RESOURCES PARALLEL COMPUTATION AND MULTIPROGRAMMED PARALLELISM
Authors: Vasilev Vasil P.
Published: November 2003

This paper introduces a new framework for the design of parallel algorithms that may be executed on multiprogrammed architectures with variable resources. These features, in combination with an implied ability to handle fault tolerance, facilitates environments such as the GRID. A new model, BSPGRID is presented, which exploits the bulk synchronous paradigm to allow existing algorithms to be easily adapted and used. It models computation, communication, external memory accesses (I/O) and synchronization. By combining the communication and I/O operations BSPGRID allows the easy design of portable algorithms while permitting them to execute on non-dedicated hardware and/or changing resources, which is typical for machines in a GRID. However, even with this degree of dynamicity, the model still offers a simple and tractable cost model. Each program runs in its own virtual BSPGRID machine. Its emulation on a real computer is demonstrated to show the practicality of the framework. A dense matrix multiplication algorithm and its emulation in a multiprogrammed environment is given as an example.
EXTENDING OPENMP FOR TASK PARALLELISM
Authors: MAROWKA AMI
Published: November 2003

In a wide variety of scientific parallel applications, both task and data parallelism must be exploited to achieve the best possible performance on a multiprocessor machine. These applications induce task-graph parallelism with coarse-grain granularity. Nevertheless, using the available task-graph parallelism and combining it with data parallelism can increase the performance of parallel applications considerably since an additional degree of parallelism is exploited.

The OpenMP standard supports data parallelism but does not support task-graph parallelism. In this paper we present an integration of task-graph parallelism in OpenMP by extending the parallel sections constructs to include task-index and precedence-relations matrix clauses. There are many ways in which task-graph parallelism can be supported in a programming environment. A fundamental design decision is whether the programmer has to write programs with explicit precedence relations, or if the responsibility of precedence relations generation is delegated to the compiler. One of the benefits provided by parallel programming models like OpenMP is that they liberate the programmer from dealing with the underlying details of communication and synchronization, which are cumbersome and error-prone tasks. If task-graph parallelism is to find acceptance, writing task-graph parallel programs must be no harder than writing data parallel programs, and therefore, in our design, precedence relations are described through simple programmer annotations, with implementation details handled by the system.

This paper concludes with a description of several parallel application kernels that were developed to study the practical aspects of task-graph parallelism in OpenMP. The examples demonstrate that exploiting data and task parallelism in a single framework is the key to achieving good performance in a variety of applications.
ALIGNED MULTITHREADED COMPUTATIONS AND THEIR SCHEDULING WITH PERFORMANCE GUARANTEES
Authors: YONG XIE , WEN-JING HSU
Published: November 2003

This paper considers the problem of scheduling dynamic parallel computations to achieve linear speedup without using significantly more space per processor than that required for a single processor execution. Earlier research in the Cilk project proposed the "strict" computational model, in which every dependency goes from a thread x only to one of x's ancestor threads, and guaranteed both linear speedup and linear expansion of space. However, Cilk threads are stateless, and the task graph that Cilk language expresses is series-parallel graph, which is a proper subset of arbitrary task graph. Moreover, Cilk does not support applications with pipelining.

We propose the "aligned" multithreaded computational model, which extends the "strict" computational model in Cilk. In the aligned multithreaded computational model, dependencies can go from arbitrary thread x not only to x's ancestor threads, but also to x's younger brother threads, that are spawned by x's parent thread but after x. We use the same measures of time and space as those used in Cilk: T1 is the time required for executing the computation on 1 processor, T∞ is the time required by an infinite number of processors, and S1 is the space required to execute the computation on 1 processor. We show that for any aligned computation, there exists an execution schedule that achieves both efficient time and efficient space. Specifically, we show that for an execution of any aligned multithreaded computation on P processors, the time required is bounded by O(T1/P + T∞), and the space required can be loosely bounded by O(λ·S1P), where λ is the maximum number of younger brother threads that have the same parent thread and can be blocked during execution. If we assume that λ is a constant, and the space requirements for elder and younger brother threads are the same, then the space required would be bounded by O(S1P).

Based on the aligned multithreaded computational model, we show that the aligned multithreaded computational model supports pipelined applications. Furthermore, we propose a multithreaded programming language and show that it can express arbitrary task graph.
FORMAL PROOFS OF FUNCTIONAL BSP PROGRAMS
Authors: GAVA FRÉDÉRIC
Published: November 2003

The Bulk Synchronous Parallel ML (BSML) is a functional language for BSP programming, a model of computing which allows parallel programs to be ported to a wide range of architectures. It is based on an extension of the ML language by parallel operations on a parallel data structure called parallel vector, which is given by intention. We present a new approach to certifying BSML programs in the context of type theory. Given a specification and a program, an incomplete proof of the specification (of which algorithmic contents corresponds to the given program) is built in the type theory, in which gaps would correspond to the proof obligation. This development demonstrates the usefulness of higher-order logic in the process of software certification of parallel applications. It also shows that the proof of rather complex parallel algorithms may be done with inductive types without great difficulty by using existing certified programs. This work has been implemented in the Coq Proof Assistant, applied on non-trivial examples and is the basis of a certified library of BSML programs.
A CALCULUS FOR DENSE ARRAY DISTRIBUTIONS
Authors: DI COSMO ROBERTO , PELAGATTI SUSANNA
Published: November 2003

We introduce a very simple, yet powerful, distribution calculus aimed at describing different strategies that can be used to distribute (ie, partition and replicate) multidimensional dense arrays over a set of processors, like what is done in the implementation of the P3L Map skeleton. We give a formal semantics, that allows to prove equations between distributions, and we show how to associate a cost to such distributions, allowing to choose between semantically equivalent distribution strategies.
TOP-DOWN DESIGN OF BULK-SYNCHRONOUS PARALLEL PROGRAMS
Authors: CHEN YIFENG , SANDERS J. W.
Published: November 2003

This paper studies top-down program development techniques for Bulk-Synchronous Parallelism. In that context a specification formalism LOGS, for 'the Logic of Global Synchrony', has been proposed for the specification and high-level development of BSP designs. This paper extends the use of LOGS to provide support for the protection of local variables in BSP programs, thus completing the link between specifications and programs.
SAC — FROM HIGH-LEVEL PROGRAMMING WITH ARRAYS TO EFFICIENT PARALLEL EXECUTION
Authors: GRELCK CLEMENS , SCHOLZ SVEN-BODO
Published: November 2003

SAC is a purely functional array processing language designed with numerical applications in mind. It supports generic, high-level program specifications in the style of APL. However, rather than providing a fixed set of built-in array operations, SAC provides means to specify such operations in the language itself in a way that still allows their application to arrays of any rank and size. This paper illustrates the major steps in compiling generic, rank- and shape-invariant SAC specifications into efficiently executable multithreaded code for parallel execution on shared memory multiprocessors. The effectiveness of the compilation techniques is demonstrated by means of a small case study on the PDE1 benchmark, which implements 3-dimensional red/black successive over-relaxation. Comparisons with HPF and ZPL show that despite the genericity of code, SAC achieves highly competitive runtime performance characteristics.
AUTOMATIC SKELETONS IN TEMPLATE HASKELL
Authors: Hammond Kevin , Berthold Jost , Loogen Rita
Published: November 2003

This paper uses Template Haskell to automatically select appropriate skeleton implementations in the Eden parallel dialect of Haskell. The approach allows implementation parameters to be statically tuned according to architectural cost models based on source analyses. This permits us to target a range of parallel architecture classes from a single source specification. A major advantage of the approach is that cost models are user-definable and can be readily extended to new data or computation structures etc.
A Portable Implementation for Objective Caml Flight
Authors: CHAILLOUX EMMANUEL , FOISY CHRISTIAN
Published: November 2003

Caml-Flight is a data-parallel extension for Caml Light. It is an intermediate, portable and mostly deterministic functional language for distributed memory multiprocessors (DMM). Its current implementation modifies the Caml Light compiler to introduce new instructions for the language and its virtual machine, and to define a kind of persistence to communicate values. Caml Light has now evolved to become Objective Caml, including an object extension and a native compiler. To benefit from this new distribution, we propose a new implementation called Objective Caml Flight. To do so we use new libraries and tools included in Objective Caml such as multi-threading, persistence and parsers, i.e. without modification to the original compiler needed with the Caml-Flight approach. This paper presents an easier way to implement parallel extensions for Objective Caml and an actual realization called Objective Caml Flight. This new implementation is compared to Caml-Flight.
LLC: A PARALLEL SKELETAL LANGUAGE
Authors: DORTA ANTONIO J. , GONZÁLEZ JESÚS A. , RODRÍGUEZ CASIANO , DE SANDE FRANCISCO
Published: November 2003

The skeletal approach to the development of parallel applications has been revealed to be one of the most successful and has been widely explored in the recent years. The goal of this approach is to develop a methodology of parallel programming based on a restricted set of parallel constructs.

This paper presents llc, a parallel skeletal language, the theoretical model that gives support to the language and a prototype implementation for its compiler. The language is based on directives, uses a C-like syntax and gives support to the most widely used skeletal constructs. llCoMP is a source to source compiler for the language built on top of MPI. We evaluate the performance of our prototype compiler using four different parallel architectures and three algorithms. We present the results obtained in both shared and distributed memory architectures. Our model guarantees the portability of the language to any platform and its simplicity greatly eases its implementation.
${\mathsf{eskimo}}$: EXPERIMENTING WITH SKELETONS IN THE SHARED ADDRESS MODEL
Authors: ALDINUCCI MARCO
Published: November 2003

We discuss the lack of expressivity in some skeleton-based parallel programming frameworks. The problem is further exacerbated when approaching irregular problems and dealing with dynamic data structures. Shared memory programming has been argued to have substantial ease of programming advantages for this class of problems. We present the [Formula: see text] library which represents an attempt to merge the two programming models by introducing skeletons in a shared memory framework.
DatTeL: A DATA-PARALLEL C++ TEMPLATE LIBRARY
Authors: BISCHOF HOLGER , GORLATCH SERGEI , LESHCHINSKIY ROMAN
Published: November 2003

The concept of C++ templates, realized in the Standard Template Library (STL), allows development of generic programs suitable for various concrete data structures. Our aim in this paper is to provide an opportunity for efficient execution of STL programs on parallel machines. We present DatTeL – a data-parallel library, which allows simple, efficient programming for various parallel architectures while staying within the paradigm of classical C++ template programming. We describe the principles of our approach and explain our design decisions and their implementation in the library. The presentation is illustrated with a case study — parallelization of a generic algorithm for carry-lookahead addition. We compare DatTeL to related work and report experimental results for the current version of our library.
HIGH-LEVEL PARALLEL SOFTWARE DEVELOPMENT WITH PYTHON AND BSP
Authors: HINSEN KONRAD
Published: November 2003

One of the main obstacles to a more widespread use of parallel computing in computational science is the difficulty of implementing, testing, and maintaining parallel programs. The combination of a simple parallel computation model, BSP, and a high-level programming language, Python, simplifies these tasks significantly. It allows the rapid development facilities of Python to be applied to parallel programs, providing interactive development as well as interactive debugging of parallel programs.
TRADE-OFFS BETWEEN LOAD AND DEGREE IN VIRTUAL PATH LAYOUTS
Authors: DESSMARK ANDERS , LINGAS ANDRZEJ , PELC ANDRZEJ
Published: November 2003

We study virtual path layouts in ATM networks. Packets are routed along virtual paths in the network by maintaining a routing field whose subfields determine intermediate destinations of the packet, i.e., the endpoints of virtual paths on its way to the final destination. Most of the research on virtual path layouts has focused on tradeoffs between load (i.e., the maximum number of virtual paths passing through a link) and the hop number of the layout (i.e., the maximum number of virtual paths needed to travel between any two nodes).

There is however another important limitation on construction of layouts, resulting from technological properties of switches situated at nodes. This bound is the degree of the layout (i.e., the maximum number of virtual paths with a common endpoint). In this paper we study relations between these three parameters of virtual path layouts, for the all-to-all problem. For any integer h, we show tradeoffs between load and degree of h-hop layouts in the ring and in the mesh by establishing upper and lower bounds on these parameters. Our bounds on the degree of an h-hop layout of given load are asymptotically tight and the bounds on the load of an h-hop layout of given degree are asymptotically tight for constant h.
Performance Evaluation of a Parallel Decoupled Data Driven Multiprocessor
Authors: THORNTON MITCHELL
Published: November 2003

The Decoupled Data-Driven (D3) architecture has shown promising results from performance evaluations based upon deterministic simulations. This paper provides performance evaluations of the D3 architecture through the formulation and analysis of a stochastic model. The D3 architecture is a hybrid control/dataflow approach that takes advantage of inherent parallelism present in a program by dynamically scheduling program threads based on data availability and it also takes advantage of locality through the use of conventional processing elements that execute the program threads. The model is validated by comparing the deterministic and stochastic model responses. After model validation, various input parameters are varied such as the number of available processing elements and average threadlength, then the performance of the architecture is evaluated. The stochastic model is based upon a closed queueing network and utilizes the concepts of available parallelism and virtual queues in order to be reduced to a Markovian system. Experiments with varying computation engine threadlengths and communication latencies indicate a high degree of tolerance with respect to exploited parallelism.
MESON MIXING AND THE MASS OF THE ISODOUBLET OF 2 1S0 NONET
Authors: LI DE-MIN , MA BING , YAO QIAN-KAI , FENG JUN-LAN , FENG XUE-CHAO , YU HONG
Published: December 2003

Based on the mass relation derived under the assumption that for the almost ideally mixing meson nonets, the corrections deduced by the flavor-dependent quarkonia transition can be ignored, the mass of the isodoublet of the 2 1S0 nonet is predicted to be 1391.8±67.7 MeV. The quarkonia content of isoscalar states of the 2 1S0 nonet, i.e. η(1295) and η(1475), is given, and some predictions on the decays of the two isoscalar state are presented. These predictions can be tested in Beijing Electron Positron Collider Bejing Spectrometers (BEPC/BES) with 58 million J/ψ events in the near future.
ON MULTICORNS AND UNICORNS I: ANTIHOLOMORPHIC DYNAMICS, HYPERBOLIC COMPONENTS AND REAL CUBIC POLYNOMIALS
Authors: NAKANE SHIZUO , SCHLEICHER DIERK
Published: December 2003

We investigate the dynamics and the bifurcation diagrams of iterated antiholomorphic polynomials: These are complex conjugates of ordinary polynomials. Their second iterates are holomorphic polynomials, but dependence on parameters is only real-analytic. The structure of hyperbolic components of the family of unicritical antiholomorphic polynomials is revealed. In case of degree two, they arise naturally in the parameter space of real cubic (holomorphic) polynomials, which we investigate as well.
A NEUROBIOLOGICAL THEORY OF MEANING IN PERCEPTION PART III: MULTIPLE CORTICAL AREAS SYNCHRONIZE WITHOUT LOSS OF LOCAL AUTONOMY
Authors: FREEMAN WALTER J. , GAÁL GYöNGYI , JORSTEN REBECKA
Published: December 2003

Information transfer and integration among functionally distinct areas of cerebral cortex of oscillatory activity require some degree of phase synchrony of the trains of action potentials that carry the information prior to the integration. However, propagation delays are obligatory. Delays vary with the lengths and conduction velocities of the axons carrying the information, causing phase dispersion. In order to determine how synchrony is achieved despite dispersion, we recorded EEG signals from multiple electrode arrays on five cortical areas in cats and rabbits, that had been trained to discriminate visual or auditory conditioned stimuli. Analysis by time-lagged correlation, multiple correlation and PCA, showed that maximal correlation was at zero lag and averaged 0.7, indicating that 50% of the power in the gamma range among the five areas was at zero lag irrespective of phase or frequency. There were no stimulus-related episodes of transiently increased phase locking among the areas, nor EEG "bursts" of transiently increased amplitude above the sustained level of synchrony. Three operations were identified to account for the sustained correlation. Cortices broadcast their outputs over divergent–convergent axonal pathways that performed spatial ensemble averaging; synaptic interactions between excitatory and inhibitory neurons in cortex operated as band pass filters for gamma; and signal coarse-graining by pulse frequency modulation at trigger zones enhanced correlation. The conclusion is that these three operations enable continuous linkage of multiple cortical areas by activity in the gamma range, providing the basis for coordinated cortical output to other parts of the brain, despite varying axonal conduction delays, something like the back plane of a main frame computer.
REVEALING THE TRICK OF TAMING CHAOS BY WEAK HARMONIC PERTURBATIONS
Authors: INABA NAOHIKO , SEKIKAWA MUNEHISA , ENDO TETSURO , TSUBOUCHI TAKASHI
Published: December 2003

Taming chaos by weak harmonic perturbations has been a hot topic in recent years. In this paper, the authors investigate a scenario for the mechanism of taming chaos via bifurcation theory, and assert that this phenomenon is caused by a slight shift of the saddle node bifurcation curves.
NEW 3D-SCROLL ATTRACTORS IN HYPERCHAOTIC CHUA'S CIRCUITS FORMING A RING
Authors: CAFAGNA DONATO , GRASSI GIUSEPPE
Published: December 2003

This paper presents an approach for generating new hyperchaotic attractors in a ring of Chua's circuits. By taking a closed chain of three circuits and exploiting sine functions as nonlinearities, the proposed technique enables 3D-scroll attractors to be generated. In particular, the paper shows that 3D-scroll dynamics can be designed by modifying six parameters related to the circuit nonlinearities.
A NEUROBIOLOGICAL THEORY OF MEANING IN PERCEPTION PART V: MULTICORTICAL PATTERNS OF PHASE MODULATION IN GAMMA EEG
Authors: FREEMAN WALTER J. , ROGERS LINDA J.
Published: December 2003

The aim of this study is to find evidence for repetitive global phase transitions occurring simultaneously over multiple areas of cortex during normal behavior. EEGs were recorded from multiple high-density arrays of 14–16 electrodes surgically fixed on the visual, auditory, somatomotor, and entorhinal cortices of trained cats and rabbits, and from a linear array of 64 electrodes on the scalp of human volunteers. Analytic phase relations between gamma EEG signals from multiple cortices were examined with high temporal resolution provided by the Hilbert transform. An index of synchronization was applied to intercortical pairs of signals to detect and display epochs of engagement between pairs. The measure was adapted to derive an index of global synchronization among all 4 cortices that was calculated as a t-value. Global epochs of phase stabilization ("locking") were found to involve all cortices under observation. The phase values were not clustered at zero but were in distributions about nonzero means. Episodic destabilization (decoherence) occurred aperiodically at intervals corresponding to rates in the delta range, with equal likelihood before the onset of the conditioned stimuli (CSs) and in post-stimulus test periods including performance of conditioned responses (CRs). Preferential pairwise phase stabilization was sought but not found between the sensory cortex receiving the auditory or visual CSs and the entorhinal or somatomotor cortex at times of CSs or CRs. The cospectrum from cross-correlating the global synchronization index with the global spatial ensemble average of the unfiltered EEG peaked in the delta range (1–3 Hz) near 2.5 Hz in cat and below 2 Hz in rabbit. The cospectrum of the EEG with the derivative of the analytic phase in humans peaked in the alpha range (7–12 Hz) The results indicated that macroscopic states of synchronized neural activity related to Gestalts formed during perception, that included the primary sensory and limbic areas and perhaps the entire neocortex of each cerebral hemisphere.
A NEUROBIOLOGICAL THEORY OF MEANING IN PERCEPTION PART IV: MULTICORTICAL PATTERNS OF AMPLITUDE MODULATION IN GAMMA EEG
Authors: FREEMAN WALTER J. , BURKE BRIAN C.
Published: December 2003

The aim of this study is to find spatial patterns of EEG amplitude in the gamma range of the EEGs from multiple sensory and limbic areas that demonstrate multisensory convergence and integration. 64 electrodes spread in small arrays were fixed on or in the olfactory, visual, auditory, somatomotor and entorhinal areas of cats and rabbits. The subjects were trained to discriminate 2 visual and then 2 auditory conditioned stimuli, one reinforced (CS+), the other not (CS-). A moving window was applied to the 6-s records from 20 trials of each CS including a 3-s prestimulus control (CS0). The root mean square amplitude was calculated for each signal in the gamma range, so each window gave a point in 64-space. EEG patterns from the CS+, CS- and CS0 conditions gave 3 clusters of points in 64-space. The Euclidean distance of each point to the nearest center of gravity of a cluster served for classification and estimation of the probability of correct classification. The results showed that the gamma activity (35–60 Hz in cats, 20–80 Hz in rabbits) in all five areas formed global patterns of amplitude modulation (AM) in time windows lasting ~100–200 ms and recurring at 2–4 Hz, which were correctly classified above chance levels (p<0.01). All areas contributed information to the AM patterns that served to classify the EEG epochs in the windows with respect to the conditioned stimuli. In conclusion, multisensory integration took place over the greater part of the hemisphere, despite lack of phase coherence among the gamma waves. The integration occurred rapidly enough that, within 300 ms of CS onset, activity in every sensory area was modified by what took place in every other sensory area.
NONLINEAR DYNAMICS OF A BOUNCING BALL DRIVEN BY ELECTRIC FORCES
Authors: KHAYARI A. , PÉREZ A. T.
Published: December 2003

This paper is devoted to a theoretical and experimental study of the dynamics of a bouncing ball driven by an electric force. The experimental model consists of a metallic ball immersed in a poorly conducting liquid between two horizontal electrodes. The ball bounces upon the lower electrode as a high voltage is applied between the two plates. The measurement of the time between successive impacts produces a time series, which depends on two control parameters, the amplitude and the frequency of the applied voltage. A theoretical model is proposed, which provides a discrete nonlinear map, and discussed in comparison with the experimental results. It is shown that the system exhibits a period doubling route to chaos and a non-Feigenbaum universal scaling at the onset of chaos. Chaotic motion is investigated using the usual tools: Lyapunov exponents, correlation dimensions and entropies. Fractal structure of the chaotic attractor is also brought to evidence in experimental time series as well as in numerical simulations.
HOMOCLINIC BRANCH SWITCHING: A NUMERICAL IMPLEMENTATION OF LIN'S METHOD
Authors: OLDEMAN BART E. , CHAMPNEYS ALAN R. , KRAUSKOPF BERND
Published: December 2003

We present a numerical method for branch switching between homoclinic orbits to equilibria of ODEs computed via numerical continuation. Starting from a 1-homoclinic orbit our method allows us to find and follow an N-homoclinic orbit, for any N>1 (if it exists nearby). This scheme is based on Lin's method and it is robust and reliable.

The method is implemented in AUTO/HOMCONT. A system of ordinary differential equations introduced by Sandstede featuring inclination and orbit flip bifurcations and homoclinic-doubling cascades, is used as a test bed for the algorithm. It is also successfully applied to reliably find multihump traveling wave solutions in the FitzHugh–Nagumo nerve-axon equations and in a fourth-order Hamiltonian system arising as a model for water waves.
BIFURCATIONS IN THE COLPITTS OSCILLATOR: FROM THEORY TO PRACTICE
Authors: DE FEO OSCAR , MAGGIO GIAN MARIO
Published: December 2003

This paper presents an experimental verification of the theoretical predictions, recently published in [Maggio et al., 1999; De Feo et al., 2000], about the bifurcation phenomena occurring in the Colpitts oscillator. Specifically, we performed an automated series of simulations based on the Spice model and, more importantly, a computer-assisted set of measurements on a concrete realization of the oscillator. It turns out that the bifurcation phenomena exhibited by the oscillator are relatively independent of the simplifying assumptions on the transistor model. Moreover, it is shown that the predicted behaviors can be reproduced experimentally, both qualitatively and quantitatively, in a robust way.
SLIDING BIFURCATIONS: A NOVEL MECHANISM FOR THE SUDDEN ONSET OF CHAOS IN DRY FRICTION OSCILLATORS
Authors: DI BERNARDO M. , KOWALCZYK P. , NORDMARK A.
Published: December 2003

Recent investigations of nonsmooth dynamical systems have resulted in the study of a class of novel bifurcations termed as sliding bifurcations. These bifurcations are a characteristic feature of so-called Filippov systems, that is, systems of ordinary differential equations (ODEs) with discontinuous right-hand sides. In this paper we show that sliding bifurcations also play an important role in organizing the dynamics of dry friction oscillators, which are a subclass of nonsmooth systems. After introducing the possible codimension-1 sliding bifurcations of limit cycles, we show that these bifurcations organize different types of "slip to stick-slip" transitions in dry friction oscillators. In particular, we show both numerically and analytically that a sliding bifurcation is an important mechanism causing the sudden jump to chaos previously unexplained in the literature on friction systems. To analyze such bifurcations we make use of a new analytical method based on the study of appropriate normal form maps describing sliding bifurcations. Also, we explain the circumstances under which the theory of so-called border-collision bifurcations can be used in order to explain the onset of complex behavior in stick-slip systems.
OSCILLATORY ORBITS OF THE PARAMETRICALLY EXCITED PENDULUM
Authors: GARIRA WINSTON , BISHOP STEVEN R.
Published: December 2003

We consider oscillatory, nonrotating periodic solutions of the parametrically excited pendulum. We determine the zones in the parameter space in which different types of oscillatory solutions are realized. In particular we determine the zones in which the T-periodic and 2T-periodic harmonic and subharmonic oscillatory solutions are the dominant type of stable solutions. The symmetry properties of these solutions and the associated scenarios of transition to tumbling chaos are also discussed.
A SIZE AND MATURITY STRUCTURED MODEL OF CELL DWARFISM EXHIBITING CHAOTIC BEHAVIOR
Authors: HOWARD KEITH E.
Published: December 2003

This work is devoted to analyzing the growth of an abnormal cell population where cellular development is characterized by a measure of its size and maturity. By size, we mean some quantified measure of cellular mass. By maturity, we refer to some measure of cellular development, other than age or size, which can be quantified. Our model is abnormal in that the size restriction for cellular division has been removed, thus allowing cells of all sizes to undergo division. This leads to production of dwarf cells. The issues treated here include: (1) existence and uniqueness of solutions, and (2) stability and instability of solutions with particular emphasis on chaotic behavior.
DESIGNING CNN GENES
Authors: ITOH MAKOTO , CHUA LEON O.
Published: December 2003

A systematic design methodology for finding CNN parameters with prescribed functions is proposed. A given function (task) is translated into several local operations, and they are realized as stable states of the CNN system. Many CNN parameters (CNN genes) with the same functions can be easily derived by using this design methodology. A genetic algorithm based CNN gene design methodology is also proposed. Two new genetic "activation and inactivation" operations are introduced to generate CNN genes effectively. Many useful CNN genes can be obtained systematically from known genes by using these genetic operations. Furthermore, the signal propagation property for activated and inactivated CNN genes is studied.
VISUALIZING BIFURCATIONS IN HIGH DIMENSIONAL SYSTEMS: THE SPECTRAL BIFURCATION DIAGRAM
Authors: ORRELL DAVID , SMITH LEONARD A.
Published: December 2003

This paper presents methods to visualize bifurcations in flows of nonlinear dynamical systems, using the Lorenz '96 systems as examples. Three techniques are considered; the first two, density and max/min diagrams, are analagous to the bifurcation diagrams used for maps, which indicate how the system's behavior changes with a control parameter. However the diagrams are generally harder to interpret than the corresponding diagrams of maps, due to the continuous nature of the flow. The third technique takes an alternative approach: by calculating the power spectrum at each value of the control parameter, a plot is produced which clearly shows the changes between periodic, quasi-periodic, and chaotic states, and reveals structure not shown by the other methods.
IMPERFECT PHASE SYNCHRONIZATION IN THE LOCOMOTOR BEHAVIOR OFHALOBACTERIUM SALINARIUM
Authors: TORRI GIANCARLO , RINALDI SERGIO , PICCARDI CARLO
Published: December 2003

A chaotic system can be used to transform a periodic input sequence of events, e.g. impulses, into a sequence of output events. Even after transient, the output sequence is often aperiodic. In particular, it might happen that the output events are basically synchronized with the input events, but that some of them are randomly skipped from the output time series (imperfect phase synchronization [Zacks et al., 1999, 2000]). This phenomenon has been neatly observed by Schimz and Hildebrand [1992] in a rich series of experiments on the locomotor behavior of Halobacterium salinarium, where the input event was a light impulse and the output event was the reversal in the swimming direction of the bacterium. In this paper, we show that the same phenomenon occurs when classical, low dimensional chaotic oscillators are forced by a periodic sequence of impulses. This proves, on one side, that imperfect phase synchronization is a common phenomenon in chaotic oscillators subjected to periodic sequences of impulses, and, on the other side, that there are high chances that the locomotor behavior of Halobacterium salinarium can be modeled by a low dimensional deterministic model.