bluuebunny/crossref_metadata_2025 huggingface dataset:
Some notes on the apex approximation
Authors: Blodgett M. L. , Palmer D. R.
Published: October 2005

We have extended the work of Munk and Zachariasen by deriving an improved apex approximation for the mean-square phase and phase-rate fluctuations. Our results are compared with Munk and Zachariasens’s results and with those obtained by numerically evaluating the exact expressions.
A study of the acoustical effects of sub-bottom absorption profiles
Authors: Hawker Kenneth E. , Williams Winifred E. , Foreman Terry L.
Published: October 2005

This paper considers the acoustical effects of variations of sediment absorption with depth for several sediment types. A simple measure of absorption effects is given by the total absorption along the sub-bottom ray paths. This total absorption is considered for a variety of absorption and sound-speed gradients for both semi-infinite and finite layers. The plane wave reflection loss (bottom loss) is then considered for several treatments of attenuation, layering, and sediment type. It is found that, for clay sediments, plausible variations in absorption gradients can result in variations in bottom loss of several decibels. These conclusions are reinforced by consideration of the absorption gradient effects on normal mode attenuation coefficients.
Effect of periodic surface corrugation on the propagation of Rayleigh waves
Authors: Seshadri S. R.
Published: October 2005

The Rayleigh wave interaction in an elastically isotropic half space having a free surface with weak sinusoidal corrugations in one direction is investigated for the case of propagation normal to the length of the corrugations. Simple and asymptotically exact analytical expressions are deduced with the help of a singular perturbation procedure for the characteristics of the wave interaction. The theory is applied to obtain the characteristics of the selective reflection of a Rayleigh wave incident on a moderately long periodic array of shallow grooves etched on the free surface. The results obtained from the present asymptotic theory are compared with those previously deduced from an empirical equivalent network approach and a phenomenological coupled mode theory.
Subjective loudness and annoyance of filtered N-wave sonic booms
Authors: Niedzwiecki A. , Ribner H. S.
Published: October 2005

The contribution of the ’’infrasonic’’ low-frequency content of sonic boom N waves to subjective loudness and annoyance has been investigated. An extended low-frequency response loudspeaker-driven simulation booth was employed, with computer-generated input test signals. For test N waves of 1 ms rise time and 150 ms duration, frequencies below 25 and 50 Hz, respectively, were cut off by digital filters simulating simple RC circuits. The filtered signal amplitude was adjusted versus the amplitude (48 Pa) of a reference unfiltered N wave (effective low-frequency cutoff ∠0.1 Hz) until the two sounded equally loud (first experiment) or equally annoying (second experiment). The amplitude differences for equality were very slight: less than 0.6 dB at most. Surprisingly, while loss of the low frequencies slightly decreased the loudness, it slightly increased the annoyance.
Temporal summation of pure tones in birds
Authors: Dooling Robert J.
Published: October 2005

Two parakeets and two field sparrows were trained by a method of avoidance conditioning to respond to pure tones. Absolute thresholds were obtained for 10 durations of a 2.86-kHz tone. The temporal integration function for these four birds can best be described by a time constant τ of 230 ms. These data are similar to those reported for a number of other species.
Sound velocity gradients in marine sediments
Authors: Hamilton Edwin L.
Published: October 2005

The presence of positive sound velocity gradients in the sea floor is of importance in underwater acoustics; especially in refracting energy back into the water mass. This report summarizes velocity–depth relations and values of velocity gradients in four principal marine sediment types as computed from measurements of velocity at the sea floor from cores and at depths from sonobuoys. Compressional wave velocity (Vp, km/s) versus depth (D, km) in three major sediment types are, for 20 turbidite areas: VP=1.511+1.304D−0.741D2+0.257D3; siliceous sediments (Bering Sea): Vp=1.509+0.869D−0.267D2; and calcareous sediments (Ontong–Java Plateau): Vp=1.559+1.713D−0.374D2. Vp gradients, surface, and 0–1000 m, average 1.3–0.8 s−1 (turbidites); 0.9–0.6 s−1 (siliceous); and 1.9–1.3 s−1 (calcareous). In sands Vp gradients vary from 18 s−1 (1–2 m) to about 4 s−1 between 1 and 20 m. Major factors in Vp gradients in silt clays and turbidites to 500 m are pressure-induced porosity reductions and effects on the sediment mineral frame (about 66% of the gradient), temperature increases due to heat flow (17%), pore-water pressure increases (2%), and increases in rigidity caused by lithification (15%). These percentages vary with sediment depth. Velocity ratios and gradients may indicate a small sediment sound channel.
Axisymmetric scattering of spherical waves by a prolate spheroid
Authors: Germon A. , Lauchle G. C.
Published: October 2005

Theoretical analyses are performed, and numerical results obtained for the axisymmetric scattering of a spherical wave by a rigid prolate spheroid. In the numerical calculations, the complex farfield reflection factor (ratio of scattered-to-incident pressure) is computed as a function of frequency and observation angle for a 7-to-1 fineness ratio prolate spheroid. Different source locations are considered, all of which lie on the axis of symmetry. In addition, the superposition of the incident and scattered fields is investigated for a variety of two-source configurations. In one instance, these two sources are assumed to have equal strengths and to vibrate in phase, while in a second instance they are assumed to be incoherent. The computations are for relatively low frequencies, where the exact tabulated forms of the spheroidal wave functions may be used. The results for the directivity functions indicate that the reflection factor depends only slightly on aspect angle for a single source, but when two in-phase sources are considered, the scattering is very dependent on angle. If the two sources are incoherent, then the patterns approach the shape of the corresponding pattern for the single source closest to the pole, particularly when the second source is relatively far from the first.
Modal resonance analysis of acoustic transmission and reflection losses in viscoelastic plates
Authors: Madigosky Walter , Fiorito Ralph
Published: October 2005

Transmission and reflection losses (TL, RL) are calculated as functions of frequency thickness (F×D) and incidence angle (ϑ) for single and multiple viscoelastic plates (steel, ABS, syntactic foam, neoprene, and Plexiglas) using a transfer matrix method modified to include complex wave velocities. The calculation of these velocities depends on four measurable material constants: longitudinal and shear phase velocities (cL, cs) and absorption coefficients (αL, αS). A physical model is developed to relate αL to αS, and shown to be experimentally accurate for a wide range of materials, temperatures and frequencies, thus providing a new way to account for shear absorption when directly measured data is not readily available. Use of actual measured data is shown to be necessary to validly compare theory with the experimentally observed TL and RL. Analysis of maxima and minima in TL, RL versus F×D or ϑ is made in detail using calculated dispersion curves for single plates, and these extrema are shown to be consistant with the coincidence rule. In the case of a plate with high loss, the maxima in TL versus F×D, e.g., observed where minima would be expected from the coincidence rule, are explained in terms of interfering ’’resonance’’ peaks using a recent theory of acoustic resonances in plates. The concept of interfering resonances is shown to be successful in interpreting some of the previously unexplained features of TL and RL observed in steel.
Nonlinear acoustoelasticity of isotropic elastic materials
Authors: Tokuoka Tatsuo
Published: October 2005

The propagation velocities in deformed isotropic elastic material are determined as functions of the strain or the stress. The velocities are expanded with respect to a strain measure and they are expressed by second-order polynomials of it, where the coefficients are given by two second-, four third-, and six fourth-order elastic constants. In the first-order approximation the velocity difference between two transverse waves is proportional to the stress difference and the stress acoustical law holds. The isotropic hyperelastic material is treated and the three conditions are derived where a general isotropic elastic material is reduced to a hyperelastic material in the third-order theory. The velocity relations in this material are depicted. The expansions of the velocity with respect to the displacement gradient are also treated. Two methods of expansion yield identical linear but different nonlinear relations.
Pulse propagation in coaxial circular cylinders of two elastic phase materials
Authors: Holtzman Z. , Lifshitz J. M.
Published: October 2005

Pulse propagation in a finite coaxial circular cylinder made of two elastic materials is solved numerically. In the first stage the natural frequencies of the free rod, including those of the higher modes, are determined and used to qualitatively predict dispersion of a pulse. In the second stage modal analysis is used to determine dispersion of the pulse and to obtain distribution of axial stress and displacement and shear stress along the radius of the cylinder. It is shown that in highly anisotropic composite rods large dispersion may occur even when the wavelength is large compared to the rod diameter.
Some experiments on the sound of silence in phonetic perception
Authors: Dorman Michael F. , Raphael Lawrence J. , Liberman Alvin M.
Published: October 2005

The results of several experiments demonstrate that silence is an important cue for the perception of stop-consonant and affricate manner. In some circumstances, silence is necessary; in others, it is sufficient. But silence is not the only cue to these manners. There are other cues that are more or less equivalent in their perceptual effects, though they are quite different acoustically. Finally, silence is effective as a cue when it is part of an utterance that is perceived as having been produced by a single male speaker, but not when it separates utterances produced by male and female speakers. These findings are taken to imply that, in these instances, perception is constrained as if by some abstract conception of what vocal tracts do when they make linguistically significant gestures.
Potential energy effects on the sound speed in liquids
Authors: Hartmann Bruce
Published: October 2005

Sound speed in liquids is calculated in terms of Mie potential parameters with the assumption that the intermolecular potential energy is the dominant factor. Using this simple model, it is shown that Beyer’s parameter of nonlinearity, Rao’s exponent, and the Gruneisen parameter are all simply related to each other. Liquids obey a law of corresponding states in terms of reduced variables c2/U0 and V/V0, where c is sound speed, U0 is the heat of vaporization, V is specific volume, and V0 specific volume at absolute zero temperature. To a first approximation, the parameter of nonlinearity is shown to be a linear function of reciprocal sound speed, and the calculated results are in reasonably good agreement with the empirical result noted by Ballou.
Dynamic Paternity Allocation as a Function of Male Plumage Color in Barn Swallows
Authors: Safran R. J. , Neuman C. R. , McGraw K. J. , Lovette I. J.
Published: September 2005

Paternity in male animals can be influenced by their phenotypic signals of quality. Accordingly, the behavior underlying patterns of paternity should be flexible as signals of quality change. To evaluate the dynamics of paternity allocation, we analyzed paternity before and after manipulating plumage coloration, a known signal of quality, in male barn swallows
Hirundo rustica
. We found that, in successive breeding bouts, only males whose plumage color was experimentally enhanced received greater paternity from their social mates, demonstrating evidence for flexible and dynamic paternity allocation and the importance for males of maintaining signals of quality well after pair bond formation.
Phylogenetic MCMC Algorithms Are Misleading on Mixtures of Trees
Authors: Mossel Elchanan , Vigoda Eric
Published: September 2005

Markov chain Monte Carlo (MCMC) algorithms play a critical role in the Bayesian approach to phylogenetic inference. We present a theoretical analysis of the rate of convergence of many of the widely used Markov chains. For
N
characters generated from a uniform mixture of two trees, we prove that the Markov chains take an exponentially long (in
N
) number of iterations to converge to the posterior distribution. Nevertheless, the likelihood plots for sample runs of the Markov chains deceivingly suggest that the chains converge rapidly to a unique tree. Our results rely on novel mathematical understanding of the log-likelihood function on the space of phylogenetic trees. The practical implications of our work are that Bayesian MCMC methods can be misleading when the data are generated from a mixture of trees. Thus, in cases of data containing potentially conflicting phylogenetic signals, phylogenetic reconstruction should be performed separately on each signal.
The Rise of Oxygen over the Past 205 Million Years and the Evolution of Large Placental Mammals
Authors: Falkowski Paul G. , Katz Miriam E. , Milligan Allen J. , Fennel Katja , Cramer Benjamin S. , Aubry Marie Pierre , Berner Robert A. , Novacek Michael J. , Zapol Warren M.
Published: September 2005

On the basis of a carbon isotopic record of both marine carbonates and organic matter from the Triassic-Jurassic boundary to the present, we modeled oxygen concentrations over the past 205 million years. Our analysis indicates that atmospheric oxygen approximately doubled over this period, with relatively rapid increases in the early Jurassic and the Eocene. We suggest that the overall increase in oxygen, mediated by the formation of passive continental margins along the Atlantic Ocean during the opening phase of the current Wilson cycle, was a critical factor in the evolution, radiation, and subsequent increase in average size of placental mammals.
Direct Evidence for a Parietal-Frontal Pathway Subserving Spatial Awareness in Humans
Authors: de Schotten Michel Thiebaut , Urbanski Marika , Duffau Hugues , Volle Emmanuelle , Lévy Richard , Dubois Bruno , Bartolomeo Paolo
Published: September 2005

Intraoperative electrical stimulation, which temporarily inactivates restricted regions during brain surgery, can map cognitive functions in humans with spatiotemporal resolution unmatched by other methods. Using this technique, we found that stimulation of the right inferior parietal lobule or the caudal superior temporal gyrus, but not of its rostral portion, determined rightward deviations on line bisection. However, the strongest shifts occurred with subcortical stimulation. Fiber tracking identified the stimulated site as a section of the superior occipitofrontal fasciculus, a poorly known parietal-frontal pathway. These findings suggest that parietal-frontal communication is necessary for the symmetrical processing of the visual scene.
Rev1 Employs a Novel Mechanism of DNA Synthesis Using a Protein Template
Authors: Nair Deepak T. , Johnson Robert E. , Prakash Louise , Prakash Satya , Aggarwal Aneel K.
Published: September 2005

The Rev1 DNA polymerase is highly specialized for the incorporation of C opposite template G. We present here the crystal structure of yeast Rev1 bound to template G and incoming 2′-deoxycytidine 5′-triphosphate (dCTP), which reveals that the polymerase itself dictates the identity of the incoming nucleotide, as well as the identity of the templating base. Template G and incoming dCTP do not pair with each other. Instead, the template G is evicted from the DNA helix, and it makes optimal hydrogen bonds with a segment of Rev1. Also, unlike other DNA polymerases, incoming dCTP pairs with an arginine rather than the templating base, which ensures the incorporation of dCTP over other incoming nucleotides. This mechanism provides an elegant means for promoting proficient and error-free synthesis through N
2
-adducted guanines that obstruct replication.
Tryptophan 7-Halogenase (PrnA) Structure Suggests a Mechanism for Regioselective Chlorination
Authors: Dong Changjiang , Flecks Silvana , Unversucht Susanne , Haupt Caroline , van Pée Karl-Heinz , Naismith James H.
Published: September 2005

Chlorinated natural products include vancomycin and cryptophycin A. Their biosynthesis involves regioselective chlorination by flavin-dependent halogenases. We report the structural characterization of tryptophan 7-halogenase (PrnA), which regioselectively chlorinates tryptophan. Tryptophan and flavin adenine dinucleotide (FAD) are separated by a 10 angstrom–long tunnel and bound by distinct enzyme modules. The FAD module is conserved in halogenases and is related to flavin-dependent monooxygenases. On the basis of biochemical studies, crystal structures, and by analogy with monooxygenases, we predict that FADH
2
reacts with O
2
to make peroxyflavin, which is decomposed by Cl
–
. The resulting HOCl is guided through the tunnel to tryptophan, where it is activated to participate in electrophilic aromatic substitution.
Colloidal Jamming at Interfaces: A Route to Fluid-Bicontinuous Gels
Authors: Stratford K. , Adhikari R. , Pagonabarraga I. , Desplat J.-C. , Cates M. E.
Published: September 2005

Colloidal particles or nanoparticles, with equal affinity for two fluids, are known to adsorb irreversibly to the fluid-fluid interface. We present large-scale computer simulations of the demixing of a binary solvent containing such particles. The newly formed interface sequesters the colloidal particles; as the interface coarsens, the particles are forced into close contact by interfacial tension. Coarsening is markedly curtailed, and the jammed colloidal layer seemingly enters a glassy state, creating a multiply connected, solidlike film in three dimensions. The resulting gel contains percolating domains of both fluids, with possible uses as, for example, a microreaction medium.
Influence of Gravity Waves on the Internal Rotation and Li Abundance of Solar-Type Stars
Authors: Charbonnel Corinne , Talon Suzanne
Published: September 2005

The Sun's rotation profile and lithium content have been difficult to understand in the context of conventional models of stellar evolution. Classical hydrodynamic models predict that the solar interior must rotate highly differentially, in disagreement with observations. It has recently been shown that internal waves produced by convection in solar-type stars produce an asymmetric, shear layer oscillation, similar to Earth's quasi-biennial oscillation, that leads to efficient angular momentum redistribution from the core to the envelope. We present results of a model that successfully reproduces both the rotation profile and the surface abundance of lithium in solar-type stars of various ages.
Imaging Spin Transport in Lateral Ferromagnet/Semiconductor Structures
Authors: Crooker S. A. , Furis M. , Lou X. , Adelmann C. , Smith D. L. , Palmstrøm C. J. , Crowell P. A.
Published: September 2005

We directly imaged electrical spin injection and accumulation in the gallium arsenide channel of lateral spin-transport devices, which have ferromagnetic source and drain tunnel-barrier contacts. The emission of spins from the source was observed, and a region of spin accumulation was imaged near the ferromagnetic drain contact. Both injected and accumulated spins have the same orientation (antiparallel to the contact magnetization), and we show that the accumulated spin polarization flows away from the drain (against the net electron current), indicating that electron spins are polarized by reflection from the ferromagnetic drain contact. The electrical conductance can be modulated by controlling the spin orientation of optically injected electrons flowing through the drain.
Extracellular DNA Plays a Key Role in Deep-Sea Ecosystem Functioning
Authors: Dell'Anno Antonio , Danovaro Roberto
Published: September 2005

The ecological role and biogeochemical relevance of extracellular DNA in the oceanic sediments are unknown. Our global estimates indicate that up to 0.45 gigatons of extracellular DNA are present in the top 10 centimeters of deep-sea sediments, representing the largest reservoir of DNA in the world oceans. We demonstrate that extracellular DNA accounts for about one fifth of the total organic phosphorus regeneration and provides almost half of the prokaryotic demand for organic phosphorus. It therefore plays a key role in deep-sea ecosystem functioning on a global scale.
Mapping the Roads to Current Science
Authors: Tresch John
Published: September 2005

Making Modern Science
. A Historical Survey.
By Peter J. Bowler and Iwan Rhys Morus
. University of Chicago Press, Chicago, 2005. 537 pp. $65, £45.50. ISBN 0-226-06860-9. Paper, $25, £17.50. ISBN 0-226-06861-7.

In a survey intended for interested readers and introductory courses, the authors examine historical episodes (from the scientific revolution to "the emergence of the human sciences") and then discuss selected themes (from "organization of science" through "science and technology" to "science and gender").
Hsp90 Potentiates the Rapid Evolution of New Traits: Drug Resistance in Diverse Fungi
Authors: Cowen Leah E. , Lindquist Susan
Published: September 2005

Hsp90 is a molecular chaperone for many signal transducers and may influence evolution by releasing previously silent genetic variation in response to environmental change. In fungi separated by ∼800 million years of evolution, Hsp90 potentiated the evolution of drug resistance in a different way, by enabling new mutations to have immediate phenotypic consequences. Resistance was abrogated by Hsp90 inhibitors and by febrile temperatures, suggesting new therapeutic strategies and a clinical benefit of fever. During selection in a human host, drug resistance that was initially Hsp90-dependent evolved toward independence. Thus, Hsp90 can act in diverse ways to couple environmental contingency to the emergence and fixation of new traits.
ON HAWKING RADIATION AS TUNNELING WITH BACK-REACTION
Authors: MEDVED A. J. M. , VAGENAS ELIAS C.
Published: September 2005

Recently, Angheben et al.1 have presented a refined method for calculating the (tree-level) black hole temperature by way of the tunneling paradigm. Here, we demonstrate how their formalism can be suitably adapted to accommodate the (higher-order) effects of the gravitational back-reaction.
ACTIVE WALKS: THE FIRST TWELVE YEARS (PART I)
Authors: LAM LUI
Published: September 2005

Active walk is a paradigm for self-organization and pattern formation in simple and complex systems, originated by Lam in 1992. In an active walk, the walker (an agent) changes the deformable landscape as it walks and is influenced by the changed landscape in choosing its next step. Active walk models have been applied successfully to various biological, chemical and physical systems from the natural sciences, and to economics and many other systems from the social sciences. More recently, it has been used to model human history. In this review, the history, basic concepts, formulation, theories, applications, new developments and open problems of active walk are summarized and discussed. New experimental, theoretical and computer modeling results are included.
EXISTENCE OF MONOTONIC TRAVELING WAVES IN LATTICE DYNAMICAL SYSTEMS
Authors: HSU CHENG-HSIUNG , YANG SUH-YUH
Published: September 2005

This paper deals with the existence of monotonic traveling and standing wave solutions for a certain class of lattice differential equations. Employing the techniques of monotone iteration coupled with the concept of upper and lower solutions in the theory of monotone dynamical systems, we can classify the monotonic traveling wave solutions with various asymptotic boundary conditions. For the case of zero wave speed, a novel discrete monotone iteration scheme is established for proving the existence of monotonic standing wave solutions. Applications are made to several models including cellular neural networks, original and modified RTD-based cellular neural networks. Numerical simulations of the monotone iteration schemes are also given.
SEMI-ANALYTICAL BIFURCATION ANALYSIS OF TWO-PHASE FLOW IN A HEATED CHANNEL
Authors: DOKHANE A. , HENNIG D. , CHAWLA R. , RIZWAN-UDDIN
Published: September 2005

Using a drift flux representation for the two-phase flow, a new reduced order model has been developed to simulate density-wave oscillations (DWOs) in a heated channel. This model is then used to perform stability and semi-analytical bifurcation analysis, using the bifurcation code BIFDD, in which the stability boundary (SB) and the nature of Hopf bifurcation are determined in a suitable two-dimensional parameter space.

A comparative study is carried out to investigate the effects of the parameters in the drift flux model (DFM) — the radially void distribution parameter C0 and the drift velocity Vgj — on the SB as well as on the nature of Hopf bifurcation. It is the first time that a systematic analysis has been carried out to investigate the effects of DFM parameters on the nature of Hopf bifurcation in a heated-channel two-phase flow.

The results obtained show that both sub- and super-critical Hopf bifurcations are encountered. In addition, it has been found that, while the SB is sensitive to both C0 and Vgj, the nature of Hopf bifurcation for lower values of N sub is more sensitive to Vgj than to C0. Numerical integration of the set of ODEs is carried out to confirm the predictions of the semi-analytical bifurcation analysis.
GLOBAL AND LOCAL CONTROL OF HOMOCLINIC AND HETEROCLINIC BIFURCATIONS
Authors: CAO HONGJUN , CHEN GUANRONG
Published: September 2005

A comprehensive resonant optimal control method is developed and discussed for suppressing homoclinic and heteroclinic bifurcations of a general one-degree-of-freedom nonlinear oscillator. Based on an adjustable phase shift, the primary resonant optimal control method is presented. By solving an optimization problem for the optimal amplitude coefficients to be used as the control parameters, the force term as the controller can be designed. Three kinds of resonant optimal control methods are compared. The control mechanism of the primary resonant optimal control method is to enlarge to the largest possible degree the control region where homoclinic and/or heteroclinic transversal intersections do not occur, and this is accomplished at lowest cost. It is shown that the primary resonant optimal control method has much better performance than the superharmonic resonant optimal control method, and it works well even when the superharmonic optimal control method fails. In particular, one new global optimal control method is presented, whose central idea is to find a frequency such that the asymmetric homoclinic bifurcations or the multiple homoclinic and heteroclinic bifurcations can attain the same critical values. On the basis of these same critical bifurcation values, chaos resulting from asymmetric homoclinic or multiple homoclinic and heteroclinic bifurcations can be effectively suppressed by the primary resonant optimal control method. This is confirmed by two illustrative examples. The theoretical analyses concerning the suppression of local and global homoclinic and heteroclinic bifurcations are in agreement with the numerical simulations, including the identification of the stable and unstable manifolds and the basins of attraction.
SYNCHRONIZING CASCADE-CONNECTED CHAOTIC SYSTEMS WITH UNCERTAINTIES AND BREAKING CHAOTIC CRYPTOSYSTEMS VIA A NOVEL ADAPTIVE CONTROL SCHEME
Authors: SU JUHNG-PERNG , WANG CHUN-CHIEH
Published: September 2005

This paper deals with synchronization problems of chaotic systems by applying a new adaptive variable structure control (AVSC) scheme. On the basis of Lyapunov synthesis method and Barbalat's Lemma, the proposed control law is shown to render the slave system asymptotically synchronized with the master system even though the parameters of the master system are unknown. A robust adaptive control scheme is presented to guarantee the robustness of the synchronization against bounded disturbances. Even for the case that the slave and master chaotic systems are not of the same type, the proposed AVSC may approximately null the synchronization error. We used an uncertain Rössler system, an uncertain Chua's circuit and an uncertain Duffing–Holmes oscillator as examples to illustrate the controller design. Both theoretical and simulation results strongly suggest that chaotic cryptosystems could be broken by the proposed adaptive control method. This reveals the fact that chaos-based cryptosystems may fail to achieve the secure communication.
BIFURCATION OF INVARIANT CONES IN PIECEWISE LINEAR HOMOGENEOUS SYSTEMS
Authors: CARMONA V. , FREIRE E. , PONCE E. , TORRES F.
Published: September 2005

Invariant surfaces in three-dimensional continuous piecewise linear homogeneous systems with two pieces separated by a plane are detected. The Poincaré map associated to this plane transforms half-straight lines passing through the origin into half-straight lines of the same type. The invariant half-straight lines under this map determine invariant cones for which the existence, stability and bifurcation are studied. This analysis lead us to consider some questions about the topological type and stability of the origin.
ENERGY-LIKE FUNCTIONS FOR SOME DISSIPATIVE CHAOTIC SYSTEMS
Authors: SARASOLA C. , D'ANJOU A. , TORREALDEA F. J. , MOUJAHID A.
Published: September 2005

Functions of the phase space variables that can considered as possible energy functions for a given family of dissipative chaotic systems are discussed. This kind of functions are interesting due to their use as an energy-like quantitative measure to characterize different aspects of dynamic behavior of associated chaotic systems. We have calculated quadratic energy-like functions for the cases of Lorenz, Chen, Lü–Chen and Chua, and show the patterns of dissipation of energy on their respective attractors. We also show that in the case of the Rössler system at least a fourth-order polynomial is required to properly represent its energy.
ON THE RELATION BETWEEN PREDICTABILITY AND HOMOCLINIC TANGENCIES
Authors: HARLE MARKUS , FEUDEL ULRIKE
Published: September 2005

The predictability of chaotic systems is investigated using paradigmatic models for the conservative and the dissipative cases. Local Lyapunov exponents are used to quantify predictability for short time scales. It is shown that, in both cases, regions of enhanced predictability have been found around homoclinic tangencies. In the dissipative case, we demonstrate that the length of these regions shrinks exponentially with increasing time of prediction.
DYNAMICS OF A FAMILY OF QUADRATIC MAPS IN THE QUATERNION SPACE
Authors: NAKANE SHIZUO
Published: September 2005

The dynamics of a family of quadratic maps in the quaternion space is investigated. In particular, connectivity of the filled-in Julia sets is completely determined. It is shown that the connectedness locus of this family is not equal to what we call the quaternionic Mandelbrot set. Hyperbolic components will also be completely characterized.
THE TRANSLINEAR PRINCIPLE: A GENERAL FRAMEWORK FOR IMPLEMENTING CHAOTIC OSCILLATORS
Authors: ODAME KOFI M. , MINCH BRADLEY A.
Published: September 2005

In this Letter, we propose a class of nonlinear dynamic translinear circuits as a viable tool for the rapid and systematic implementation of chaotic oscillators in analog integrated circuits. In this regard, our primary focus is on multiple-input translinear element (MITE) networks and their particular merits. We also describe, as an illustrative example, our monolithic implementation of the Lorenz equations, and report on results from a test chip fabricated in a 0.5 μm CMOS process through MOSIS. We also show that Chua's circuit can be implemented easily in our framework.
SYNCHRONIZATION OF TIME-DELAYED T–S FUZZY CHAOTIC SYSTEMS VIA SCALAR OUTPUT VARIABLE
Authors: KIM JAE-HUN , SHIN HYUNSEOK , KIM EUNTAI , PARK MIGNON
Published: September 2005

It has been known that very complex chaotic behaviors can be observed in a simple first-order system with time-delay. This paper presents a fuzzy model-based approach for synchronization of time-delayed chaotic system via a scalar output variable. Takagi–Sugeno (T–S) fuzzy model can represent a general class of nonlinear system and we employ it for fuzzy modeling of the chaotic drive and response system with time-delay. Since only a scalar output variable is available for synchronization, a fuzzy observer based on T–S fuzzy model is designed and applied to chaotic synchronization. We analyze the stability of the overall fuzzy synchronization system by applying Lyapunov–Krasovskii theory and derive stability conditions by solving linear matrix inequalities (LMI's) problem. A numerical example is given to demonstrate the validity of the proposed synchronization approach.
CONTROLLING CHAOS IN A CHAOTIC NEURON MODEL
Authors: LIN WEI , CHEN TIANPING
Published: September 2005

In this paper we investigate several methods for controlling chaos in Aihara's chaotic neuron model. We first discuss the stability of exponential feedback control method for this model. To obviate predetermining the unstable periodic orbits of the system, two other methods are developed. We analyze why the conventional delayed feedback control method cannot be employed here, and then give a modified form for recursive delayed feedback control and apply it to control chaos in this model. To obtain high-periodic orbits more easily, a delayed exponential feedback control method is proposed, by which we can obtain different periodic orbits by changing parameters. Computer simulations show good control effects and robustness against noise.
BIFURCATION AND CHAOTIC TRANSITION TO RELAXATION OSCILLATIONS IN AN INDUCTIVELY DRIVEN ELECTRONEGATIVE PLASMA
Authors: LICHTENBERG A. J. , MARAKHTANOV A. M.
Published: September 2005

Regular and chaotic relaxation oscillations in charged particle densities, light and floating potential are seen in low-pressure inductive discharges, in the transition between lower power capacitive operation and higher power inductive operation, if the plasma is electronegative, i.e. contains negative ions. As pressure or power is varied to cross a threshold, either from stable capacitive or stable inductive operation, the instability goes through a series of oscillatory, sometimes chaotic, states to large scale relaxation oscillations between higher and lower densities. A volume-averaged model, to describe the instability, contains time varying densities of charged species and temperature, indicating that the separation of the time scales of electron and negative ion motion is the driver of the complicated dynamics. The particle and energy balance equations are integrated to produce the dynamical behavior. A phase plane description of negative ions versus electrons is used to gain understanding of the instability. The theory shows that, depending on specific choices of parameters, as power is increased, the oscillations, born at Hopf bifurcation, can grow to a large amplitude relaxation oscillations, sometimes traversing chaotically between basins of attraction. The model qualitatively agrees with experimental observations which show the same range of behaviors, but with quantitative differences to be explained.
HOPF BIFURCATION AND CHAOS IN TABU LEARNING NEURON MODELS
Authors: LI CHUNGUANG , CHEN GUANRONG , LIAO XIAOFENG , YU JUEBANG
Published: September 2005

In this paper, we consider the nonlinear dynamical behaviors of some tabu learning neuron models. We first consider a tabu learning single neuron model. By choosing the memory decay rate as a bifurcation parameter, we prove that Hopf bifurcation occurs in the neuron. The stability of the bifurcating periodic solutions and the direction of the Hopf bifurcation are determined by applying the normal form theory. We give a numerical example to verify the theoretical analysis. Then, we demonstrate the chaotic behavior in such a neuron with sinusoidal external input, via computer simulations. Finally, we study the chaotic behaviors in tabu learning two-neuron models, with linear and quadratic proximity functions respectively.
TRACING THE SOLUTION SURFACE WITH FOLDS OF A TWO-PARAMETER SYSTEM
Authors: CHANG S.-L. , CHIEN C.-S. , JENG B.-W.
Published: September 2005

We describe a special Gauss–Newton method for tracing solution manifolds with singularities of multiparameter systems. First we choose one of the parameters as the continuation parameter, and fix the others. Then we trace one-dimensional solution curves by using continuation methods. Singularities such as folds, simple and multiple bifurcations on each solution curve can be easily detected. Next, we choose an interval for the second continuation parameter, and trace one-dimensional solution curves for certain values in this interval. This constitutes a two-dimensional solution surface. The procedure can be generalized to trace a k-dimensional solution manifold. Numerical results in 1D, 2D and 3D second-order semilinear elliptic eigenvalue problems given by Lions [1982] are reported.
Coupled expression of troponin T and troponin I isoforms in single skeletal muscle fibers correlates with contractility
Authors: Brotto Marco A. , Biesiadecki Brandon J. , Brotto Leticia S. , Nosek Thomas M. , Jin Jian-Ping
Published: September 2005

Striated muscle contraction is powered by actin-activated myosin ATPase. This process is regulated by Ca2+ via the troponin complex. Slow- and fast-twitch fibers of vertebrate skeletal muscle express type I and type II myosin, respectively, and these myosin isoenzymes confer different ATPase activities, contractile velocities, and force. Skeletal muscle troponin has also diverged into fast and slow isoforms, but their functional significance is not fully understood. To investigate the expression of troponin isoforms in mammalian skeletal muscle and their functional relationship to that of the myosin isoforms, we concomitantly studied myosin, troponin T (TnT), and troponin I (TnI) isoform contents and isometric contractile properties in single fibers of rat skeletal muscle. We characterized a large number of Triton X-100-skinned single fibers from soleus, diaphragm, gastrocnemius, and extensor digitorum longus muscles and selected fibers with combinations of a single myosin isoform and a single class (slow or fast) of the TnT and TnI isoforms to investigate their role in determining contractility. Types IIa, IIx, and IIb myosin fibers produced higher isometric force than that of type I fibers. Despite the polyploidy of adult skeletal muscle fibers, the expression of fast or slow isoforms of TnT and TnI is tightly coupled. Fibers containing slow troponin had higher Ca2+ sensitivity than that of the fast troponin fibers, whereas fibers containing fast troponin showed a higher cooperativity of Ca2+ activation than that of the slow troponin fibers. These results demonstrate distinct but coordinated regulation of troponin and myosin isoform expression in skeletal muscle and their contribution to the contractile properties of muscle.
Pharmacological rescue of the dystrophin-glycoprotein complex in Duchenne and Becker skeletal muscle explants by proteasome inhibitor treatment
Authors: Assereto Stefania , Stringara Silvia , Sotgia Federica , Bonuccelli Gloria , Broccolini Aldobrando , Pedemonte Marina , Traverso Monica , Biancheri Roberta , Zara Federico , Bruno Claudio , Lisanti Michael P. , Minetti Carlo
Published: September 2005

In this report, we have developed a novel method to identify compounds that rescue the dystrophin-glycoprotein complex (DGC) in patients with Duchenne or Becker muscular dystrophy. Briefly, freshly isolated skeletal muscle biopsies (termed skeletal muscle explants) from patients with Duchenne or Becker muscular dystrophy were maintained under defined cell culture conditions for a 24-h period in the absence or presence of a specific candidate compound. Using this approach, we have demonstrated that treatment with a well-characterized proteasome inhibitor, MG-132, is sufficient to rescue the expression of dystrophin, β-dystroglycan, and α-sarcoglycan in skeletal muscle explants from patients with Duchenne or Becker muscular dystrophy. These data are consistent with our previous findings regarding systemic treatment with MG-132 in a dystrophin-deficient mdx mouse model (Bonuccelli G, Sotgia F, Schubert W, Park D, Frank PG, Woodman SE, Insabato L, Cammer M, Minetti C, and Lisanti MP. Am J Pathol 163: 1663–1675, 2003). Our present results may have important new implications for the possible pharmacological treatment of Duchenne or Becker muscular dystrophy in humans.
Leptin and CCK modulate complementary background conductances to depolarize cultured nodose neurons
Authors: Peters J. H. , Ritter R. C. , Simasko S. M.
Published: September 2005

We have previously reported that intraceliac infusion of leptin induces a reduction of meal size that depends on intact vagal afferents. This effect of leptin is enhanced in the presence of cholecystokinin (CCK). The mechanisms by which leptin and CCK activate vagal afferent neurons are not known. In the present study, we have begun to address this question by using patch-clamp electrophysiological techniques to examine the mechanisms by which leptin and CCK activate cultured vagal afferents from adult rat nodose ganglia. We found that leptin depolarized 41 (60%) of 68 neurons. The magnitude of membrane depolarization was dependent on leptin concentration and occurred in both capsaicin-sensitive and capsaicin-insensitive neurons. We also found that a majority (16 of 22; 73%) of nodose neurons activated by leptin were also sensitive to CCK. CCK-induced depolarization was primarily associated with the increase of an inward current (11 of 12), whereas leptin induced multiple changes in background conductances through a decrease in an outward current (7 of 13), an increase in an inward current (3 of 13), or both (3 of 13). However, further isolation of background currents by recording in solutions that contained only sodium or only potassium revealed that both leptin and CCK were capable of increasing a sodium-dependent conductance or inhibiting a potassium-dependent conductance. Our results support the hypothesis that vagal afferents are a point of convergence and integration of leptin and CCK signaling for control of food intake and suggest multiple ionic mechanisms by which leptin and CCK activate vagal afferent neurons.
SGK1 activates Na+-K+-ATPase in amphibian renal epithelial cells
Authors: Alvarez de la Rosa Diego , Gimenez Ignacio , Forbush Biff , Canessa Cecilia M.
Published: September 2005

Serum- and glucocorticoid-induced kinase 1 (SGK1) is thought to be an important regulator of Na+ reabsorption in the kidney. It has been proposed that SGK1 mediates the effects of aldosterone on transepithelial Na+ transport. Previous studies have shown that SGK1 increases Na+ transport and epithelial Na+ channel (ENaC) activity in the apical membrane of renal epithelial cells. SGK1 has also been implicated in the modulation of Na+-K+-ATPase activity, the transporter responsible for basolateral Na+ efflux, although this observation has not been confirmed in renal epithelial cells. We examined Na+-K+-ATPase function in an A6 renal epithelial cell line that expresses SGK1 under the control of a tetracycline-inducible promoter. The results showed that expression of a constitutively active mutant of SGK1 (SGK1 TS425D) increased the transport activity of Na+-K+-ATPase 2.5-fold. The increase in activity was a direct consequence of activation of the pump itself. The onset of Na+-K+-ATPase activation was observed between 6 and 24 h after induction of SGK1 expression, a delay that is significantly longer than that required for activation of ENaC in the same cell line (1 h). SGK1 and aldosterone stimulated the Na+ pump synergistically, indicating that the pathways mediated by these molecules operate independently. This observation was confirmed by demonstrating that aldosterone, but not SGK1 TS425D, induced an ∼2.5-fold increase in total protein and plasma membrane Na+-K+-ATPase α1-subunit abundance. We conclude that aldosterone increases the abundance of Na+-K+-ATPase, whereas SGK1 may activate existing pumps in the membrane in response to chronic or slowly acting stimuli.
Central neuropeptide Y induces proximal stomach relaxation via Y1 receptors in the dorsal vagal complex of the rat
Authors: Kobashi Motoi , Shimatani Yuichi , Shirota Keisuke , Xuan Song-Yu , Mitoh Yoshihiro , Matsuo Ryuji
Published: September 2005

Effects of neuropeptide Y (NPY) on motility of the proximal stomach was examined in anesthetized rats. Intragastric pressure was measured using a balloon situated in the proximal part of the stomach. Administration of NPY into the fourth ventricle induced relaxation of the proximal stomach in a dose-dependent manner. Administration of an Y1 receptor (Y1R) agonist [Leu31, Pro34]NPY induced a larger relaxation than NPY. The administration of an Y2 receptor agonist (NPY 13-36) did not induce significant changes in motility. Microinjections of [Leu31, Pro34]NPY into the caudal part of the dorsal vagal complex (DVC) induced relaxation of the proximal stomach. In contrast, similar injections into the intermediate part of the DVC increased IGP of the proximal stomach. Administration of NPY into the fourth ventricle did not induce relaxation after bilateral injections of the Y1R antagonist (1229U91) into the caudal DVC. These results indicate that NPY induces relaxation in the proximal stomach via Y1Rs situated in the DVC. Because bilateral vagotomy below the diaphragm abolished the relaxation induced by the administration of NPY into the fourth ventricle, relaxation induced by NPY is probably mediated by vagal preganglionic neurons. Intravenous injection of atropine methyl nitrate reduced relaxation induced by administration of NPY. Therefore, relaxation induced by NPY is likely mediated by peripheral cholinergic neurons.
Molecular and functional characterization of adrenomedullin receptors in pufferfish
Authors: Nag Kakon , Kato Akira , Nakada Tsutomu , Hoshijima Kazuyuki , Mistry Abinash Chandra , Takei Yoshio , Hirose Shigehisa
Published: September 2005

The receptors for the calcitonin gene-related peptide (CGRP)/adrenomedullin (AM) family peptides were characterized in the mefugu Takifugu obscurus, a euryhaline fugu species very close to Takifugu rubripes, which has as many as five adrenomedullin genes (AM1–5). CGRP and AM share a G protein-coupled core receptor called calcitonin receptor-like receptor (CLR), and the specificity of the CLR is determined by the interaction with receptor activity-modifying proteins (RAMPs). Through database mining, three CLRs (CLR1–3) and five RAMPs (RAMP1–5) were identified, and all of them were cloned by RT-PCR and characterized by functional expression in COS7 cells in every possible combination of CLR-RAMP. The following combinations generated cAMP in response to physiological concentrations of CGRP, AM1 (an ortholog of mammalian AM), AM2, and AM5: CLR1-RAMP1/4 (CGRP), CLR1-RAMP2/3/5 (AM1), CLR2-RAMP2 (AM1), CLR1-RAMP3 (AM2), and CLR1-RAMP3 (AM5). Their expressions were found by Northern blot analysis to be tissue specific and salinity dependent. For example, CLR1-RAMP5 and CLR1-RAMP2 are expressed specifically in the gill and kidney, respectively, suggesting their involvement in osmoregulation. Furthermore, relatively high levels of CLRs and RAMPs were found in the spleen and ovary, suggesting roles in the immune and female reproductive systems. Immunohistochemistry revealed that AM receptors of the following types are expressed in the locations, indicated in brackets, of the mefugu gill and kidney: CLR1-RAMP5 (interlamellar vessels), CLR2-RAMP2 (pillar cells), and CLR1-RAMP2 (apical side of renal proximal tubule cells).