bluuebunny/crossref_metadata_2025 huggingface dataset:
The vegetation and ecological gradients of calcareous mires in the South Park valley, Colorado
Authors: Johnson J Bradley , Steingraeber David A
Published: April 2003

The vegetation, environment, and ecological gradients present on three calcareous mires in the South Park valley, Park County, Colorado, were investigated. Vegetation was classified into four habitat classes, nine subclasses, and twelve species associations using two-way species indicator analysis (TWINSPAN). Detrended correspondence analysis (DCA) was used to ordinate vegetation samples along two axes representing the three predominant ecological gradients: water table height, miremargin to expanse, and region. Canonical correspondence analysis (CCA) was used to directly relate local environmental conditions to vegetation. Water table depth, microtopographical development, soil and water pH and nutrient level, soil organic matter, and hydraulic head were significantly correlated with vegetation gradients. The mire soils consist of intermixed areas of organic and mineral soils. Mire soils and water are highly alkaline and nutrient-rich. Mean pore water calcium concentration on these mires is 115 mg/L, electrical conductivity averages 575 µS, and mean pH is 7.4. Owing to these conditions, the fen floras include a number of highly minerophilic species. Based on water chemistry and species criteria, each site was classified as rich to extremely rich fen, with the two fen types mixing in complex patterns according to local environmental conditions. The species Trichophorum pumilum, Salix candida, Salix myrtillifolia, Carex microglochin, Carex viridula, Carex scirpoidea, Eriophorum gracile, Triglochin maritimum, Triglochin palustris, Kobresia myosuroides, Kobresia simpliciuscula, Thalictrum alpinum, Scorpidium scorpioides, Scorpidium turgescens, and Calliergon trifarium were determined to be indicative of extremely rich fen conditions in the southern Rocky Mountains.Key words: Colorado, canonical correspondence analysis, detrended correspondence analysis, extremely rich fen, gradient analysis, mire.
Dehydration and dehiscence in siliques of Brassica napus and Brassica rapa
Authors: Squires Timothy M , Gruwel Marco LH , Zhou Rong , Sokhansanj Shahab , Abrams Suzanne R , Cutler Adrian J
Published: April 2003

Silique dehiscence (shattering) in Brassica species has a pronounced effect on agricultural yields. Shattering is highly variable and difficult to quantify, and consequently there have been few studies that explore interspecies variation in shattering in relation to silique development. In this paper, a rapid and simple method has been developed for quantifying silique dehiscence. The variable-speed pod splitter is a mechanical device that provides a measure of the impact force required to trigger shattering of individual siliques. We have used the variable-speed pod splitter to show that siliques of Brassica rapa cv. Parkland were significantly more resistant to shattering than those of Brassica napus cv. Quantum. Siliques of both species became prone to shattering following a short period of rapid dehydration during which their water content fell from approx. 70% to approx. 10% (based on weight). Magnetic resonance imaging of individual siliques of varying ages revealed that water loss occurred from the inside the pericarp in B. napus cv. Quantum and from the outside of the pericarp in B. rapa cv. Parkland. We suggest a mechanism for how this difference in the pattern of water loss contributed to the difference in susceptibility to shatter between the two cultivars.Key words: shattering, magnetic resonance imaging, canola, valve.
Morphology and molecular diversity of arbuscular mycorrhizal fungi in wild and cultivated yew (Taxus baccata)
Authors: Wubet Tesfaye , Weiß Michael , Kottke Ingrid , Oberwinkler Franz
Published: April 2003

Taxus baccata L. roots collected from two sites in southern Germany were heavily colonized by arbuscular mycorrhizal fungi (AMF). The colonization pattern was of the Paris type. The diversity of the colonizing AMF species was investigated using polymerase chain reaction based molecular techniques. The internal transcribed spacer (ITS) region of the DNA from AMF within the roots was amplified using Glomeromycota-specific primers and then cloned and sequenced. Phylogenetic analysis using a data set of 5.8S rDNA sequences from a wide range of glomeralean taxa as well as data sets of partial ITS2 sequences from glomeralean subgroups indicated root colonization by four sequence types of Glomus and one sequence type of Archaeospora. These sequence types are distinct from any previously published sequences and differed between the two study sites.Key words: arbuscular mycorrhiza, Paris-type AM, molecular diversity, ribosomal internal transcribed spacers, Taxus baccata.
Culture experiments and DNA sequence data confirm the identity ofLobariaphotomorphs
Authors: Stenroos Soili , Stocker-Wörgötter Elfriede , Yoshimura Isao , Myllys Leena , Thell Arne , Hyvönen Jaakko
Published: April 2003

Lichens consist of a fungal component that associates with either a green alga or cynobacterium, resulting in diverse morphologies. Resynthesis experiments of isolated myco- and photobionts, as well as internal transcribed spacer (ITS) rDNA phylogenies, suggest that the notoriously dissimilar photomorphs of Lobaria fendleri (Tuck. ex Mont.) Lindau and Lobaria amplissima (Scop.) Forss. both have a single mycobiont, which can simultaneously lichenize two unrelated photobionts, a eukaryote and a prokaryote. In the phylogenetic analyses, the genera Sticta and Durietzia appear monophyletic; whereas Lobaria and Pseudocyphellaria are both nonmonophyletic. Furthermore, the phylogenetic relationships of Durietzia, Lobarina, and Sticta relative to Lobaria and Pseudocyphellaria are in need of re-evaluation.Key words: internal transcribed spacer (ITS), photosymbiodeme, phylogeny, lichen-forming fungi, Lobaria amplissima, Lobaria fendleri, Pseudocyphellaria, Sticta.
LIGHTFRONT HOLOGRAPHY AND AREA DENSITY OF ENTROPY ASSOCIATED WITH LOCALIZATION ON WEDGE-HORIZONS
Authors: SCHROER BERT
Published: April 2003

It is shown that a suitably formulated algebraic lightfront holography (LFH), in which the lightfront is viewed as the linear extension of the upper causal horizon of a wedge region, is capable of overcoming the shortcomings of the old lightfront quantization. The absence of transverse vacuum fluctuations which this formalism reveals is responsible for an area (edge of the wedge) — rearrangement of degrees of freedom which in turn leads to the notion of area density of entropy for a "split localization." This area proportionality of horizon associated entropy has to be compared to the volume dependence of ordinary heat bath entropy. The desired limit, in which the split distance vanishes and the localization on the horizon becomes sharp, can at most yield a relative area density which measures the ratio of area densities for different quantum matter. In order to obtain a normalized area density one needs a (yet unknown) analog of a second fundamental law of thermodynamics in case the thermalization is caused by vacuum fluctuation through localization on causal horizons. This is similar to the role of the classical Gibbs form of that law which relates Bekenstein's classical area formula with the Hawking quantum mechanism for thermalization from black holes.
LAGRANGIAN AND HAMILTONIAN FORMULATIONS OF HIGHER ORDER CHERN–SIMONS THEORIES
Authors: KUMAR SARMISHTHA
Published: April 2003

We consider models involving the higher (third) derivative extension of the Abelian Chern–Simons (CS) topological term in D = 2 + 1 dimensions. The polarization vectors in these models reveal an identical structure with the corresponding expressions for usual models which contain, at most, quadratic structures. We also investigate the Hamiltonian structure of these models and show how Wigner's little group acts as a gauge generator.
CP, T AND CPT VIOLATIONS IN THE $K^0-\overline{K^0}$ SYSTEM: PRESENT STATUS
Authors: TAKEUCHI YOSHIHIRO , TSAI S. Y.
Published: April 2003

The possible violation of CP, T and CPT symmetries in the [Formula: see text] system is studied in a way as phenomenological and comprehensive as possible. For this purpose, we first introduce parameters which represent violation of these symmetries in mixing parameters and decay amplitudes in a convenient and well-defined way and, treating these parameters as small, derive formulas which relate them to the experimentally measured quantities. We then perform numerical analyses to derive constraints to these symmetry-violating parameters, with the latest data reported by KTeV Collaboration, NA48 Collaboration and CPLEAR Collaboration, along with those compiled by Particle Data Group, used as inputs. The result obtained by CPLEAR Collaboration from an unconstrained fit to a time-dependent leptonic asymmetry, aided by the Bell–Steinberger relation, enables us to determine or constrain most of the parameters separately. It is shown among the other things that (1) CP and T symmetries are violated definitively at least at the level of 10-4in 2π decays, (2) CP and T symmetries are violated at least at the level of 10-3in the [Formula: see text] mixing, and (3) CPT symmetry is at present tested to the level of 10-5at the utmost.
STRONG-COUPLING REGIME IN $g\phi^4_2$ THEORY
Authors: EFIMOV G. V. , GANBOLD G.
Published: April 2003

The problem of the strong-coupling regime is considered in the scalar superrenormalizable field theory [Formula: see text]. By using the Gaussian transform, we have found an optimal representation within which the exact strong-coupling behavior of the free energy is already obtained in the leading-order approximation. Within this representation, the interaction becomes slower as the bare coupling constant grows, so the higher-order corrections can be systematically estimated by using a modified perturbation scheme. The next-to-leading terms give rise in insignificant corrections for finite coupling. The regularization procedure regroups the initial counterterms so that the divergencies are exactly removed in final expressions. The main idea is demonstrated in the simplest examples of a plain quartic integral and the anharmonic oscillator.
AdS DYNAMICS FOR MASSIVE SCALAR FIELD: EXACT SOLUTIONS vs. BULK-BOUNDARY PROPAGATOR
Authors: CHANG ZHE , GUAN CHENG-BO , GUO HAN-YING
Published: April 2003

AdS dynamics for massive scalar field is studied both by solving exactly the equation of motion and by constructing bulk-boundary propagator. A Robertson–Walker-like metric is deduced from the familiar SO (2, n) invariant metric. The metric allows us to present a timelike Killing vector, which is not only invariant under spacelike transformations but also invariant under the isometric transformations of SO (2, n) in certain sense. A horizon appears in this coordinate system. Singularities of field variables at boundary are demonstrated explicitly. It is shown that there is a one-to-one correspondence among the exact solutions and the bulk fields obtained by using the bulk-boundary propagator.
EXTENDED OPERATOR ALGEBRA AND REDUCIBILITY IN THE WZW PERMUTATION ORBIFOLDS
Authors: HALPERN M. B. , HELFGOTT C.
Published: April 2003

Recently the operator algebra, including the twisted affine primary fields, and a set of twisted KZ equations were given for the WZW permutation orbifolds. In the first part of this paper we extend this operator algebra to include the so-called orbifold Virasoro algebra of each WZW permutation orbifold. These algebras generalize the orbifold Virasoro algebras (twisted Virasoro operators) found some years ago in the cyclic permutation orbifolds. In the second part, we discuss the reducibility of the twisted affine primary fields of the WZW permutation orbifolds, obtaining a simpler set of single-cycle twisted KZ equations. Finally we combine the orbifold Virasoro algebra and the single-cycle twisted KZ equations to investigate the spectrum of each orbifold, identifying the analogues of the principal primary states and fields also seen earlier in cyclic permutation orbifolds. Some remarks about general WZW orbifolds are also included.
THE SCALAR SECTOR IN 331 MODELS
Authors: TULLY M. B. , JOSHI G. C.
Published: April 2003

We calculate the exact tree-level scalar mass matrices resulting from symmetry breaking using the most general gauge-invariant scalar potential of the 331 model, both with and without the condition that the lepton number is conserved. Physical masses are also obtained in some cases, as well as couplings to standard and exotic gauge bosons.
DYONIC FLUX TUBE STRUCTURE OF NONPERTURBATIVE QCD VACUUM
Authors: CHANDOLA H. C. , PANDEY H. C.
Published: April 2003

We study the flux tube structure of the nonperturbative QCD vacuum in terms of its dyonic excitations by using an infrared effective Lagrangian and show that the dyonic condensation of QCD vacuum has a close connection with the process of color confinement. Using the fiber bundle formulation of QCD, the magnetic symmetry condition is presented in a gauge covariant form and the gauge potential has been constructed in terms of the magnetic vectors on global sections. The dynamical breaking of the magnetic symmetry has been shown to lead the dyonic condensation of QCD vacuum in the infrared energy sector. Deriving the asymptotic solutions of the field equations in the dynamically broken phase, the dyonic flux tube structure of QCD vacuum is explored which has been shown to lead the confinement parameters in terms of the vector and scalar mass modes of the condensed vacuum. Evaluating the charge quantum numbers and energy associated with the dyonic flux tube solutions, the effect of electric excitation of monopole is analyzed using the Regge slope parameter (as an input parameter) and an enhancement in the dyonic pair correlations and the confining properties of QCD vacuum in its dyonically condensed mode has been demonstrated.
A NON-SM CHARGE RADIUS AND NON-SM ANAPOLE MOMENT OF A DIRAC NEUTRINO AND THE HIGH PRECISION MEASUREMENT OF THE MUON (g - 2)
Authors: GARCÍA-HIDALGO R. M. , ROSADO A.
Published: April 2003

We assume that the Dirac neutrino possesses a physical non-standard model charge radius [Formula: see text] and a physical non-standard model anapole moment [Formula: see text] and calculate the contribution of these quantities to the anomalous magnetic moment of the muon aμ using an unsubtracted dispersion relation. We find that these contributions can be important and allow us to set the bound [Formula: see text].
THE CASIMIR ENERGY OF A MASSIVE FERMIONIC FIELD CONFINED IN A (d + 1)-DIMENSIONAL SLAB-BAG
Authors: ELIZALDE E. , SANTOS F. C. , TORT A. C.
Published: April 2003

We evaluate the fermionic Casimir effect associated with a massive fermion confined within a planar (d + 1)-dimensional slab-bag, on which MIT bag model boundary conditions of the standard type, along a single spatial direction, are imposed. A simple and effective method for adding up the zero-point energy eigenvalues, corresponding to a quantum field under the influence of arbitrary boundary conditions, imposed on the field on flat surfaces perpendicular to a chosen spatial direction, is proposed. Using this procedure, an analytic result is obtained, from which small and large fermion mass limits, valid for an arbitrary number of dimensions, are derived. They match some known results in particular cases. The method can be easily extended to other configurations.
MASSIVE YANG–MILLS THEORY IN ABELIAN GAUGES
Authors: ELLWANGER ULRICH , WSCHEBOR NICOLÁS
Published: April 2003

We prove the perturbative renormalizability of pure SU(2) Yang–Mills theory in the Abelian gauge supplemented with mass terms. Whereas mass terms for the gauge fields charged under the diagonal U(1) allow us to preserve the standard form of the Slavnov–Taylor identities (but with modified BRST variations), mass terms for the diagonal gauge fields require the study of modified Slavnov–Taylor identities. We comment on the renormalization group equations, which describe the variation of the effective action with the different masses. Finite renormalized masses for the charged gauge fields, in the limit of vanishing bare mass terms, are possible provided a certain combination of wave function renormalization constants vanishes sufficiently rapidly in the infrared limit.
NUMERICAL STUDY OF DELOCALIZED STATES IN AN EXTENDED NETWORK MODEL
Authors: MATSUMOTO T. , HATSUGAI Y.
Published: April 2003

We have extended the Chalker–Coddington network model to a coupled double layer system with reversed magnetic field directions. The model is investigated numerically and focused on the behavior of the delocalized states. When the hybridization between the layers is small, there are two separate energies of the delocalized states with opposite sign. At some randomness strength, we have observed large fluctuation of the extended state energies. Furthermore, with sufficient strong hybridization, we do not find the delocalized states which suggests the disappearance of the delocalized states at finite hybridization strength. The critical property is also investigated in the weak randomness case which is consistent with the standard single layer case.
THERMODYNAMICS OF A CLASSICAL IDEAL GAS AT ARBITRARY TEMPERATURES
Authors: PAL PALASH B.
Published: April 2003

We propose a fundamental relation for a classical ideal gas that is valid at all temperatures with remarkable accuracy. All thermodynamical properties of classical ideal gases can be deduced from this relation at arbitrary temperature.
CORRELATION ENERGY OF AN ELECTRON GAS: A FUNCTIONAL APPROACH
Authors: REBEI A. , HITCHON W. N. G.
Published: April 2003

Correlation effects of an electron gas in an external potential are derived using an Effective Action functional method. Corrections beyond the random phase approximation (RPA) are naturally incorporated by this method. The Effective Action functional is made to depend explicitly on two-point correlation functions. The calculation is carried out at imaginary time. For a homogeneous electron gas, we calculate the effect of exchange on the ring diagrams at zero temperature and show how to include some of the ladder diagrams. Our results agree well with known numerical calculations. We conclude by showing that this method is in fact a variant of the time dependent density functional method and suggest that it is suitable to be applied to the study of correlation effects in the non-homogeneous case.
REMARKS ON THE GENERALIZED SOLUTION OF ELECTRON DIFFUSION
Authors: DOLOCAN ANDREI
Published: April 2003

A generalized solution of the diffusion equation for a beam of electrons, accelerated in a constant electric field, hitting a solid parallelepiped probe is presented. The solution is taken for the n-dimensional case. We propose a few formula for the boundary functions which can provide useful information about the electron distribution on the hit surface of the probe. Furthermore a time dependence for the surface distribution, as well as for the inner one, is achieved by integration over the correspondent spaces. A short discussion about the case of the accelerated electrons in the presence of electromagnetic fields, constant and variable, is done in the end.
GENERALIZED EXCITED NEGATIVE BINOMIAL STATES OF ELECTROMAGNETIC FIELD AND SOME OF THEIR NON-CLASSICAL PROPERTIES
Authors: SALAH H. H. , DARWISH M. , OBADA A.-S. F.
Published: April 2003

New states of electromagnetic field, generalized excited negative binomial states are introduced here. These states interpolate between the superposition of two excited coherent states and number states. The non-classical properties for these states are discussed, such as, second order correlation function, squeezing phenomena [normal squeezing and amplitude squared squeezing], phase properties in Pegg–Barnett formalism and the quasi-probability distribution functions (Q-function and Wigner function).
SPIN DYNAMICS OF MOLECULAR MAGNET INTERACTING WITH INJECTED ELECTRONS
Authors: HU DONG-SHENG , XIONG SHI-JIE
Published: April 2003

We investigate the time evolution of the local spin in a molecular magnet interacting with injected electrons. By solving the time-dependent Schrödinger equations, we find that the variation in the magnetization of the molecular magnet and the electron spin crucially depends on the strength of the exchange interaction. We calculate the time evolution of the entanglement between the injected electron and the molecular magnet. It is found that the entanglement oscillates in time and the oscillations are closely related to the changes in the spins. The study provides an estimation of the feasibility of the encoding and read-out by using the polarization of the molecular magnets and the injected electrons.
EFFECT OF A LARGE NUMBER OF RANDOM VACANCIES ON BAND-GAP WIDENING IN A POROUS SEMICONDUCTOR
Authors: SUKPITAK J. , SA-YAKANIT V. , SRITRAKOOL W.
Published: April 2003

The electronic density of a states (DOS) of porous semiconductor is calculated by modelling the semiconductor as a system consisting of electrons (or holes) moving in a large number of repulsive random potentials generated by the vacancies. Assuming Gaussian form for each random potential and Gaussian statistics for the potential distribution, we apply the Feynman path-integral approach to obtain two asymptotic expressions for low- and high-energy band-tail DOS's. Both asymptotic expressions show that the DOS's near the band edges are much smaller than parabolic DOS's which seems to create band-gap widening. The band-gap widening can be seen also in terms of mobility gap, which can be approximated as a function of the strength of the random potentials, number density of the vacancies and atomic nearest neighbor distance.
MIXED SPIN-1 AND SPIN-$\frac{3}{2}$ BLUME–CAPEL ISING FERRIMAGNETIC SYSTEM ON THE BETHE LATTICE
Authors: ALBAYRAK ERHAN
Published: April 2003

The mixed spin-1 and spin-[Formula: see text] Blume–Capel Ising ferrimagnetic system for the central spin with spin-1 is studied on the Bethe lattice using the exact recursion equations. The exact expressions for the magnetization, the quadrupolar moment, the Curie temperature and the free energy are found and the phase diagrams are constructed on the Bethe lattice with the coordination numbers q = 3, 4 and 6 for the various values of the single-ion anisotropy constants dA = DA/J for spin-1 and dB = DB/J for spin-[Formula: see text]. The existence of a tricritical point is investigated for different values of q and the single-ion anisotropy constants. The phase diagrams in the (kTc/J, dA) plane for the central spin are obtained for two different cases; (1) dA = dB and (2) dA is varied for selected values of dB. The results are compared with those of other approximate methods.
RIGOROUS PROOF OF PSEUDOSPIN FERROMAGNETISM IN TWO-COMPONENT BOSONIC SYSTEMS WITH COMPONENT-INDEPENDENT INTERACTIONS
Authors: YANG KUN , LI YOU-QUAN
Published: April 2003

For a two-component bosonic system, the components can be mapped onto a pseudo-spin degree of freedom with spin quantum number S = 1/2. We provide a rigorous proof that for a wide-range of real Hamiltonians with component independent mass and interaction, the ground state is a ferromagnetic state with pseudospin fully polarized. The spin-wave excitations are studied and found to have quadratic dispersion relations at long wavelength.
STRUCTURAL AND DYNAMICAL PROPERTIES IN LIQUID Ni AND Ag BY COMPUTER SIMULATION
Authors: URRUTIA-BAÑUELOS EFRAÍN , POSADA-AMARILLAS ALVARO
Published: April 2003

We studied the temperature dependence of the structural and dynamical properties for liquid nickel and silver by modeling the interatomic interaction through a tight-binding n-body potential in the second-moment approximation (TB-SMA). A common-neighbor analysis was performed to explore the microstructural changes with temperature in Ni and Ag in the liquid state in terms of their inherent structures (IS). A tendency to the formation of more symmetric IS characteristic of the BCC crystalline and icosahedral order is observed as the temperature is raised. At the same time, the FCC and HCP crystalline order is reduced while the BCC-type order increases. The simulated diffusion coefficients are in reasonable agreement with the available experimental information and with other theoretical results. The simple liquid behavior is shown by an Arrhenius plot for both nickel and silver.
ENERGY-CONSTRAINED VDD HOPPING SCHEME WITH RUN-TIME POWER ESTIMATION FOR LOW-POWER REAL-TIME VLSI SYSTEMS
Authors: LEE SEONGSOO , LEE SEUNGJUN , SAKURAI TAKAYASU
Published: April 2003

In this paper, we propose a novel dynamic voltage scaling algorithm on a variable-voltage processor. It determines the supply voltage on timeslot-by-timeslot basis within the task boundary, and significantly reduces the power consumption by fully exploiting the slack time. Also, we modify this algorithm and propose an energy-constrained dynamic voltage scaling algorithm for low-power multimedia applications. In the multimedia applications, there are usually several alternative algorithms with different performance and power. Considering the trade-off between performance and power, the proposed algorithm adaptively determines the optimal alternative to achieve optimal performance under given energy constraint. Compared with the conventional algorithms, the power consumption is reduced to 1/14.4 ~ 1/5.6 without performance degradation.
HETEROCLINIC ORBITS ARISING FROM COUPLED CHUA'S CIRCUITS
Authors: CHAN WHEI-CHING C. , SHI SHAOYUN
Published: April 2003

In this paper, we study the existence of heteroclinic orbits for ordinary differential equations which arise from a one-dimensional array of Chua's circuits. By using the upper and lower solutions method, and a zero-order approximation we show that for a certain set of parameters there exist traveling wave solutions for some given wave speeds.
SOME RESULTS ON CHUA'S EQUATION NEAR A TRIPLE-ZERO LINEAR DEGENERACY
Authors: ALGABA A. , MERINO M. , FREIRE E. , GAMERO E. , RODRÍGUEZ-LUIS A. J.
Published: April 2003

In this work we study a wide class of symmetric control systems that has the Chua's circuit as a prototype. Namely, we compute normal forms for Takens–Bogdanov and triple-zero bifurcations in a class of symmetric control systems and determine the local bifurcations that emerge from such degeneracies. The analytical results are used as a first guide to detect numerically several codimension-three global bifurcations that act as organizing centres of the complex dynamics Chua's circuit exhibits in the parameter range considered. A detailed (although partial) bifurcation set in a three'parameter space is presented in this paper. We show relations between several high-codimension bifurcations of equilibria, periodic orbits and global connections. Some of the global bifurcations found have been neither analytically nor numerically treated in the literature.
PROPERTIES OF THE INVARIANT DISK PACKING IN A MODEL BANDPASS SIGMA–DELTA MODULATOR
Authors: ASHWIN PETER , FU XIN-CHU , DEANE JONATHAN
Published: April 2003

In this paper we discuss the packing properties of invariant disks defined by periodic behavior of a model for a bandpass Σ–Δ modulator. The periodically coded regions form a packing of the forward invariant phase space by invariant disks. For this one-parameter family of PWIs, by introducing codings underlying the map operations we give explicit expressions for the centers of the disks by analytic functions of the parameters, and then show that tangencies between disks in the packings are very rare; more precisely they occur on parameter values that are at most countably infinite. We indicate how similar results can be obtained for other plane maps that are piecewise isometries.
FINDING CYCLES IN SYNCHRONOUS BOOLEAN NETWORKS WITH APPLICATIONS TO BIOCHEMICAL SYSTEMS
Authors: HEIDEL JACK , MALONEY JOHN , FARROW CHRISTOPHER , ROGERS J. A.
Published: April 2003

This paper is an analytical study of Boolean networks. The motivation is our desire to understand the large, complicated and interconnected pathways which comprise intracellular biochemical signal transduction networks. The simplest possible conceptual model that mimics signal transduction with sigmoidal kinetics is the n-node Boolean network each of whose elements or nodes has the value 0 (off) or 1 (on) at any given time T = 0, 1, 2, …. A Boolean network has 2nstates all of which are either on periodic cycles (including fixed points) or transients leading to cycles. Thus one understands a Boolean network by determining the number and length of its cycles. The problem one must circumvent is the large number of states (2n) since the networks we are interested in have 100 or more elements. Thus we concentrate on developing size n methods rather than the impossible task of enumerating all 2nstates. This is done as follows: the dynamics of the network can be described by n polynomial equations which describe the logical function which determines the interaction at each node. Iterating the equations one step at a time finds all fixed points, period two cycles, period three cycles, etc. This is a general method that can be used to determine the fixed points and moderately large periodic cycles of any size network, but it is not useful in finding the largest cycles in a large network. However, we also show that the network equations can often be reduced to scalar form, which makes the cycle structure much more transparent. The scalar equations method is a true "size n" method and several examples (including nontrivial biochemical systems) are examined.
NONORIENTABLE MANIFOLDS IN THREE-DIMENSIONAL VECTOR FIELDS
Authors: OSINGA HINKE M.
Published: April 2003

It is well known that a nonorientable manifold in a three-dimensional vector field is topologically equivalent to a Möbius strip. The most frequently used example is the unstable manifold of a periodic orbit that just lost its stability in a period-doubling bifurcation. However, there are not many explicit studies in the literature in the context of dynamical systems, and so far only qualitative sketches could be given as illustrations. We give an overview of the possible bifurcations in three-dimensional vector fields that create nonorientable manifolds. We mainly focus on nonorientable manifolds of periodic orbits, because they are the key building blocks. This is illustrated with invariant manifolds of three-dimensional vector fields that arise from applications. These manifolds were computed with a new algorithm for computing two-dimensional manifolds.
CLOSED CURVES OF GLOBAL BIFURCATIONS IN CHUA'S EQUATION: A MECHANISM FOR THEIR FORMATION
Authors: ALGABA ANTONIO , MERINO MANUEL , FERNÁNDEZ-SÁNCHEZ FERNANDO , RODRÍGUEZ-LUIS ALEJANDRO J.
Published: April 2003

In this work, the presence of closed bifurcation curves of homoclinic and heteroclinic connections has been detected in Chua's equation. We have numerically found and qualitatively described the mechanism of the formation/destruction of such closed curves. We relate this phenomenon to a failure of transversality in a curve of T-points in a three-dimensional parameter space.
A RETURN MAP REGRESSION APPROACH FOR NONCOHERENT DETECTION IN CHAOTIC DIGITAL COMMUNICATIONS
Authors: TSE CHI K. , LAU FRANCIS C. M.
Published: April 2003

Chaos-based communications can be applied advantageously if the property of chaotic systems is suitably exploited. In this Letter a simple noncoherent detection method for chaos-shift-keying (CSK) modulation is proposed, exploiting some distinguishable property of chaotic maps for recovering the digital message. Specifically, the proposed method exploits the difference in the return maps of the signals representing the digital symbols. The determining parameter of the return maps is estimated using a simple regression algorithm. If the parameter strongly characterizes the chaotic map, the detection can achieve very good accuracy. This strong parametric characterization can be achieved by defining the regression model with only one parameter. Using the tent maps as chaos generators, the bit-error-rate under additive white Gaussian noise is studied by computer simulations.
BIFURCATION FOR DYNAMICAL SYSTEMS OF PLANET–BELT INTERACTION
Authors: JIANG ING-GUEY , YEH LI-CHIN
Published: April 2003

The dynamical systems of planet–belt interaction are studied by the fixed-point analysis, and the bifurcation of solutions on the parameter space is discussed. For most cases, our analytical and numerical results show that the locations of fixed points are determined by the parameters and these fixed points are either structurally stable or unstable. In addition to that, there are two special fixed points: The one on the inner edge of the belt is asymptotically stable and the one on the outer edge of the belt is unstable. This is consistent with the observational picture of Asteroid Belt between Mars and Jupiter: Mars moves steadily close to the inner edge but Jupiter is quite far from the outer edge.
DYNAMIC ASSOCIATIVE MEMORY BASED ON NEURAL NETWORK WITH CHAOTIC CONTROL
Authors: CHEN HONGPING , CAO ZHITONG , JIN JINSHENG
Published: April 2003

Dynamic associative memory is realized by chaotic neural network with feedback pinnings. When the inputs deviate obviously from the reference samples, which give the result that the correct association cannot be obtained through the inherent tolerance function of the chaotic neural network, the pinnings can quickly retrieve the original memory of the chaotic neural network. The simulation experiments of both the dynamic associative memory and the retrieval process are done by using the above method for the faults of broken rotor bars on an induction motor. The results show that the feedback pinning is a simple and effective control method to the chaotic neural network.
A NOTE ON BIFURCATION CONTROL
Authors: CHEN GUANRONG , LI CHANGPIN
Published: April 2003

In the Letter, we propose a simple, yet general and mathematically rigorous bifurcation control method for bifurcation suppression in an abstract system setting that covers both continuous and discrete cases defined by nonlinear operators in Banach spaces.
BIFURCATIONS IN SYNAPTICALLY COUPLED HODGKIN–HUXLEY NEURONS WITH A PERIODIC INPUT
Authors: TSUMOTO KUNICHIKA , YOSHINAGA TETSUYA , AIHARA KAZUYUKI , KAWAKAMI HIROSHI
Published: April 2003

We investigate bifurcations in responses of two Hodgkin–Huxley neurons coupled to each other and forced by a periodic pulse train, through the characteristics of synaptic transmissions with an α-function and a time delay. Based on a computational method we previously presented, we show a mechanism of transitions among various kinds of nonperiodic as well as harmonic and subharmonic frequency-locked oscillations. The bifurcation analysis clarifies dependence of sub- and supra-threshold dynamics on coupling and forcing effects.
DIGITAL SPEECH COMMUNICATION BY TRUNCATED CHAOTIC SYNCHRONIZATION
Authors: ZHANG Y. , DU G. H. , HUA Y. M. , JIANG J. J.
Published: April 2003

The method of truncated chaotic synchronization is suggested for digital speech communication. The sequence, composed by truncating some byte segments from the low-dimensional chaotic attractor, demonstrates complicated dynamics and high dimension. Predicting the dynamics of the truncated map through the local approximation method becomes very difficult. However, synchronization lets the message be exactly recovered. The synchronization condition is deduced to synchronize two systems of the truncated one-way coupled ring maps. The sensitivity of synchronization to parameter mismatch is discussed for the security in communication. For the mismatch of parameters or keys, the probability of decoding the message through guessing the keys is below 2-200. The scheme of truncated chaotic synchronization has strong security in encoding message.
POLYTOPIC OBSERVER FOR GLOBAL SYNCHRONIZATION OF SYSTEMS WITH OUTPUT MEASURABLE NONLINEARITIES
Authors: MILLERIOUX GILLES , DAAFOUZ JAMAL
Published: April 2003

Chaos synchronization has been tackled by considering the problem as a special case of an observer design. The considered dynamical systems to be synchronized have measurable nonlinearities. Their dynamical matrix is described in a polytopic way. By using the notion of polyquadratic stability, the problem of the observer synthesis is turned into the resolution of a set of Linear Matrix Inequalities (LMI) which are less conservative compared to the case of an usual quadratic Lyapunov approach. This enables to enlarge the class of systems for which synchronization can take place. The resulting matrix gain of the observer is computed by interpolating vertices gains resulting from the solution of the LMI's.
LYAPUNOV EXPONENTS FOR BILINEAR SYSTEMS: APPLICATION TO THE BUCK CONVERTER
Authors: BATLLE CARLES , MASSANA IMMA , MIRALLES ALICIA
Published: April 2003

Using the QR decomposition of the tangent map, we explicitly write the differential equations satisfied by the Lyapunov exponents of a two-dimensional bilinear system, and specialize them to the buck converter in continuous current mode. These equations are solved numerically for an arbitrary value of the bifurcation parameter, and analytically for periodic orbits, recovering for the later results already known from the computation of Floquet exponents.
SOLITARY WAVES AND CHAOTIC BEHAVIOR FOR A CLASS OF COUPLED FIELD EQUATIONS
Authors: KWEK KENG-HUAT , LI JIBIN
Published: April 2003

Using the theory of Hamiltonian systems and dynamical systems to a class of coupled field equations, the existence of uncountably infinite many solitary wave solutions, arbitrarily many distinct periodic solutions and chaotic behavior is obtained. Some sufficient conditions to guarantee the existence of the above solutions are given.
DYNAMICAL CORRELATIONS ON RECONSTRUCTED INVARIANT DENSITIES AND THEIR EFFECT ON CORRELATION DIMENSION ESTIMATION
Authors: GALKA ANDREAS , PFISTER GERD
Published: April 2003

We investigate the structure of dynamical correlations on reconstructed attractors which were obtained by time-delay embedding of periodic, quasi-periodic and chaotic time series. Within the specific sampling of the invariant density by a finite number of vectors which results from embedding, we identify two separate levels of sampling, corresponding to two different types of dynamical correlations, each of which produces characteristic artifacts in correlation dimension estimation: the well-known trajectory bias and a characteristic oscillation due to periodic sampling. For the second artifact we propose random sampling as a new correction method which is shown to provide improved sampling and to reduce dynamical correlations more efficiently than it has been possible by the standard Theiler correction. For accurate numerical analysis of correlation dimension in a bootstrap framework both corrections should be combined. For tori and the Lorenz attractor we also show how to construct time-delay embeddings which are completely free of any dynamical correlations.
CAN WE MEASURE CONSCIOUSNESS WITH EEG COMPLEXITIES?
Authors: GU FANJI , MENG XIN , SHEN ENHUA , CAI ZHIJIE
Published: April 2003

Several complexity measures, especially approximate entropy (ApEn) and a new defined complexity measure [Formula: see text], of EEG signals or the ones of the mutual information transmission between different channels of EEGs were calculated to distinguish different consciousness levels for different brain functional states. All of the measures decreased with the following order of brain states: rest with eyes open, eyes closed, light sleep and deep sleep. They decreased during epileptic seizures. On the contrary, the averaged mutual information between different channels increased significantly during the epileptic seizure; there is no significant difference among the averaged mutual information for the subject resting with eyes open, closed, being in light sleep and in deep sleep. Thus, the former indexes seem to be promising candidates to characterize different consciousness levels, while the latter seems not.
BIFURCATION TAILORING VIA NEWTON FLOW-AIDED ADAPTIVE CONTROL
Authors: WANG XIAO FAN , DI BERNARDO M. , STOTEN D. P. , LOWENBERG M. H. , CHARLES G.
Published: April 2003

The aim of bifurcation tailoring is to design an appropriate control law such that the controlled system has a desired bifurcation diagram. After describing two open-loop bifurcation tailoring techniques, this paper proposes a new open-loop plus close-loop bifurcation tailoring method based on a combination of the Newton-flow algorithm and the minimal control synthesis (MCS) adaptive control strategy. This method is applied to the Duffing system as an illustrative example.
OBSERVATION OF A PERIOD DOUBLING BIFURCATION DURING ONSET OF HUMAN VENTRICULAR FIBRILLATION
Authors: SMALL MICHAEL , YU DEJIN , HARRISON ROBERT G.
Published: April 2003

We find evidence of a period doubling bifurcation and transition from pseudo-periodic chaos to a stable limit cycle during onset of ventricular fibrillation (VF) in humans. Novel radial basis modeling techniques are applied to time series of spontaneous VF to estimate time dependent changes in the dynamics. Furthermore, we show that the spectral power content may be used as a surrogate for the underlying bifurcation parameter. With this spectral power measure we demonstrate a characteristic transition from pseudo-periodic chaos to a second pseudo-periodic chaotic regime. The methods described in this paper are generic and applicable to any time series data.
ON LOGARITHMIC ASYMPTOTICS OF STOCHASTIC RESONANCE FREQUENCIES
Authors: CARMONA S. C. , FREIDLIN M. I.
Published: April 2003

Stochastic resonance effects due to arbitrarily small amplitude deterministic perturbations in dynamical systems with noise are studied. The concept of Log-Asymptotic Resonance Frequency is introduced and the relationship between its existence and some types of symmetries in the stochastic system is established; the spectrum of this kind of frequencies is determined. These symmetries are defined through the quasi-deterministic approximation of the system. The large deviation theory gives the basic machinery for this analysis.
Lp-GENERIC COCYCLES HAVE ONE-POINT LYAPUNOV SPECTRUM
Authors: ARBIETO ALEXANDER , BOCHI JAIRO
Published: April 2003

We show that the sum of the first k Lyapunov exponents of linear cocycles is an upper semicontinuous function in the Lp topologies, for any 1 ≤ p ≤ ∞ and k. This fact, together with a result from Arnold and Cong, implies that the Lyapunov exponents of the Lp-generic cocycle, p < ∞, are all equal.
STABLE LIMITS FOR PROBABILITY PRESERVING MAPS WITH INDIFFERENT FIXED POINTS
Authors: ZWEIMÜLLER ROLAND
Published: April 2003

We consider probability preserving maps with indifferent fixed points and prove distributional convergence to stable laws for observables measurable with respect to a dynamical partition.
PULLBACK ATTRACTORS OF NONAUTONOMOUS SEMIDYNAMICAL SYSTEMS
Authors: KLOEDEN P. E.
Published: April 2003

A nonautonomous semidynamical system is a skew-product semi-flow consisting of a cocycle mapping on a state space which is driven by a semidynamical system on a base space. It is shown that the driving system can be extended backwards in time on a compact invariant set, such as a global attractor, as a set-valued semidynamical system. Pullback attraction and invariance with respect to the cocycle mapping are then reformulated in terms of the set-valued backwards extension of the driving system.
A NOTE ON AVERAGING AND HOMOGENIZATION
Authors: KHASMINSKII R. , KLEBANER F.
Published: April 2003

Recently an averaging principle for diffusion processes with a null-recurrent fast component without a drift term was obtained in [4]. In this note this result is widened to allow a drift in the fast component. As a corollary a new result on the homogenization for parabolic PDE's is obtained.
A NOISY SYSTEM WITH A FLATTENED HAMILTONIAN AND MULTIPLE TIME SCALES
Authors: O'BRYANT NATELLA V.
Published: April 2003

We consider a two-dimensional weakly dissipative dynamical system with time-periodic drift and diffusion coefficients. The average of the drift is governed by a degenerate Hamiltonian whose set of critical points has an interior. The dynamics of the system is studied in the presence of three time scales. Using the martingale problem approach and separating the time scales, we average the system to show convergence to a Markov process on a stratified space. The averaging combines the deterministic time averaging of periodic coefficients, and the stochastic averaging of the resulting system. The corresponding strata of the reduced space are a two-sphere, a point and a line segment. Special attention is given to the description of the domain of the limiting generator, including the analysis of the gluing conditions at the point where the strata meet. These gluing conditions, resulting from the effects of the hierarchy of time scales, are similar to the conditions on the domain of skew Brownian motion and are related to the description of spider martingales.
Holocene Earthquake Records from the Cascadia Subduction Zone and Northern San Andreas Fault Based on Precise Dating of Offshore Turbidites
Authors: Goldfinger Chris , Nelson C. Hans , Johnson Joel E. ,   The Shipboard Scientific Party
Published: April 2003

▪ Abstract  We present preliminary evidence for a ∼10,000-year earthquake record from two major fault systems based on sediment cores collected along the continental margins of western North America. New stratigraphic evidence from Cascadia demonstrates that 13 earthquakes ruptured the entire margin from Vancouver Island to at least the California border since the eruption of the Mazama ash 7700 years ago. The 13 events above this prominent stratigraphic marker have an average repeat time of 600 years, and the youngest event ∼300 years ago coincides with the coastal record. We also extend the record of past earthquakes to the base of the Holocene (at least 9800 years ago), during which 18 events correlate along the same region. The sequence of Holocene events in Cascadia appears to contain a repeating pattern of events, a tantalizing first look at what may be the long-term behavior of a major fault system.

The northern California margin cores show a cyclic record of turbidite beds that may represent Holocene earthquakes on the northern segment of the San Andreas Fault. Preliminary results are in reasonably good agreement with onshore paleoseismic data that indicate an age for the penultimate event in the mid-1600s at several sites and the most likely age for the third event of ∼AD 1300.
Catastrophic Flooding of the Black Sea
Authors: Ryan William B.F. , Major Candace O. , Lericolais Gilles , Goldstein Steven L.
Published: April 2003

▪ Abstract  Decades of seabed mapping, reflection profiling, and seabed sampling reveal that throughout the past two million years the Black Sea was predominantly a freshwater lake interrupted only briefly by saltwater invasions coincident with global sea level highstand. When the exterior ocean lay below the relatively shallow sill of the Bosporus outlet, the Black Sea operated in two modes. As in the neighboring Caspian Sea, a cold climate mode corresponded with an expanded lake and a warm climate mode with a shrunken lake. Thus, during much of the cold glacial Quaternary, the expanded Black Sea's lake spilled into to the Marmara Sea and from there to the Mediterranean. However, in the warm climate mode, after receiving a vast volume of ice sheet meltwater, the shoreline of the shrinking lake contracted to the outer shelf and on a few occasions even beyond the shelf edge. If the confluence of a falling interior lake and a rising global ocean persisted to the moment when the rising ocean penetrated across the dividing sill, it would set the stage for catastrophic flooding. Although recently challenged, the flood hypothesis for the connecting event best fits the full set of observations.