bluuebunny/crossref_metadata_2025 huggingface dataset:
A GEOMETRIC ANALYSIS OF STABILITY REGIONS FOR A LINEAR DIFFERENTIAL EQUATION WITH TWO DELAYS
Authors: MAHAFFY JOSEPH M. , JOINER KATHRYN M. , ZAK PAUL J.
Published: November 2004

We describe an algorithmic approach for determining the geometry of the region of stability for a linear differential equation with two delays. Numerous applications utilize two-delay differential equations and require a framework to assay stability. The imaginary and zero solutions of the characteristic equation, where bifurcations in stability occur, produce an infinite set of surfaces in the coefficient parameter space. A methodology is outlined for identifying which of these surfaces form the boundary of the stability region. For a range of delays, the stability region changes in only three ways, starting at an identified initial point and becoming more complex as one coefficient increases. Detailed graphical analyses, including three-dimensional plots, show the evolution of the stability surface for given ratios of delays, highlighting variations across delays. The results demonstrate that small changes in the delay ratio cause significant changes in the size and shape of the stability region.
COMPLEX FEIGENBAUM’S SCENARIO IN DISCRETELY-COUPLED ARRAYS OF NONLINEAR CIRCUITS
Authors: CASTRO M. DE , PÉREZ-MUÑUZURI V. , CHUA L.O. , PÉREZ-VILLAR V.
Published: November 2004

Complex Feigenbaum’s scenarios were numerically and experimentally observed in discretely coupled arrays of nonlinear circuits. The dependence of the double-period bifurcation scheme on the number of the cells in the array, the coupling between cells, and external noise, was investigated. The complexity of this scenario is highlighted when a two-parameters study was carried out. The unfolding of an inverse double-period cascade was observed in the two-parameter space.
FEEDBACK CONTROL OF CHAOS IN SPATIOTEMPORAL SYSTEMS
Authors: HU GANG , QU ZHILIN , HE KAIFEN
Published: November 2004

This paper reviews the recent development in controlling and synchronizing chaos in spatiotemporal systems. In the first section we make a brief survey of the theoretical and experimental studies of controlling chaos in temporal systems. Section 2 is devoted to the dynamical variable feedback control approach by taking some temporal systems as examples. Some advantages of the variable feedback control over the parametric feedback control are emphasized. In Sec. 3, controlling and synchronizing spatiotemporal chaos in extended systems are presented by investigating the coupled map lattice models. In Sec. 4, we consider nonlinear systems described by partial differential equations, where momentum-space control by injecting feedback waves and coordinate-space control by injecting feedback signals at space points are used for successfully suppressing chaos and directing the system to certain regular motions.
OPCL MIGRATION CONTROLS BETWEEN FIVE ATTRACTORS OF THE CHUA SYSTEM
Authors: JACKSON E. ATLEE
Published: November 2004

Jackson and Grosu [1995a] have recently proved that a new OPCL control method, involving both closed and open loop components, always has a basin of entrainment to any smooth goal dynamics, g(t) ⊂ Rn, for any dynamic system (Lipschitz flow), dx/dt = F (x, t), x ⊂ Rn. Moreover, they showed that the basins of entrainment can be made the entire phase space ("global") for many standard dynamic systems, and in particular for the Chua system [Chua et al., 1986]. In contrast to entrainment, it has been pointed out [Jackson, 1990] that migration controls, which act only for limited time and produce transfers between attractors of a multiple-attractor system, can be of great importance. The Chua system can possess five attractors, and the present study shows how it is possible to reliably produce migrations between any of these attractors using only five experimentally-obtained data points in the phase space. This migration control does not require any knowledge about the basins of attraction, nor the state of the system when the control is initiated. Moreover, the OPCL method can be used to obtain refined models of the physical system, by applying the general resonance method proposed previously [Chang et al., 1991].
THIRTY YEARS AFTER SHARKOVSKIĬ'S THEOREM
Authors: MISIUREWICZ MICHAŁ
Published: November 2004

Thirty years ago Sharkovskiĭ's theorem was published. This started a new branch of dynamical systems — combinatorial dynamics. I will try to summarize briefly its developments and current trends.
DRY TURBULENCE AND PERIOD-ADDING PHENOMENA FROM A 1-D MAP WITH TIME DELAY
Authors: SHARKOVSKY A. N. , DEREGEL PH. , CHUA L. O.
Published: November 2004

In this tutorial paper, we consider an infinite-dimensional extension of Chua's circuit, as shown in Fig. 1, where the transmission line is lossless. As we shall see, if the capacitance C1 is set to zero, the dynamics of this so-called time-delayed Chua's circuit can be reduced, without any approximation, to that of a continuous scalar nonlinear difference equation. This type of equation can lead to space-time chaos which, due to the absence of viscosity in our system, will be termed "dry turbulence". Another interesting property of this system occurs under certain conditions, when the corresponding 1-D map has two segments and is piecewise-linear. The extreme simplicity of this map will allow us to derive, without any approximation, the exact analytical solution of the stability boundaries of stable cycles of every period n. Since the stability region is non-empty for each n, this proves rigorously that the time-delayed Chua's circuit exhibits the "period-adding" phenomenon where every two consecutive cycles are separated by a chaotic region.
PERIODIC POINTS OF ${\mathcal C}^1$ MAPS AND THE ASYMPTOTIC LEFSCHETZ NUMBER
Authors: GUASCHI JOHN , LLIBRE JAUME
Published: November 2004

We study the set of periodic points and the set of periods of different classes of [Formula: see text] self maps of a compact manifold. We give sufficient conditions in order that these sets be infinite. Our main tools are the Lefschetz fixed point theory and homology.
MAPS WITH RANDOM PERTURBATIONS ARE GENERICALLY NOT CHAOTIC
Authors: JANKOVÁ K. , SMÍTAL J.
Published: November 2004

For dynamical systems generated by iterates of continuous maps of the interval with trajectories subjected to small random perturbations, we prove that with probability 1, any trajectory is transitive in a system of compact intervals forming a periodic orbit, but generically these intervals are arbitrarily small when the perturbations are sufficiently small.
A CHARACTERIZATION OF THE SET Ω (f)\ ω (f) FOR CONTINUOUS MAPS OF THE INTERVAL WITH ZERO TOPOLOGICAL ENTROPY
Authors: BALIBREA F. , SMÍTAL J.
Published: November 2004

We give a characterization of the set of nonwandering points of a continuous map f of the interval with zero topological entropy, attracted to a single (infinite) minimal set Q. We show that such a map f can have a unique infinite minimal set Q and an infinite set B ⊂ Ω (f)\ ω (f) (of nonwandering points that are not ω-limit points) attracted to Q and such that B has infinite intersections with infinitely many disjoint orbits of f.
DYNAMICS OF THE NONAUTONOMOUS CHUA'S CIRCUIT
Authors: ANISHCHENKO V. C. , VADIVASOVA T. E. , POSTNOV D. E. , SOSNOVTSEVA O. V. , WU C. W. , CHUA L. O.
Published: November 2004

In this paper, we investigate via physical experiments and computer simulations the response of Chua's circuit under periodic external forcing. The amplitude and frequency of the external forcing form two additional control parameters, and we present bifurcation diagrams on the plane of these two parameters. We investigate the behavior of Chua's circuit due to external forcing when the unforced circuit is in various dynamical regimes. We finally compare our results with those obtained from a nonautonomous oscillator with an inertial nonlinearity.
EFFECTS OF THE SAMPLING TIME ON THE DYNAMICS AND IDENTIFICATION OF NONLINEAR MODELS
Authors: BILLINGS S. A. , AGUIRRE LUIS ANTONIO
Published: November 2004

This paper investigates how the choice of the sampling time affects the identification of nonlinear models. It is shown how the choice of the sampling interval can affect structure selection and parameter estimation in different ways so that a compromise is required to properly select an appropriate sampling time. The use of a nonlinear correlation function to aid in the choice of the sampling rate is investigated. Several numerical examples are included to illustrate the main points of the paper.
ON THE DETERMINATION OF THE STOCHASTICITY THRESHOLD OF INVARIANT CURVES
Authors: CELLETTI ALESSANDRA , FROESCHLÉ CLAUDE
Published: November 2004

We consider the problem of determining the stochasticity transition value in nearly-integrable mappings. We perform explicitly a canonical transformation, which conjugates the original mapping to an integrable one, up to a given order in the perturbing parameter. Then we derive a numerical evidence of the existence of an invariant curve associated with the transformed system and, correspondingly, to the original one. In the second part of the paper we implement a numerical method due to M. Hénon [Hénon] for the computation of the rotation number corresponding to a given initial condition. Following an idea of Laskar et al. [1992] and Laskar [1993], we determine with high accuracy the critical breakdown threshold of invariant curves for standard-mapping like systems which allows not only to test Hénon's method but also to compare our analytical results with an accurate numerical one. An application is also made about the accuracy of the leap frog method.
PAPERFOLDING, GENERALIZED RUDIN-SHAPIRO SEQUENCES, AND THE THUE-MORSE SEQUENCE
Authors: RODENHAUSEN ANNA
Published: November 2004

It is known that a family of generalized Rudin-Shapiro sequences can be derived from paperfolding sequences. We will show that the component wise sum modulo 2 of a generalized Rudin-Shapiro sequence with the well known Thue-Morse sequence again is a generalized Rudin-Shapiro sequence of the same family. Moreover, it is proved that the classical Rudin-Shapiro sequence can be recovered as a generalized Rudin-Shapiro sequence associated to paperfolding with alternating instruction.
DISTRIBUTIONS OF LOCAL MANDELBROT-HURST EXPONENTS: MOTOR ACTIVITY IN FETAL RATS OF COCAINIZED MOTHERS AND MANIC-DEPRESSIVE PATIENTS
Authors: SELZ KAREN A. , MANDELL ARNOLD J. , ANDERSON CARL M. , SMOTHERMAN WILLIAM P. , TEICHER MARTIN H.
Published: November 2004

Intermittency, in which the normalized weight of large fluctuations grows for increasingly longer statistical samples, is seen as irregular bursting activity in time and is characteristic of the behavior of many brain and behavioral systems. This pattern has been related to the brain-stabilizing interplay of the general mechanisms of silence-evoked sensitization and activity-evoked desensitization, which can be found at most levels of neurobiological function and which vary more smoothly and at much longer times than the phasic observables. We use both the global Mandelbrot-Hurst exponent and the distribution of local Mandelbrot-Hurst exponents, in combination with dynamical entropies, to quantitate the property of nonuniform persistence which we treat as both deterministically expansive and statistically diffusive. For example, varying the parameter of the one-dimensional, Manneville-Pomeau intermittency map generated time series which demonstrated systematic changes in these statistical indices of persistence. Relatively small doses of cocaine administered to pregnant rats increased statistical indices of expansiveness and persistence in fetal motor behavior. These techniques also model and characterize a breakdown of statistical scaling in 72-hour time series of the amount of motor activity in some hospitalized manic-depressive patients.
WAVEFORM INVERSION AND MULTI-LAYER NEURAL NETWORK
Authors: FEI DONGYU , KUO JOHN T. , TENG YU-CHIUNG
Published: November 2004

This paper presents the concept of neural network inversion. The basic mathematical problem is to establish the mapping between two multi-dimensional spaces, addressing the continuous function mapping between two close intervals. It introduces the 3-layer neural network existence theorem and proves that the multi-layer neural network can approximate any continuous function in the sense of supernorm or mean-squares-norm, provided that the activation function is locally Riemann integrable and nonpolynomial. With an initial guess of the target parameter, which, in the present case, is acoustic velocity, in a prescribed sphere, which contains the true parameter, the neural network inversion method ensures the search reaching the global minima. The principle of the neural network inversion on the basis of the least-squares minimization (L2 norm) is developed. As its application, this method is employed to perform seismic waveform inversions — Model 1, for a homogeneous isotropic earth with a 2-D rectangle embedded body, and Model 2, for a layered earth with an elliptically elongated inclusion. A fast computation algorithm of the finite element method is adopted to generate a series of synthetic shot records for training the 3-layer neural network. The trained neural network possesses the capability to find the acoustic velocity of the embedded body in both Model 1 and 2 with a real-time solution within a sufficient accuracy.
SOUND FIELD IN A WATER LAYER OF CHANGEABLE DEPTH EXCITED BY A SOURCE MOVING IN AIR
Authors: BULDYREV VLADIMIR , GRIGORIEVA NATALIE
Published: November 2004

The subject of this paper is the construction of the nonstationary normal waves excited in the ocean of changeable depth by a source moving in the atmosphere. In the atmosphere, the sound speed is assumed to be constant and in water it depends on depth, slow horizontal coordinates as well as slow time. The bottom is assumed to be rigid. The source is radiating a signal with varying amplitude and phase. It is moving with a speed which is smaller than the sound speed in liquid. To find the nonstationary normal waves, the nonstationary variant of the well-known method of horizontal rays/vertical modes is used. Arising Sturm–Liouville problems in the semi-infinite interval are reduced to the Sturm–Liouville problems in the finite interval. The reduction allows one to avoid the regularization of improper integrals involving the eigenfunctions of the considered Sturm–Liouville problems. The variation of diverse characteristics of the normal waves in time is also investigated. It is shown that in a wedge–shaped domain, the nonstationary normal waves excited by the moving point source will be registered at the observation point before the source passes over it.
AN ACOUSTIC INVERSE PROBLEM: NUMERICAL EXPERIMENT
Authors: GILBERT R. P. , LIN ZHONGYAN
Published: November 2004

As a sequel to Refs. 1 and 2, this paper gives a numerical treatment of the inverse problem associated with the determination of the index of refraction. We show that the problem can be solved in two steps. First we must recover a function from its moments, problem (IM), which we may reformulate as a Fredholm integral equation of the first kind, problem (IE). Second we solve an inverse Goursat problem, (IG). Numerical schemes for both steps are given along with the results of some numerical experiments.
AN EVALUATION OF FINITE VOLUME DIRECT SIMULATION AND PERTURBATION METHODS IN CAA APPLICATIONS
Authors: STOKER ROBERT W. , SMITH MARILYN J.
Published: November 2004

A number of questions have emerged in the field of Computational Aeroacoustics (CAA) over the capability of applying conventional Computational Fluid Dynamics (CFD) methodologies to capture the physical attributes of acoustic fields. One of the more fundamental questions is the capability of direct simulation techniques versus perturbation techniques to capture the acoustic phenomena. This issue is the topic of this research; wherein one such methodology, an explicit four stage Runge–Kutta finite volume scheme, has been utilized for acoustic simulations using both direct simulation and perturbation approaches. The two-dimensional unsteady Euler equations are solved directly for the direct simulation methodology, while in the perturbation method the steady mean flow Euler equations are subtracted from the fully unsteady Euler equations, and the remaining perturbed equations are then solved for the acoustic flow quantities. These methodologies have been compared by applying them to a standard acoustic problem, the acoustic field of a point monopole. Emphasis has been placed on the ability of the methodology to capture the physics of the problem. The effects of dissipation, grid spacing, and amplitude have been addressed and compared for both methodologies. While both methods gave comparable results for most of the cases, the direct simulation methodology was found to have difficulties resolving small amplitude acoustic waves.
ENHANCED SCREENING OF CORE HOLES AT TRANSITION-METAL SURFACES
Authors: METHFESSEL M. , HENNIG D. , SCHEFFLER M.
Published: November 2004

Ab initio calculations based on density-functional theory were used to obtain surface core-level shifts for the 4d transition metals and silver in the initial-state model and in the full-impurity formulation, giving an unambiguous separation into initial state and screening terms. This shows that the screening of the core hole is substantially better at the surface than in the bulk for a transition metal. For Ag, an opposite and even larger effect is found, showing the central role of d-electron screening in the surface core-level shift of the transition metals.
BENZENE ADSORPTION ON Pt(111): A THEORETICAL STUDY
Authors: MINOT CHRISTIAN , VAN HOVE MICHEL A. , SOMORJAI GABOR A.
Published: November 2004

From crystal orbital calculations, benzene is found to chemisorb with nearly equal binding energy on a hollow site and on a bridge site of the Pt (111) face. The chemisorption is stronger and involves larger molecular distortions than on palladium and rhodium surfaces in agreement with experiment. On the hollow site, the benzene molecule undergoes a Kekulé distortion. On the bridge site found experimentally (with or without coadsorbed CO), the benzene molecule undergoes a local C2v distortion with long and short C-C bonds also in qualitative agreement with experiment. The favored azimuthal orientation of pure benzene coincides with that found experimentally only in the presence of CO. According to calculations, CO adsorption is found to weaken the benzene adsorption and reduce its metal-induced distortions but preserved the same orientation.
ALKALI-METAL ADSORPTION ON COPPER AND NICKEL SURFACES
Authors: DIEHL RENEE D. , MCGRATH RÓNÁN
Published: November 2004

This paper reviews most of the experimental results for the submonolayer adsorption of alkali metals on copper and nickel surfaces, with emphasis on the structural findings. Where possible, comparisons are made between the overlayers on copper and those on nickel. The goal is to point out some of the most interesting recent structural results and to move toward a general understanding of these systems. The few structural results of coadsorption of gases with alkali metals are also described.
FORMATION OF INTERFACES AND TEMPLATES IN THE Si(111)-Cr SYSTEM
Authors: PLUSNIN N.I. , GALKIN N.G. , LIFSHITS V.G. , LOBACHEV S.A.
Published: November 2004

The literature data and new data on investigation of the Si(111)-Cr system were systematized to the diagram of structural phase transitions. The ranges on this diagram give the formation conditions of various phases and reflect the mechanism of the Cr/Si (111) and CrSi 2/ Si (111) interface formation during room-temperature Cr deposition following annealing. The proofs of the multilayer surface phase formation and the data about transitions between the multilayer surface phases and bulk silicides during formation of the Cr/Si (111) and CrSi 2/ Si (111) interfaces were presented. The investigation of A- and B-type CrSi 2 templates formation was carried out. It was discovered that nucleation conditions and, in particular, the type of surface phases determine the azimuthal orientation of the epitaxial CrSi 2 islands relative to Si (111) under their nucleation. The A- and B-type CrSi 2 epitaxial films were grown by means of the template technique. The A-type CrSi 2 semiconductor film with low concentration and high mobility of holes was obtained.
XPS OBSERVATIONS OF THE ACCELERATED OXIDATION OF NIOBIUM IN THE PRESENCE OF IRON
Authors: WONG P.C. , WONG K.C. , LI Y.S. , MITCHELL K.A.R.
Published: November 2004

A NbO film (~ 8 Å thick) deposited on a gold substrate is shown by XPS to be relatively inert to a H 2/ H 2 O treatment. However, when the same treatment is made following the deposition of iron (layer ~ 12 Å thick), the NbO shows a much enhanced reactivity; it is converted to a higher oxide while the Fe converts to Fe 2 O 3. Heating this sample to 300°C under UHV conditions caused a more complete conversion of NbO to a NbO 2-like oxide, while simultaneously the Fe 2 O 3 is reduced to FeO . Further heating at 500°C yielded a pure Nb 2 O 5 film, while the FeO appears to reduce to the metallic form which then dissolves into the gold.
NEW ELECTRONIC STATES ON CLEAN Si(110)-“16×2” SURFACES
Authors: CRICENTI A. , NESTERENKO B. , PERFETTI P. , LE LAY G. , SEBENNE C.
Published: November 2004

The electronic properties of a clean Si (110)-“16×2” surface have been studied by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and surface differential reflectivity (SDR). Four surface states have been recognized by ARUPS and their dispersions have been mapped along the main symmetry lines in the surface Brillouin zone. SDR experiments revealed transitions between filled and empty surface states at ~ 1.8, 2.4, and 2.9 eV. The results are explained on the basis of a new structural model of the Si (110)-“16×2” phase.
COSEGREGATION-INDUCED MORPHOLOGICAL INSTABILITIES OF (110)- AND (111)-ORIENTED SURFACES OF RANDOM MIXING BODY-CENTERED-CUBIC ALLOYS
Authors: UEBING CHRISTIAN
Published: November 2004

Cosegregation-induced morphological instabilities of (110)- and (111)-oriented surfaces of random mixing body-centered-cubic alloys have been studied with Auger electron spectroscopy, low-energy electron diffraction, and scanning electron microscopy. Surface cosegregation has been investigated on (110)-and (111)-oriented Fe-15%Cr-N, Fe-3%V-C, Fe-3%V-N, and Fe-3%V-C, N single crystals. Cosegregation induces the faceting of the bcc(111) and (110) alloy surfaces. In all cases studied the facet orientation is {100} allowing the epitaxial stabilization of the binary and ternary surface compounds and surface precipitates CrN, VC, VN, and V(C, N). The morphological instability of the bcc(110) surface is rationalized by a missing- and added-row reconstruction model which demonstrates the formation of {100} microfacets.
CESIUM-INDUCED QUANTIZED 2D ELECTRON CHANNEL ON THE InAs(110) SURFACE
Authors: ARISTOV V. YU. , LE LAY G. , GREHK M. , ZHILIN V.M. , TALEB-IBRAHIMI A. , INDLEKOFER G. , SOUKIASSIAN P.
Published: November 2004

We present the first clear evidence of electron emission arising directly from a quantized two-dimensional electron channel from the InAs (110) surface covered by a few Cs atoms (≈ 0.01 Cs ML). Spectral features observed by photoemission spectroscopy using synchrotron radiation reveal discrete-energy electronic states resulting from quantization in the direction normal to the surface. The electron photoemission originates from the vicinities of [Formula: see text] points in the first and second surface Brillouin zones corresponding to the bottom of the conduction band. These findings are in agreement with self-consistent theoretical energy-level calculations using a jellium-like model.
XPS STUDIES FOR AN IRON-ZIRCONIUM INTERFACE IN AN OXIDIZING ENVIRONMENT
Authors: LI Y.S. , LIU W. , WONG P.C. , MITCHELL K.A.R.
Published: November 2004

A bimetallic film of iron and zirconium (thicknesses about 17 and 52 Å respectively) was deposited on a gold substrate and studied by XPS after exposing to O 2 (approximately 103 L) at room temperature, and then heating at progressively higher temperatures up to 400°C. An iron-oxide/iron/zirconiumoxide sandwich structure is present after the room-temperature exposure to O 2, and this work shows the ready transfer of O from the iron side to the zirconium side of the Fe/Zr interface. Fe migration also occurs at 220°C and above, while by 300°C this diffusion appears to cause a substantial restructuring of the ZrO 2 layer.
SPACE-CHARGE LAYERS AND SURFACE STATES AT THE SILICON/ELECTROLYTE INTERFACE
Authors: SAVIR E. , MANY A. , GOLDSTEIN Y. , WEISZ S.Z. , AVALOS J.
Published: November 2004

Pulse measurements on the silicon/electrolyte interface have been used to study space-charge layers and surface states on the (100) and (111) faces of silicon. The techniques used enable both the creation and study of space-charge layers at the semiconductor surface, ranging from large-depletion to strong-accumulation conditions. What is more important, they permit a straightforward separation of the different components of the induced charge at the silicon/electrolyte interface, so as to yield the variation of both the free-electron density in the space-charge layer and the density of occupied surface states with barrier height. The measured space-charge characteristics are in very good agreement with theory. The data in strong-accumulation layers indicate the presence of an insulating buffer layer (such as an oxide), 1–2 monolayers thick. As to surface states, we find that for CP-4 etched silicon, a discrete distribution of shallow states exists, located 0.1 eV on the (100) face and 0.14 eV on the (111) face below the conduction-band edge, with a total density of ~6×1012 cm −2. Furthermore, except for a very low continuous background, deeper surface states are absent over most of the energy gap. Addition of a minute amount of hydrofluoric acid to the indifferent electrolyte used reduces the density of the surface states by nearly two orders of magnitude. The distribution of the shallow states remains discrete but their energy position becomes somewhat deeper. It appears that Si-H bonds are formed at the Si/electrolyte interface, just as has been reported for the HF-treated free Si surface. It is very likely that the formation of such bonds leaves, on both types of surface, considerably fewer dangling bonds and hence considerably fewer surface states.
DETERMINATION OF THE OVERLAYER/SUBSTRATE REGISTRY IN Ni(1 ML)/Pt(111) BY ANGLE-SCANNED PHOTOELECTRON DIFFRACTION
Authors: SAMBI M. , PIN E. , GRANOZZI G.
Published: November 2004

The site (fcc or hcp) occupied by the atoms of a Ni ML deposited on Pt (111) is determined in this paper using angle-scanned photoelectron diffraction (PD). A full 2π MgK α-excited Ni-2p 3/2 PD pattern from 1-ML Ni deposited on Pt(111) is compared to single scattering cluster-spherical wave (SSC-SW) simulations and the agreement between experimental and theoretical data is quantified by R-factor analysis. From the present investigation it turns out that Ni atoms occupy hcp sites. In addition, the Ni-Pt distance has been estimated to be 2.5±0.1 Å.
EMPIRICAL METHODS FOR ESTIMATING THE DETONATION PROPERTIES OF ENERGETIC TNAZ MOLECULAR DERIVATIVES
Authors: LIU MIN-HSIEN , CHEN CHENG , HONG YAW-SHUN
Published: November 2004

Following the successful synthesis of the TNAZ (1,3,3-trinitroazetidine), the amine reactant is theoretically replaced to yield the hypothesized TNAZ molecular derivatives. Hybrid density-functional theory (DFT) calculation method was applied to model TNAZ and its derivatives. In this investigation, the target molecular volumes were initially obtained using the group additivity approach, and then transferred into molecular densities. The densities and the least squares estimated enthalpies of formation (ΔHf) of TNAZ, and the corresponding derivatives, were obtained and the Kamlet–Jacobs empirical equations were used to determine the related detonation velocity and detonation pressure. The simulation results reveal that four of the TNAZ molecular derivatives perform similarly to the traditionally used RDX (1,3,5-trinitro-1,3,5-triazacyclohexane). Two other derivatives outperform RDX, with performance that approach that of HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane).
Effects of chronic administration of clenbuterol on function and metabolism of adult rat cardiac muscle
Authors: Soppa Gopal K. R. , Smolenski Ryszard T. , Latif Najma , Yuen Ada H. Y. , Malik Aalya , Karbowska Joanna , Kochan Zdzislaw , Terracciano Cesare M. N. , Yacoub Magdi H.
Published: November 2004

Clenbuterol (Clen), a β2-agonist, is known to produce skeletal and myocardial hypertrophy. This compound has recently been used in combination with left ventricular assist devices for the treatment of end-stage heart failure to reverse or prevent the adverse effects of unloading-induced myocardial atrophy. However, the mechanisms of action of Clen on myocardial cells have not been fully elucidated. In an attempt to clarify this issue, we examined the effects of chronic administration of Clen on Ca2+ handling and substrate preference in cardiac muscle. Rats were treated with either 2 mg·kg−1·day−1 Clen or saline (Sal) for 4 wk with the use of osmotic minipumps. Ventricular myocytes were enzymatically dissociated. Cells were field stimulated at 0.5, 1, and 2 Hz, and cytoplasmic Ca2+ transients were monitored with the use of the fluorescent indicator indo-1 acetoxymethyl ester. Two-dimensional surface area and action potentials in current clamp were also measured. We found that in the Clen group there was significant hypertrophy at the organ and cellular levels compared with Sal. In Clen myocytes, the amplitude of the indo-1 ratio transients was significantly increased. Sarcoplasmic reticulum Ca2+ content, estimated by rapid application of 20 mM caffeine, was significantly increased in the Clen group. The action potential was prolonged in the Clen group compared with Sal. Carbohydrate contribution to the tricarboxylic cycle (Krebs cycle) flux was increased several times in the Clen group. This increase was associated with decreased expression of peroxisome proliferator-activated receptor-α. This study shows that chronic administration of Clen induces cellular hypertrophy and increases oxidative carbohydrate utilization together with an increase in sarcoplasmic reticulum Ca2+ content, which results in increased amplitude of the Ca2+ transients. These effects could be important when Clen is used in conjunction with left ventricular assist devices treatment.
Hypoxia reveals posterior thalamic, cerebellar, midbrain, and limbic deficits in congenital central hypoventilation syndrome
Authors: Macey P. M. , Woo M. A. , Macey K. E. , Keens T. G. , Saeed M. M. , Alger J. R. , Harper R. M.
Published: November 2004

Congenital central hypoventilation syndrome (CCHS) patients show deficient respiratory and cardiac responses to hypoxia and hypercapnia, despite apparently intact arousal responses to hypercapnia and adequate respiratory motor mechanisms, thus providing a model to evaluate functioning of particular brain mechanisms underlying breathing. We used functional magnetic resonance imaging to assess blood oxygen level-dependent signals, corrected for global signal changes, and evaluated them with cluster and volume-of-interest procedures, during a baseline and 2-min hypoxic (15% O2, 85% N2) challenge in 14 CCHS and 14 age- and gender-matched control subjects. Hypoxia elicited significant ( P < 0.05) differences in magnitude and timing of responses between groups in cerebellar cortex and deep nuclei, posterior thalamic structures, limbic areas (including the insula, amygdala, ventral anterior thalamus, and right hippocampus), dorsal and ventral midbrain, caudate, claustrum, and putamen. Deficient responses to hypoxia included no, or late, changes in CCHS patients with declining signals in control subjects, a falling signal in CCHS patients with no change in controls, or absent early transient responses in CCHS. Hypoxia resulted in signal declines but no group differences in hypothalamic and dorsal medullary areas, the latter being a target for PHOX2B, mutations of which occur in the syndrome. The findings extend previously identified posterior thalamic, midbrain, and cerebellar roles for normal mediation of hypoxia found in animal fetal and adult preparations and suggest significant participation of limbic structures in responding to hypoxic challenges, which likely include cardiovascular and air-hunger components. Failing structures in CCHS include areas additional to those associated with PHOX2B expression and chemoreceptor sites.
Development of DX-9065a, a novel direct factor Xa antagonist, in cardiovascular disease
Authors: Alexander John , Dyke Christopher , Harrington Robert , Becker Richard
Published: November 2004

The development of anticoagulants for treating patients with atherothrombotic disorders of the arterial circulatory system has focused, either directly or indirectly, on thrombin – a pleuripotential effector enzyme with prothrombotic and proinflammatory properties. The pivotal role of factor (f) Xa in thrombin generation, coupled with its direct cellular effects and widely recognized limitations of currently available anticoagulants, has led to the development of pharmacologic inhibitors of this important protease. The following review focuses on DX9065a – first in a class of direct, selective and reversible fXa antagonists – and its potential applications in the management of patients with cardiovascular disease.
Treatment of 51 pregnancies with danaparoid because of heparin intolerance
Authors: Kreutzenbeck Hans-Joachim , Magnani Harry , Lindhoff-Last Edelgard
Published: November 2004

Pregnant patients with acute venous thrombosis or a history of thrombosis may need alternative anticoagulation, when heparin intolerance occurs. Only limited data on the use of the heparinoid danaparoid are available in literature.We reviewed the use of danaparoid in 51 pregnancies of 49 patients identified in literature between 1981 and 2004.All patients had developed heparin intolerance (32 due to heparin-induced thrombocytopenia, 19 mainly due to heparin-induced skin rashes) and had a current and/or past history of thromboembolic complications.The initial danaparoid dose regimens ranged from 1000 to 7500 U/day administered s.c.or i.v..The median duration of danaparoid use was 10 weeks. Danaparoid was used until delivery of a healthy infant in 37 pregnancies. In the remaining 14 pregnancies it was stopped earlier, because anticoagulant treatment was no longer required (3/14) or an adverse event led to a treatment discontinuation (11/14). Four maternal bleeding events were recorded during pregnancy, delivery or postpartum, two of them were fatal due to placental problems. Three fetal deaths were recorded, all associated with maternal complications antedating danaparoid use. Danaparoid cross-reactivity was suspected in 4 HIT patients and 5 non-HIT patients with skin reactions and was confirmed serologically in one of the two HIT patients tested. In none of five fetal cord blood- and three maternal breast milksamples anti-Xa activity transfer was observed.In conclusion danaparoid can be used as an alternative antithrombotic agent in pregnant women with high thrombotic risk and intolerance to heparins.
Disturbed apoptosis of T-cells in patients with active idiopathic thrombocytopenic purpura
Authors: Andersson Per-Ola , Jacobsson Stefan , Carlsson Lena , Wadenvik Hans , Olsson Bob
Published: November 2004

Idiopathic thrombocytopenic purpura (ITP) is an organ specific autoimmune disorder in whichT-lymphocyte abnormalities have pathogenetic importance.In a DNA microarray screen of CD3+ T-lymphocytes from ITP patients and healthy controls we found an altered expression of genes associated with apoptosis, e.g. A20, caspase-8 and Bax.This together with our previous findings of increased gene expression of Fas,interferon-g and IL-2 receptor beta (IL2RB) indicated an altered activation induced cell death (AICD) of T-cells in ITP. Using a proliferation assay we found that CD3+ lymphocytes from ITP patients were significantly more resistant to dexamethasone induced suppression compared to normal lymphocytes.We also found that cultured CD3+ lymphocytes from ITP patients in remission were more susceptible to apoptosis both in the presence and absence of dexamethasone compared to cells from patient with active ITP and healthy controls, as indicated by increased staining of AnnexinV binding. Our findings suggest that apoptotic resistance of activated T-lymphocytes in patients with active ITP may lead to defective clearance of autoreactive T-lymphocytes through AICD, which might cause a continued immune destruction of platelets. Conversely, a loss of resistance to AICD in ITP patients in remission might be an important mechanism for the achievement of remission.
Scavenger Receptor Class B Type I Mediates the Selective Uptake of High-Density Lipoprotein–Associated Cholesteryl Ester by the Liver in Mice
Authors: Brundert May , Ewert Anne , Heeren Joerg , Behrendt Barbara , Ramakrishnan Rajasekhar , Greten Heiner , Merkel Martin , Rinninger Franz
Published: November 2004

Objective—High-density lipoprotein (HDL) cholesteryl esters (CE) are taken up by liver and adrenals selectively, ie, independent from particle internalization. Class B type I scavenger receptor (SR-BI) mediates this uptake in vitro. The role of SR-BI in HDL metabolism was explored in mice.

Methods and Results—Mice with a mutation in the SR-BI gene (SR-BI KO) and wild-type (WT) littermates were used. Mutants had increased HDL cholesterol. HDL was labeled with125I (protein) and [3H] (CE). After HDL injection, blood samples were drawn and finally the mice were euthanized. In WT, the plasma decay of HDL-associated [3H] is faster compared with125I and this represents whole-body selective CE uptake. In SR-BI KO, the decay of both tracers is similar, yielding no selective CE removal. In WT liver and adrenals, uptake of [3H] is higher than125I, showing selective uptake. In SR-BI KO, liver uptake of [3H] and125I are similar, proposing no selective HDL CE uptake. In SR-BI KO adrenals, selective uptake is reduced; however, even in the absence of SR-BI, this uptake is detected using WT-HDL.

Conclusions—SR-BI mediates selective uptake of HDL CE by the liver. In adrenals, an alternative mechanism or mechanisms can play a role in selective CE uptake.
Absence of Alpha-1 Antitrypsin Deficiency Alleles (
S
and
Z
) in Japanese and Korean Patients With Aneurysmal Subarachnoid Hemorrhage
Authors: Yoneyama Taku , Kasuya Hidetoshi , Akagawa Hiroyuki , Onda Hideaki , Nakajima Toshiaki , Hori Tomokatsu , Inoue Ituro , Lee Jung-Chung , Yang Tae-Ki , Kim Chul-Jin
Published: November 2004

Background and Purpose—

A possible association has been proposed for the formation of intracranial aneurysm (IA) and deficiency alleles (
S
and
Z
) of the α
1
-antitrypsin (
AAT
) gene. We extensively screened this gene in Japanese and Korean patients with aneurysmal subarachnoid hemorrhage.

Methods—

Seven allelic variants, including
S
and
Z
alleles, were genotyped by direct sequencing of genomic DNA obtained from 195 and 189 ruptured IA patients and 195 and 94 controls in Japanese and Koreans, respectively. The haplotype in phase-unknown samples was constructed with the expectation–maximization method. Differences in allelic frequencies between patients and controls were evaluated by Fisher exact test.

Results—

No significant differences in allelic frequencies were observed at all 7 variants between ruptured IA patients and controls. We could not detect the
S
and
Z
alleles of the
AAT
gene in Japanese and Korean populations.

Conclusions—

AAT
deficiency may not be a common genetic risk factor for aneurysmal subarachnoid hemorrhage in Japanese and Koreans.
Novel Mutations of the Chloride Channel Kb Gene in Two Japanese Patients Clinically Diagnosed as Bartter Syndrome with Hypocalciuria
Authors: Fukuyama Shigeru , Hiramatsu Misako , Akagi Motohiro , Higa Mutumi , Ohta Takao
Published: November 2004

Hypokalemic metabolic tubulopathy, such as in Bartter syndrome and Gitelman syndrome, is caused by the dysfunction of renal electrolyte transporters. Despite advances in molecular genetics with regard to hypokalemic metabolic tubulopathy, recent reports have suggested that the phenotype-genotype correlation is still confusing, especially in classic Bartter and Gitelman syndromes. We report here two Japanese patients who suffered from clinically diagnosed classic Bartter syndrome but who presented hypocalciuria. Hypocalciuria is generally believed to be a pathognomonic finding of NCCT malfunction. To better understand the genotype-phenotype correlation in these two cases, we screened four renal electrolyte transporter genes [Na-K-2Cl cotransporter (NKCC2), renal outer medullary K channel (ROMK), Cl channel Kb (ClC-Kb), and Na-Cl cotransporter (NCCT)] by the PCR direct sequencing method. We identified three ClC-Kb allelic variants, including two new mutations (L27R and W610X in patient 1 and a G to C substitution of a 3′ splice site of intron 2 and W610X in patient 2). We did not find any mutations in the other three genes. Our present data suggest that some ClC-Kb mutations may affect calcium handling in renal tubular cells.
Characterization of Novel Nucleoside Analogs by Electrospray Ionization Mass Spectra
Authors: Yan Liu , Xiao-Lan Chen , Juan He , Jian-Bo Hou , Ling-Bob Qu , Yu-Fen Zhao
Published: November 2004

In this paper, we synthesized a novel nucleoside analog by coupling thymine with dimethyl dicarboxylate biphenyl (DDB). The structure of the target compound was determined using 1H nuclear magnetic resonance (NMR) and electrospray ionization tandem mass spectrometry (ESI-MS/MS). The fragmentation pathways were studied in detail through ESI-MS/MS. By comparing with unsubstituted nucleosides, such as AZT, MCI, d4T and DDI, it was found that the nucleoside analog coupled with DDB would not yield the daughter ions corresponding to the fragments of the nucleoside base and arabinofuranose analogs, but would lose a neutral molecule HF and DDB easily. However, the unsubstituted nucleosides could lightly yield the fragment ions of the nucleoside base and sugar ring. Hence, electrospray ionization mass spectrometry combined with tandem mass spectrometry provides a convenient method to recognize the substituted and unsubstituted nucleosides.
A paired study of Perthes’ disease comparing conservative and surgical treatment
Authors: Kamegaya M. , Saisu T. , Ochiai N. , Hisamitsu J. , Moriya H.
Published: November 2004

We performed a paired study of mature patients with Perthes’ disease to compare the radiological results after treatment between conservatively- and surgically-treated groups. One patient was selected from each group to create the pairs for this study. Each pair was strictly matched for gender, body mass index, age at onset, stage at the first visit, necrotic area and radiological at-risk signs and each was assessed by comparing the values of six radiological measurements.

Eighteen pairs (36 hips) fitted the criteria. The radiological measurements which showed a statistically better result in the surgical groups were Mose’s method, the acetabular-head index and leg-length discrepancy. There were no statistical differences in the slope of the acetabular roof and the articulotrochanteric distance. Four hips in the conservative group were in Stulberg class II, five in class III and nine in class IV. In the surgical group, 13 were in Stulberg class II, four in class III and one in class IV.

We conclude that surgical treatment improved the sphericity of the femoral head and provided greater acetabular cover, but did not reform the acetabular roof.

It was noteworthy that a greater leg-length discrepancy and a smaller articulotrochanteric distance were not seen in the surgical group. Our study suggests that surgical treatment is preferable in patients with severe Perthes’ disease.
Supramalleolar derotation osteotomy of the tibia, with T plate fixation
Authors: Selber P. , Filho E. R. , Dallalana R. , Pirpiris M. , Nattrass G. R. , Graham H. K.
Published: November 2004

Torsional deformities of the tibia are common in children, but in the majority both the torsion and the associated disturbance of gait resolve without intervention. There are, however, a significant number of children and adults with neuromuscular disease who present with pathological tibial torsion, which may require surgical correction.

We conducted a prospective study in two centres, to investigate the outcome of supramalleolar derotation osteotomy of the tibia, using internal fixation with the AO-ASIF T plate. A range of outcome variables was collected, prospectively, for 57 patients (91 osteotomies), including thigh foot angle, foot progression angle, post-operative complications and serial radiographs. Correction of thigh foot angle and foot progression angle was satisfactory in all patients. Three major complications were recorded; one aseptic nonunion, one fracture through the osteotomy site after removal of the plate and one distal tibial growth arrest.

We found that supramalleolar derotation osteotomy of the tibia, with AO-ASIF T plate fixation is an effective method for the correction of torsional deformities of the tibia and the associated disturbances of gait in children and adults with neuromuscular disease, with a 5.3% risk of major complications.
Epidemiology of femoral fractures in children in the West Midlands region of England 1991 to 2001
Authors: Bridgman S. , Wilson R.
Published: November 2004

We have attempted to describe the epidemiology of femoral fractures in children in the West Midlands region of the National Health Service in England. Our source of data was the Regional Hospital Episode Statistics database for the years 1991-2 to 2001-2. Cases were defined as emergency hospital admissions in patients aged under 16 years, with a diagnostic code of femoral fractures in any field, and resident in the West Midlands.

Between 1991-2 and 2001-2, 3272 children aged under 16 years with femoral fractures were admitted to hospital. The crude incidence during this period decreased from 0.33 to 0.22 femoral fractures/1000/year. Those caused by traffic accidents decreased by 43%, and by falls by 29%. The peak age-gender-specific incidence (0.91/1000/year) was in two-year-old boys, and this was 50% higher than in the next highest age-gender group. In the first year of life, the incidence in boys and girls was the same. Thereafter the rate in boys exceeded that in girls, varying from 1.6 times at 11 years to 4.7 times at 14 years. Falls accounted for 49% of the fractures, varying from 77% in one-year-olds to 26% in eight-year-old children. Traffic accidents were responsible for 26% of fractures varying from 55% in ten-year-old to 2% in one-year-old children. Maltreatment was recorded in 1.3% of all cases, and in 8.5% of children under one year. Twice as many fractures were seen in May to August than in January (winter). The rates of fractures were associated with deprivation for all age-gender groups. Fractures of the shaft accounted for 58% of all fractures, varying from 70% in three-year-old to 34% in 13-year-old children.

Our findings show that there has been a decrease in the incidence of femoral fractures during the 1990s and early 2000s. Two-year-old boys had twice the rate than any other single-year age-gender group. More deprived areas had much higher rates which suggests the potential for greater prevention. A relatively low rate of maltreatment was recorded compared with that in some other studies.
Intra-operative arthrography facilitates accurate screw fixation of a slipped capital femoral epiphysis
Authors: Burke J. G. , Sher J. L.
Published: November 2004

We report the case of a 13-year-old obese child presenting with bilateral stable slipped capital femoral epiphyses, which were managed by percutaneous single screw fixation in situ under image intensifier control using arthrography.