Large Absolute Values Research Articles

Kink-antikink, trapping bags and five-dimensional Gauss-Bonnet gravity

Five-dimensional Gauss-Bonnet gravity, with one warped extra-dimension, allows classes of solutions where two scalar fields combine either in a kink-antikink system or in a trapping-bag configuration. While the kink-antikink system can be interpreted as a pair of gravitating domain walls with opposite topological charges, the trapping-bag solution consists of a domain wall supplemented by a nontopological defect. In both classes of solutions, for large absolute values of the bulk coordinate (i.e. far from the core of the defects), the geometry is given by five-dimensional anti--de Sitter space.

The effect of topographical and atmospheric masses on spaceborne gravimetric and gradiometric data

Current satellite missions dedicated to global mapping of the Earth’s gravity field are providing accurate global models of the geopotential. Harmonic (Stokes) coefficients of the geopotential derived from satellite observations of its functionals, a potential gradient vector and/or gravity gradient tensor, correspond to the (time-averaged) gravitational potential that is generated by the geoid, topography and atmosphere. The manuscript deals with the effect of static topographical and atmospheric masses on spaceborne observations of the potential gradient vector and gravity gradient tensor that should be applied during their inversion into the geopotential at the geoid level. They would allow for derivation of a harmonic representation of the potential generated only by solid masses inside the geoid and ocean, i.e., harmonicity of the geopotential would apply to the entire space outside the geoid. The geopotential could be then synthesized without problems with diverging harmonic series, i.e., the fundamental condition for application of a truncated harmonic series everywhere outside the geoid would be met. Due to its large numerical values, compensation of topographical masses is outlined using a single-layer potential. Although not entirely sufficient from a geophysical point of view, this model is often applied in geoid-related computations. Corresponding parameters are evaluated in manners that are consistent with spatial resolution and accuracy of current spaceborne data using spherical harmonic representation of topographical heights and corresponding mass distributions. Theoretical formulations are followed by numerical evaluations.

The QSPR (quantitative structure–property relationship) study about the anaerobic biodegradation of chlorophenols

In this study, based on quantum chemical and physicochemical descriptors, by the use of partial least squares analysis, a good prediction quantitative structure–property relationship for the disappearance rate constant (log K) of chlorophenols (CPs) in the anaerobic culture was obtained. It was found that the resonance energy of the two-center term ( J), which described the character of the weakest carbon–chlorine bond, played an important role in the reductive chlorine processes, the greater the sizes of CPs molecules, the higher the log K values. Increasing energy of the lowest unoccupied molecular orbital ( E lumo) values of the CPs lead to decreasing log K values, and CPs with large absolute hardness values tended to have big log K values.

The use of negative penalty functions in linear systems of equations

Contrary to what is commonly thought, it is possible to obtain convergent results with negative (rather than positive) penalty functions. This has been shown and proven on various occasions for vibration analysis, but in this contribution it will also be shown and proven for systems of linear equations subjected to one or more constraints. As a key ingredient in the developed arguments, a pseudo-force is identified as the derivative of the constrained degree of freedom with respect to the inverse of the penalty parameter. Since this pseudo-force can be proven to be constant for large absolute values of the penalty parameter, it follows that the exact solution is bounded by the results obtained with negative and positive penalty parameters. The mathematical proofs are presented and two examples are shown to illustrate the principles.

The exchange bias and coercivity of FM/AFM films: Monte Carlo simulation

The exchange bias ( H E) and coercivity ( H C) of the ferromagnet/antiferromagnet (FM/AFM) films have been simulated with Monte Carlo method. The simulated results indicate that, the value of H E decreases with increasing temperature, and the values of H E and the blocking temperature T b at which H E= 0 reduce evidently with decreasing absolute value of interlayer exchange coupling JI. It also is found that for the large absolute values of JI, the maximum in H C occurs very close to T b. At the same time, it is observed that the diluted ratio of FM at FM/AFM interface influences clearly the value of H E. The simulated results are consistent with the experimental facts. The maximum behaviour in the H C− T curves has been explained by the interplay of the softening of some fraction of the spins in the AFM layer near T N′ and the disorder of the spins in FM layer near Curie temperature T C.

Three-dimensional investigation of the texture and microstructure below a nanoindent in a Cu single crystal using 3D EBSD and crystal plasticity finite element simulations

This paper reports a three-dimensional (3D) study of the microstructure and texture below a conical nanoindent in a (111) Cu single crystal at nanometer-scale resolution. The experiments are conducted using a joint high-resolution field emission scanning electron microscopy/electron backscatter diffraction (EBSD) set-up coupled with serial sectioning in a focused ion beam system in the form of a cross-beam 3D crystal orientation microscope (3D EBSD). The experiments (conducted in sets of subsequent (112¯) cross-section planes) reveal a pronounced deformation-induced 3D patterning of the lattice rotations below the indent. In the cross-section planes perpendicular to the (111) surface plane below the indenter tip the observed deformation-induced rotation pattern is characterized by an outer tangent zone with large absolute values of the rotations and an inner zone closer to the indenter axis with small rotations. The mapping of the rotation directions reveals multiple transition regimes with steep orientation gradients and frequent changes in sign. The experiments are compared to 3D elastic–viscoplastic crystal plasticity finite element simulations adopting the geometry and boundary conditions of the experiments. The simulations show a similar pattern for the absolute orientation changes but they fail to predict the fine details of the patterning of the rotation directions with the frequent changes in sign observed in the experiment. Also the simulations overemphasize the magnitude of the rotation field tangent to the indenter relative to that directly below the indenter tip.

Alkylcyanoacrylate nanocapsules prepared from mini-emulsions: A comparison with the conventional approach

Polyalkylcyanoacrylate nanocapsules are being prepared using two different types of o/w-emulsions: a conventional emulsion generated by intensive stirring with a home-made device and a mini-emulsion produced by the action of ultrasonic dispersion, using the alkylcyanoacrylate monomer as a hydrophobic agent. The emulsions and the resulting nanocapsule dispersions are compared using various methods of physical characterization. The formation of solid capsules is indicated by solid state NMR spectra and atomic force microscopy. Differences between the results of both synthetic approaches are found in terms of particle size distribution, zeta potential and tendency towards particle agglomeration. Capsules prepared by ultrasound via the mini-emulsion pathway tend to be smaller and more monodisperse. Their zeta potential is negative with larger absolute values as compared to capsules obtained from conventional emulsions, leading to stronger repulsive interactions and a higher stability against capsule agglomeration.

Transport and magnetic properties ofGdBaCo2O5+xsingle crystals: A cobalt oxide with square-latticeCoO2planes over a wide range of electron and hole doping

Single crystals of the layered perovskite GdBaCo_{2}O_{5+x} (GBCO) have been grown by the floating-zone method, and their transport, magnetic, and structural properties have been studied in detail over a wide range of oxygen contents. The obtained data are used to establish a rich phase diagram centered at the "parent'' compound GdBaCo_{2}O_{5.5} -- an insulator with Co ions in the 3+ state. An attractive feature of GBCO is that it allows a precise and continuous doping of CoO_{2} planes with either electrons or holes, spanning a wide range from the charge-ordered insulator at 50% electron doping (x=0) to the undoped band insulator (x=0.5), and further towards the heavily hole-doped metallic state. This continuous doping is clearly manifested in the behavior of thermoelectric power which exhibits a spectacular divergence with approaching x=0.5, where it reaches large absolute values and abruptly changes its sign. At low temperatures, the homogeneous distribution of doped carriers in GBCO becomes unstable, and both the magnetic and transport properties point to an intriguing nanoscopic phase separation. We also find that throughout the composition range the magnetic behavior in GBCO is governed by a delicate balance between ferromagnetic (FM) and antiferromagnetic (AF) interactions, which can be easily affected by temperature, doping, or magnetic field, bringing about FM-AF transitions and a giant magnetoresistance (MR) phenomenon. An exceptionally strong uniaxial anisotropy of the Co spins, which dramatically simplifies the possible spin arrangements, together with the possibility of continuous ambipolar doping turn GBCO into a model system for studying the competing magnetic interactions, nanoscopic phase separation and accompanying magnetoresistance phenomena.

The impact of lee-side stratification on the spatial distribution of orographic precipitation

Numerical simulations are presented in order to investigate the effect of the lee-side stratification on the spillover of orographic precipitation. The simulations are conducted with idealized topography as well as with idealized large-scale flow conditions and consider both moist neutral and convectively unstable situations. Strong lee-side static stability is achieved by creating a basin enclosed by four mountain ridges that is filled with a cold-air pool. Sensitivity tests are also performed with a plateau topography, representing the limit of an infinitely stable cold-air pool. It is found that the presence a cold-air pool in the lee of a mountain ridge greatly increases the precipitation spillover because the cold pool suppresses the lee-side downslope air motion that otherwise leads to a rapid evaporation of the precipitation. The maximum fractional enhancement of the lee-side precipitation ranges between one order of magnitude in a convectively unstable environment and two orders of magnitude in a nonconvective one. However, the largest absolute values are found in the convective cases because convective cells decay more slowly than stratiform precipitation. In all simulations with a lee-side cold pool, the precipitation decay in the lee of the mountain tends to be approximately exponential. Sensitivity experiments indicate that the lee-side precipitation enhancement due to a cold pool depends only weakly on the height and the width of the mountain. The precipitation on the upstream side of the mountain also tends to be enhanced by a lee-side cold pool due to a change of the gravity-wave pattern. However, this side effect is comparatively small, never exceeding a factor of three in the cases tested in this study. A notable precipitation enhancement over the mountain crest is found for low mountains only. Copyright © 2005 Royal Meteorological Society

Determination of optimal switching angles in the Dual‐Euler method based on round‐off error models

PurposeOptimal switching angles are investigated for minimizing accumulated numerical errors when the dual‐Euler method is used in the simulation of angular rotation.Design/methodology/approachFirst, round‐off errors are theoretically modeled with a simplified mathematical representation of rotation. Round‐off errors take critical roles in the vicinity of indefinite points because they cause major numerical inaccuracy in very large numerical values represented with limited binary numbers. Optimal switching angles of (±π/4, ±3π/4) are derived and numerically examined. With a more practical and severe rotational model, the switching angles are numerically tested.FindingsIn conclusion, switching pitch angles of (±π/4, ±3π/4) yield near minimum numerical errors in angular parameters of pitch, yaw, and roll if truncation errors are not dominant by using high‐order integration algorithms and small step sizes. It is also noticed that accumulated numerical errors increase dramatically if pitch and roll angles are switched beyond the optimal angles with a little margin.Originality/valueOptimal switching angles in the dual‐Euler method are identified based on the truncation error analysis. The mechanism of accumulated numerical errors in the dual‐Euler method, which depends on switching angles, is also revealed.

Theoretical note: the C/T ratio in artificial neural networks

This paper describes computer simulations of the effect of the C/T ratio on acquisition rate in artificial neural networks. The networks consisted of neural processing elements that functioned according to a neurocomputational model whose learning rule is consistent with information on dopaminergic mechanisms of reinforcement. In Simulation 1, three comparisons were made: constant C and variable T, variable C and constant T, and a constant C/T with variable C and T. In the last two comparisons, C was manipulated by changing the probability of reinforcement within the intertrial interval (ITI), in the absence of the conditioned stimulus (CS). Acquisition rate tended to increase with C/T, and the invariant ratio had no effect. In Simulation 2, C was manipulated by changing the ITI, with continuous reinforcement in the presence of the CS and no reinforcements in its absence. Results were comparable to those obtained in Simulation 1. Simulation 3 further explored the effect of the invariant ratio, but with larger absolute values of C and T, which slowed acquisition significantly. The results parallel some experimental findings and theoretical implications of the Gibbon-Balsam model, showing that they can emerge from the moment-to-moment dynamics of a neural-network model. In contrast to that model, however, Simulation 3 suggests that the effect of invariant C/T ratios may be bounded.

Advanced discrete wavelet transform fusion algorithm and its optimization by using the metric of image quality index

Of the many image fusion methods, the discrete wavelet transform (DWT) and various pyramids (e.g., the Laplacian pyramid) are among the most common and effective. For quantitative evaluation of the quality of fused imagery, the root mean square error (RMSE) is the most reasonable measure of quality if a "ground truth" image is available; otherwise, the entropy, spatial frequency, or image quality index (IQI) can be calculated and evaluated. Here, an advanced discrete wavelet transform (aDWT) method that incorporates principal component analysis (PCA) and morphological processing into a regular DWT fusion algorithm is presented. Specifically, a principle vector is derived from two input images and then applied to two of the images' approximation coefficients at the highest DWT transform scale. For the detail coefficients at each transform scale, the larger absolute values are chosen and subjected to a neighborhood morphological processing procedure that serves to verify the selected pixels by using a "filling" and "cleaning" operation. Furthermore, the aDWT has two adjustable parameters—the number of DWT decomposition levels and the length of the selected wavelet that determinately affect the fusion result. An iterative fusion process that was optimized with the established metric—IQI—is then implemented. Experimental results tested on four types of inhomogeneous imagery show that the iterative aDWT achieves the best fusion compared to the pyramid or the DWT methods judged on both the IQI metric and visual inspection.

Spontaneous Vesicle Formation in Aqueous Mixtures of Cationic Gemini Surfactant and Sodium Lauryl Ether Sulfate

Molecular aggregates of surfactant molecules consisting of one or more bilayers arranged in a hollow, closed, usually spherical geometry are termed “esicles”or “iposomes” In recent years it has been found that in certain systems the vesicular structure forms spontaneously and is long lived, and it has been suggested that these structures may in fact constitute the equilibrium state in these cases (as is true of micelles) This paper deals with the mixed CMC, vesicles, phase behavior, phase transition, geometrical structure, their formation and characterization in the aqueous solutions of mixed cationic/anionic surfactants systems. TEM micrographs revealed that the vesicles were of spherical shape and that their size was of around 180 nm. The zeta potentials are positive at CGS1-rich regions and negative at SLES-rich regions. In the region where SLES/CGS1 (6/4), the zeta potentials are very small, implying that the vesicles at this surfactant ratio may be less stable. At other surfactant ratios, the vesicles are thought to be stable, supported by large absolute values of zeta potentials and little change in UV absorbance for several months.

発作性心房細動のアブレーションにおける検査プロトコルの検討および患者皮膚吸収線量の測定

The ablation for atrial fibrillation minute movement done in our hospital is 250 minutes or less, within an average time of 150 minutes during a fluoroscopic time of about 7 hours, with very large average inspection times numerical values. However, the skin-absorbed dose could be understood only from the numerical value of the area dosimeter. It was considered that the total dose that reached the threshold was sufficient, although radiation injury would not be reported from the ablation currently done at our hospital. Therefore, we aimed to examine the inspection protocol in this hospital, and to request the patient be given an inspection dose that was the average skin-absorbed dose by using the acryl board. The amount of a total dose for an inspection of 150 minutes of fluoroscopic time was about 2.7 Gy. Moreover, a value of 1.5 Gy was indicated in the hot spot as a result of repetition in some exposure fields. However, it was thought that the possibility of exceeding the threshold of 2 Gy depending on the inspection situation in the future and other factors was tolerable because these measurements were done so as not to overvalue it more than the necessary.

Quantization of the potential amplitude in the one-dimensional Schrödinger equation

A consistent scheme is proposed for quantizing the potential amplitude in the one-dimensional Schrodinger equation in the case of negative energies (lying in the discrete-spectrum domain). The properties of the eigenfunctions ϕn(x) and eigenvalues αn corresponding to zero, small, and large absolute values of energy E < 0 are analyzed. Expansion in the set ϕn(x) is used to develop a regular perturbation theory (for E < 0), and a general expression is found for the Green function associated with the time-independent Schrodinger equation. A similar method is used to solve several physical problems: the polarizability of a weakly bound quantum-mechanical system, the two-center problem, and the tunneling of slow particles through a potential barrier (or over a potential well). In particular, it is shown that the transmission coefficient for slow particles is anomalously large (on the order of unity) in the case of an attractive potential is characterized by certain critical values of well depth. The proposed approach is advantageous in that it does not require the use of continuum states.

Diffusion–Migration Currents on Microelectrodes: Comparing Two Approximate Approaches

Two electroneutrality and constant-field solutions of the diffusion–migration problem in steady-state conditions on microelectrodes, where both approximations admit analytical solutions, are compared. Analytical equations for the potential drop across the diffusion layer φ0 in terms of RT/F and the migration factor Y are obtained for three- and four-component systems containing two and three types of electroactive ions, respectively, and one type of ions that takes no part in the reaction. Both methods yield virtually identical φ0. The migration coefficients at large absolute values of φ0 noticeably differ. The Y vs. φ0 dependences in the two approaches different. The Y values yielded by these methods are close only at |φ0| ≪ 1. For real electrochemical reactions considered, the electroneutrality condition at the limiting current is fulfilled at electrode radii >1 μm and electrolyte concentrations >0.1 mM.

Number bias for the discrimination of large visual sets in infancy

This brief report attempts to resolve the claim that infants preferentially attend to continuous variables over number [e.g. Psychol. Sci. 10 (1999) 408; Cognit. Psychol.44 (2002) 33] with the finding that when continuous variables are controlled, infants as young as 6-months of age discriminate large numerical values [e.g. Psychol. Sci. 14 (2003) 396; Cognition 89 (2003) B15; Cognition 74 (2000) B1]. In two parallel experiments, we compare 6-month-old infants' ability to discriminate number and ignore continuous variables with their ability to form a representation of a cumulative surface area and ignore number. We find that infants discriminate a 2-fold change in number but fail to discriminate a 2-fold change in cumulative surface area. The results point to a more complicated relationship between discrete and continuous dimensions than implied by previous literature.

Confluence expansions of the generalized hypergeometric function

By confluencing a subset of upper and lower parameters in the generalized hypergeometric function FQP(a1,,…,aP,c1,…,cQ;z) with the variable z one obtains a lower-order hypergeometric function in the limit when the confluence parameters go to infinity. It is shown that this function is the first term in a convergent expansion in terms of functions of the same type with parameters increasing stepwise by integers ν and coefficients which are polynomials in the reciprocals of the confluence parameters. These polynomials have nonvanishing lowest degree terms whose power increases with ν. The expansion can hence be used to derive asymptotic expansions for large but finite absolute values of the confluence parameters.

Effect of chromatic dispersion on nonlinear phase noise.

We consider the combined effects of amplified spontaneous emission noise, optical Kerr nonlinearity, and chromatic dispersion on phase noise in an optical communication system. The effect of amplified spontaneous emission noise and Kerr nonlinearity were considered previously by Gordon and Mollenauer [Opt. Lett. 15, 1351 (1990)], and the effect of nonlinearity was found to be severe. We investigate the effect of chromatic dispersion on phase noise and show that it can either enhance or suppress the nonlinear noise amplification. For large absolute values of dispersion the nonlinear effect is suppressed, and the phase noise is reduced to its linear value. For a range of negative values of dispersion, however, nonlinear phase noise is enhanced and exhibits a maximum related to the modulation instability found in amplitude fluctuations. Nonlinear phase noise is quenched by these effects even in dispersion-compensated systems; the degree of suppression is sensitively dependent on the dispersion map. We demonstrate these results analytically with a simple linearized model.

High-|m|Rydberg states in strong magnetic fields

We calculate spectra and wave functions of Rydberg atoms in strong magnetic fields using adiabatic basis sets, which reflect the different time scales of the electronic motion parallel and transverse to the magnetic field. For large absolute values of the azimuthal quantum number m, nonadiabatic corrections are found to be negligible, and the adiabatic basis states and their energies are exact solutions. With decreasing value of $|m|,$ the system turns nonadiabatic, and the statistical behavior of the spectra changes from being consistent with classically regular to being consistent with classically chaotic motion. A relation describing the parameter region in which this transition occurs is obtained.