bluuebunny/crossref_metadata_2025 huggingface dataset:
NON-FACTORIZABLE TERMS, HEAVY QUARK MASSES, AND SEMILEPTONIC DECAYS OF D AND B MESONS
Authors: VOLOSHIN M. B.
Published: July 2002

The non-factorizable terms in the operator product expansion have been recognized as one of the theoretical obstacles for precision determination of the mixing parameter Vub from semileptonic B decays. It is pointed out here that the recent CLEO data on the parameters of the heavy quark expansion λ1 and [Formula: see text], combined with a theoretical bound on λ1 strongly favor the existence of a sizeable contribution of non-factorizable terms in semileptonic decays of D mesons. Thus these terms are likely to solve the long-standing problem of the deficit of semileptonic decay rate of the D mesons, and with better data their magnitude can be determined and used in studies of the parameter Vub.
NONFACTORIZABLE CONTRIBUTIONS IN NONLEPTONIC WEAK INTERACTIONS OF K MESONS
Authors: TERASAKI K.
Published: July 2002

K→ππ, KL-KS mass difference (Δ mK) and KL→γγ(*) are studied systematically by decomposing their amplitude into a sum of factorizable and nonfactorizable ones. The former is calculated by using the naive factorization while the latter is assumed to be controlled by hadron dynamics. Nonfactorizable amplitudes for the K→ππ decays which are estimated by using a hard pion technique dominates the |ΔI| = ½ amplitude. It is seen that the naively factorized short distance term dominates ΔmK as usual since contributions of pseudoscalar-meson poles and ππ intermediate states as the nonfactorizable long distance effects interfere destructively with each other. The K*-meson pole survives in the KL→γγ decay and plays an important role in the present perspective in contrast with the existing theories which are restricted by the theory of field algebra. The form factor for the Dalitz decays of KL and their rates are compared with the existing data.
CORRELATION FUNCTIONS IN QUANTUM SPIN CHAINS AND VERTEX MODELS
Authors: MASTROPIETRO VIERI
Published: July 2002

Some correlation functions of critical models, like the anisotropic spin chain with nearest and next-to-nearest neighbor interaction, or the eight vertex model, are computed as a corollary of the study of the XYZ model in [2].
ON KOOPMAN–VON NEUMANN WAVES
Authors: MAURO D.
Published: July 2002

In this paper we study the classical Hilbert space introduced by Koopman and von Neumann in their operatorial formulation of classical mechanics. In particular we show that the states of this Hilbert space do not spread, differently from what happens in quantum mechanics. The role of the phases associated to these classical "wave functions" is analyzed in detail. In this framework we also perform the analog of the two-slit interference experiment and compare it with the quantum case.
RELATIONSHIP BETWEEN THE FERMI SURFACE AND THE SYMMETRY OF THE GAP FUNCTION IN UNCONVENTIONAL SUPERCONDUCTORS
Authors: SU GANG , SUZUKI MASUO
Published: July 2002

The relationship between the Fermi surface (FS) and the symmetry of the gap function in unconventional superconductors is argued. It is found that the shapes of the FS are indeed related to the symmetry of the superconducting gap function, and is also influenced by the next nearest-neighbor overlapping. The application of the arguments to cuprate superconductors is briefly discussed. There is observed an interesting property that Luttinger's theorem perfectly holds for various pure gap symmetries in the weak-coupling limit while it is violated for dx2 - y2- and dx2 - y2 + idxy-wave symmetries in a few cases.
METALLIC STRIPES IN OXYGEN DOPED La2CuO4
Authors: DI CASTRO DANIELE , COLAPIETRO MARCELLO , BIANCONI GINESTRA
Published: July 2002

We have investigated the charge ordering in an oxygen doped La 2 CuO 4 crystal by diffuse high-resolution x-ray diffraction using synchrotron radiation. The micro-strain ε in the CuO 2 plane is close to the micro-strain ε0 for the formation of static charge ordered phases. The crystal shows the co-existence of a first phase with an insulating crystal of charge strings and a second superconducting phase of "supestripes". The first insulating phase is due to charges at the critical doping 1/8 self trapped into a crystal of ordered strings of finite length (~60 Å) and a commensurate period of 4 lattice units. The superconducting phase shows diffuse diffraction peaks with short coherence length due to fluctuations of stripes with an incommensurate period of about 4.8 unit cells and length longer than 500 Å.
SINGLE-PARTICLE SPECTRAL WEIGHT IN THE ANTIFERROMAGNETIC STRIPE PHASE
Authors: WRÓBEL PIOTR , EDER ROBERT
Published: July 2002

Recent angle-resolved photoemission (ARPES) studies of the La2-xSrxCuO4 (LSCO) compound provide a new piece of information on the evolution of the electronic structure in cuprate systems with doping. Our aim is to analyze that evolution by means of the spin polaron approach based on the string picture. We study the motion of a single mobile hole in the stripe phase of a doped antiferromagnet. Holes within the stripes are taken to be static, undoped antiferromagnetic domains between hole stripes are assumed to have an alternating staggered magnetization, as it has been suggested by neutron scattering experiments. The system is described by the t-t′-t′′-J model with realistic parameters and we compute the single particle spectral density. In this paper we concentrate on the filling level 1/12. Theoretical spectra and results of measurements performed at that hole concentration show reasonable agreement. In both cases we observe, along the direction (0,0)→(π,0), "splitting" of the spectrum and formation of new low energy states around (π,0). This splitting is also observed in the direction (0,π)→ (π,π). The spectra along the direction (π,0)→ (π,π) are much broader. That hinders us in assignment of any band for some range of k points in that direction. Finally, the spectra along the direction (0,0)→ (π,π) are very broad and it is also practically impossible to distinguish any sharp band.
PHASE ORDERING DYNAMICS OF ϕ4 THEORY WITH HAMILTONIAN EQUATIONS OF MOTION
Authors: ZHENG B. , LINKE V. , TRIMPER S.
Published: July 2002

Phase ordering dynamics of the (2+1)- and (3+1)-dimensional ϕ4 theory with Hamiltonian equations of motion is investigated numerically. Dynamic scaling is confirmed. The dynamic exponent z is different from that of the Ising model with dynamics of model A, while the exponent λ is the same.
INFINITE NUCLEAR MATTER ON THE LIGHT FRONT: A MODERN APPROACH TO BRUECKNER THEORY
Authors: MILLER G. A.
Published: July 2002

Understanding an important class of experiments requires that light-front dynamics and the related light cone variables k+, k⊥ be used. If one uses k+=k0+k3 as a momentum variable the corresponding canonical spatial variable is x-=x0-x3 and the time variable is x0+x3. This is the light front (LF) approach of Dirac. A relativistic light front formulation of nuclear dynamics is developed and applied to treating infinite nuclear matter in a method which includes the correlations of pairs of nucleons. This is light front Brueckner theory.
ANISOTROPIC STEP, SURFACE CONTACT, AND AREA WEIGHTED DIRECTED WALKS ON THE TRIANGULAR LATTICE
Authors: OPPENHEIM A. C. , BRAK R. , OWCZAREK A. L.
Published: July 2002

We present results for the generating functions of single fully-directed walks on the triangular lattice, enumerated according to each type of step and weighted proportional to the area between the walk and the surface of a half-plane (wall), and the number of contacts made with the wall. We also give explicit formulae for total area generating functions, that is when the area is summed over all configurations with a given perimeter, and the generating function of the moments of heights above the wall (the first of which is the total area). These results generalise and summarise nearly all known results on the square lattice: all the square lattice results can be obtaining by setting one of the step weights to zero. Our results also contain as special cases those that already exist for the triangular lattice. In deriving some of the new results we utilise the Enumerating Combinatorial Objects (ECO) and marked area methods of combinatorics for obtaining functional equations in the most general cases. In several cases we give our results both in terms of ratios of infinite q-series and as continued fractions.
FIELD EMISSION FROM NANOSTRUCTURE CARBON FILMS
Authors: LIM SUNG HOON , KIM HONG SIK , JANG JIN , LEE CHOONG HUN
Published: July 2002

We studied the field emission properties of carbon nanostructure, which comprised of high density carbon nanotips on Si. These carbon nanotips are grown on metal coated Si by a high density plasma chemical vapor deposition (HDPCVD) using an inductively coupled plasma. The emission current increases with increasing the growth temperature. They exhibited an emission current density of 1 mA/cm 2 at a field of 1.95 V /μ m when the growth temperature was 700°C. We developed high brightness field emission lamps using the carbon nanotips.
THE STUDY OF THE MAGNETIC MULTIVALUED RECORDING AT THE EXIST OF DIPOLAR INTERACTION
Authors: LI HAIJIN
Published: July 2002

A classical method is established to study the conditions for the magnetic multivalued (MMV) recording at the exist of dipolar interaction. In order to simplify the problem, we adopt the approximation that the spins in the same layer have the same direction. With this approximation, a set of nonlinear equations is derived, from which what area of parameters is suitable for the MMV recording can be decided. We use this method to detailedly discuss the two magnetic layers system that can be solved analytically. For this system, the area of parameters, in which the MMV recording can be realized, is presented. We find that a small value of antiferromagnetic coupling between layers will be advantage to MMV recording. And the perpendicular anisotropy must be large enough to overcome the in-plane anisotropy caused by dipolar interaction. We also use the method of spin dynamics to simulate the system. The results show that the theory is applicable.
SPECTRAL FLOW OF HERMITIAN WILSON–DIRAC OPERATOR AND THE INDEX THEOREM IN ABELIAN GAUGE THEORIES ON FINITE LATTICES
Authors: FUJIWARA T.
Published: July 2002

The spectral flows of the hermitian Wilson-Dirac operator for a continuous family of abelian gauge fields connecting different topological sectors are shown to have a characteristic structure leading to the lattice index theorem. The index of the overlap Dirac operator is shown to coincide with the topological charge for a wide class of gauge field configurations. It is also argued that in two dimensions the eigenvalue spectra for some special but nontrivial background gauge fields can be described by a set of universal polynomials and the index can be found exactly.
CORRELATIONS WEAK AND STRONG: DIVERS GUISES OF THE TWO-DIMENSIONAL ELECTRON GAS
Authors: MACDONALD A. H.
Published: July 2002

The three-dimensional electron-gas model has been a major focus for many-body theory applied to the electronic properties of metals and semiconductors. Because the model neglects band effects, whereas electronic systems are generally more strongly correlated in narrow band systems, it is most widely used to describe the qualitative physics of weakly correlated metals with unambiguous Fermi liquid properties. The model is more interesting in two space dimensions because it provides a quantitative description of electrons in quantum wells and because these can form strongly correlated many-particle states. We illustrate the range of possible many-particle behaviors by discussing the way correlations are manifested in 2D tunneling spectroscopy experiments.
BOUNDARY POTENTIAL EFFECT FOR THE KONDO PROBLEM IN A LUTTINGER LIQUID: INTEGRABLE CASE
Authors: WANG YUPENG , JIN DUO , PU FU-CHO
Published: July 2002

To study the impurity potential effect to the Kondo problem in a Luttinger liquid, we introduce a model of ferromagnetic single-impurity Kondo problem in a multi-band one-dimensional δ-potential Fermi gas, which is exactly solvable for a special Kondo coupling constant via Bethe ansatz. It is found that the boundary potential modifies the local moment seriously due to the charge-spin coupling and the strong backward scattering off the impurity, and thus strongly affects the fixed point of the system. Generally, their is a residual entropy for the ground state which depends on the strength of the boundary potential. In addition, the tunneling effect through the impurity and the breakdown of the open boundary induced by the impurity are also discussed.
TRANSMISSION PROPERTIES OF ELECTRONS IN A T-TYPE OPENED QUANTUM WAVEGUIDE WITH INHOMOGENEOUS MAGNETIC FIELDS
Authors: CHEN KE-QIU , GU BEN-YUAN , LIN YU-KAE , CHUU D. S.
Published: July 2002

We calculate the quantum-mechanical transmission of electrons in a T-shaped opened quantum waveguide (TOQW) subjected to an inhomogeneous magnetic field perpendicular to the TOQW plane with the use of the mode-matching technique. An electron incident through one branch of the waveguide can travel into the other two channels in the quantum ballistic regime. We find that transmission coefficients in two channels exhibit quite difference from each other and depend sensitively on geometric parameters and magnetic configurations. Sharp peaks with unity amplitude and deep dips are observed in transmission spectrum as a function of the Fermi energy of the incident electrons at some high fields. We also study the variation of transmission with magnetic field and find that the transmission exhibits various patterns such as step drop, deep dips, wide valley, large oscillations, or without any structure, sensitively depending on the incident electron energy and magnetic confinement configurations. It is expected that by applying inhomogeneous magnetic fields to the TOQW with appropriate magnetic configuration one may provide an available way to control transmission property of the TOQW to match practical requirements in devices.
STRIPES, CARRIERS, PSEUDOGAP, AND SUPERCONDUCTIVITY IN THE CUPRATES
Authors: ASHKENAZI JOSEF
Published: July 2002

The electronic structure of the high-Tc cuprates is studied on the basis of both "large-U" and "small-U" orbitals. A striped structure is obtained, and three types of carriers: polaron-like "stripons" carrying charge, "quasielectrons" carrying charge and spin, and "svivons" carrying spin and lattice distortion. Anomalous properties of the cuprates and specifically their transport properties are derived. Pairing is found to result from transitions between pair states of quasielectrons and stripons through the exchange of svivons. The pairing results in superconductivity when the stripons conduction is coherent, and in a pseudogap phase when it is not.
STUDY OF THE OPTICAL ABSORPTION OF Cu CLUSTERS IN THE Cu/ZnO SYSTEM
Authors: VAZQUEZ-CUCHILLO O. , BAUTISTA-HERNANDEZ A. , PAL U. , MEZA-MONTES L.
Published: July 2002

Optical absorption of Cu/ZnO composite films grown by r.f. sputtering are presented. We calculated the optical absorption spectra based on a colloidal-copper model with mean-free-path (MFP) and size corrections to the bulk dielectric constant. All effective-medium theory is used to analyze the presence of the coated nanoparticles and the ZnO matrix. The parameters of the model are fitted to reproduce the experimental spectra.
A NEW PHENOMENOLOGY FOR THE DISORDERED MIXED PHASE
Authors: MENON GAUTAM I.
Published: July 2002

A universal phase diagram for type-II superconductors with weak point pinning disorder is proposed. In this phase diagram, two thermodynamic phase transitions generically separate a "Bragg glass" from the disordered liquid. Translational correlations in the intervening "multi-domain glass" phase are argued to exhibit a significant degree of short-range order. This phase diagram differs significantly from the currently accepted one, but provides a more accurate description of experimental data on high and low-T c materials, simulations and current theoretical understanding.
MORE EVIDENCES FOR DOUBLE EXCHANGE-RELATED INTERFACIAL TUNNELING IN NANOSTRUCTURED PEROVSKITE La0.82Sr0.18MnO3
Authors: ZHANG NING , WANG WEI
Published: July 2002

The intergranular tunneling in nanostructured perovskites La 0.82 Sr 0.18 MnO 3 has been investigated. A series of experimental evidences including magnetization, heat capacity, structure distortions and magnetoresistance, have been given to demonstrate that the intergranular tunneling originates from an interfacial effect associated with the double exchange interaction, and the related tunnel-type magnetoresistance results from a field-induced change of interfacial magnetic configuration.
A SPECIAL MODEL ON OPTICAL ABSORPTION OF AMORPHOUS GaAs IN THE FAR-INFRARED RANGE
Authors: GRADO-CAFFARO M. A. , GRADO-CAFFARO M.
Published: July 2002

The optical absorption coefficient of amorphous GaAs for the far-infrared range is calculated. Results from this calculation are compared with experimental data and with other theoretical results. In our approach, spectrum contribution corresponding to structural disorder is neglected. Moreover, total electronic density of states is determined.
CONTINUATION FOR NONLINEAR ELLIPTIC PARTIAL DIFFERENTIAL EQUATIONS DISCRETIZED BY THE MULTIQUADRIC METHOD
Authors: FEDOSEYEV A. I. , FRIEDMAN M. J. , KANSA E. J.
Published: July 2002

The Multiquadric Radial Basis Function (MQ) Method is a meshless collocation method with global basis functions. It is known to have exponentional convergence for interpolation problems. We descretize nonlinear elliptic PDEs by the MQ method. This results in modest-size systems of nonlinear algebraic equations which can be efficiently continued by standard continuation software such as AUTO and CONTENT. Examples are given of detection of bifurcations in 1D and 2D PDEs. These examples show high accuracy with small number of unknowns, as compared with known results from the literature.
CALCULATION AND BIFURCATION OF FLUID FILM WITH CAVITATION BASED ON VARIATIONAL INEQUALITY
Authors: ZHANG JIAZHONG
Published: July 2002

The variational inequality principle originated from a class of elliptic obstacle problem applied to the prediction of cavitation in the fluid film bearing and squeeze film damper, and the finite element method has been used to discretize the resulting elliptic variational inequality. Based on the Taylor series, the Jacobian matrix of film force with respect to location and velocity of journal and bearing house has been constructed, and it can be obtained from resolving a set of partial differential equations. An iteration algorithm based on the complementary property of the elliptic variational inequality has been also constructed to determine the rupture boundary, namely, free boundary.

On the basis of the fixed-interface eigen-mode and quasi-static modes, a method is constructed to condense the system. Furthermore, the Poincaré map is introduced to discretize the continuous flow, and the fixed point in the Poincaré section is the periodic solution and a method for calculating the Floquet multipliers is also constructed by resolving two sets of secondary ordinary differential equations in the form of matrix. The long-term dynamic behaviors and bifurcation of imbalance response of a rotor dynamic system, amounted in finite length fluid film bearings with squeeze film dampers in series, has been investigated based on the computation method mentioned above. In addition to the above, the influence of the truncation of mode series on the accuracy of solution in nonlinear dynamic system has been investigated tentatively by the comparison between mode series truncations, and the result obtained from the condensation method has been compared with the result obtained from the direct integration. All the results show that the method presented in this paper is effective in the prediction of cavitation in the fluid film and the bifurcation analysis of the system with fluid film.
FRACTALS, SEMIFRACTALS AND MARKOV OPERATORS
Authors: LASOTA A. , MYJAK J.
Published: July 2002

The paper contains a review of results concerning the theory of iterated function systems (IFS) acting on an arbitrary metric space (without any assumption of compactness). First we discuss IFS acting on sets and we define fractals and semifractals using topological limits. Then we study IFS with probabilities acting on measures and we show a relationship with the theory of Markov operators and Markov processes.
PARAMETER RENORMALIZATION FOR ASYMMETRICALLY COUPLED MAPS
Authors: MATSUBA IKUO
Published: July 2002

The parameter renormalization group method proposed in the previous papers is applied to the case where the system is described by two coupled one-dimensional maps to investigate the critical behavior of periodic-doubling. Particular attention is given to the asymmetric case where the maps have different bifurcation parameters. The first-order parameter renormalization equations are found to give qualitatively correct critical behaviors by comparing with numerical simulation. Furthermore, using the parameter reduction technique, it is found that critical behaviors of the coupled maps having a set of parameters on several critical lines are equivalent to those for the corresponding uncoupled maps.
ON A CODIMENSION-THREE UNFOLDING OF THE INTERACTION OF DEGENERATE HOPF AND PITCHFORK BIFURCATIONS
Authors: ALGABA A. , FREIRE E. , GAMERO E. , RODRÍGUEZ-LUIS A. J.
Published: July 2002

We consider a codimension-three unfolding for the Hopf-zero linear degeneracy with ℤ2-symmetry, in the presence of an additional nonlinear degeneracy. In fact, we assume that the term ρ3 in the radial component of the normal form vanishes.

We find up to 12 distinct topological equivalence classes for the unfolding, obtaining a rich variety of dynamical and bifurcation behaviors. In particular, we point out the existence of two codimension-two bifurcations of periodic orbits, and also of Arnold's resonance zones with bananas and banana split shapes.

The results obtained are applied to a modified van der Pol-Duffing electronic circuit. Numerical continuation of the bifurcation curves in the vicinity of the degenerate Hopf-pitchfork shows agreement with the analysis.
ON THE EFFECT OF APEX GEOMETRY ON WALL SHEAR STRESS AND PRESSURE IN TWO-DIMENSIONAL MODELS OF ARTERIAL BIFURCATIONS
Authors: HALJASMAA I. V. , ROBERTSON A. M. , GALDI G. P.
Published: July 2002

There is strong evidence to support the hypothesis that vascular geometry plays an important role in the initiation and development of cerebral aneurysms (see e.g. Refs. 24, 40 and 41) as well as other vascular diseases (see e.g. Refs. 25, 31 and 35) through its influence on hemodynamics. Cerebral aneurysms are nearly always found at arterial bifurcations in and near the circle of Willis.42 It is commonly believed that the cause of initiation and development of cerebral aneurysms is at least indirectly related to the effect of hemodynamic wall pressure and shear stress on the arterial tissue at arterial bifurcations (see e.g. Refs. 24, 39–41 and 44). In this work, we use analytical and numerical approaches to investigate the hypothesis that local geometric factors can have a significant impact on the magnitude and spatial gradients of wall pressure and shear stress at the apex of arterial bifurcations. We consider steady flow of incompressible, Newtonian fluids. We find that sharp corners such as those at arterial bifurcations and the juncture between grafted vessels can be a source of localized high wall pressure and shear stress. In fact, it can be shown analytically that perfectly sharp corners (zero radius of curvature) will lead to unbounded magnitudes of shear stress and pressure.26 Significantly, the unboundedness of the pressure and shear stress at perfectly sharp corners is unrelated to the fluid inertia. Whereas for zero radius of curvature, both the maximum pressure and shear stress occur at the apex; for nonzero radius of curvature, the pressure maximum is found at the apex, the shear stress is zero at the apex, and the shear stress maximum shifts to the lateral sides of the bifurcation. These results show that arterial bifurcations should not be idealized as perfectly sharp for studies of initiation and development of cerebral aneurysms.
THE LIFSHITZ–SLYOZOV EQUATION WITH ENCOUNTERS
Authors: LAURENÇOT PHILIPPE
Published: July 2002

The Lifshitz–Slyozov theory of coarsening in alloys describes the time evolution of the sizes of the grains of a new phase growing by mass transfer from a supersaturated solid solution. When the encounters between the grains are taken into account, the volume distribution function of the grains obeys a transport equation with a nonlocal nonlinearity and an integral source term. Global existence of solutions is proved for a large class of data including the ones derived by Lifshitz and Slyozov.
MULTIFRACTALITY IN MULTIPARTICLE PRODUCTION AT HIGH ENERGIES
Authors: HASAN R. , MOHIB-UL HAQ M. , ISLAM SAIFUL
Published: July 2002

We apply Takagi methodology to study the multifractal behavior of shower particles produced in 12 C -Em collisions at 3.6 A GeV and p-Em collisions at 400 GeV. The multiplicity moments are found to have a power law dependence on the mean multiplicity in the varying bin sizes for different nuclear targets. The values of the generalized dimensions are evaluated and found to decrease with q, thereby supporting multifractality in multiparticle production. The values of the multifractal specific heat are also evaluated for our data and for collisions of other heavy ions. We find that the multifractal specific heat seems to have a universal value (~1/4) that does not depend on the type of ions and their energy.
PION CONDENSATION BASED ON A RELATIVISTIC DESCRIPTION OF PARTICLE-HOLE AND DELTA-HOLE EXCITATIONS
Authors: NAKANO MASAHIRO , TATSUMI TOSHITAKA , LIU LIANG-GANG , MATSUURA HIROYUKI , NAGASAWA TAISUKE , MAKINO KEN-ICHI , TUCHITANI KUNITO , SAKAMOTO KATSUAKI , IWASAKI YOSITAKA , KOUNO HIROAKI , HASEGAWA AKIRA
Published: July 2002

The critical density of neutral pion condensation is reinvestigated based on the relativistic framework and compared with nonrelativistic results. The particle-hole and delta-hole polarizations of the pion selfenergy are calculated in the relativistic way by using a new set of Landau–Migdal parameters derived from recent experimental data. It is concluded that the use of relativistic particle-hole and delta-hole excitations for the pion selfenergy increases the critical density, but still leads to condensation for densities from two to three times the normal nuclear matter density within the random phase approximation.
FREQUENCY INDEPENDENT EVOLUTIONARY MODELS
Authors: APALOO JOSEPH
Published: July 2002

Using general classes of evolutionary models in which fitnesses are frequency independent and density dependent, we show that a phenotype is an ESS if and only if it is a NIS. This result is seen to hold in single species and multi species evolutionary models with and without structure. Frequency independent and density dependent evolutionary models are thus more likely to attain an ESS.
STATISTICAL AND LINGUISTIC FEATURES OF DNA SEQUENCES
Authors: HAVLIN S. , BULDYREV S.V. , GOLDBERGER A.L. , MANTEGNA R.N. , PENG C.-K. , SIMONS M. , STANLEY H.E.
Published: July 2002

We present evidence supporting the idea that the DNA sequence in genes containing noncoding regions is correlated, and that the correlation is remarkably long range—indeed, base pairs thousands of base pairs distant are correlated. We do not find such a long-range correlation in the coding regions of the gene. We resolve the problem of the “non-stationarity” feature of the sequence of base pairs by applying a new algorithm called Detrended Fluctuation Analysis (DFA). We address the claim of Voss that there is no difference in the statistical properties of coding and noncoding regions of DNA by systematically applying the DFA algorithm, as well as standard FFT analysis, to all eukaryotic DNA sequences (33 301 coding and 29 453 noncoding) in the entire GenBank database. We describe a simple model to account for the presence of long-range power-law correlations which is based upon a generalization of the classic Lévy walk. Finally, we describe briefly some recent work showing that the noncoding sequences have certain statistical features in common with natural languages. Specifically, we adapt to DNA the Zipf approach to analyzing linguistic texts, and the Shannon approach to quantifying the “redundancy” of a linguistic text in terms of a measurable entropy function. We suggest that noncoding regions in plants and invertebrates may display a smaller entropy and larger redundancy than coding regions, further supporting the possibility that noncoding regions of DNA may carry biological information.
SMOOTHING DIMENSIONS FOR TIME SERIES CHARACTERIZATION
Authors: MUNTEANU FLORIN , IOANA CRISTIAN , ŞUŢEANU CRISTIAN , CREŢU EDMOND
Published: July 2002

The paper refers to a recently introduced fractal signal analysis method, which relies on scaling properties of signal parameters regarding the cutoff frequency used to smoothen the signal’s graph. The relations between the smoothing dimensions and other exponents (fractal dimension df, power spectrum exponent ß, Hurst exponent H) are determined theoretically and tested by numerical experiments.
LONG RANGE ORDER IN ULTRATHIN Pt–Co(111) ALLOYS
Authors: SANTIS M. DE , BAUDOING-SAVOIS R. , DOLLE P. , SAINT-LAGER M. C. , GAUTHIER Y.
Published: July 2002

Long range order (LRO) in ultrathin Pt–Co films was studied by surface X-ray diffraction (XRD). Several fcc alloys of nanometric thickness were grown in situ by annealing at 460°C Co layers deposited onto a Pt(111) single crystal. Superstructure reflections were observed, which agreed with the extinction rules of either the L1 2 or the L1 0 chemically ordered bulk phases. The relationship between their structure factor and the atomic scattering factors was found with anomalous scattering performed near both Pt L III and Co K edges. This method is very promising for studies of surface alloying. The films were also studied in real time during annealing. They evolved in a quite different way, depending on the initial Co thickness, but LRO always occurred by heating above 400°C. At this temperature the films became Pt-rich, with a stoichiometry close to Pt 60 Co 40. We did not succeed in obtaining long range chemical order in a Co-rich alloy by annealing a Co/Pt(111) deposit, contrary to what happens in films grown by codeposition.
MORPHOLOGY, STRAIN AND MICROSTRUCTURE INTERRELATION IN Si-ON-SAPPHIRE HETEROSTRUCTURE
Authors: GARTSTEIN E. , MOGILYANSKI D. , METZGER H.
Published: July 2002

The interfacial region at the substrate, the morphology of the interface and the surface were studied for a number of Si-on-saphire (SOS) samples using X-ray scattering techniques, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). A strained interfacial layer is formed in this high misfit system. The dislocations created in this layer and at the interfacial steps accommodate the elastic strain buildup. The misfit relaxation is accompanied by the misorientation of the epilayer with respect to the substrate, which itself depends on the substrate miscut parameters and the thickness of the epilayer. The observed azimuthal rotation of the epilayer miscut is attributed to the effect of the anisotropic microtwinning evolving with the increasing epilayer thickness. This azimuthal rotation is reflected by the step morphology on the surface of the epilayers.
The Second Toe Plantar Flap for Finger Reconstruction
Authors: Slattery Philip
Published: July 2002

A new microvascular flap from the plantar aspect of the second toe is described. The flat is usually cutaneous, but it may also include nerve and tendon. It is ideal for finger reconstruction and its use and versatility is illustrated in five cases.
HERBERT SCREW FIXATION FOR THE TREATMENT OF SCAPHOLUNATE LIGAMENT RUPTURE
Authors: Filan Susan L. , Herbert Timothy J.
Published: July 2002

Complete rupture of the scapholunate ligament was treated by open reduction, ligament repair and internal splintage with a Herbert bone screw. After an average of 12 months, the screw was removed to allow full loading of the repair. In 33 procedures, there were 22 good and 11 poor results. In five cases with a poor outcome, the screw pulled or fractured out of the scaphoid or lunate. Grip and range of wrist motion improved in patients with a good outcome, and repair of the ligament was noted at all revision and open screw removal surgeries. A comparison of the good and poor results leads us to recommend this technique for patients with relatively recent injuries and light to moderate activity levels. Longstanding injuries and heavy occupational wrist loading led to poorer results.
PATELLOFEMORAL JOINT COMPRESSIVE FORCES DURING BACKWARD AND FORWARD RUNNING AT THE SAME SPEED
Authors: Sussman Donald H. , Alrowayeh Hesham , Walker Martha L.
Published: July 2002

A previous study found that the patellofemoral joint compressive force (PFJRF) during backward running was less than during forward running at a self-selected speed. Therefore, the purpose of this study was to compare the patellofemoral joint compressive forces during backward and forward running at the same speed. Ten runners (four females, six males) between the ages of 20–25 (X=22.25, SD=2.25) ran in backward and forward directions at a very slow speed of 2.3 mph (1.0 ms-1). Using a mathematical model of patellofemoral joint that does not assume equal forces of the quadriceps and patellar tendon, the PFJRFs during the very slow backward and forward running were calculated. Results showed that the PFJRF and knee extensor moment during backward and forward running were similar. The PFJRF and knee extensor moment were 3.51 BW and 144.52 Nm, respectively, during the very slow backward running, and 3.41 BW and 141.60 Nm, respectively, during the very slow forward running. In conclusion, slow backward and forward running put similar compressive forces on the patellofemoral joint. Moreover, backward running does not protect the patellofemoral joint from higher compression forces, but very slow speed does.
ASPIRATION-BASED REINFORCEMENT LEARNING IN REPEATED INTERACTION GAMES: AN OVERVIEW
Authors: BENDOR JONATHAN , MOOKHERJEE DILIP , RAY DEBRAJ
Published: July 2002

In models of aspiration-based reinforcement learning, agents adapt by comparing payoffs achieved from actions chosen in the past with an aspiration level. Though such models are well-established in behavioural psychology, only recently have they begun to receive attention in game theory and its applications to economics and politics. This paper provides an informal overview of a range of such theories applied to repeated interaction games. We describe different models of aspiration formation: where (1) aspirations are fixed but required to be consistent with longrun average payoffs; (2) aspirations evolve based on past personal experience or of previous generations of players; and (3) aspirations are based on the experience of peers. Convergence to non-Nash outcomes may result in either of these formulations. Indeed, cooperative behaviour can emerge and survive in the long run, even though it may be a strictly dominated strategy in the stage game, and despite the myopic adaptation of stage game strategies. Differences between reinforcement learning and evolutionary game theory are also discussed.
A BASIS OF THE BASIC $\mathfrak{sl} ({\bf 3}, {\mathbb C})^~$-MODULE
Authors: MEURMAN ARNE , PRIMC MIRKO
Published: July 2002

J. Lepowsky and R. L. Wilson initiated the approach to combinatorial Rogers–Ramanujan type identities via the vertex operator constructions of representations of affine Lie algebras. In this approach the first new combinatorial identities were discovered by S. Capparelli through the construction of the level 3 standard [Formula: see text]-modules. We obtained several infinite series of new combinatorial identities through the construction of all standard [Formula: see text]-modules; the identities associated to the fundamental modules coincide with the two Capparelli identities. In this paper we extend our construction to the basic [Formula: see text]-module and, by using the principal specialization of the Weyl–Kac character formula, we obtain a Rogers–Ramanujan type combinatorial identity for colored partitions. The new combinatorial identity indicates the next level of complexity which one should expect in Lepowsky–Wilson's approach for affine Lie algebras of higher ranks, say for [Formula: see text], n ≥ 2, in a way parallel to the next level of complexity seen when passing from the Rogers–Ramanujan identities (for modulus 5) to the Gordon identities for odd moduli ≥7.
MODELING SEGMENTATION VIA GEOMETRIC DEFORMABLE REGULARIZERS, PDE AND LEVEL SETS IN STILL AND MOTION IMAGERY: A REVISIT
Authors: SURI JASJIT , WU DEE , REDEN LAURA , GAO JIANBO , SINGH SAMEER , LAXMINARAYAN SWAMY
Published: July 2002

Partial Differential Equations (PDEs) have dominated image processing research recently. The three main reasons for their success are: first, their ability to transform a segmentation modeling problem into a partial differential equation framework and their ability to embed and integrate different regularizers into these models; second, their ability to solve PDEs in the level set framework using finite difference methods; and third, their easy extension to a higher dimensional space.

This paper is an attempt to survey and understand the power of PDEs to incorporate into geometric deformable models for segmentation of objects in 2D and 3D in still and motion imagery. The paper first presents PDEs and their solutions applied to image diffusion. The main concentration of this paper is to demonstrate the usage of regularizers in PDEs and level set framework to achieve the image segmentation in still and motion imagery. Lastly, we cover miscellaneous applications such as: mathematical morphology, computation of missing boundaries for shape recovery and low pass filtering, all under the PDE framework. The paper concludes with the merits and the demerits of PDEs and level set-based framework for segmentation modeling. The paper presents a variety of examples covering both synthetic and real world images.
INFORMATION TRANSFER RATE OF NEURONS: STOCHASTIC RESONANCE OF SHANNON'S INFORMATION CHANNEL CAPACITY
Authors: KISH LASZLO B. , HARMER GREGORY P. , ABBOTT DEREK
Published: July 2002

The information channel capacity of neurons is calculated in the stochastic resonance region using Shannon's formula. This quantity is an effective measure of the quality of signal transfer, unlike the information theoretic calculations previously used, which only characterize the entropy of the output and not the rate of information transfer. The Shannon channel capacity shows a well pronounced maximum versus input noise intensity. The location of the maximum is at a higher input noise level than has been observed for classical measures, such as signal-to-noise ratio.
Experiments with a component theory of probabilistic information retrieval based on single terms as document components
Authors: Kwok K. L.
Published: July 2002

A component theory of information retrieval using single content terms as component for queries and documents was reviewed and experimented with. The theory has the advantages of being able to (1) bootstrap itself, that is, define initial term weights naturally based on the fact that items are self relevent; (2) make use of within-item term frequencies; (3) account for query-focused and document-focused indexing and retrieval strategies cooperatively; and (4) allow for component-specific feedback if such information is available. Retrieval results with four collections support the effectiveness of all the first three aspects, except for predictive retrieval. At the initial indexing stage, the retrieval theory performed much more consistantly across collections than croft's model and provided results comparable to Salton's tf*idf approach. An inverse collection term frequency (ICTF) formula was also tested that performed much better than the inverse document frequency (IDF). With full feedback retrospective retrieval, the component theory performed substantially better than Croft's, because of the highly specific nature of document-focused feedback. Repetitive retireval results with partial relevance feedback mirrored those for the retrospective. However, for the important case of predictive retrieval using residual ranking, results were not unequivocal.
Performance bounds on parallel self-initiating discrete-event simulations
Authors: Nicol David M.
Published: July 2002

This paper considers the use of massively parallel architectures to execute discrete-event simulations of what we term “self-initiating” models. A logical process in a self-initiating model schedules its own state reevaluation times, independently of any other logical process, and sends its new state to other logical processes following the reevaluation. Our interest is in the effects of that communication on synchronization. Using a model that idealizes the communication topology of a simulation, we consider the performance of various synchronization protocols by deriving upper and lower bounds on optimal performance, upper bounds on Time Warp's performance, and lower bounds on the performance of a new consevative protocol. Our analysis of Time Warp includes some of the overhead costs of state saving and rollback; the effects of propogating rollbacks are ignored. The analysis points out sufficient conditions for the conservitive protocol to outperform Time Warp. The analysis also quantifies the sensitivity of performance to message fanout, lookahead ability, and the probability distributions underlying the simulation.
The complexity of operations on a fragmented relation
Authors: Meghini C. , Thanos C.
Published: July 2002

Data fragmentation is an important aspect of distributed database design, in which portions of relations, tailored to the specific needs of local applications, are defined to be further allocated to the sites of the computer network supporting the database system. In this paper we present a theory of fragmentation with overlapping fragments to study the complexity of the problems involved in checking the completeness of a fragmentation schema and in querying and updating a fragmented relation. We analyze these problems from the complexity viewpoint and present sound and complete algorithms for their solution.
Principles and realization strategies of multilevel transaction management
Authors: Weikum Gerhard
Published: July 2002

One of the demands of database system transaction management is to achieve a high degree of concurrency by taking into consideration the semantics of high-level operations. On the other hand, the implementation of such operations must pay attention to conflicts on the storage representation levels below. To meet these requirements in a layered architecture, we propose a multilevel transaction management utilizing layer-specific semantics. Based on the theoretical notion of multilevel serializability, a family of concurrency control strategies is developed. Suitable recovery protocols are investigated for aborting single transactions and for restarting the system after a crash. The choice of levels involved in a multilevel transaction strategy reveals an inherent trade-off between increased concurrency and growing recovery costs. A series of measurements has been performed in order to compare several strategies. Preliminary results indicate considerable performance gains of the multilevel transaction approach.
An accurate elementary mathematical library for the IEEE floating point standard
Authors: Gal Shmuel
Published: July 2002

The algorithms used by the IBM Israel Scientific Center for the elementary mathematical library using the IEEE standard for binary floating point arithmetic are described. The algorithms are based on the “accurate tables method.” This methodology achieves high performance and produces very accurate results. It overcomes one of the main problems encountered in elementary mathematical functions computations: achieving last bit accuracy. The results obtained are correctly rounded for almost all arguement values.

Our main idea in the accurate tables method is to use “nonstandard tables,” which are different from the natural tables of equally spaced points in which the rounding error prevents obtaining last bit accuracy. In order to achieve a small error we use the following idea: Perturb the original, equally spaced, points in such a way that the table value (or tables values in case we need several tables) will be very close to numbers which can be exactly represented by the computer (much closer than the usual double percision representation). Thus we were able to control the error introduced by the computer representation of real numbers and extended the accuracy without actually using extended precision arithmetic.
On recursive calculation of the generalized inverse of a matrix
Authors: Mohideen Saleem , Cherkassky Vladimir
Published: July 2002

The generalized inverse of a matrix is an extension of the ordinary square matrix inverse which applies to any matrix (e.g., singular, rectangular). The generalized inverse has numerous important applications such as regression analysis, filtering, optimization and, more recently, linear associative memories. In this latter application known as Distributed Associative Memory, stimulus vectors are associated with response vectors and the result of many associations is spread over the entire memory matrix, which is calculated as the generalized inverse. Addition/deletion of new associations requires recalculation of the generalized inverse, which becomes computationally costly for large systems. A better solution is to calculate the generalized inverse recursively. The proposed algorithm is a modification of the well known algorithm due to Rust et al. [2], originally introduced for nonrecursive computation. We compare our algorithm with Greville's recursive algorithm and conclude that our algorithm provides better numerical stability at the expense of little extra computation time and additional storage.
VirtualClock
Authors: Zhang Lixia
Published: July 2002

One of the challenging research issues in building high-speed packet-switched networks is how to control the transmission rate of statistical data flows. This paper describes a new traffic control algorithm,
VirtualClock
, for high-speed network applications. VirtualClock monitors the average transmission rate of statistical data flows and provides every flow with guaranteed throughput and low queueing delay. It provides firewall protection among individual flows, as in a TDM system, while retaining the statistical multiplexing advantages of packet switching. Simulation results show that the VirtualClock algorithm meets all its design goals.
An efficient and fault-tolerant solution for distributed mutual exclusion
Authors: Agrawal Divyakant , El Abbadi Amr
Published: July 2002

In this paper, we present an efficient and fault-tolerant algorithm for generating quorums to solve the distributed mutual exclusion problem. The algorithm uses a logical tree organization of the network to generate tree quorums, which are logarithmic in the size of the network in the best case. Our approach is resilient to both site and communication failures, even when such failures lead to network partitioning. Furthermore, the algorithm exhibits a property of graceful degradation, i.e., it requires more messages only as the number of failures increase in the network. We describe how tree quorums can be used for various distributed applications for providing mutually exclusive access to a distributed resource, managing replicated objects, and atomically commiting a distributed transaction.