bluuebunny/crossref_metadata_2025 huggingface dataset:
The elusive structural role of ubiquitinated histones
Authors: Moore Susan C , Jason Laure , Ausió Juan
Published: July 2002

It is increasingly apparent that histone posttranslational modifications are important in chromatin structure and dynamics. However, histone ubiquitination has received little attention. Histones H1, H3, H2A, and H2B can be ubiquitinated in vivo, but the most prevalent are uH2A and uH2B. The size of this modification suggests some sort of structural impact. Physiological observations suggest that ubiquitinated histones may have multiple functions and structural effects. Ubiquitinated histones have been correlated with transcriptionally active DNA, implying that it may prevent chromatin folding or help maintain an open conformation. Also, in some organisms during spermiogenesis, a process involving extensive chromatin remodeling, uH2A levels increase just prior to histone replacement by protamines. Determination of chromatin's structural changes resulting from histone ubiquitination is therefore important. Recent work using reconstituted nucleosomes and chromatin fibers containing uH2A indicate that in the absence of linker histones, ubiquitination has little structural impact. DNase I digests and analytical ultracentrifugation of reconstituted ubiquitinated nucleosomes show no structural differences. Solubility assays using reconstituted chromatin fibers in the presence of divalent ions demonstrate that uH2A fibers are slightly more prone to aggregation than controls, and analytical ultracentrifugation results with different MgCl2and NaCl concentrations determined that chromatin folding is not affected by this modification. Additional work to assess possible synergistic affects with histone acetylation also precludes any structural implications. Protamine displacement experiments concluded that the presence of uH2A does not significantly affect the ability of the protamines to displace histones. In addition, uH2A does not interfere with histone H1 binding to the nucleosome. While work with uH2B remains insufficient to come to any definitive conclusions about its structural impact, current work with uH2A indicates that, contrary to predictions, this histone modification does not affect either nucleosome or chromatin structure. Consequently, the search for a structural role for ubiquitinated histones continues and their effect on and importance in chromatin dynamics remains elusive.Key words: ubiquitinated histones, chromatin, nucleosome structure.
Electrocatalytic dechlorination of atrazine
Authors: Stock Naomi L , Bunce Nigel J
Published: July 2002

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), a photosynthetic inhibitor that is used in large quantities for weed control in corn and sorghum, is dechlorinated in aqueous solution upon electrolysis at a reticulated vitreous carbon cathode in the presence of noble-metal catalysts. Electrocatalytic hydrogenolysis to 2-ethylamino-4-isopropylamino-s-triazine occurs in quantitative yield, and is most efficient with palladium-based catalysts. Current efficiency increases with atrazine and catalyst concentration, and decreasing current density. A previously unobserved phenomenon with Pd catalysts is that current must be passed for a certain time before dechlorination commences. This lag time is explained in terms of the palladium lattice absorbing a finite amount of hydrogen before catalytically active hydrogen atoms appear on the catalyst surface.Key words: electrocatalytic hydrogenoloysis, dechlorination, atrazine, palladium catalysts.
Patterns of above- and below-ground response of understory conifer release 6 years after partial cutting
Authors: Kneeshaw Daniel D , Williams Harry , Nikinmaa Eero , Messier Christian
Published: July 2002

An increased pressure to use silvicultural techniques not based on clear-cutting followed by planting has led to an interest in systems that take advantage of existing understory seedlings (advance regeneration). Earlier studies have suggested that following harvesting, understory seedlings may experience growth reductions before responding with growth increases. We hypothesize that this "growth shock" following release results because seedlings are ill adjusted to the new growing conditions and that this can be investigated through a comparison of growth in different parts of the tree over a 6-year period. This study compares the growth response of three size classes of lodgepole pine (Pinus contorta Dougl. ex Loud.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings to a partial overstory removal in relatively dry conifer forests of central British Columbia. Growth was evaluated in four parts of the studied trees: radial increment in roots, in the base of the stem, and in branches, as well as leader height growth extension. Our findings show that following release from the overstory, early growth increases were largest in the roots and stems irrespective of the species or the size class. Differences between the species were observed in greater absolute height growth for pine, whereas Douglas-fir invested in greater stem growth, especially in the larger individuals. Important differences also occurred temporally. Both species (and all size classes) responded with an immediate increase in root growth followed, after a 1-year delay, by an increase in stem growth. Branch radial increment (for pine) and leader height growth (both species), however, experienced 2 to 3 year growth reductions before responding. It is therefore suggested that individuals restore the rootshoot balance by greater initial investments to root growth to offset the increased transpiration losses associated with the greater light and higher temperature conditions and the relative changes in the photosynthetic versus nutrient uptake capacity following the canopy opening. Foresters may therefore be able to manipulate tree growth responses by using an appropriate degree of overstory removal or opening size.
THE MAXWELL–DIRAC EQUATIONS: ASYMPTOTIC COMPLETENESS AND THE INFRARED PROBLEM
Authors: FLATO MOSHÉ , SIMON JACQUES , TAFLIN ERIK
Published: July 2002

In this article we present an announcement of results concerning:

a) A solution to the Cauchy problem for the M-D equations, namely global existence, for small initial data at t = 0, of solutions for the M-D equations.

b) Arguments from which asymptotic completeness for the M-D equations follows.

c) Cohomological interpretation of the results in the spirit of nonlinear representation theory and its connection to the infrared tail of the electron in M-D classical field theory.

The full detailed results will be published elsewhere.
ON THE ESSENTIAL SELF-ADJOINTNESS OF THE RELATIVISTIC HAMILTONIAN WITH A NEGATIVE SCALAR POTENTIAL
Authors: ICHINOSE TAKASHI , ICHINOSE WATARU
Published: July 2002

The relativistic quantum Hamiltonian H describing a spinless particle in an electromagnetic field is considered. H is associated with the classical Hamiltonian [Formula: see text] via Weyl’s correspondence. In the previous papers the second author has proved that H is essentially self-adjoint on [Formula: see text] if the scalar potential V(x) is a function bounded from below by a polynomial in x. In the present paper this result will be extended to show that H is essentially self-adjoint there if V(x) is bounded from below by -C exp a|x| for some positive constants C and a. Ameliorated is also the condition on the vector potential A(x). The result of this kind is quite different from that on the non-relativistic operator, i.e. the Schrödinger operator, but much closer to that on the Dirac operator.
ASYMPTOTIC BEHAVIOR OF THE GINZBURG-LANDAU FUNCTIONAL ON COMPLEX LINE BUNDLES OVER COMPACT RIEMANN SURFACES
Authors: ORLANDI GIANDOMENICO
Published: July 2002

Motivated by the works of F. Bethuel, H. Brezis, F. Hélein [5] and of F. Bethuel, T. Rivière [6], an asymptotic analysis is carried out for minimizers of the Ginzburg-Landau functional depending on a parameter ε, in the more general case of complex line bundles with prescribed Chern class over compact Riemann surfaces. Such a functional describes a 2-dimensional abelian Higgs model and is also related to phenomena in superconductivity. A suitable renormalized energy is defined which characterizes the singularities (degree one vortices) of the limiting configuration.
Quantizations of Flag Manifolds and Conformal Space Time
Authors: Fioresi R.
Published: July 2002

In this paper we work out the deformations of some flag manifolds and of complex Minkowski space viewed as an affine big cell inside G(2,4). All the deformations come in tandem with a coaction of the appropriate quantum group. In the case of the Minkowski space this allows us to define the quantum conformal group. We also give two involutions on the quantum complex Minkowski space, that respectively define the real Minkowski space and the real euclidean space. We also compute the quantum De Rham complex for both real (complex) Minkowski and euclidean space.
Energy Dependent Boundary Conditions and the Few-Body Scattering Problem
Authors: Kurasov P.
Published: July 2002

An exactly solvable problem with energy dependent interaction is investigated in the present paper. The selfadjoint model operator describes the scattering problem for three one-dimensional particles. It is shown that this problem is equivalent to the diffraction problem in the sector with energy dependent boundary conditions. The problem is solved with the help of the Sommerfeld–Maluzhinetz representation, which transforms the partial differential equation for the eigenfunctions to a functional equation on the integral densities. The solution of the functional equation can be constructed explicitly in the case of identical particles. The three-body scattering matrix describing rearrangement and excitation processes is represented in terms of analytic functions.
Quantum Nekhoroshev Theorem for Quasi-Periodic Floquet Hamiltonians
Authors: Monti F. , Jauslin H. R.
Published: July 2002

A quantum version of Nekhoroshev estimates for Floquet Hamiltonians associated to quasi-periodic time dependent perturbations is developped. If the unperturbed energy operator has a discrete spectrum and under finite Diophantine conditions, an effective Floquet Hamiltonian with pure point spectrum is constructed. For analytic perturbations, the effective time evolution remains close to the original Floquet evolution up to exponentially long times. We also treat the case of differentiable perturbations.
Some Properties of Massless Particles in Arbitrary Dimensions
Authors: Laoues Mourad
Published: July 2002

Various properties of two kinds of massless representations of the n-conformal (or (n+1)-De Sitter) group [Formula: see text] are investigated for n≥2. It is found that, for space-time dimensions n≥3, the situation is quite similar to the one of the n=4 case for Sn-massless representations of the n-De Sitter group [Formula: see text]. These representations are the restrictions of the singletons of [Formula: see text]. The main difference is that they are not contained in the tensor product of two UIRs with the same sign of energy when n>4, whereas it is the case for another kind of massless representations. Finally some examples of Gupta–Bleuler triplets are given for arbitrary spin and n≥3.
GEOMETRY OF QUANTUM HOMOGENEOUS VECTOR BUNDLES AND REPRESENTATION THEORY OF QUANTUM GROUPS I
Authors: GOVER A. R. , ZHANG R. B.
Published: July 2002

Quantum homogeneous vector bundles are introduced in the context of Woronowicz type compact quantum groups. The bundles carry natural topologies, and their sections furnish finite type projective modules over algebras of functions on quantum homogeneous spaces. Further properties of the quantum homogeneous vector bundles are investigated, and applied to the study of the geometrical structures of induced representations of quantum groups.
COVARIANT TECHNIQUES FOR COMPUTATION OF THE HEAT KERNEL
Authors: AVRAMIDI I. G.
Published: July 2002

The heat kernel associated with an elliptic second-order partial differential operator of Laplace type acting on smooth sections of a vector bundle over a Riemannian manifold, is studied. A general manifestly covariant method for computation of the coefficients of the heat kernel asymptotic expansion is developed. The technique enables one to compute explicitly the diagonal values of the heat kernel coefficients, so called Hadamard–Minakshisundaram–De Witt–Seeley coefficients, as well as their derivatives. The elaborated technique is applicable for a manifold of arbitrary dimension and for a generic Riemannian metric of arbitrary signature. It is very algorithmic, and well suited to automated computation. The fourth heat kernel coefficient is computed explicitly for the first time.

The general structure of the heat kernel coefficients is investigated in detail. On the one hand, the leading derivative terms in all heat kernel coefficients are computed. On the other hand, the generating functions in closed covariant form for the covariantly constant terms and some low-derivative terms in the heat kernel coefficients are constructed by means of purely algebraic methods. This gives, in particular, the whole sequence of heat kernel coefficients for an arbitrary locally symmetric space.
SELF-ORGANIZED CRITICALITY IN A MODEL OF COLLECTIVE BANK BANKRUPTCIES
Authors: ALEKSIEJUK AGATA , HOŁYST JANUSZ A. , KOSSINETS GUEORGI
Published: July 2002

The question we address here is of whether phenomena of collective bankruptcies are related to self-organized criticality. In order to answer it we propose a simple model of banking networks based on the random directed percolation. We study effects of one bank failure on the nucleation of contagion phase in a financial market. We recognize the power law distribution of contagion sizes in 3d- and 4d-networks as an indicator of SOC behavior. The SOC dynamics was not detected in 2d-lattices. The difference between 2d- and 3d- or 4d-systems is explained due to the percolation theory.
ENERGY LEVELS OF A POLARON IN A FINITE PARABOLIC QUANTUM WELL
Authors: ZHAO FENG-QI , LIANG XI XIA , BAN SHILIANG
Published: July 2002

The effects of the electron–phonon interaction on the electron (or hole) energy levels in parabolic quantum well (PQW) structures are studied. The ground state, the first excited state and the transition energy of the electron (or hole) in the GaAs/Al 0.3 Ga 0.7 As parabolic quantum well are calculated by using a modified Lee–Low–Pines Variational method. The numerical results are given and discussed. A comparison between the theoretical and experimental results is made.
TIME-DEPENDENT DENSITY FUNCTIONAL THEORY BEYOND THE ADIABATIC APPROXIMATION
Authors: VIGNALE G.
Published: July 2002

I review recent advances in understanding the physical character of the exchange-correlation (xc) potential in time-dependent density functional theory. I show that in an electron gas of slowly varying density the dynamical part of the xc potential is an extremely nonlocal functional of the density. This difficulty can be circumvented by introducing an xc vector potential that is a function of the local current density. The form of this vector potential is entirely specified by symmetry. Its physical effects are analogous to those of the viscous force in the Navier-Stokes equation of classical hydrodynamics. Recent applications of the xc vector potential to the calculation of infrared absorption linewidths in quantum wells are described.
INTERPLAY OF ANTIFERROMAGNETISM AND SUPERCONDUCTIVITY IN RARE EARTH NICKEL BOROCARBIDES
Authors: BEHERA S. N. , PANDA B. N. , ROUT G. C. , ENTEL P.
Published: July 2002

A review of some of the anomalous properties observed in rare earth nickel borocarbide superconductors is presented. A model proposed earlier for heavy fermion superconductors is adopted to the rare earth nickel borocarbides. Even though the model is solved in the mean field approximation, it provides qualitative explanation to many of the anomalous experimental observations.
THE GENESIS OF WASHBOARD ROADS
Authors: KURTZE DOUGLAS A. , HONG DANIEL C. , BOTH JOSEPH A.
Published: July 2002

We consider a model of cars driving along a compressible or erodible road. Each car is modeled as a mass supported above a wheel by a damped spring. We find conditions under which a flat road surface is unstable and gives way to a regular pattern of corrugations. The instability is mitigated by the damping of the cars' springs and also by the tendency of the road surface to harden as it is compressed. Similar phenomena occur in railroad rails and in calendaring of paper.
CANONICAL TRANSFORMATION APPROACH TO THE ULTRAFAST NONLINEAR OPTICAL DYNAMICS OF SEMICONDUCTORS
Authors: PERAKIS I. E. , SHAHBAZYAN T. V.
Published: July 2002

We develop a theory describing the effects of many-particle Coulomb correlations on the coherent ultrafast nonlinear optical response of semiconductors and metals. Our approach is based on a mapping of the nonlinear optical response of the "bare" system onto the linear response of a "dressed" system. The latter is characterized by effective time-dependent optical transition matrix elements, electron/hole dispersions, and interaction potentials, which in undoped semiconductors are determined by the single-exciton and two-exciton Green functions in the absence of optical fields. This mapping is achieved by eliminating the optically-induced charge fluctuations from the Hamiltonian using a Van Vleck canonical transformation. It takes into account all many-body contributions up to a given order in the optical fields as well as important Coulomb-induced quantum dynamics to all orders in the optical field. Our approach allows us to distinguish between optical nonlinearities of different origins and provides a physically-intuitive interpretation of their manifestations in ultrafast coherent nonlinear optical spectroscopy.
MINIMAL ENTANGLEMENT FIDELITIES OF SOME SINGLE QUBIT QUANTUM NOISY CHANNELS
Authors: LIANG XIAN-TING
Published: July 2002

The minimal entanglement fidelities of the phase damping channel, depolarizing channel, two-Pauli channel and amplitude damping channel are calculated. It is shown that for the same condition, the minimal fidelity of the phase damping channel is the biggest among the four channels. The minimal fidelity of the depolarizing channel is bigger than the other two.
STRUCTURAL TRANSFORMATION IN NANOPHASE TITANIUM DIOXIDE
Authors: WU MUYING , ZHANG WEIFENG , DU ZULIANG , HUANG YABIN
Published: July 2002

Nanophase TiO 2 was prepared by a stearic acid sol–gel technique. X-ray measurements showed that the as-prepared sample is anatase TiO 2 phase with an average grain size of 10.4 nm. Raman spectroscopy was used to investigate the structural transformation from anatase-to-rutile in the nanophase TiO 2 annealed at a series of temperatures from 450 to 650°C. The results showed that the transformation took place in a wide annealing temperature range. The related mechanism to the phase transformation is discussed according to nanometer size effect.
OBSERVATION OF TWO TYPES OF GROWTH MODES ON (111) FACE IN CVD DIAMOND FILMS
Authors: HAN SIJIN , FANG RONGCHUAN , LIAO YUAN , LE DEFEN , LI FANQING
Published: July 2002

Both spiral growth and terrace flow growth were observed on the vicinal (111) faces of a multiply twinned diamond particle by scanning electron microscopy (SEM). Furthermore, both left- and right-handed spirals were obtained on a fivefold multiply twinned particle. The SEM results provide direct evidence for which two types of growth modes could exist at the same time during the chemical vapor deposition (CVD) diamond growth. It depends strongly on whether there exists a screw dislocation on the underlying diamond substrate for each respective growth on (111) faces. We explained all the features using the classical crystal growth theory of Burton, Cabrera and Frank.
A COMBINATION OF FRACTAL AND WAVELET FOR FEATURE EXTRACTION
Authors: TAO YU , LAM ERNEST C. M. , TANG YUAN Y.
Published: July 2002

In this paper, a novel approach to feature extraction with wavelet and fractal theories is presented as a powerful technique in pattern recognition. The motivation behind using fractal transformation is to develop a high-speed feature extraction technique. A multiresolution family of the wavelets is also used to compute information conserving micro-features. In this study, a new fractal feature is reported. We employed a central projection method to reduce the dimensionality of the original input pattern, and a wavelet transform technique to convert the derived pattern into a set of subpatterns, from which the fractal dimensions can readily be computed. The new feature is a measurement of the fractal dimension, which is an important characteristic that contains information about the geometrical structure. This new scheme includes utilizing the central projection transformation to describe the shape, the wavelet transformation to aid the boundary identification, and the fractal features to enhance image discrimination. The proposed method reduces the dimensionality of a 2-D pattern by way of a central projection approach, and thereafter, performs Daubechies' wavelet transform on the derived 1-D pattern to generate a set of wavelet transform subpatterns, namely, curves that are non-self-intersecting. Further from the resulting non-self-intersecting curves, the divider dimensions are computed with a modified box-counting approach. These divider dimensions constitute a new feature vector for the original 2-D pattern, defined over the curve's fractal dimensions. We have conducted several experiments in which a set of printed Chinese characters, English letters of varying fonts and other images were classified. Based on the formulation of our new feature vector, the experiments have satisfying results.
COMPLEX NETWORKS: TOPOLOGY, DYNAMICS AND SYNCHRONIZATION
Authors: WANG XIAO FAN
Published: July 2002

Dramatic advances in the field of complex networks have been witnessed in the past few years. This paper reviews some important results in this direction of rapidly evolving research, with emphasis on the relationship between the dynamics and the topology of complex networks. Basic quantities and typical examples of various complex networks are described; and main network models are introduced, including regular, random, small-world and scale-free models. The robustness of connectivity and the epidemic dynamics in complex networks are also evaluated. To that end, synchronization in various dynamical networks are discussed according to their regular, small-world and scale-free connections.
ROLES IN AGENT-ORIENTED MODELING
Authors: DEPKE RALPH , HECKEL REIKO , KÜSTER JOCHEN MALTE
Published: July 2002

For the generic specification of protocols, goals, or workflows, many approaches to agent-oriented modeling provide a concept of role. Roles abstract from the concrete agents involved in an interaction. They provide means for the evolution of agents and serve as components of agent design. Despite the widespread usage of roles in agent-oriented modeling, a systematic analysis of the different aspects and properties of this concept is still missing. In this paper, we perform such an analysis and identify requirements for a general role concept. We develop such a role concept for a modeling approach based on the UML and graph transformation systems and exemplify its use for the specification (and application) of protocols. Finally, we provide a run-time semantics for roles based on concepts from the theory of graph transformation.
REPRESENTING BRAIDS BY AUTOMORPHISMS
Authors: SHPILRAIN VLADIMIR
Published: July 2002

Based on a normal form for braid group elements suggested by Dehornoy, we prove several representations of braid groups by automorphisms of a free group to be faithful. This includes a simple proof of the standard Artin's representation being faithful.
POINTLIKE SETS, HYPERDECIDABILITY AND THE IDENTITY PROBLEM FOR FINITE SEMIGROUPS
Authors: RHODE JOHN , STEINBERG BENJAMIN
Published: July 2002

In this paper, we give a relationship between the identity problem and the problem of deciding whether certain subsets of nilpotent semigroups are pointlike. We then use this to give an example of a pseudovariety which has a decidable membership problem, but for which one cannot decide pointlike sets. Then, by modifying the equations, we show that no graph is fundamentally hyperdecidable by constructing, for each graph, a labeling over a nilpotent semigroup for which we cannot decide inevitability with respect to the pseudovariety defined by these equations.
SOME RESULTS ON PARTIAL DIFFERENTIAL EQUATIONS AND ASIAN OPTIONS
Authors: BARUCCI E. , POLIDORO S. , VESPRI V.
Published: July 2002

We analyze partial differential equations arising in the evaluation of Asian options. The equations are strongly degenerate partial differential equations in three dimensions. We show that the solution of the no-arbitrage partial differential equation is sufficiently regular and standard numerical methods can be employed to approximate it.
NUCLEATION AND GROWTH DURING FACETING OF THE PLATINUM-COVERED W(111) SURFACE
Authors: PELHOS K. , MADEY T. E. , HANNON J. B. , KELLOGG G. L.
Published: July 2002

Low energy electron microscopy (LEEM) and scanning tunneling microscopy (STM) have been used to investigate the faceting of W(111) as induced by Pt. The atomically rough W(111) surface, when fully covered with a monolayer film of Pt and annealed to temperatures higher than ~750 K, experiences a significant morphological restructuring: the initially planar surface undergoes a faceting transition and forms three-sided pyramids with {211} faces. When Pt is dosed onto the heated surface, the transition from planar to faceted structure proceeds through the nucleation and growth of spatially separated faceted region, as shown by LEEM. STM reveals the atomic structure of the partially faceted surface, with large planar regions, dotted by clusters of pyramids of various sizes.
ATOMISTIC CALCULATIONS OF (110) SURFACE RELAXATION FOR PEROVSKITE TITANATES
Authors: HEIFETS E. , KOTOMIN E. A. , BORSTEL G.
Published: July 2002

Using a shell model, for the first time the (110) surface relaxations are calculated for SrTiO 3 and BaTiO 3 perovskites. The positions of atoms in 16 near-surface layers placed atop a slab of rigid ions are calculated. Strong surface rumpling and surface-induced dipole moments perpendicular to the surface are predicted for both the O-terminated and Ti-terminated surfaces.
ALLOGRAFT REPLACEMENT IN GIANT CELL TUMOUR OF THE HAND
Authors: Patradul Adisorn , Kitidumrongsook Pravit , Parkpian Vinai , Ngarmukos Chaithavat
Published: July 2002

Allografts were used to replace excised bone segments affected by giant cell tumour of the hand in three patients. The tumour involved the second, third and fourth metacarpals and the capitate in one case; the first metacarpal and the trapezium in one, and the proximal phalanx of the index in one.

All had histological confirmation of diagnosis. One patient had recurrence one year after marginal resection of his third metacarpal and required resection of the two adjacent metacarpals and the capitate. He had no recurrence two years after the secondary treatment. The other two had no recurrence at two and three years after their primary procedures. Their affected hands were functioning well.
HOW DOES THE EURODOLLAR INTEREST RATE BEHAVE?
Authors: DI MATTEO TIZIANA , ASTE TOMASO
Published: July 2002

An empirical analysis on Eurodollar interest rates daily data in the time period 1990–1996, is performed and compared with Libor data in the time period 1984–1998. The complementary cumulative distributions for the daily fluctuations at different maturity dates and the Power Spectral Density are computed. We find that the probability distribution shows "fat" tails with non-Gaussian behaviours. Moreover, we study the correlations among Eurodollar interest rates fluctuations with different maturity dates. By using an original clustering linkage, we show how the collective motion of the interest rates curve can be analyzed in sub-groups of maturity dates with similar behaviours.
THE FIVE INDEPENDENCES AS QUASI-UNIVERSAL PRODUCTS
Authors: MURAKI NAOFUMI
Published: July 2002

A notion of "quasi-universal product" for algebraic probability spaces is introduced as a generalization of Speicher's "universal product". It is proved that there exist only five quasi-universal products, namely, tensor product, free product, Boolean product, monotone product and anti-monotone product. This result means that, in a sense, there exist only five independences which have nice properties of "associativity" and "(quasi-)universality".
ADVERTISING IN A COMPETITIVE PRODUCT LINE
Authors: FRUCHTER GILA E.
Published: July 2002

In many markets, competing but differentiated firms offer a product line in order to target each product to a different type of customer. Under competition, firms, while trying to target different products to different segments, are also interested in "stealing" customers from the competitors and, in particular, customers from the most profitable segments. How should a profit-maximising firm allocate the advertising budget along a competitive product line? Devel oping a closed-loop time-variant Nash equilibrium strategy for a multi-player multi-product advertising game, we find the determinants of the optimal advertising budget allocation in a product line in an oligopoly growing market. Moreover, for a symmetric competition in a fixed market, we derive an analytic feedback time-variant Nash equilibrium strategy. Marketing implications regarding the firm's strategic orientation in product preference advertising spending, as well as comparison to rivals' spending, are discussed. Finally, we show that using a single-product advertising game instead of a multi-product advertising game, leads to over-advertising.
SURFACE ROUGHNESS IN MOLECULAR BEAM EPITAXY
Authors: BLÖMKER DIRK , MAIER-PAAPE STANISLAUS , WANNER THOMAS
Published: July 2002

This paper discusses the roughness of surfaces described by nonlinear stochastic partial differential equations on bounded domains. Roughness is an important characteristic for processes arising in molecular beam epitaxy, and is usually described by the mean interface width of the surface, i.e. the expected value of the squared Lebesgue norm. By employing results on the mean interface width for linear stochastic partial differential equations perturbed by colored noise, which have been previously obtained, we describe the evolution of the surface roughness for two classes of nonlinear equations, asymptotically both for small and large times.
SELF-SIMILARITY IN THE TAXONOMIC CLASSIFICATION OF HUMAN LANGUAGES
Authors: ZANETTE DAMIAN H.
Published: July 2002

Statistical properties of the taxonomic classification of human languages are studied. It is shown that, at the highest levels of the taxonomic hierarchy, the frequency of taxon members as a function of the number of languages belonging to each member decays as a power law. This feature reveals that a self-similar structure underlies the taxonomy of languages, exactly as observed in the taxonomic classification of biological species. Such an analogy is a clue to the evolutionary foundation of language classification based on long-range comparison.
Coalition factor in the evolution of non-kin altruism
Authors: Dessalles Jean-Louis
Published: July 2002

Animal behavior is often altruistic. In the frame of the theory of natural selection, altruism can only exist under specific conditions like kin selection or reciprocal cooperation. We show that reciprocal cooperation, which is generally invoked to explain non-kin altruism, requires very restrictive conditions to be stable. Some of these conditions are not met in many cases of altruism observed in nature. In search of another explanation of non-kin altruism, we consider Zahavis's theory of prestige. We extend it to propose a "political" model of altruism. We give evidence showing that non-kin altruism can evolve in the context of inter-subgroup competition. Under such circumstances, altruistic behavior can be used by individuals to advertise their quality as efficient coalition members. In this model, only abilities which positively correlate with the subgroup success can evolve into altruistic behaviors.
PROJECT-LEVEL INFLUENCES ON THE MANAGEMENT AND ORGANISATION OF PRODUCT DEVELOPMENT IN ENGINEERING
Authors: ALDERMAN NEIL , THWAITES ALFRED , MAFFIN DAVID
Published: July 2002

Many current models of the product development process pay insufficient attention to the impact of project-level influences. This paper looks at the case of the engineering industry in which product development is seen to proceed in two very distinct ways: the traditional process in which development takes place "off-line", and the contract process in which development takes place as part of a contract to manufacture a product for a specific customer. Drawing on two recent studies of engineering product development projects, the paper looks at how project-level influences lead to differences in project organisation and management in terms of the particular project structure adopted and in the involvement of different disciplines, internal and external to the company. This has implications for the way in which companies should interpret generic prescriptions regarding product development.
Designing for cooperation: cooperating in design
Authors: Kyng Morten
Published: July 2002

This article will discuss how to design computer applications that enhance the quality of work and products, and will relate the discussion to current themes in the field of Computer-Supported Cooperative Work (CSCW). Cooperation is a key element of computer use and work practice, yet here a specific “CSCW approach is not taken.” Instead the focus is cooperation as an important aspect of work that should be integrated into most computer support efforts in order to develop successful computer support, however, other aspects such as power, conflict and control must also be considered.
Wide-area collaboration
Authors: Press Larry
Published: July 2002

Since my temperament draws me to groupware, I have read about and taught it, and tried many groupware programs. This has been interesting, but the only groupware that has really affected my work is electronic mail on wide-area networks. My “invisible college,” my colleagues, are not the people in the offices down the corridor, they are people on the Internet, many of whom I have never seen or spoken with.
Automated selection of mathematical software
Authors: Lucks Michael , Gladwell Ian
Published: July 2002

Current approaches to recommending mathematical software are qualitative and categorical. These approaches are unsatisfactory when the problem to be solved has features that can “trade-off” in the recommendation process. A quantitative system is proposed that permits tradeoffs and can be built and modified incrementally. This quantitative approach extends other knowledge-engineering techniques in its knowledge representation and aggregation facilities. The system is demonstrated on the domain of ordinary differential equation initial value problems. The results are significantly superior to an existing qualitative (decision tree) system.
The development and proof of a formal specification for a multilevel secure system
Authors: Glasgow Janice I. , MacEwen Glenn H.
Published: July 2002

This paper describes current work on the design and specification of a multilevel secure distributed system called SNet. It discusses security models in general, the various problems of information flows in SNet, and the abstract and concrete security model components for SNet. It also introduces Lucid as a language for specifying distributed systems. The model components are expressed in Lucid; these Lucid partial specifications are shown to be correct with respect to the formal model, and the two model components are shown to be consistent. The complete functional specification of SNet in Lucid, its implementation in Concurrent Euclid, and the verification of the implementation with respect to the Lucid specification are not discussed.
Learning read-once formulas with queries
Authors: Angluin Dana , Hellerstein Lisa , Karpinski Marek
Published: July 2002

A read-once formula is a Boolean formula in which each variable occurs, at most, once. Such formulas are also called μ-formulas or Boolean trees. This paper treats the problem of exactly identifying an unknown read-once formula using specific kinds of queries.

The main results are a polynomial-time algorithm for exact identification of monotone read-once formulas using only membership queries, and a polynomial-time algorithm for exact identification of general read-once formulas using equivalence and membership queries (a protocol based on the notion of a
minimally adequate teacher
[1]). The results of the authors improve on Valiant's previous results for read-once formulas [26]. It is also shown, that no polynomial-time algorithm using only membership queries or only equivalence queries can exactly identify all read-once formulas.
A model for input and output of multilingual text in a windowing environment
Authors: Kataoka Yutaka , Morisaki Masato , Kuribayashi Hiroshi , Ohara Hiroyoshi
Published: July 2002

The layered multilingual input/output(I/O) sytems we designed, based on typological studies of major-language writing conventions, unifies common features of such conventions to enable international and local utilization. The internationalization layer input module converts keystroke sequences to phonograms and ideograms. The corresponding output module displays position-independent and dependent characters. The localization layer positions language-specific functions outside the structure, integrating them as tables used by finite automaton interpreters and servers to add new languages and code sets without recompilation.

The I/O system generates and displays stateful and stateless code sets, enabling interactive language switching. Going beyond POSIX locale model bounds, the system generates ISO 2022, ISO/DIS 10646 (1990), and Compound Text, defined for the interchange encoding format in X11 protocols, for basic polyglot text communication and processing. Able to generate multilingual code sets, the I/O system clearly demonstrates that code sets should be selected by applications which have purposes beyond selecting one element from a localization set. Functionality and functions related to text manipulation in an operating sytem (OS) must also be determined by such applications.

A subset of this I/O system was implemented in the X window system as a basic use of X11R5 I/O by supplying basic code set generation and string manipulation to eliminate OS interference. To ensure polyglot string manipulation, the I/O system must clearly be implemented separately from an OS and its limitations.
IP = PSPACE
Authors: Shamir Adi
Published: July 2002

In this paper, it is proven that when both randomization and interaction are allowed, the proofs that can be verified in polynomial time are exactly those proofs that can be generated with polynomial space.
IP = SPACE
Authors: Shen A.
Published: July 2002

Lund et al. [1] have proved that PH is contained in IP. Shamir [2] improved this technique and proved that PSPACE = IP. In this note, a slightly simplified version of Shamir's proof is presented, using degree reductions instead of simple QBFs.
The design and implementation of a log-structured file system
Authors: Rosenblum Mendel , Ousterhout John K.
Published: July 2002

This paper presents a new technique for disk storage management called alog-structured file system. A log-structured file system writes all modifications to disk sequentially in a log-like structure, thereby speeding up both file writing and crash recovery. The log is the only structure on disk; it contains indexing information so that files can be read back from the log efficiently. In order to maintain large free areas on disk for fast writing, we divide the log intosegmentsand use asegment cleanerto compress the live information from heavily fragmented segments. We present a series of simulations that demonstrate the efficiency of a simple cleaning policy based on cost and benefit. We have implemented a prototype log-structured file system called Sprite LFS; it outperforms current Unix file systems by an order of magnitude for small-file writes while matching or exceeding Unix performance for reads and large writes. Even when the overhead for cleaning is included, Sprite LFS can use 70% of the disk bandwidth for writing, whereas Unix file systems typically can use only 5–10%.
An
O
(log
N
) deterministic packet-routing scheme
Authors: Upfal Eli
Published: July 2002

A deterministic
O
(log
N
)-time algorithm for the problem of routing an aribitrary permutation on an
N
-processor bounded-degree network with bounded buffers is presented.

Unlike all previous deterministic solutions to this problem, our routing scheme does not reduce the routing problem to sorting and does not use the sorting network of Ajtai, et al. [1]. Consequently, the constant in the run time of our routing scheme is substantially smaller, and the network topology is significantly simpler.
On the complexity of functions for random access machines
Authors: Bshouty Nader H.
Published: July 2002

Tight bounds are proved for Sort, Merge, Insert, Gcd of integers, Gcd of polynomials, and Rational functions over a
finite
inputs domain, in a random access machine with arithmetic operations, direct and indirect addressing, unlimited power for answering YES/NO questions, branching, and tables with bounded size. These bounds are also true even if additions, subtractions, multiplications, and divisions of elements by elements of the field are not counted.

In a random access machine with finitely many constants and a bounded number of types of instructions, it is proved that the complexity of a function over a countable infinite domain is equal to the complexity of the function in a sufficiently large
finite
subdomain.
No assembly required
Authors: Tarditi David , Lee Peter , Acharya Anurag
Published: July 2002

C has been used as a portable target language for implementing languages like Standard ML and Scheme. Previous efforts at compiling these languages to C have produced efficient code, but have compromised on portability and proper tail recursion. We show how to compile Standard ML to C wihout making such compromises. The compilation technique is based on converting Standard ML to a continuation-passing style λ-calculus intermediate language and then compiling this language to C. The code generated by this compiler achieves an execution speed that is about a factor of two slower than that generated by a native code compiler. The compiler generates highly portable code, yet still supports advanced features like garbage collection and first-class continuations. We analyze the performance and determine the aspects of the compilation method that lead to the observed slowdown. We also suggest changes to C compilers that would better support such compilation methods.
Shortest path by approximation in logic programs
Authors: Dietrich Suzanne W.
Published: July 2002

An approximation paradigm is proposed for logic programming as a simple modification to a complete evaluation strategy. The motivational example illustrates how a straigthforward transformation of a declarative specification of the distance between two vertices in a directed graph leads to sophisticated algorithms for computing shortest paths. The goal of the work presented in this paper is
not
to provide a more efficient computation of shortest paths but to investigate how the intermediate tables, known as extension tables, generated by the complete evaluation strategy might be used in approximation algorithms. We present the ET
distance
algorithm in perspective, its execution is compared to those of Dijkstra's single-source and Floyd's all-pairs shortest path algorithms.
Open commit protocols tolerating commission failures
Authors: Rothermel Kurt , Pappe Stefan
Published: July 2002

To ensure atomicity of transactions in distributed systems so-called 2-phase commit (2PC) protocols have been proposed. The basic assumption of these protocols is that the processing nodes involved in transactions are “sane,” i.e., they only fail with omission failures, and nodes eventually recover from failures. Unfortunately, this assumption is not realistic for so-called Open Distributed Systems (ODSs), in which nodes may have totally different reliability characteristics. In ODSs, nodes can be classified into trusted nodes (e.g., a banking server) and nontrusted nodes (e.g., a home PC requesting a remote banking service). While trusted nodes are assumed to be sane, nontrusted nodes may fail permanently and even cause commission failures to occur.

In this paper, we propose a family of 2PC protocols that tolerate any number of omission failures at trusted nodes and any number of commission and omission failures at nontrusted nodes. The proposed protocols ensure that (at least) the trusted nodes participating in a transaction
eventually
terminate the transaction in a
consistent
manner. Unlike Byzantine commit protocols, our protocols do
not
incorporate mechanisms for achieving Byzantine agreement, which has advantages in terms of complexity: Our protocols have the same or only a slightly higher message complexity than traditional 2PC protocols.
Definitions of dependence distance
Authors: Pugh William
Published: July 2002

Data dependence distance is widely used to characterize data dependences in advance optimizing compilers. The standard definition of dependence distance assumes that loops are normalized (have constant lower bounds and a step of 1); there is not a commonly accepted definition for unnormalized loops. We have identified several potential definitions, all of which give the same answer for normalized loops. There are a number of subtleties involved in choosing between these definitions, and no one definition is suitable for all applications.
Distributed timestamp generation in planar lattice networks
Authors: Ammann Paul , Jajodia Sushil
Published: July 2002

Timestamps are considered for distributed environments in which information flow is restricted to one direction through a planar lattice imposed on a network. For applications in such networks, existing timestamping algorithms require extension and modification. For example, in secure environments, typical timestamps provide a potential signaling channel between incomparable levels. In hierarchical databases, typical timestamps cause peripheral sites to unnecessarily affect the behavior at main sites.

Algorithms are presented by which a network node may generate and compare timestamps using timestamp components maintained at dominated nodes in the network. The comparison relation is shown to be acyclic for timestamps produced by the generation algorithm. We discuss ways to safely relax the requirement that the network be a lattice. By example, we show how to modify a simple nonplanar lattice so that the generation algorithm can be applied. Uses of the timestamp generation algorithm in the motivating applications are outlined.
Algorithm 728: FORTRAN subroutines for generating quadratic bilevel programming test problems
Authors: Calamai Paul H. , Vicente Luis N.
Published: July 2002

This paper describes software for generating test problems for quadratic bilevel programming. The algorithm constructs problems with a number of favorable properties that can be selected and controlled by the user. The intention is to provide a set of FORTRAN 77 routines that can be used for testing, verifying, and comparing solution techniques for these problems.