bluuebunny/crossref_metadata_2025 huggingface dataset:
A FOUR-WING BUTTERFLY ATTRACTOR FROM A FULLY AUTONOMOUS SYSTEM
Authors: ELWAKIL A. S. , ÖZOǦUZ S. , KENNEDY M. P.
Published: December 2003

A novel system of nonlinear differential equations is proposed. This system is capable of generating a complex four-wing butterfly chaotic attractor by relying on two embedded state-controlled binary switches. Hence, the system is fully autonomous and does not require external forcing to create this attractor. Furthermore, digital logic operations (e.g. AND/OR) performed on the outputs of the two switches are permitted and effectively alter the dynamics of the system. Our findings are validated via experimental results.
CHAOTIFICATION OF LINEAR CONTINUOUS-TIME SYSTEMS USING SIMPLE NONLINEAR FEEDBACK
Authors: TANG WALLACE K. S. , ZHONG G. Q.
Published: December 2003

A nonlinear state feedback controller is proposed for the generation of chaos in third-order linear autonomous continuous time systems. With a simple feedback controller of the form g(x)=βx|x|, chaotic dynamics can be observed. Bifurcation analysis and the verification of the existence of chaos are given based on numerical continuation techniques and the Shil'nikov theorem. Both computer simulation and circuit implementation demonstrate the chaotification effect of this simple feedback controller.
THE DOUBLE-CUSP MAP FOR THE FORCED LORENZ SYSTEM
Authors: MEHTA MITAXI , MITTAL A. K. , DWIVEDI S.
Published: December 2003

It is found that adding constant forcing terms to the Lorenz equations breaks the (x,y)→(-x,-y) symmetry of the system. As a result of the symmetry breaking the consecutive z max return map (the cusp map) gets split into a double-cusp map. We investigate the double-cusp map for the forced Lorenz system using approximate invariant manifolds about the fixed points and use the double-cusp map to understand the stability of the attractor.
CONTROL OF OBSERVABLE CHAOTIC DYNAMICAL SYSTEMS USING NONLINEAR APPROXIMATIONS
Authors: HILL D. L.
Published: December 2003

A technique of using nonlinear approximations to control chaotic dynamical systems is extended so it can be used to control such systems when only data generated can be observed.
PROBLEMS WITH A PROBABILISTIC ENCRYPTION SCHEME BASED ON CHAOTIC SYSTEMS
Authors: LI SHUJUN , MOU XUANQIN , YANG BOLIYA L. , JI ZHEN , ZHANG JIHONG
Published: December 2003

Recently S. Papadimitriou et al. have proposed a new probabilistic encryption scheme based on chaotic systems. In this letter, we point out some problems with Papadimitriou et al.'s chaotic cryptosystem: (1) the size of the ciphertext and the plaintext cannot simultaneously ensure practical implementation and high security; (2) the estimated number of all possible virtual states is wrong; (3) the practical security to exhaustive attack is overestimated; (4) the fast encryption speed is dependent on the first defect; (5) problems about the dynamical degradation of digital chaotic systems; (6) no explicit indications are given to explain how to construct the virtual state space with the 2d virtual attractors, the 2e virtual states and the permutation matrix P. The detailed analyses and discussions on the above problems show that the proposed chaotic cipher is insecure and unpractical. Also, we give our suggestions on the design of general digital chaotic ciphers, and give some open topics in this area.
ESTIMATION OF INITIAL CONDITIONS AND SECURE COMMUNICATION
Authors: MAYBHATE ANIL , AMRITKAR R. E. , KULKARNI D. R.
Published: December 2003

We estimate the initial conditions of a multivariable dynamical system from a scalar signal, using a modified Newton–Raphson method incorporating the time evolution. We can estimate initial conditions of periodic and chaotic systems and the required length of scalar signal is very small. An important application of the method is in secure communications. The communication procedure has several advantages as compared to others using dynamical systems.
CONTROLLING CHAOS IN MAPS WITH MULTIPLE STRANGE ATTRACTORS
Authors: RICHTER HENDRIK
Published: December 2003

We study chaotic maps with multiple coexisting strange attractors and show how such systems can be controlled. To this end, a control scheme is proposed which is capable of stabilizing a desired motion within one strange attractor as well as taking the system dynamics from one strange attractor to another. To demonstrate the given control scheme, several examples are considered.
BIFURCATION BEHAVIOR OF A POWER-FACTOR-CORRECTION BOOST CONVERTER
Authors: DRANGA OCTAVIAN , TSE CHI K. , IU HERBERT H. C. , NAGY ISTVÁN
Published: December 2003

The aim of the paper is to investigate the bifurcation behavior of the power-factor-correction (PFC) boost converter under a conventional peak current-mode control. The converter is operated in continuous-conduction mode. The bifurcation analysis performed by computer simulations reveals interesting effects of variation of some chosen parameters on the stability of the converter. The results are illustrated by time-domain waveforms, discrete-time maps and parameter plots. An analytical investigation confirms the results obtained by computer simulations. Such an analysis allows convenient prediction of stability boundaries and facilitates the selection of parameter values to guarantee stable operation.
GLOBAL ANALYSIS OF STOCHASTIC BIFURCATION IN DUFFING SYSTEM
Authors: XU WEI , HE QUN , FANG TONG , RONG HAIWU
Published: December 2003

Stochastic bifurcation of a Duffing system subject to a combination of a deterministic harmonic excitation and a white noise excitation is studied in detail by the generalized cell mapping method using digraph. It is found that under certain conditions there exist two stable invariant sets in the phase space, associated with the randomly perturbed steady-state motions, which may be called stochastic attractors. Each attractor owns its attractive basin, and the attractive basins are separated by boundaries. Along with attractors there also exists an unstable invariant set, which might be called a stochastic saddle as well, and stochastic bifurcation always occurs when a stochastic attractor collides with a stochastic saddle. As an alternative definition, stochastic bifurcation may be defined as a sudden change in character of a stochastic attractor when the bifurcation parameter of the system passes through a critical value. This definition applies equally well either to randomly perturbed motions, or to purely deterministic motions. Our study reveals that the generalized cell mapping method with digraph is also a powerful tool for global analysis of stochastic bifurcation. By this global analysis the mechanism of development, occurrence and evolution of stochastic bifurcation can be explored clearly and vividly.
DEFECT-INDUCED PROPAGATION IN EXCITABLE MEDIA
Authors: ZHENG ZHIGANG , CROSS MICHAEL C.
Published: December 2003

Wave dynamics in the coupled FitzHugh–Nagumo oscillators with pacemaker defects is studied. It is found that with increasing the coupling strength, the lattice experiences a dynamical transition from a local wave to the global propagation. For large enough coupling, a transition from global wave propagation to the propagation failure can be observed. Noise-enhanced wave propagation in the propagation-failure regime is revealed.
A HOPF BIFURCATION IN A FREE BOUNDARY PROBLEM DEPENDING ON THE SPATIAL AVERAGE OF AN ACTIVATOR
Authors: HAM YOONMEE
Published: December 2003

We shall consider an activator–inhibitor system proposed by Radehaus [1990]. In this system, the activator is inhibited by not only the inhibitor but also its own spatial average. The purpose of this paper is to analyze the dynamics of interfaces in an interfacial problem which is reduced from the system in order to examine how this problem is different from an activator–inhibitor system [Ham-Lee et al., 1994].
STRUCTURE ANALYSIS OF ${\rm Si}(111)(\sqrt{3}\times\sqrt{3}$)–Al BY ENERGY-FILTERED RHEED
Authors: HORIO Y.
Published: December 2003

Rocking curves of energy-filtered reflection high-energy electron diffraction (EF-RHEED) intensities from the Si(111)([Formula: see text])–Al surface have been measured. The EF-RHEED apparatus is a recently developed one, equipped with a retarding field analyzer to exclude inelastic scattering component from an entire RHEED pattern. The energy-filtered rocking curves measured at E loss =90 eV and 0 eV are compared. It is found that when the E loss value comes close to 0 eV the relative intensities of reflection beams become remarkably weak at the lower angle side. Three structure models, which have already been presented as the T4 model, and additionally two simple rigid sphere models, are examined by dynamical calculations of RHEED. It is found that Hanada et al.'s structure model is the most favorable one among them. In the analysis of zero-loss rocking curves, especially, an extended imaginary potential distribution into the vacuum is tentatively used to express the absorption due to surface plasmon loss and fairly good agreements between the calculated and experimental rocking curves are obtained.
COMPOSITIONAL OSCILLATIONS AND STRAIN EFFECTS AT THE ANNEALED Co/Pd(100) INTERFACE: A STUDY BY X-RAY PHOTOELECTRON DIFFRACTION AND LOW ENERGY ION SCATTERING
Authors: ATREI ANDREA , GIORDANO HÉlÈNE , TORRINI MARCO , BARDI UGO , GLEESON MICHAEL , BARNES COLIN
Published: December 2003

The properties of the interface obtained by cobalt deposition on the Pd(100) surface and successive annealing have been studied by X-ray photoelectron diffraction (XPD) and low energy ion scattering (LEIS). The "as deposited" cobalt layer shows considerable lattice strain (about 10%) for coverages up to approximately 20-monolayer equivalents. Annealing at temperatures of the order of 700 K leads to intermixing with the formation of a surface alloy and the partial release of the strain. The combination of LEIS and XPD measurements shows that cobalt in the surface phase is preferentially located in the second outermost layer from the surface.
AN UNEXPECTED SURFACE SEGREGATION PHENOMENON OF GOLD ON THE SURFACE OF A Pb(Au) SOLID SOLUTION
Authors: OUGHADDOU H. , AUFRAY B. , BIBÉRIAN J. P. , BERNARDINI J.
Published: December 2003

At 260°C, at the surface of a lead–gold (96·10-6 at/at) solid solution we observe by Auger electron spectroscopy an unexpected surface equilibrium segregation of gold. A quantitative evaluation of the Auger data obtained at the end of the segregation kinetics shows that the segregation of gold is consistent with the formation of a surface alloy with a chemical composition close to AuPb 3, with gold atoms situated under a layer of lead. We propose that this unusual segregation is related to the lower surface energy of this intermetallic compound AuPb 3 compared to the gold and lead ones.
EVIDENCE BY ANGLE-SCANNED PHOTOELECTRON DIFFRACTION FOR A CO-INDUCED RESTRUCTURING OF A Ni/Pt(111) MONOLAYER
Authors: SAMBI MAURO , ZARATIN LAURA , SANGIOVANNI GUIDO , PIN ERICA , GRANOZZI GAETANO
Published: December 2003

Angle-scanned photoelectron diffraction measurements have been performed prior to and after CO exposure onto a Ni monolayer deposited on Pt(111). Ni is known to grow epitaxially on Pt(111), but there is evidence for an adsorbate-induced restructuring such that the initial atomically flat Ni layer gives place to at least two-layer-high Ni islands. As far as the driving force for the restructuring is concerned, some hypotheses can be put forward considering the Ni–Ni nearest neighbor distances in the Ni monolayer and in the restructured layer, along with some thermodynamical arguments.
THE GROWTH AND ATOMIC STRUCTURE OF THALLIUM ON COPPER(001)
Authors: NICKLIN C. L. , NORRIS C. , BINNS C. , JONES N. , ALVAREZ J. , TORRELLES X.
Published: December 2003

We report a determination of the room temperature growth and atomic structure of ultrathin films of thallium on copper(001) using surface X-ray diffraction. The results show clearly that the growth is layerwise up to two monolayers and islanded thereafter. This is contrary to earlier reports which suggested that the islanding commenced at one monolayer. The first submonolayer structure to appear is a c(4×4) arrangement. Reflectivity scans suggest that there is significant reordering of the substrate at this coverage.
INITIAL STAGES OF GROWTH OF IRON ON Ag(100) AT LOW TEMPERATURE
Authors: CANEPA M. , CANTINI P. , TERRENI S. , MATTERA L.
Published: December 2003

The initial stages of growth of Fe on a well-defined single crystal Ag(100) surface have been investigated by means of thermal energy helium diffraction. We report on specular beam spot profiles obtained at 0.5 monolayer for several temperatures of deposition in the range of 135–300 K. Typical sidebands ("satellites") in diffraction patterns allow one to estimate the mean separation  between islands. Experimental data in the range of 135–228 K show a linear dependence of ln < L> as a function of the inverse of the temperature of deposition, while at higher temperatures a clear deviation from this law is found, indicating a change in the regime of growth. The nucleation of small islands turns out to be the factor which favors two-dimensional growth at low temperature.
LOW-ENERGY 4He+ SCATTERING FROM DEUTERIUM ADSORBED ON STEPPED Pd(331)
Authors: ELLIS W. P. , BASTASZ R.
Published: December 2003

We have taken angle-resolved data for the scattering of low-energy (<1 keV) 4 He + from deuterium adsorbed on a stepped Pd (331) surface. The impact geometry was "up the staircase," i.e. the 4 He + beam was perpendicular to and directly incident onto the unshadowed <011> Pd ledge atoms. A strong quasielastic scattering signal of 4 He + from D (4 He +/D) was observed at a forward-scattering angle of θ= 25° and an incidence angle of α= 76° from the (331) normal. The results agree with shadow-cone calculations of scattering first from Pd ledge atoms followed by a second event, 4 He +/D. The resultant adsorption geometry shows D to reside in the quasi-threefold ledge site on the surface directly above the bulk fcc octahedral void. These results are consistent with the previous 4 He + scattering study of the geometrically related Pd(110)-D(ads) system.
COMBINED X-RAY AND STM STUDY OF THE OXYGEN-INDUCED RESTRUCTURING OF THE Au(111) SURFACE
Authors: ORTEGA L. , HUANG L. , CHEVRIER J. , ZEPPENFELD P. , GAY J. M. , RIEUTORD F. , COMSA G.
Published: December 2003

Au(111) surfaces exposed to oxygen under high pressure (p O2 =1 bar) and at high temperature (T≈800°C) during an extended period of time (several hours) exhibit a ([Formula: see text]R30° structure and, at larger scales (a few nanometers), a long range hexagonal height modulation with a period of 72 Å. This is evidenced by X-ray diffraction at grazing incidence performed at the ESRF. These results confirm and complete previous surface analysis in direct space by scanning tunneling microscopy (STM). This new evidence for a long range superstructure by X-ray diffraction provides new insights into the origin of the moiré patterns observed in the STM study.
SURFACE FACETING ON Cu(115) INDUCED BY OXYGEN ADSORPTION
Authors: REITER S. , TAGLAUER E.
Published: December 2003

The clean Cu (115) surface shows the regular step arrangement of a vicinal surface in scanning tunneling microscopy. Upon oxygen adsorption the surface reconstructs completely. For temperatures around 500 K during or after oxygen adsorption, pronounced faceting into (104), (014) and (113) facets is observed. Details of the facet structures are analyzed. The (113) facet exhibits an additional reconstruction which can be described as a c(7×12) superstructure. The development of Cu–O–Cu atomic chains is suggested to be the driving force for the oxygen-induced surface reconstruction. This reconstruction is reversible; oxygen desorption re-establishes the initial (115) structure.
ELECTRONIC STATES OF MONOLAYER GRAPHITE COADSORBED WITH ALKALI ATOMS ON Ni(111) SURFACE
Authors: SOUZU Y. , TSUKADA M.
Published: December 2003

The energy bands of the monolayer graphite (MG) on a Ni(111) surface, and that coadsorbed with alkali atoms, are calculated by the discrete variational Xα method. The π bands at the K point of the original MG show various different features depending on the alkali species and the structure parameters. For the case of the Na and Cs ternary system, the surface reconstruction of the Ni substrate is indicated.
INFLUENCE OF SURFACE STRUCTURE ON THE MECHANISM OF CO ADSORPTION AND CATALYTIC OXIDATION ON PALLADIUM
Authors: STARÁ I. , MATOLÍN V.
Published: December 2003

The adsorption and oxidation of carbon monoxide on small alumina-supported Pd particles have been studied by temperature-programmed desorption (TPD) using molecular beam techniques. The results of size effect studies show clearly different surface properties of bulk metal and supported clusters. Surprising effect of partical CO dissociation was observed on small Pd particles deposited on γ-alumina, prepared by thermal oxidation of aluminum, and not on Pd/α-alumina model catalysts. The activation energy of CO desorption, Ed, was determined as a function of particle size. The Ed decreased with decreasing particle size. The CO and oxygen sticking probability measurements indicated the CO and oxygen diffusion over the support. It was shown that the oxygen adsorption capacity and the reactivity of alumina-supported catalysts were higher than those of Pd(111).
STRUCTURE-SENSITIVITY IN THE DYNAMICS OF CO OXIDATION OVER Pd SURFACES: INFRARED CHEMHEMILUMINESCENCE OF THE PRODUCT CO2
Authors: UETSUKA H. , WATANABE K. , OHNUMA H. , KUNIMORI K.
Published: December 2003

Infrared-chemiluminescence spectra of CO 2 molecules formed by steady-state CO oxidation on Pd (111), Pd (110), Pd (100) and polycrystalline- Pd surfaces have been measured to get information on the surface reaction dynamics. In all cases, the product CO 2 was vibrationally and rotationally excited. The CO 2 molecules desorbed from Pd (100) and Pd (111), which have flat surfaces, were vibrationally more excited than those from Pd (110) (stepped surface) and polycrystalline Pd . These results show that the dynamics of CO oxidation on Pd surfaces are structure-sensitive, i.e. the structure of the activated CO 2 complex depends on the surface structures of the reaction sites. Furthermore, the activities of steady-state CO oxidation as a function of surface temperature were different among these Pd surfaces, which indicates that the CO oxidation on Pd is also structure-sensitive in the kinetics.
RAIRS OF SMALL HYDROCARBONS ON Pd(100)
Authors: CAMPLIN J. P. , EVE J. K. , McCASH E. M.
Published: December 2003

Ethyne was seen to physisorb on the Pd(100) surface at temperatures below 210 K and chemisorb at temperatures above. Physisorbed multilayers of propyne were observed above a chemisorbed monolayer in the temperature range of 80–130 K. Both alkynes exhibited chemisorption on the Pd surface with the C ≡ C bond parallel to the surface. This led to substantial rehybridisation of the C ≡ C carbon atoms, causing the C–H and C–CH 3 bonds to tilt well away from the surface plane. Ethene was found to form physisorbed multilayers on the Pd (100) surface at temperatures between 28 and 70 K. The RAIR spectra were dominated by crystal field effects and bore a close resemblance to spectra of the crystalline solid. This indicated that the Pd(100) surface does not play a dominant role in determining the structure of the phase formed on the surface.
SOME SUBGROUPS OF THE NORMALIZER OF Γ0(μ) IN ${\bf PSL}(2, {\mathbb C})$
Authors: KESKİN REFİK
Published: December 2003

In this study, we introduce some discrete subgroups of the normalizer of Γ0(μ) which are commensurable with some Bianchi groups and then we calculate the numbers of the cusps of the 3-manifolds associated to these groups.
PUSHOUTS OF PARTIAL HOMOMORPHISMS OF PARTIAL ALGEBRAS II: CLOSED QUOMORPHISMS
Authors: ALBERICH R. , ROSSELLÓ F.
Published: December 2003

We characterize the pairs of closed homomorphisms and closed quomorphisms of partial Σ-algebras that have a pushout in the corresponding category, for an arbitrary signature Σ. The latter characterization solves the basic problem previous to the development of a single-pushout approach to the transformation of partial algebras based on closed quomorphisms.
PURE-INJECTIVE ENVELOPES
Authors: HERZOG IVO
Published: December 2003

It is proved that if C is a locally finitely presented additive category, then every object X of C admits a pure-injective envelope. Considered as a morphism, the pure-injective envelope is a pure-monomorphism.
PROJECTIVE MODULES AND DIVISOR HOMOMORPHISMS
Authors: FACCHINI ALBERTO , HALTER-KOCH FRANZ
Published: December 2003

We study some applications of the theory of commutative monoids to the monoid [Formula: see text] of all isomorphism classes of finitely generated projective right modules over a (not necessarily commutative) ring R.
FREE MALCEV SUPERALGEBRA ON ONE ODD GENERATOR
Authors: SHESTAKOV IVAN P.
Published: December 2003

A base of the free Malcev superalgebra on one odd generator is constructed. Some corollaries for skew-symmetric functions and central elements in free Malcev and free alternative algebras are obtained.
THE DISCRIMINANT OF SUBFIELDS OF ℚ(ζ2r)
Authors: LOPES JOSÉ OTHON DANTAS
Published: December 2003

A formula for computing the discriminant of any number field K ⊂ ℚ(ζ2r), with r ≥ 3, is derived. The formula consists of two expressions, depending on whether K is cyclotomic or not. However, both expressions depend solely on m, the degree of K over ℚ, and they are derived from the Conductor-Discriminant Formula for Abelian extensions of ℚ.
SMOOTH ORDER SINGULARITIES
Authors: BOCKLANDT RAF , BRUYN LIEVEN LE , DE WEYER GEERT VAN
Published: December 2003

In [4] it was shown that the center of Cayley–Hamilton smooth orders is smooth whenever the central dimension is at most 2 and that there may be singularities in higher dimensions. In this paper, we give methods to classify central singularities of smooth orders up to smooth equivalence in arbitrary dimension and show that these methods are strong enough to complete the classification in dimension ≤ 6. In particular we show that there is exactly one possible singularity type in dimension 3: the conifold singularity. In dimensions 4 (resp. 5 and 6) there are precisely 3 (resp. 10 and 53) types of singularities.
ON ALGEBRAIC SUPERGROUPS AND QUANTUM DEFORMATIONS
Authors: FIORESI R.
Published: December 2003

We give the definitions of affine algebraic supervariety and affine algebraic supergroup through the functor of points and we relate them to the other definitions present in the literature. We study in detail the algebraic supergroups GL(m|n) and SL(m|n) and give explicitly the Hopf algebra structure of the algebra representing the functors of points. In the end we also give the quantization of GL(m|n) together with its coaction on suitable quantum spaces according to Manin's philosophy.
COMBINING MULTIGRID AND WAVELET IDEAS TO CONSTRUCT MORE EFFICIENT MULTISCALE ALGORITHMS
Authors: GOEDECKER STEFAN , CHAUVIN CLAIRE
Published: December 2003

It is shown how various ideas that are well established for the solution of Poisson's equation using plane wave and multigrid methods, can be combined with wavelet concepts. The combination of wavelet concepts and multigrid techniques turns out to be particularly fruitful. We propose a modified multigrid V cycle scheme that is not only much simpler, but also more efficient than the standard V cycle. Whereas in the traditional V cycle the residue is passed to the coarser grid levels, this new scheme does not require the calculation of a residue. Instead it works with copies of the charge density on the different grid levels that were obtained from the underlying charge density on the finest grid by wavelet transformations. This scheme is not limited to the pure wavelet setting, where it is faster than the preconditioned conjugate gradient method, but equally well applicable for finite difference discretizations.
MULTISCALE ALGORITHMS FOR EIGENVALUE PROBLEMS
Authors: WIJESEKERA NIMAL , FENG GUOGANG , BECK THOMAS L.
Published: December 2003

Iterative multiscale methods for electronic structure calculations offer several advantages for large-scale problems. Here we examine a nonlinear full approximation scheme (FAS) multigrid method for solving fixed potential and self-consistent eigenvalue problems. In principle, the expensive orthogonalization and Ritz projection operations can be moved to coarse levels, thus substantially reducing the overall computational expense. Results of the nonlinear multiscale approach are presented for simple fixed potential problems and for self-consistent pseudopotential calculations on large molecules. It is shown that, while excellent efficiencies can be obtained for problems with small numbers of states or well-defined eigenvalue cluster structure, the algorithm in its original form stalls for large-molecule problems with tens of occupied levels. Work is in progress to attempt to alleviate those difficulties.
ALGEBRAIC EQUATION AND ITERATIVE OPTIMIZATION FOR THE OPTIMIZED EFFECTIVE POTENTIAL IN DENSITY FUNCTIONAL THEORY
Authors: WU QIN , YANG WEITAO
Published: December 2003

We further develop our recent direct method for the optimized effective potential (OEP) in density functional theory (DFT) [Yang and Wu, Phys. Rev. Lett.89, 143002 (2002)]. First, we show that the stationary condition in our optimization approach leads to a proper nonlinear algebraic equation for the OEP in a finite basis set, which differs from other finite basis set approaches. Then by constructing an approximate second derivative matrix of the energy functional in conjunction with the use of the Newton method, we significantly accelerate the convergence of the iterative optimization for OEP. Enhancement of the method is made in using the Tikhonov regularization method for the inversion of the second derivative matrix when it is singular or nearly singular and the direct inversion in the iterative space. It is shown that under a fixed stepsize condition, the optimization approach is equivalent to the self-consistent solution to the nonlinear algebraic equation for OEP. Because the approximate second derivatives are easy to compute and the iteration numbers are small now, the computation costs of OEP become comparable to that of regular DFT calculations as shown by calculations of some molecules, small and larger ones. We show how to find balanced results between energies and potentials when choosing a basis set for potentials.
Recent Advances in the (Molecular) Phylogeny of Vertebrates
Authors: Meyer Axel , Zardoya Rafael
Published: December 2003

▪ Abstract  The analysis of molecular phylogenetic data has advanced the knowledge of the relationships among the major groups of living vertebrates. Whereas the molecular hypotheses generally agree with traditional morphology-based systematics, they sometimes contradict them. We review the major controversies in vertebrate phylogenetics and the contribution of molecular phylogenetic data to their resolution: (a) the mono-paraphyly of cyclostomes, (b) the relationships among the major groups of ray-finned fish, (c) the identity of the living sistergroup of tetrapods, (d) the relationships among the living orders of amphibians, (e) the phylogeny of amniotes with particular emphasis on the position of turtles as diapsids, (f) ordinal relationships among birds, and (g) the radiation of mammals with specific attention to the phylogenetic relationships among the monotremes, marsupial, and placental mammals. We present a discussion of limitations of currently used molecular markers and phylogenetic methods as well as make recommendations for future approaches and sets of marker genes.
Protective Ant-Plant Interactions as Model Systems in Ecological and Evolutionary Research
Authors: Heil Martin , McKey Doyle
Published: December 2003

▪ Abstract  Protective ant-plant interactions, important in both temperate and tropical communities, are increasingly used to study a wide range of phenomena of general interest. As antiherbivore defenses “worn on the outside,” they pose fewer barriers to experimentation than do direct (e.g., chemical) plant defenses. This makes them tractable models to study resource allocation to defense and mechanisms regulating it. As multi-trophic level interactions varying in species specificity and impact on fitness of participants, ant-plant-herbivore associations figure prominently in studies of food-web structure and functioning. As horizontally transmitted mutualisms that are vulnerable to parasites and “cheaters,” ant-plant symbioses are studied to probe the evolutionary dynamics of interspecies interactions. These symbioses, products of coevolution between plants and insect societies, offer rich material for studying ant social evolution in novel contexts, in settings where colony limits, resource supply, and nest-site availability are all more easily quantifiable than in the ground-nesting ants hitherto used as models.
Development and the Genetics of Evolutionary Change Within Insect Species
Authors: Brakefield Paul M. , French Vernon , Zwaan Bas J.
Published: December 2003

▪ Abstract  Changes in genes and in developmental processes generate the phenotypic variation that is sorted by natural selection in adaptive evolution. We review several case studies in which artificial selection experiments in insects have led to divergent morphologies, and where further work has revealed information about the underlying changes at both the genetic and developmental levels. In addition, we examine several studies of phenotypic plasticity where multidisciplinary approaches are also beginning to reveal more about how developmental processes are modulated. Such integrated research will lead to a richer understanding of the changes in development that occur during evolutionary responses to natural selection, and it will also more rigorously examine how developmental processes can influence the tempo and direction of evolutionary change.
Avian Sexual Dichromatism in Relation to Phylogeny and Ecology
Authors: Badyaev Alexander V. , Hill Geoffrey E.
Published: December 2003

▪ Abstract  The extent and diversity of sexual dichromatism in birds is thought to be due to the intensity of current sexual selection on the plumage ornamentation of males and females. This view leads to an expectation of concordance between ecological conditions and sexual dichromatism. Yet, because expression of dichromatism is the result of not only current selection, but also historical patterns of development, function, and selection, the concordance between ecology and current sexual dichromatism is not straightforward. Recent studies have revealed a number of trends in the evolution of avian sexual ornamentation that seem contrary to what is expected if current sexual selection is the primary force shaping dichromatism. For example, change in sexual dichromatism is often the result of evolutionary changes in female rather than male ornamentation. Moreover, sexual dichromatism is often an ancestral rather than a derived state; current expression of dichromatism is frequently the result of selection for lesser ornamentation in one sex and not for ornament elaboration. Loss and gain of sexual ornamentation sometimes precedes changes in preference for sexual ornamentation, and sexual ornaments can have high evolutionary lability despite their developmental and functional complexity. These findings emphasize that phylogenetic reconstructions must play a central role in attempts to understand the function and evolution of sexual dichromatism. With a historical perspective, one can test the relative importance of direct selection, indirect selection, and drift in relation to changes of sexual dichromatism. If sexual selection is invoked, the mechanisms of sexual selection can be explored by examining the concordance between the elaboration of ornamentation and the preferences for ornamentation across species and by tracing phylogenetic trajectories of sexual ornaments. Finally, placing physiological, genetic, and developmental mechanisms of sexual ornamentation into such a phylogenetic framework will enable greater inference about the past evolution and current function of sexual dichromatism in birds.
Latitudinal Gradients of Biodiversity: Pattern, Process, Scale, and Synthesis
Authors: Willig M.R. , Kaufman D.M. , Stevens R.D.
Published: December 2003

▪ Abstract  The latitudinal gradient of decreasing richness from tropical to extratropical areas is ecology's longest recognized pattern. Nonetheless, notable exceptions to the general pattern exist, and it is well recognized that patterns may be dependent on characteristics of spatial scale and taxonomic hierarchy. We conducted an extensive survey of the literature and provide a synthetic assessment of the degree to which variation in patterns (positive linear, negative linear, modal, or nonsignificant) is a consequence of characteristics of scale (extent or focus) or taxon. In addition, we considered latitudinal gradients with respect to generic and familial richness, as well as species evenness and diversity. We provide a classification of the over 30 hypotheses advanced to account for the latitudinal gradient, and we discuss seven hypotheses with most promise for advancing ecological, biogeographic, and evolutionary understanding. We conclude with a forward-looking synthesis and list of fertile areas for future research.
Diffusive instability in a prey‐predator system withtime‐dependent diffusivity
Authors: Bhattacharyya Rakhi , Mukhopadhyay Banibrata , Bandyopadhyay Malay
Published: November 2003

An ecological model for prey‐predator planktonic species has been
considered, in which the growth of prey has been assumed to follow
a Holling type II function. The model consists of two
reaction‐diffusion equations and we extend it to time‐varying
diffusivity for plankton population. A comparative study of local
stability in case of constant diffusivity and time varying
diffusivity has been performed. It has been found that the
system would be more stable with time varying diffusivity
depending upon the values of system parameter.
Two‐point distortion theorems for certain families of analyticfunctions in the unit disc
Authors: Polatoğlu Yaşar , Bolcal Metın , Şen Arzu
Published: November 2003

We give two‐point distortion theorems for various subfamilies of
analytic univalent functions. We also find the necessary and
sufficient condition for these subclasses of analytic functions.
On a class of holomorphic functions defined by the Ruscheweyh derivative
Authors: Oros Georgia Irina
Published: November 2003

By using the Ruscheweyh operator Dmf(z), z ∈ U, we will introduce a class of holomorphic functions, denoted by
, and obtain some inclusion relations.
Reconstruction in time‐warped weighted shift‐invariant spaces with application to spline subspaces
Authors: Xian Jun , Li Yongjin
Published: November 2003

We discuss the reproducing kernel structure in shift‐invariant
spaces and the weighted shift‐invariant spaces, and obtain the
reconstruction formula in time‐warped weighted shift‐invariant
spaces, then apply them to a spline subspace. In the spline
subspace, we give a reconstruction formula in a time‐warped spline
subspace.
Duality models for some nonclassical problems in the calculus ofvariations
Authors: Zalmai G. J.
Published: November 2003

Parametric and nonparametric necessary and sufficient optimality
conditions are established for a class of nonconvex variational
problems with generalized fractional objective functions and
nonlinear inequality constraints containing arbitrary norms.
Based on these optimality criteria, ten parametric and
parameter‐free dual problems are constructed and appropriate
duality theorems are proved. These optimality and duality results
contain, as special cases, similar results for minmax fractional
variational problems involving square roots of positive
semidefinite quadratic forms as well as for variational problems
with fractional, discrete max, and conventional objective
functions, which are particular cases of the main problem
considered in this paper. The duality models presented here
subsume various existing duality formulations for variational
problems and include variational generalizations of a great
variety of cognate dual problems investigated previously in the
area of finite‐dimensional nonlinear programming by an assortment
of ad hoc methods.
A renorming of ℓ2, rare but with the fixed‐point property
Authors: Jiménez-Melado Antonio , Llorens-Fuster Enrique
Published: November 2003

We give an example of a renorming of ℓ2 with the
fixed‐point property (FPP) for nonexpansive mappings, but which seems
to fall out of the scope of all the commonly known sufficient
conditions for FPP.
Some properties of linear right ideal nearrings
Authors: Magill K. D.
Published: November 2003

In a previous paper, we determined all those topological nearrings 𝒩n whose additive groups are the n‐dimensional Euclidean groups, n > 1, and which contain n one‐dimensional linear subspaces which are
also right ideals of the nearring with the property that for each
w ∈ 𝒩n, there exist wi ∈ Ji, 1 ≤ i ≤ n, such that w = w1 + w2 + ⋯+wnand vw = vwn for each v ∈ 𝒩n. In this paper, we determine the properties of these nearrings,
their ideals, and when two of these nearrings
are isomorphic, and we investigate the multiplicative semigroups of
these nearrings.
Diagnostic performance of complete lower limb venous ultrasound in patients with clinically suspected acute pulmonary embolism
Authors: Colombier Daniel , Victor Gérard , Elias Marie , Arnaud Catherine , Juchet Henri , Ducassé Jean-Louis , Didier Alain , Colin Cyrille , Rousseau Hervé , Nguyen Françoise , Joffre Francis , Elias Antoine
Published: December 2003

A limited ultrasound (US) confined to the popliteal and femoral veins is usually performed to detect deep vein thrombosis (DVT) in patients with clinically suspected acute pulmonary embolism (PE). Our objective was to assess the diagnostic accuracy of complete lower limb US examining both the proximal and distal veins in this setting. In this prospective study, 210 consecutive patients were included. Complete US was performed by independent operators and compared blindly with a reference strategy combining clinical probability, ventilation perfusion scan and pulmonary angiography to a three-month clinical follow-up. Simultaneously,VIDAS D-dimer (DD) assay and helical computed tomography (HCT) of the lungs were assessed independently and blindly. PE was present in 74 patients (35%). Complete US detected DVT in 91 patients (43%), proximal in 51 and distal in 40. Sensitivity and specificity with a 0.95 confidence interval were respectively 0.93 [0.85 – 0.97] and 0.84 [0.77 – 0.89]. Limited US detected DVT in only 46 patients (22%). Sensitivity and specificity were respectively 0.55 [0.44 – 0.66] and 0.96 [0.92 – 0.98]. For DD they were 0.92 [0.83 – 0.96] and 0.24 [0.17 – 0.32] and for HCT 0.84 [0.73 – 0.90] and 0.87 [0.80 – 0.92]. Complete lower limb US has higher sensitivity and capacity to exclude PE than limited US, but a slightly lower specificity. Complete US results also compared favourably with those of HCT and DD.The utility of including this method in diagnostic strategies for PE needs to be assessed in cost-effectiveness analysis and in outcome studies.
Low-dose warfarin in atrial fibrillation leads to more thromboembolic events without reducing major bleeding when compared to adjusted-dose
Authors: Perret-Guillaume Christine , Wahl Denis
Published: December 2003

The use of warfarin with a range INR of 2.0-3.0 is recommended in prevention of stroke for nonvalvular atrial fibrillation (AF) patients, in particular those older than 75 years. The risk of bleeding that is associated with this range of INR has led to evaluate lower ranges (low-dose or fixed minidose) in terms of risks and benefits. A meta-analysis of all randomized controlled trials evaluating ‘low-intensity’ ‘minidose’ or ‘low-dose anticoagulant’ treatment for prevention of thromboembolic events in AF was conducted by two independent reviewers. Study quality was evaluated in a blinded fashion. Four original studies were retrieved. Outcome events were determined in various treatment groups: ischemic stroke, systemic embolism, thromboses (ischemic stroke, systemic embolism or myocardial infarction), vascular death, major hemorrhage and hemorrhagic death. Results obtained with a random effects model were expressed as a common relative risk. Adjusted-dose warfarin compared with lower dose warfarin (INR ≤1.6) in 2108 randomised patients significantly reduced the risk of any thrombosis: Relative risk (RR): 0.50 (95% CI; 0.25 to 0.97).The RR was 0.46 (95%CI ; 0.2 to 1.07) for ischemic stroke. Inversely lower dose did not statistically decrease the risk for major hemorrhage compared to adjusted-dose: RR adjusted-dose vs lower dose: 1.23 (95% CI ; 0.67-2.27). The RR was 0.97 (95 % CI 0.27-3.54) for hemorrhagic death. Our meta-analysis showed that adjusted-dose compared with low-dose or minidose warfarin therapy (INR ≤1.6) was more effective to prevent ischemic thromboembolic events in patients with atrial fibrillation.
Recommendations of the National Heart, Lung, and Blood Institute Nanotechnology Working Group
Authors: Buxton Denis B. , Lee Stephen C. , Wickline Samuel A. , Ferrari Mauro
Published: December 2003

Recent rapid advances in nanotechnology and nanoscience offer a wealth of new opportunities for diagnosis and therapy of cardiovascular, pulmonary, and hematologic diseases and sleep disorders. To review the challenges and opportunities offered by these nascent fields, the National Heart, Lung, and Blood Institute convened a Working Group on Nanotechnology. Working Group participants discussed the various aspects of nanotechnology and its applications to heart, lung, blood, and sleep (HLBS) diseases. This report summarizes their discussions according to scientific opportunities, perceived needs and barriers, specific disease examples, and recommendations on facilitating research in the field. An overarching recommendation of the Working Group was to focus on translational applications of nanotechnology to solve clinical problems. The Working Group recommended the creation of multidisciplinary research centers capable of developing applications of nanotechnology and nanoscience to HLBS research and medicine. Centers would also disseminate technology, materials, and resources and train new investigators. Individual investigators outside these centers should be encouraged to conduct research on the application of nanotechnology to biological and clinical problems. Pilot programs and developmental research are needed to attract new investigators and to stimulate creative, high-impact research. Finally, encouragement of small businesses to develop nanotechnology-based approaches to clinical problems was considered important.
Introduction
Authors:   Busuttil
Published: December 2003

No Abstract
Silencing of the p18INK4c gene by promoter hypermethylation in Reed-Sternberg cells in Hodgkin lymphomas
Authors: Sánchez-Aguilera Abel , Delgado Julio , Camacho Francisca I. , Sánchez-Beato Margarita , Sánchez Lydia , Montalbán Carlos , Fresno Manuel F. , Martín Carmen , Piris Miguel A. , García Juan F.
Published: December 2003

p18INK4c is a cyclin-dependent kinase (CDK) inhibitor that interferes with the Rb-kinase activity of CDK6/CDK4. Disruption of p18INK4c in mice impairs B-cell terminal differentiation and confers increased susceptibility to tumor development; however, alterations of p18INK4c in human tumors have rarely been described. We used a tissue-microarray approach to analyze p18INK4c expression in 316 Hodgkin lymphomas (HLs). Nearly half of the HL cases showed absence of p18INK4c protein expression by Reed-Sternberg (RS) cells, in contrast with the regular expression of p18INK4c in normal germinal center cells. To investigate the cause of p18INK4c repression in RS cells, the methylation status of the p18INK4c promoter was analyzed by methylation-specific polymerase chain reaction (PCR) and bisulfite sequencing. Hypermethylation of the p18INK4c promoter was detected in 2 of 4 HL-derived cell lines, but in none of 7 non-Hodgkin lymphoma (NHL)–derived cell lines. We also detected p18INK4c hypermethylation, associated with absence of protein expression, in 5 of 26 HL tumors. The correlation of p18INK4c immunostaining with the follow-up of the patients showed shorter overall survival in negative cases, independent of the International Prognostic Score. These findings suggest that p18INK4c may function as a tumor suppressor gene in HL, and its inactivation may contribute to the cell cycle deregulation and defective terminal differentiation characteristic of the RS cells.
Differential proteome analysis of TRAP-activated platelets: involvement of DOK-2 and phosphorylation of RGS proteins
Authors: García Angel , Prabhakar Sripadi , Hughan Sascha , Anderson Tom W. , Brock Chris J. , Pearce Andrew C. , Dwek Raymond A. , Watson Steve P. , Hebestreit Holger F. , Zitzmann Nicole
Published: December 2003

We have applied a proteomics approach to analyze signaling cascades in human platelets stimulated by thrombin receptor activating peptide (TRAP). By analyzing basal and TRAP-activated platelets using 2-dimensional gel electrophoresis (2-DE), we detected 62 differentially regulated protein features. From these, 41 could be identified by liquid chromatography–coupled tandem mass spectrometry (LC-MS/MS) and were found to derive from 31 different genes, 8 of which had not previously been reported in platelets, including the adapter downstream of tyrosine kinase 2 (Dok-2). Further studies revealed that the change in mobility of Dok-2 was brought about by tyrosine phosphorylation. Dok-2 tyrosine phosphorylation was also found to be involved in collagen receptor, glycoprotein VI (GPVI), signaling as well as in outside-in signaling through the major platelet integrin, αIIbβ3. These studies also provided the first demonstration of posttranslational modification of 2 regulator of G protein signaling (RGS) proteins, RGS10 and 18. Phosphorylation of RGS18 was mapped to Ser49 by MS/MS analysis. This study provides a new approach for the identification of novel signaling molecules in activated platelets, providing new insights into the mechanisms of platelet activation and building the basis for the development of therapeutic agents for thrombotic diseases.
Molecular response to imatinib in late chronic-phase chronic myeloid leukemia
Authors: Rosti Gianantonio , Martinelli Giovanni , Bassi Simona , Amabile Marilina , Trabacchi Elena , Giannini Barbara , Cilloni Daniela , Izzo Barbara , De Vivo Antonio , Testoni Nicoletta , Cambrin Giovanna Rege , Bonifazi Francesca , Soverini Simona , Luatti Simona , Gottardi Enrico , Alberti Daniele , Pane Fabrizio , Salvatore Francesco , Saglio Giuseppe , Baccarani Michele ,   the Study and Writing Committee of the Italian Cooperative Study Group [ICSG] on Chronic Myeloid Leukemia
Published: December 2003

Imatinib is a tyrosine-kinase inhibitor that binds to ABL proteins and induces cytogenetic remissions in patients with chronic myeloid leukemia (CML). In these patients measuring response by molecular techniques is clearly required. We determined the cytogenetic and molecular response (CgR, MR) to imatinib in 191 patients with late chronic-phase Philadelphia-positive (Ph+) CML, previously treated with interferon α. MR was assessed with real-time quantitative (TaqMan) reverse transcription–polymerase chain reaction and was expressed as the ratio between BCR/ABL and β2-microglobulin × 100, the lowest level of detectability of the method being 0.00001. A complete CgR (CCgR) was achieved in 85 (44%) of 191 patients and was maintained for 2 years in 67 (79%) of 85 patients. A reduction of the transcript level of more than 2 logs was achieved in all but 9 patients with CCgR versus none of 23 with partial CgR. In the CCgRs the median value of the MR was 0.0008 after 12 months and 0.0001 after 24 months, with the transcript level undetectable in 22 cases. We conclude that in CCgRs the degree of MR may vary from 2 to more than 4 logs, and that there is a progressive decrease of transcript level by time. Only 1 of 22 negative cases has had a relapse as yet.