Radial Domain Research Articles

Postural control and thigh muscle activity in men with knee osteoarthritis

The aim of this study was to examine the standing balance and the function of vastus medialis (VM) and biceps femoris (BF) muscles with surface electromyography (EMG). Fifty-four subjects with uni- or bilateral knee osteoarthritis (OA) (aged 50–69 years) and 53 age-matched randomly selected clinically and radiologically healthy men participated in this study. Postural control was assessed on a force platform with a bipedal stance with eyes open (EO) and closed (EC) and a monopedal stance with EO. The balance parameters, mean sway velocity, velocity along AP and ML axes, elliptical area, standard deviation of center of pressure, average radial displacement, mean frequency and frequency domain balance parameters and different power spectral density frequency bands were determined. Root mean square (RMS) for EMG amplitude, mean EMG frequency ( f EMG,mean) and median EMG frequency ( f EMG,med) of motor unit activity were calculated from the normalized EMG data. During bipedal stance with EC and EO, there were no significant differences in balance parameters between groups, but during bipedal stance with EO, the RMS in VM was about 56% higher ( p < 0.05) in subjects with knee OA than in the control subjects and the values of f EMG,mean and f EMG,med were about 48% higher ( p < 0.05) in control subjects than subjects with knee OA. It is concluded that subjects with knee OA do not have any standing balance deficit, but they do exhibit increased muscle activity in VM muscle compared to control subjects.

The effects of temperature and frequency on the magnetization switching mode in circular MI sensors

This paper presents results computed using a meshless method in a point collocation formulation to investigate the effects of temperature and frequency on the magnetization switching mode in the circular amorphous magneto-impedance sensor (element). Specifically, the solutions characterizing the MI effect are solved from a set of coupled nonlinear equations consisting of the Maxwell’s equations, the Landau–Lifshitz–Gilbert equation, and the thermal diffusion equation. This coupled nonlinear space–time model predicts the formation and propagation of dynamic domain walls in switching and it is shown how they contribute to experimentally observed temperature and frequency effects. Computed results (that agree well with reported experimental data) suggest radial domain walls may play a larger role in the MI effect than originally believed even for the realistic conditions considered here at 1 MHz or more.

Radial Spoke Protein 3 Is a Mammalian Protein Kinase A-anchoring Protein That Binds ERK1/2

Initially identified in Chlamydomonas, RSP3 (radial spoke protein 3) is 1 of more than 20 identified radial spoke structural components of motile cilia and is required for axonemal sliding and flagellar motility. The mammalian orthologs for this and other radial spoke proteins, however, remain to be characterized. We found mammalian RSP3 to bind to the MAPK ERK2 through a yeast two-hybrid screen designed to identify interacting proteins that have a higher affinity for the phosphorylated, active form of the protein kinase. Consistent with the screening result, the human homolog, RSPH3, interacts with and is a substrate for ERK1/2. Moreover, RSPH3 is a protein kinase A-anchoring protein (AKAP) that scaffolds the cAMP-dependent protein kinase holoenzyme. The binding of RSPH3 to the regulatory subunits of cAMP-dependent protein kinase, RIIalpha and RIIbeta, is regulated by ERK1/2 activity and phosphorylation. Here we describe an ERK1/2-interacting AKAP and suggest a mechanism by which cAMP-dependent protein kinase-AKAP binding can be modulated by the activity of other enzymes.

Numerical simulation of turbulent flow in a Ranque–Hilsch vortex tube

The present work is about numerical simulations of the internal flow in a commercial model of a Ranque–Hilsch vortex tube (RHVT) operating in jet impingement. Simulation of the turbulent, compressible, high swirling flow was performed by both RANS and LES techniques. The effect of different turbulence closure models have been tested in RANS simulations using a first order closure RNG k–ε and, for the first time in this kind of flow, a second order RSM (Reynolds Stress differential Model) closure. RANS computations have been executed on an axis-symmetric two-dimensional mesh and results have been compared with LES ones, obtained over a three-dimensional computational grid. Smagorinsky sub-grid scale model was used in LES. All the calculations were performed using FLUENT ™ 6.3.26. The use of a common code for the different simulations allowed the comparison of the performances of the different techniques and turbulence models, avoiding the introduction of other variables. In all the simulations performed, consistency with the real commercial vortex tube model in jet impingement operation has been followed by substituting an axial hot computational exit to the usual radial one. Comparison of the results between RANS simulations performed on both a traditional radial hot outlet computational domain and one with an axial hot outlet, demonstrates the suitability of the computational model adopted in this work, closer to the real geometry of the device, particularly in RANS RSM simulations. Results in different sections of the tube show significant differences in the velocity profiles, temperature profiles and secondary vortex structures, varying turbulence model. The accurate numerical simulation of the flow in a RHVT, resulting in an improved prediction capability of the kinematic and thermal properties of outgoing jets, could allow a correct estimation of the cooling performance of this device in jet impingement operation.

A general method to obtain Sturmian functions for continuum and bound state problems with Coulomb interactions

AbstractIn this article, we investigate discretization schemes to represent Sturmian functions for both positive and negative energies in the presence of a long range Coulomb potential. We explore two methods to obtain Sturmian functions for positive energy. The first one involves the expansion of the radial wave function in a L2 finite basis set, whereas the second one introduces the discretization of the radial coordinate domain of the Hamiltonian or, alternatively, the Green function. We apply them to find the bound states and scattering phase shift for ${\cal N}$‐electron atoms close to the critical charge. Both methods are able to describe bound states near threshold, as well as continuum states with very good convergence properties. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010

Development of a Model for Analysing Radial Flow of Slightly Compressible Fluids

In this work, we develop a finite element-finite difference method to solve the differential equation governing the radial flow of slightly compressible fluids. The finite element method is used to carry out spatial approximations so as to study the variation of fluid properties at the various nodes to which effect we divided the entire radial domain of the fluid into a mesh of four radial 1-D quadratic elements which exposes nine nodes to intense study. Time approximation is done with the aid of the Crank-Nicolson finite difference scheme.

Simplified vacuum energy expressions for radial backgrounds and domain walls

We extend our previous results of simplified expressions for functional determinants for radial Schrödinger operators to the computation of vacuum energy, or mass corrections, for static but spatially radial backgrounds, and for domain wall configurations. Our method is based on the zeta function approach to the Gel'fand–Yaglom theorem, suitably extended to higher-dimensional systems on separable manifolds. We find new expressions that are easy to implement numerically, for both zero and non-zero temperatures.

Piezoelectric Resonators with Engineered Domain Structures

Domain engineered structures prepared in PZT ceramics are studied for the possible application for piezoelectric resonators. Bar shaped resonators segmented into several domain volumes with antiparallel polarization show multiplication of the fundamental resonant frequency for the length extensional vibration mode. Radial vibration mode for thin disc with two radial domain segments poled in antiparallel direction is further studied theoretically and experimentally. Results reveal that the fundamental resonance could not be shifted by the domain volumes distribution in the resonator, on the contrary to bar resonators. Temperature coefficients for the fundamental resonant frequency of twin domain disc are calculated and measured as a function of domain segment distribution. They were found to be independent on the domain size. Higher overtones might change their frequencies as a function of domain distribution.

Temperature Dependence of the Magnetization Reversal Process and Domain Structure in Fe$_{77.5 - {\rm x}}$Ni$_{\rm x}$Si$_{7.5}$B$_{15}$ Magnetic Microwires

We have studied the effect of glass coating on the magnetic domain structure and magnetic properties of amorphous glass-coated Fe77.5-xNixSi7.5B15 (x=0-40) microwires. The existence of the radial domain structure is confirmed by the Bitter technique. The stresses introduced by the glass coating increase, when the temperature decreases, changing the domain structure of amorphous microwires. The radial domain structure calculated from the magnetization measurements has a thickness from 5 to 750 nm. Finally, the temperature dependence of the switching field shows the increase of the switching field at low temperatures as a result of the stresses introduced by the glass coating.

Gyrokinetic particle simulations of toroidal momentum transport

Simulations of toroidal angular momentum transport have been carried out using global toroidal gyrokinetic particle-in-cell code. The significant redistribution of toroidal momentum is observed, driven by the ion temperature gradient turbulence with adiabatic electrons, resulting in a peaked momentum profile in the central region of the radial domain. Cases with rigid and sheared plasma rotation are considered. Diffusive and off-diagonal (pinchlike) fluxes are identified. Toroidal momentum diffusivity is calculated by subtracting pinch contribution from the total momentum flux, and compared to quasilinear estimates. It is found that the ratio of momentum to heat conductivity is smaller than unity even after subtracting pinch contribution when wave-particle resonance energy is larger than thermal energy.

Surface‐Driven Asymmetry and Instability in the Acceleration Region of Hall Thruster

AbstractIt has been shown experimentally that the channel wall material has a substantial effect on the behaviour of Hall discharges. For this reason, the radial profile inside the Hall thruster SPT‐100 is investigated in detail. This is done by a one‐dimensional fully kinetic self‐consistent Particle‐in‐Cell model between the two walls in the acceleration region of the channel. A detailed Monte Carlo probabilistic model for secondary electron emission is implemented as boundary module. Using the local field approximation, two different operative conditions (axial electric field Ez =100 V/cm and 300 V/cm) have been simulated. For high discharge voltage case, a strong radial asymmetry and a stream instability propagating all along the radial domain are detected, while in the low voltage case a stable classical situation is recovered. The critical parameters for triggering this unstable regime are the electron azimuthal drift energy and the induced secondary electron emission, while the saturation mechanism is the increasing of the temperature of the initially cold secondary‐electrons. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Radial and circular slit maps of unbounded multiply connected circle domains

Infinite product formulae for conformally mapping an unbounded multiply connected circle domain to an unbounded canonical radial or circular slit domain, or to domains with both radial and circular slit boundary components are derived and implemented numerically and graphically. The formulae are generated by analytic continuation with the reflection principle. Convergence of the infinite products is proved for domains with sufficiently well-separated boundary components. Some recent progress in the numerical implementation of infinite product mapping formulae is presented.

Disruption of Foxg1 expression by knock-in of Cre recombinase: Effects on the development of the mouse telencephalon

The cre/ loxP system is used routinely to manipulate gene expression in the mouse nervous system. In order to delete genes specifically from the telencephalon, the Foxg1-cre line was created previously by replacing the intron-less Foxg1 coding region with cre, resulting in a Foxg1 heterozygous mouse. As the telencephalon of heterozygous Foxg1 mice was reported to be normal, this genotype often has been used as the control in subsequent analyses. Here we describe substantial disruption of forebrain development of heterozygous mice in the Foxg1-cre line, maintained on the C57BL/6J background. High resolution magnetic resonance microscopy reveals a significant reduction in the volume of the neocortex, hippocampus and striatum. The alteration in the neocortex results, in part, from a decrease in its tangential dimension, although gross patterning of the cortical sheet appears normal. This decrease is observed in three different Foxg1 heterozygous mouse lines, independent of the method of achieving deletion of the Foxg1 gene. Although Foxg1 is not expressed in the diencephalon, three-dimensional magnetic resonance microscopy revealed that thalamic volume in the adult is reduced. In contrast, at postnatal day 4, thalamic volume is normal, suggesting that interactions between cortex and dorsal thalamus postnatally produce the final adult thalamic phenotype. In the Foxg1-cre line maintained on the C57BL/6J background, the radial domain of the cerebral cortex also is disrupted substantially, particularly in supragranular layers. However, neither Foxg1 heterozygous mice of the Foxg1-tet (tetracycline transactivator) line, nor those of the Foxg1-lacZ and Foxg1-cre lines maintained on a mixed background, displayed a reduced cortical thickness. Thus Cre recombinase contributes to the radial phenotype, although only in the context of the congenic C57BL/6J background. These observations highlight an important role for Foxg1 in cortical development, reveal noteworthy complexity in the invocation of specific mechanisms underlying phenotypes expressed following genetic manipulations and stress the importance of including appropriate controls of all genotypes.

Numerical solution for biharmonic equation using multilevel radial basis functions and domain decomposition methods

Biharmonic equation has significant applications in physics and engineering, but is difficult to solve due to the existing fourth order derivatives. One of the domain-type mashless methods is obtained by simply applying the radial basis functions (RBFs) as a direct collocation, which has shown to be effective in solving complicated physical problems with irregular domains. In this paper, we utilize overlapping domain decomposition and multilevel RBF methods for solving biharmonic equation. Numerical results indicate that these two methods circumvent the ill-conditioning problem resulted from using the radial basis function as a global interpolant.

Nanoscale studies of domain wall motion in epitaxial ferroelectric thin films

Atomic force microscopy was used to investigate ferroelectric switching and nanoscale domain dynamics in epitaxial Pb(Zr0.2Ti0.8)O3 thin films. Measurements of the writing time dependence of domain size reveal a two-step process in which nucleation is followed by radial domain growth. During this growth, the domain wall velocity exhibits a v∝exp−(1∕E)μ dependence on the electric field, characteristic of a creep process. The domain wall motion was analyzed both in the context of stochastic nucleation in a periodic potential as well as the canonical creep motion of an elastic manifold in a disorder potential. The dimensionality of the films suggests that disorder is at the origin of the observed domain wall creep. To investigate the effects of changing the disorder in the films, defects were introduced during crystal growth (a-axis inclusions) or by heavy ion irradiation, producing films with planar or columnar defects, respectively. The presence of these defects was found to significantly decrease the creep exponent μ, from 0.62–0.69 to 0.38–0.5 in the irradiated films and 0.19–0.31 in the films containing a-axis inclusions.

On the blow-up rate of large solutions for a porous media logistic equation on radial domain

In this paper we establish the exact blow-up rate of the large solutions of a porous media logistic equation. We consider the carrying capacity function with a general decay rate at the boundary instead of the usual cases when it can be approximated by a distant function. Obtaining the accurate blow-up rate allows us to establish the uniqueness result. Our result covers all previous results on the ball domain and can be further adapted in a more general domain.

Simulation of washing of packed bed of porous particles by orthogonal collocation on finite elements

A mathematical model related to diffusion–dispersion during flow through multiparticle system is presented. The technique of orthogonal collocation on finite elements is applied on the axial and radial domain of the system of governing partial differential equations. The convergence and stability of the solutions is also checked. Effect of different parameters like axial dispersion coefficient, reaction rate kinetics, interstitial velocity, bed porosity, cake thickness, particle radius on exit solute concentration is presented. Numerical results are matching the experimental results significantly. The technique is simple, elegant and convenient for solving two point boundary value problems with no limit on the range of parameters.

Thermoelastic analysis of a functionally graded rotating disk

A semi-analytical thermoelasticity solution for hollow and solid rotating axisymmetric disks made of functionally graded materials is presented. The radial domain is divided into some virtual sub-domains in which the power-law distribution is used for the thermomechanical properties of the constituent components. Imposing the necessary continuity conditions between adjacent sub-domains, together with the global boundary conditions, a set of linear algebraic equations are obtained. Solution of the linear algebraic equations yields the thermoelastic responses for each sub-domain as exponential functions of the radial coordinate. Some results for the stress, strain and displacement components along the radius are presented due to centrifugal force and thermal loading. Results obtained within this solution are compared with those of a finite element analysis in the literature. Based on the results, it is shown that the property gradation correlates with thermomechanical responses of FG disks.

Two-dimensional Fourier transform of arbitrarily sampled NMR data sets

A new procedure for Fourier transform with respect to more than one time variable simultaneously is proposed for NMR data processing. In the case of two-dimensional transform the spectrum is calculated for pairs of frequencies, instead of conventional sequence of one-dimensional transforms. Therefore, it enables one to Fourier transform arbitrarily sampled time domain and thus allows for analysis of high dimensionality spectra acquired in a short time. The proposed method is not limited to radial sampling, it requires only to fulfill the Nyquist theorem considering two or more time domains at the same time. We show the application of new approach to the 3D HNCO spectrum acquired for protein sample with radial and spiral time domain sampling.

Grid Cell Distortion and MODFLOW’s Integrated Finite‐Difference Numerical Solution

The ground water flow model MODFLOW inherently implements a nongeneralized integrated finite-difference (IFD) numerical scheme. The IFD numerical scheme allows for construction of finite-difference model grids with curvilinear (piecewise linear) rows. The resulting grid comprises model cells in the shape of trapezoids and is distorted in comparison to a traditional MODFLOW finite-difference grid. A version of MODFLOW-88 (herein referred to as MODFLOW IFD) with the code adapted to make the one-dimensional DELR and DELC arrays two dimensional, so that equivalent conductance between distorted grid cells can be calculated, is described. MODFLOW IFD is used to inspect the sensitivity of the numerical head and velocity solutions to the level of distortion in trapezoidal grid cells within a converging radial flow domain. A test problem designed for the analysis implements a grid oriented such that flow is parallel to columns with converging widths. The sensitivity analysis demonstrates MODFLOW IFD's capacity to numerically derive a head solution and resulting intercell volumetric flow when the internal calculation of equivalent conductance accounts for the distortion of the grid cells. The sensitivity of the velocity solution to grid cell distortion indicates criteria for distorted grid design. In the radial flow test problem described, the numerical head solution is not sensitive to grid cell distortion. The accuracy of the velocity solution is sensitive to cell distortion with error <1% if the angle between the nonparallel sides of trapezoidal cells is <12.5 degrees. The error of the velocity solution is related to the degree to which the spatial discretization of a curve is approximated with piecewise linear segments. Curvilinear finite-difference grid construction adds versatility to spatial discretization of the flow domain. MODFLOW-88's inherent IFD numerical scheme and the test problem results imply that more recent versions of MODFLOW 2000, with minor modifications, have the potential to make use of a curvilinear grid.