bluuebunny/crossref_metadata_2025 huggingface dataset:
Solution of the Phonon Boltzmann Transport Equation Employing Rigorous Implementation of Phonon Conservation Rules
Authors: Wang Tianjiao , Murthy Jayathi Y.
Published: April 2008

A finite volume scheme is developed to solve the phonon Boltzmann transport equation in an energy form accounting for phonon dispersion and polarization. The physical space and the first Brillouin zone are discretized into finite volumes and the phonon BTE is integrated over them. Second-order accurate differencing schemes are used for the discretization. The scattering term employs a rigorous implementation of phonon momentum and energy conservation laws in determining the rate of normal and Umklapp processes. The method is applied to a variety of bulk silicon and silicon thin-film conduction problems and shown to perform satisfactorily.
A Road Map for CFD Modelling of Forced Cooled Packages
Authors: O¨ztu¨rk Emre , Tari Ilker
Published: April 2008

In this study, Computational Fluid Dynamics, which has taken its position in the thermal design of electronic packages, was used in order to draw a CFD road map for forced cooling conjugate heat transfer analyses in heat generating electronic systems. The main sources of error in CFD analyses arise from inappropriate numerical models including turbulence models, radiation modeling and discretization schemes, insufficient grid resolution, and lack of convergence. A complete computer chassis model with heat sinks and fans inside was created and parametric analyses were performed to compare the effects of different turbulence models, discretization schemes, mesh resolutions, convergence criteria, and radiative heat transfer. Two commercially available CFD software packages were used, Icepak™ for pre-processing, Fluent™ for solution and post-processing. The road map was applied to three different heat sinks modeled into the full chassis. Numerical results were compared with the available experimental data and they were in good agreement.
A Numerical Study of the Thermal Behaviour of Calibrators for Polymer Extrusion
Authors: Lobarinhas P. A. M. , Teixeira J. C. F. , Teixeira S. F. C. F.
Published: April 2008

In polymer processing by extrusion, the thermal behavior of the components downstream of the extruder dye is of great relevance to the final characteristics of the product. In fact, the process productivity, the product dimensional quality and the physical/mechanical properties are strongly dependent upon the cooling process. In the present work, a numerical model adequate to describe the thermal behavior of the calibrator and the polymer profile is developed and implemented as a computer code. The model is fully 3D, transient and includes a formulation for the polymer movement inside the calibrator based upon the VOF method [1]. Although for practical purposes, a steady solution is desired, the model was implemented as a transient case, to enable its accurate validation with experimental data. The interface between the extrudate and the calibrator is described through a coefficient for the thermal contact resistance. The equations were discretized in a finite volume formulation [2] and the code implemented in Fortran. The good agreement between the model and the experimental data has vindicated the accuracy of the computer model and its subsequent application in the analysis and optimization of complete calibration units. A parametric analysis for the most relevant variables, such as polymer velocity and calibrator length, demonstrated the consistency of the numerical model.
Numerical Simulation With Lattice Boltzman Method (LBM) in the Curved Square Duct
Authors: Liao Quan , Jen Tien-Chien , Chen Qinghua , Cui Wenzhi , Li Long-Jian
Published: April 2008

In this paper, the 3DQ19 model of Lattice Boltzmann Method (LBM) was employed to simulate the flow in the curved square duct with curvature ratio (0.2–2.0) and Dean Number (0 – 250). The so-called Dean instability in the curved square duct is fully investigated and a stability diagram is obtained in the domain of curvature ratio and Dean number. It is found that for the square duct with high curvature ratio the onset of transition from single vortex pair to double vortex pairs depends on the Dean number and curvature ratio, while at the small curvature the onset can be characterized by the Dean number alone. This trend is consistent with the conventional Computational Fluid Dynamic (CFD) and experimental results, and the differences between those are very small. For the friction coefficient, which is a function of Dean number, it is found that the numerical results are in good agreement with the available experimental data and conventional CFD results within the given parameters in this project.
Modeling of Pressure Drop During Condensation in Circular and Non-Circular Microchannels
Authors: Agarwal Akhil , Garimella Srinivas
Published: April 2008

This paper presents a multiple flow-regime model for pressure drop during condensation of refrigerant R134a in horizontal microchannels. Condensation pressure drops measured in two circular and six non-circular channels ranging in hydraulic diameter from 0.42 mm to 0.8 mm are considered here. For each tube under consideration, pressure drop measurements were taken over the entire range of qualities from 100% vapor to 100% liquid for five different refrigerant mass fluxes between 150 kg/m2-s and 750 kg/m2-s. Results from previous work by the authors on condensation flow mechanisms in microchannel geometries were used to assign the applicable flow regime to the data points. Garimella et al. [1] reported a comprehensive model for circular tubes that addresses the progression of the condensation process from the vapor phase to the liquid phase by modifying and combining the pressure drop models for intermittent [2] and annular [3] flows reported earlier by them. In this paper, the multiple flow regime model of Garimella et al. [1] for circular microchannels has been extended to horizontal non-circular microchannels of a variety of cross-sections. This combined model accurately predicts condensation pressure drops in the annular, disperse wave, mist, discrete wave, and intermittent flow regimes for both circular and non-circular microchannels of similar hydraulic diameters. Overlap and transition regions between the respective regimes are also addressed using an appropriate interpolation technique that results in relatively smooth transitions between the predicted pressure drops. The resulting model predicts 80% of the data within ±25%. The effect of tube shape on pressure drop is also demonstrated.
Design and Evaluation of Copper Metal Foams in Cold Plates
Authors: Floyd Donald E. , Topolski Mark J. , Darabi Jeff
Published: April 2008

This paper present an analytical and experimental investigation of the performance of metal foams in an impinging flow application. Microstructures of the foam as well as the foam-to-solid braze interface are presented. Aditionally, the effects of brazing procedure on the performance of the heat exchanger are investigated and the results are compared to CFD analysis assuming perfect braze joints. Finally, the results are compared to commercially available micro-channel heat exchangers.
Convergence Acceleration for Heat Transfer and Structural Simulations Using Adaptive Mesh Refinement
Authors: Nie Jianhu , Chen Yitung , Hopkins David A. , Sun Lijian , Hsieh Hsuan-Tsung
Published: April 2008

A finite element program with h-type mesh adaptation is developed and several test cases for heat transfer, fluid mechanics and structural mechanics are selected for code validations. The element division method is used because of its advantage of avoiding overly twisted elements during mesh refinement and recovery. The adaptive mesh is refined only in the localization region where the feature gradient is high. The overall mesh refinement and the h-adaptive mesh refinement are justified with respect to the computational accuracy and the CPU time cost. Both can improve the computational accuracy. The overall mesh refinement causes the CPU time to greatly increase. However, the CPU time does not increase very much with the increase of the level of h-adaptive mesh refinement. The CPU time cost can be saved using the developed program by orders of magnitude, especially for the system with a large number of elements and nodes.
An Urban Energy Balance for the Phoenix, Arizona USA Metropolitan Area
Authors: Bhardwaj R. , Phelan P. E. , Golden J. , Kaloush K.
Published: April 2008

The pressures of rapid urbanization, including the worsening of the urban heat island (UHI) effect, are causing city leaders and other policymakers to consider how to best allocate resources and develop policies to improve their urban environment. The focus of this paper is on UHI, that is, the long-term trend observed in the metropolitan Phoenix, Arizona region and other cities in which both daytime and nighttime temperatures are increasing. An analytical tool is developed to predict the relative effects of various policy measures, such as increasing the average albedo of a city through highly-reflective pavement coatings, or encouraging the adoption of "green" roofs to improve latent heat transfer. This tool is based on a fundamental "lumped" thermal model of the metropolitan area, where transient energy inputs and outputs are considered to generate a single temperature that is characteristic of the entire metropolitan area. Actual electricity, natural gas, vehicular traffic, and solar radiation data are utilized to predict how the temperature changes on an hourly basis. Of the measures evaluated, decreasing the quantity of paved surfaces to reduce daytime temperatures, and increasing the prevalence of green roofs to reduce nighttime temperatures, are the most effective means to alleviate UHI.
An HP-Adaptive Finite Element Model for Convective Heat Transfer in an Attic Space
Authors: Wang Xiuling , Pepper Darrell W.
Published: April 2008

An hp-adaptive finite element algorithm is used to simulate heat transfer within attic spaces driven by buoyancy forces. The element size (h-) and shape function order (p-) are dynamically controlled by an a-posteriori error estimator based on the L2 norm. A three-step process is used to solve the system of equations. The hp-adaptive algorithm is validated using natural convection heat transfer within a differentially heated enclosure. Application of the model is used to simulate heat transfer within attic spaces subjected to natural convection for Rayleigh numbers ranging from 7.1×102 to 7.1×105. Attic aspect ratios range from 0.2 to 1.0. Heat transfer rates typical of summer days in Las Vegas are considered: roofs (inclined surfaces) of attics are hot; bases (bottom surfaces) are cold and vertical walls are insulated. Results are compared with data in literature when possible; good agreement is generally observed.
CFD Analysis of Heat Exchanger and Aftercooler for Diesel Marine Engines
Authors: Campbell Andrew S. , Ladendorf Jeff , Zhou Chenn Q.
Published: April 2008

Shell and tube heat exchangers and bar and plate aftercoolers are used in a diesel marine engine to remove heat from the engine coolant and to cool the pressurized air going into the engine. In order to improve the overall effectiveness of these two components, analyses have been performed using heat exchanger theory and the Computational Fluid Dynamics (CFD) software FLUENT®. Detailed information of flow property distributions and heat transfer was obtained in order to provide a fundamental understanding of the component operation. Comparisons have been made between CFD results, theoretical calculations, and measurement data. Parametric investigations and feasibility studies have been conducted to find optimum conditions for the engine and component performance.
The Application of an Adaptive Wavelet Method to the 3-D Natural-Convection Flow in a Differentially Heated Cavity
Authors: Wirasaet Damrongsak , Paolucci Samuel
Published: April 2008

In this work, we describe a dynamically adaptive wavelet method for solving the natural-convection flow a differentially heated cavity in three spatial dimensions. The adaptive method takes advantage of an interpolating wavelet for the adaptive approximation in the design of a simple refinement strategy that reflects the local demand of the physical solution. The derivative approximation is computed via consistent finite-difference approximation on an adaptive grid. To demonstrate the versatility of the algorithm, we simulate the 3-D differentially heated cavity with various values of Rayleigh number. The results are compared with those obtained by other computational approaches.
Finite Difference Schemes for Diffusion Problems Based on a Hybrid Perturbation Galerkin Method
Authors: Geer James , Fillo John
Published: April 2008

A new technique for the development of finite difference schemes for diffusion equations is presented. The model equations are the one space variable advection diffusion equation and the two space variable diffusion equation, each with Dirichlet boundary conditions. A two-step hybrid technique, which combines perturbation methods, based on the parameter ρ = Δt / (Δx)2, with the Galerkin method, provides a systematic way to develop new finite difference methods, referred to as hybrid equations. The main contributions of this paper include: 1) recovery of classical explicit or implicit finite difference schemes using only the perturbation terms; 2) development of new finite difference schemes, referred to as hybrid equations, which have better stability properties than the classical finite difference equations, permitting the use of larger values of the parameter ρ; and 3) higher order accurate methods, with either O((Δx)4) or O((Δx)6) truncation error, formed by convex linear combinations of the classical and hybrid equations. The solution of the hybrid finite difference equations requires only a tridiagonal equation solver and, hence, does not lead to excessive computational effort.
On the Boundary Conditions for Heat Transfer Using Immersed Boundary Methods
Authors: Pacheco J. Rafael , Rodic Tamara , Pacheco-Vega Arturo
Published: April 2008

We describe the implementation of a general interpolation technique which allows the accurate imposition of the Dirichlet, Neumann and mixed boundary conditions on complex geometries when using the immersed boundary technique on Cartesian grids. The scheme is general in that it does not involve any special treatment to handle either one of the three types of boundary conditions. The accuracy of the interpolation algorithm on the boundary is assessed using three heat transfer problems: (1) forced convection over a cylinder placed in an unbounded flow, (2) natural convection on a cylinder placed inside a cavity, and (3) heat diffusion inside an annulus. The results show that the accuracy of the scheme is second order and are in agreement with analytical and/or numerical data.
Physical activity throughout life reduces the atherosclerotic wall process in the carotid artery
Authors: Sandrock M , Schulze C , Schmitz D , Dickhuth H-H , Schmidt-Trucksaess A
Published: April 2008

Background:

Good cardiorespiratory fitness has been associated with a reduced risk for clinical events of atherosclerotic vascular diseases. It is still unclear how this relates to a slower progression of the early atherosclerosis wall process.

Method:

Using a dynamic model, we generated new parameters for describing the pathologic wall process in the carotid artery, based on an automatic layer detection system. In this study, we scrutinised the influence of two ultrasonographic parameters, intima–media thickness (IMT) and roughness, by comparing two groups: a healthy inactive group (PIP) (mean (SD) age 64.37 (5.10) years; n = 50) and a healthy lifelong physically active group (PA) (mean (SD) age 64.48 (3.45) years; n = 51). All subjects underwent a blood test, spiroergometry, echocardiography and carotid ultrasound examination.

Results:

There was a significant difference in the well known risk factors for cardiovascular disease (for example, high density lipoprotein cholesterol, triglyceride) between groups. PIP compared to PA had a significantly higher roughness (PIP 0.073 (0.015)vsPA 0.065 (0.0156); p<0.01). No significantly higher IMT was found for PIP (PIP 0.89 (0.18)vsPA 0.90 (0.22); p = 0.63) compared to PA. In this cross sectional study of middle aged men, Vo2max was inversely associated with carotid atherosclerotic parameters.

Conclusion:

In this study, good cardiorespiratory fitness was associated with an increase of the proven risk factors and a reduction of atherosclerosis in the common carotid artery. Roughness seems to be significantly more sensitive than IMT for characterising the changes of the arterial wall. We suggest measuring roughness in addition to IMT to gain additional information about the atherosclerotic wall.
Breast carcinomas that co-express E- and P-cadherin are associated with p120-catenin cytoplasmic localisation and poor patient survival
Authors: Paredes J , Correia A L , Ribeiro A S , Milanezi F , Cameselle-Teijeiro J , Schmitt F C
Published: April 2008

Background:

Changes in junctional catenin expression may compromise cadherin-mediated adhesion, increasing cell malignant properties such as invasive and metastatic abilities. Altered expression of α-, β-, γ- and p120-catenin has been reported to be associated with E-cadherin loss or decreased expression, in both breast carcinomas and breast cancer cell lines.

Aims and Methods:

To investigate the expression and subcellular localisation of p120- and β-catenin in a series of human invasive breast carcinomas, and correlate it with biological markers and clinicopathological parameters.

Results:

Both catenins frequently exhibited a reduced membranous or cytoplasmic staining pattern. These alterations were significantly correlated with lack of both E-cadherin and oestrogen receptor-α expression. It was possible to associate the expression of β-catenin with histological grade, tumour size and nodal status, suggesting a relevant role for this catenin as a prognostic factor. The majority of E- and P-cadherin co-expressing tumours were related to cytoplasmic expression of p120-catenin; in this group of breast carcinomas, patient survival was poor.

Conclusion:

Results indicate that p120-catenin cytoplasmic accumulation may play an important role in mediating the oncogenic effects derived from P-cadherin aberrant expression, including enhanced motility and invasion, particularly in tumours which maintain E-cadherin expression.
Neurologically presenting Whipple disease: case report and review of the literature
Authors: Buckle M J , Ellis R W , Bone M , Lockman H
Published: April 2008

A previously healthy male with subacute onset right leg weakness was suspected to have an astrocytoma as imaging showed a lesion. Subsequent biopsy showed the presence of foamy macrophages containing periodic acid-Schiff staining granules, suggesting Whipple disease as a possible diagnosis.
GAUGE INVARIANT ACTION FOR THE OPEN BOSONIC STRING
Authors: SATHIAPALAN B.
Published: April 2008

The issue of space–time gauge invariance for the bosonic string has been earlier addressed using the loop variable formalism. In this paper the question of obtaining a gauge invariant action for the open bosonic string is discussed. The derivative with respect to ln a (where a is a worldsheet cutoff) of the partition function — which is first normalized by dividing by the integral of the two-point function of a marginal operator — is a candidate for the action. Applied to the zero-momentum tachyon it gives a tachyon potential that is similar to those that have been obtained using Witten's background independent formalism. This procedure is easily made gauge invariant in the loop variable formalism by replacing ln a by Σ which is the generalization of the Liouville mode that occurs in this formalism. We also describe a method of resumming the Taylor expansion that is done in the loop variable formalism. This allows one to see the pole structure of string amplitudes that would not be visible in the original loop variable formalism.
ASYMPTOTIC EXPANSIONS OF FEYNMAN AMPLITUDES IN A GENERIC COVARIANT GAUGE
Authors: LINHARES C. A. , MALBOUISSON A. P. C. , RODITI I.
Published: April 2008

We show in this paper how to construct Symanzik polynomials and the Schwinger parametric representation of Feynman amplitudes for gauge theories in a generic covariant gauge. The complete Mellin representation of such amplitudes is then established in terms of invariants (squared sums of external momenta and squared masses). From the scaling of the invariants by a parameter we extend for the present situation a theorem on asymptotic expansions, previously proven for the case of scalar field theories, valid for both ultraviolet or infrared behaviors of Feynman amplitudes.
REDUCTION FORMALISM FOR DIRAC FERMIONS ON DE SITTER SPACE–TIME
Authors: CRUCEAN COSMIN , RACOCEANU RADU
Published: April 2008

The reduction formulas for Dirac fermions is derived using the exact solutions of free Dirac equation on de Sitter space–time. In the framework of the perturbation theory one studies the Green functions and derives the scattering amplitude in the first orders of perturbation theory.
MICROCANONICAL MODEL FOR A GAS OF EVAPORATING BLACK HOLES AND STRINGS, SCATTERING AMPLITUDES AND MASS SPECTRUM
Authors: CIRILO-LOMBARDO D. J. , SANCHEZ N. G.
Published: April 2008

We study the system formed by a gas of black holes and strings within a microcanonical formulation. The density of mass levels grows asymptotically as [Formula: see text], (i = 1,…,N). We derive the microcanonical content of the system: entropy, equation of state, number of components N, temperature T and specific heat. The pressure and the specific heat are negative reflecting the gravitational unstability and a nonhomogeneous configuration. The asymptotic behavior of the temperature for large masses emerges as the Hawking temperature of the system (classical or semiclassical phase) in which the classical black hole behavior dominates, while for small masses (quantum black hole or string behavior) the temperature becomes the string temperature which emerges as the critical temperature of the system. At low masses, a phase transition takes place showing the passage from the classical (black hole) to quantum (string) behavior. Within a microcanonical field theory formulation, the propagator describing the string–particle–black hole system is derived and from it the interacting four-point scattering amplitude of the system is obtained. For high masses it behaves asymptotically as the degeneracy of states ρ(m) of the system (i.e. duality or crossing symmetry). The microcanonical propagator and partition function are derived from a (Nambu–Goto) formulation of the N-extended objects and the mass spectrum of the black hole–string system is obtained: for small masses (quantum behavior) these yield the usual pure string scattering amplitude and string–particle spectrum [Formula: see text]; for growing mass the spectrum describes all the intermediate states up to the pure black hole behavior. The different black hole behaviors according to the different mass ranges: classical, semiclassical and quantum or string behaviors are present in the model.
RADIATIVE LEPTON FLAVOR VIOLATING DECAYS IN THE RANDALL–SUNDRUM BACKGROUND WITH LOCALIZED LEPTONS
Authors: ILTAN E. O.
Published: April 2008

We study the radiative lepton flavor violating li→ ljγ decays in the two-Higgs doublet model, respecting the Randall–Sundrum scenario and estimate the contributions of the KK modes of left- (right-)handed charged lepton doublets (singlets) on the branching ratios. We observe that the branching ratios are sensitive to the contributions of the charged lepton KK modes.
ENTANGLEMENT DYNAMICS OF TWO TWO-MODE TWO-PHOTON JAYNES–CUMMINGS MODELS IN THE PRESENCE OF PHASE DECOHERENCE
Authors: ZHANG JIAN-SONG , XU JING-BO
Published: April 2008

We investigate the entanglement of two two-mode two-photon Jaynes–Cummings models in the presence of phase decoherence. We find an explicit analytical solution of the system and discuss the influence of the phase decoherenc on the entanglement dynamics. Our results shows that the entanglement of the two initially entangled atoms can remain zero for a finite time and revive later. However, if the phase decoherence is taken into accounted, the entanglement cannot revive completely.
INVESTIGATION OF DECOHERENCE OF SUPERCONDUCTING FLUX QUBIT ENTANGLED WITH THE ENVIRONMENT
Authors: JI YING-HUA , JIANG YAN-YAN
Published: April 2008

In the Born–Markov approximation, decoherence property of superconducting quantum circuit with a flux qubit is investigated. Using Kirchhoff's laws of classical circuit and quantum theory, we derive a Hamiltonian of the circuit. Then, combining with the Bloch–Redfield equation and in the two-level approximation, the energy relaxation time and the decoherence time of superconducting qubits is studied. Compared to the spin-boson model, this method not only investigates a decoherence being caused by the dissipative environment, but also the decoherence being generated by the dissipative elements in a superconducting electronic circuit. Hence, it is good for studying the decoherence of superconducting qubits.
SIMULTANEOUS MEASUREMENTS OF THE RESISTANCE AND CAPACITANCE USING A CYLINDRICAL SENSOR SYSTEM
Authors: GOLNABI H. , AZIMI P.
Published: April 2008

In this article, the design and operation of a cylindrical capacitive sensor based on the dielectric reactance capacitance and conductance changes of the gap medium is reported. The proposed system was used to determine characteristics of different water liquids as a result of the capacitance and resistance variations. The air gap capacitance (dry signal) is measured and then by filling the gap with a liquid, the capacitance (wet signal) is monitored for different liquids. A reported sensor is used for the distilled, tap, boiled, and salt water measurements and the capacitance and resistance results are compared. A big difference of about 38.5 μF in the measured capacitance values for the salt and distilled water shows a high sensitivity, which can be used to recognize different water liquids. The experimental results are promising for water liquids and verify the successful operation of such a device as a liquid sensor, a useful method for checking the electrical quality of the water that is required for different applications. It is also possible to monitor the resistance change of the filling medium as a function of time.
A KIND OF EXPLICIT QUASI-PERIODIC SOLUTION AND ITS LIMIT FOR THE TODA LATTICE EQUATION
Authors: HON Y. C. , FAN ENGUI , QIN ZHENYUN
Published: April 2008

Based on the Riemann theta function, the Hirota bilinear method is extended to directly construct a kind of explicit quasi-periodic solution of the Toda lattice equation. The asymptotic property of the quasi-periodic solution is analyzed in detail. It is of interest to see that the well-known soliton solution can be obtained as a limit of the quasi-periodic solution.
ANALYSIS OF TREMBLING HAND PERFECT EQUILIBRIA IN QUANTUM GAMES
Authors: PAKUŁA IRENEUSZ
Published: April 2008

We analyse Selten' concept of trembling hand perfect equilibria in the context of quantum game theory. We define trembles as mixed quantum strategies by replacing discrete probabilities with probability distribution functions. Explicit examples of analysis are given.
COMMENTS ON 'REVERSE AUCTION: THE LOWEST UNIQUE POSITIVE INTEGER GAME'
Authors: FLITNEY A. P.
Published: April 2008

In Zeng et al. [Fluct. Noise Lett. 7 (2007) L439–L447] the analysis of the lowest unique positive integer game is simplified by some reasonable assumptions that make the problem tractable for arbitrary numbers of players. However, here we show that the solution obtained for rational players is not a Nash equilibrium and that a rational utility maximizer with full computational capability would arrive at a solution with a superior expected payoff. An exact solution is presented for the three- and four-player cases and an approximate solution for an arbitrary number of players.
GENERALIZED FINITE ELEMENT METHOD FOR NONLINEAR THREE-DIMENSIONAL ANALYSIS OF SOLIDS
Authors: PROENÇA SERGIO PERSIVAL BARONCINI , TORRES IVAN FRANCISCO RUIZ
Published: April 2008

The Generalized Finite Element Method (GFEM) is employed in this paper for the numerical analysis of three-dimensional solids under nonlinear behavior. A brief summary of the GFEM as well as a description of the formulation of the hexahedral element based on the proposed enrichment strategy are initially presented. Next, in order to introduce the nonlinear analysis of solids, two constitutive models are briefly reviewed: Lemaitre's model, in which damage and plasticity are coupled, and Mazars's damage model suitable for concrete under increased loading. Both models are employed in the framework of a nonlocal approach to ensure solution objectivity. In the numerical analyses carried out, a selective enrichment of approximation at regions of concern in the domain (mainly those with high strain and damage gradients) is exploited. Such a possibility makes the three-dimensional analysis less expensive and practicable since re-meshing resources, characteristic of h-adaptivity, can be minimized. Moreover, a combination of three-dimensional analysis and the selective enrichment presents a valuable good tool for a better description of both damage and plastic strain scatterings.
PSEUDO-ELASTIC ANALYSIS OF ELASTIC–PLASTIC CRACK TIP FIELDS USING ELEMENT-FREE GALERKIN METHOD
Authors: SETHURAMAN RAJU , SRIDHAR REDDY CH.
Published: April 2008

A methodology for the characterization of asymptotic elastoplastic crack tip stress fields is presented by coupling the pseudo-elastic analysis with the element-free Galerkin method (EFGM). An iterative linear elastic analysis using EFGM is carried out for the determination of elastic–plastic crack tip stress fields by treating material parameters as spatial field variables. Effective material parameters are used to describe the constitutive behavior of the continuum and are defined by using the Hencky's total deformation theory of plasticity. The effective material parameters are updated in an iterative manner based on strain controlled projection method using experimental uniaxial tension test curve. The effectiveness of the method is illustrated by predicting the stress fields near the crack tip region of a square plate subjected to asymptotic linear elastic displacement field on the outer boundary of the plate. Different geometries subjected to mode-I and mode-II loadings are considered for the present study. The material model considered in these problems is Ramberg–Osgood model with different hardening exponent values. The predictions of the asymptotic elastic–plastic stress fields near the crack tip are compared with the results of nonlinear finite element analysis and also with the HRR singular stress fields and found to be in good agreement. J-integral values which characterize the amplitude of HRR stress field are also evaluated for the considered geometries and are found to close matching with the EPRI estimation scheme.
EXISTENCE OF SOLUTIONS FOR THE AW–RASCLE TRAFFIC FLOW MODEL WITH VACUUM
Authors: GODVIK MARTE , HANCHE-OLSEN HARALD
Published: April 2008

In this paper, the macroscopic model for traffic flow proposed by Aw and Rascle in 2000 is considered. The model is a 2 × 2 system of hyperbolic conservation laws, or, when the model includes a relaxation term, a 2 × 2 system of hyperbolic balance laws. The main difficulty is the presence of vacuum, which makes control of the total variation of the conservative variables impossible. We allow vacuum to appear and prove the existence of a weak entropy solution to the Cauchy problem.
NONLINEAR WELL-POSEDNESS AND RATES OF DECAY IN THERMOELASTICITY WITH SECOND SOUND
Authors: RACKE REINHARD , WANG YA-GUANG
Published: April 2008

The Cauchy problem in nonlinear thermoelasticity with second sound in one space dimension is considered. Due to Cattaneo's law, replacing Fourier's law for heat conduction, the system is hyperbolic. The local well-posedness as a strictly hyperbolic system is investigated first, and then the relation between energy estimates for non-symmetric hyperbolic systems and well-posedness are discussed. For the global small solution, the long time behavior is described and the decay rates of the L2-norm are obtained.
FINITE DIFFERENCE APPROXIMATIONS TO THE POISSON EQUATION IN A CLASS OF ANALYTIC FUNCTIONS
Authors: NISHIDA KOTOBA
Published: April 2008

The initial value problem for the Poisson equation in a class of analytic functions is considered. We prove that the central finite difference scheme applied to this problem converges to the desired analytic solution.
Micturition-suppressing region in the periaqueductal gray of the mesencephalon of the cat
Authors: Numata Atsushi , Iwata Tatsuya , Iuchi Hiromichi , Taniguchi Narumi , Kita Masafumi , Wada Naoki , Kato Yuji , Kakizaki Hidehiro
Published: April 2008

The periaqueductal gray (PAG) of the mesencephalon has been implicated to be involved in the control of micturition. We investigated the micturition-suppressing region in the PAG of the cat. Decerebrated 27 adult cats were used. A microelectrode was inserted stereotaxically into the PAG, and a region was searched where electrical stimulation suppressed isovolumetric bladder contractions. Simultaneous stimulation of the pontine micturition center (PMC) and micturition-suppressing region in the PAG was performed before and after an injection of bicuculline (GABAA blocker) into the PMC. The micturition-suppressing region was found at the dorsolateral margin of the rostral PAG. Bladder contractions were not provoked by simultaneous stimulation of the PMC and micturition-suppressing region in the PAG. However, after bicuculline injection into the PMC, partial bladder contractions were provoked by simultaneous stimulation of the PMC and the micturition-suppressing region in the PAG. These results suggest that the dorsolateral margin of the rostral PAG includes the micturition-suppressing region that seems to have neural connections with the PMC. GABA is assumed to be one of the neurotransmitters that are involved in the PMC inhibition from the micturition-suppressing region in the PAG.
Heidelberg Phoneme Discrimination Test (HLAD): Normative Data for Children of the Third Grade and Correlation with Spelling Ability
Authors: Brunner M. , Baeumer C. , Dockter S. , Feldhusen F. , Plinkert P. , Proeschel U.
Published: April 2008

Objective: The Heidelberg Phoneme Discrimination Test (HLAD), developed and standardized in 1998, is widely used in the differential diagnosis of dyslexia. Normative data have only been available for children of the 2nd and 4th grades, while norms for the 3rd grade are still missing. Patients andMethods: We assessed three HLAD subtests [auditory phoneme discrimination, kinesthetic phoneme discrimination (repeating minimal pairs) and phoneme analysis] in 140 children of the 3rd grade from eight elementary schools. Writing capacity was tested via DRT3. Results: Comparing children of the 2nd, 3rd and 4th grades, we found a continuing increase in phoneme discrimination capacity with age. This increase was especially evident for the task of auditory comparison. For the 3rd grade, the correlation between HLAD and writing test (qualitative analysis) was 0.55, and 0.36 between HLAD and writing (quantitative analysis). The correlation with writing tasks was highest in the 2nd grade. Conclusion: The steady increase in phoneme discrimination capacity from the 2nd to 4th grade may indicate maturation and learning effects at least until the age of 10 years.
Cerebellar Posterior Superior Vermis and Cognitive Cluster Scores in Drug-Naive Patients with First-Episode Schizophrenia
Authors: Okugawa Gaku , Nobuhara Kenji , Takase Katsunori , Kinoshita Toshihiko
Published: April 2008

Previously, we performed an MRI study that revealed smaller volumes of the subregions of the cerebellar vermis in men and women with chronic schizophrenia. An issue that arose from that study was whether similar structural changes in the cerebellum are found in patients with first-episode schizophrenia. In the present study, MRI scans were acquired from 14 drug-naive patients with first-episode schizophrenia and 16 healthy subjects, and used to measure the volumes of their cerebellar subregions. Positive symptom, negative symptom and cognitive cluster scores were attained using the Positive and Negative Syndrome Scale. Patients with first-episode schizophrenia had reduced volumes of the anterior vermis and posterior superior vermis compared with healthy subjects. We confirmed that there was a volume reduction of the cerebellar vermis in drug-naive patients with first-episode schizophrenia. Smaller volumes of the posterior superior vermis were associated with worse cognitive cluster scores in patients with first-episode schizophrenia.
Vitamin D: A Candidate for the Environmental Effect in Multiple Sclerosis – Observations from Norway
Authors: Kampman Margitta T. , Brustad Magritt
Published: April 2008

Multiple sclerosis (MS) is a chronic disease of the central nervous system, pathologically characterized by inflammation, demyelination, and axonal damage, presumably auto-immune in nature. Complex interactions between genetic susceptibility and environmental factors, such as vitamin D status and primary Epstein-Barr virus infection in adolescence or later in life, probably determine the MS risk. Norway at a latitude 58–71°N is a discrete exception to the hypothesis that solar UV radiation exposure, mediated by vitamin D, coheres with the latitude gradient seen for MS prevalence. Where UV radiation exposure is low in Norway,vitamin D sufficiency is maintained through a traditional diet providing vitamin D as well as marine omega–3 polyunsaturated fatty acids. This observation supports an environmental interaction between diet and latitude, with vitamin D as the common mediator. The potential roles of vitamin D, other environmental exposures, and genes in the complex aetiology of MS are discussed in this review.
Incidence of Dementia, Alzheimer Disease, and Vascular Dementia in a Japanese Population: Radiation Effects Research Foundation Adult Health Study
Authors: Yamada Michiko , Mimori Yasuyo , Kasagi Fumiyoshi , Miyachi Takafumi , Ohshita Tomohiko , Sudoh Shinji , Ikeda Junko , Matsui Kazuko , Nakamura Shigenobu , Matsumoto Masayasu , Fujiwara Saeko , Sasaki Hideo
Published: April 2008

Objective: To determine the age-, sex-, and subtype-specific incidence of dementia and to assess the effect of education level on the incidence in a Japanese population. Methods: 2,286 dementia-free subjects, aged ≧60 years, were followed for 5.9 years through biennial two-phase examinations. Results: 206 cases of dementia were newly diagnosed based on DSM IV. The incidence per 1,000 person-years was 12.0 for men and 16.6 for women. Based on NINCDS-ADRDA criteria, 80 cases of probable Alzheimer disease (AD) and 50 cases of possible AD were diagnosed. Based on NINDS-AIREN criteria, 36 cases of probable vascular dementia (VaD) and 40 cases of possible VaD were diagnosed. Age and education showed the most statistically significant effects for all dementia. Probable AD showed the most remarkable increase with age and decreased with increasing education level (p = 0.001). Probable VaD showed significant effects of sex (p = 0.033) and sex-age interaction (p = 0.048), but not education (p = 0.26). Conclusion: AD was the predominant type of dementia in this recent incidence study conducted in Japan, suggesting a reduction in VaD and an increase in AD. Age, sex, and education effects differed by dementia subtype.
Prevalence and Incidence of Multiple Sclerosis in Western Greece: A 23-Year Survey
Authors: Papathanasopoulos Panagiotis , Gourzoulidou Efthimia , Messinis Lambros , Georgiou Vasillis , Leotsinidis Michalis
Published: April 2008

Background: The frequency of multiple sclerosis (MS) in Greece remains speculative, as data from many parts are still lacking. Objective: To estimate trends in MS prevalence and annual incidence in western Greece from January 1, 1984 to December 31, 2006. Methods: Patients were identified from the patient records of the Department of Neurology at Patras University Hospital in Rion-Patras. Only patients with a definite MS diagnosis according to Poser’s criteria and retrospective application of the McDonald’s criteria were included. We calculated age- and sex-specific prevalence rates for patients living in the study area on December 31, 2006. Annual incidence rates were calculated for the period 1984–2006. Results: The crude prevalence rate of definite MS cases increased significantly in 23 years from 10.1/100,000 recorded in northeastern Greece in 1984 to 119.61/100,000 on December 31, 2006 in western Greece for the 780 cases still alive. The mean annual incidence rate increased from 2.71/100,000 recorded during the period 1984–1989 to 10.73/100,000 in the 5-year period of 2002–2006. Conclusion: The prevalence rates were higher than expected, but closer than in previous surveys conducted in Greece to those reported recently in Sicily and Istanbul. These findings place the area in the high-risk zone.
An in vivo Investigation on the Wound-Healing Effect of Two Medicinal Herbs Using an Animal Model with Foot Ulcer
Authors: Lau T.W. , Sahota D.S. , Lau C.H. , Chan C.M. , Lam F.C. , Ho Y.Y. , Fung K.P. , Lau C.B.S. , Leung P.C.
Published: April 2008

Background/Aim: Over 190 million people in the world suffer from diabetes mellitus. Diabetics are 25 times more likely to have a leg amputated because of unhealing foot ulcers. Herbal medicine has been used in China to salvage the ulcerated limb. With the aim to study the efficacy of two commonly used herbs for ulcer healing, namely Radix Astragali and Radix Rehmanniae, a good animal model needs to be developed for a proper in vivo investigation. Methods: Firstly, a diabetic animal model was established by streptozotocin injection. Then standard wounds were created on the feet of the diabetic rats. Digital photographs were taken and analyzed by a novel image analysis software. Results: The average ulcer area in the Radix Rehmanniae treatment group was 11.45 mm2, which was significantly smaller than the 15.12 mm2 in the water treatment group (p = 0.04). Radix Astragali, on the other hand, was found to have no significant effect on ulcer shrinkage. Conclusion: Further investigation is needed for the identification of the active principles of Radix Rehmanniae.
Distribution of Thyrotropin-Releasing Hormone (TRH) Immunoreactivity in the Brain of Urodele Amphibians
Authors: Domínguez Laura , López Jesús M. , González Agustín
Published: April 2008

To improve knowledge of the peptidergic systems in the brain of amphibians we have conducted a comparative analysis of the distribution of TRH immunoreactive cell bodies and fibers in three species of urodeles. Fiber labeling was observed in all main brain subdivisions suggesting different control functions for TRH in extrahypothalamic systems. However, as in other vertebrates, TRH neurons were abundant in the hypothalamic nuclei that presumably project to the median eminence and the neural lobe of the hypophysis. Considerable interspecies differences were noted mainly related to innervation of the olfactory and visual centers (thalamus and mesencephalic tectum) and the precise localization of immunoreactive cell bodies, which was assessed by double labeling with tyrosine hydroxylase. The comparison of the distribution of TRH immunoreactive neurons and fibers found in urodeles with those reported for other vertebrates, in particular with anamniotes, reveals a strong resemblance but also notable variations not only across vertebrate classes but also within the same class. In this respect, the virtual lack in urodeles of TRH innervation of the intermediate lobe of the hypophysis clearly contrasts with the innervation found in anurans. Therefore, the important role of skin color adaptation proposed for TRH in anurans on the basis of the direct innervation of the intermediate lobe is not applicable for urodeles.
Pharmacokinetics of Isoflurane in Human Blood
Authors: Lu Chih-Cherng , Tsai Chien-Song , Hu Oliver Yao-Pu , Chen Ruei-Ming , Chen Ta-Liang , Ho Shung-Tai
Published: April 2008

Investigation of isoflurane washout from the human body and brain provides more precise information about elimination in anesthesia. The elimination pattern of isoflurane remains poorly quantified, and therefore this study tried to clarify the pharmacokinetic pattern of isoflurane elimination. Sixteen patients (aged 48–78 years), undergoing coronary arterial bypass grafting surgery were enrolled in this study. Sixty minutes prior to the end of surgery, we kept a fixed 2% inspired isoflurane in 6,000 ml min–1 oxygen flow. Isoflurane supplement was then discontinued to study the 20-min isoflurane elimination. An infrared analyzer was used to determine both inspired isoflurane and end-tidal isoflurane. The isoflurane concentration in the internal jugular bulb blood, arterial blood and pulmonary arterial blood were analyzed by gas chromatography. Biexponential decay function was the best fitted for the end-tidal isoflurane- and arterial blood isoflurane-time curves. There were two distinct components, including initial 5-min fast component and the next 15-min slow component. Monoexponential decay function was the best fitted for the pulmonary arterial blood- and jugular bulb blood-time curves. During elimination, the initial washout of isoflurane from functional residual capacity of lungs is reflected in the fast component of the isoflurane concentration time curves. The later slow component is dominated by the tangible manifestation of physiological membrane barriers, including the existence of alveoli-pulmonary capillary, blood-brain barriers.
Donepezil Treatment of Patients with Severe Alzheimer’s Disease in a Japanese Population: Results from a 24-Week, Double-Blind, Placebo-Controlled, Randomized Trial
Authors: Homma Akira , Imai Yukimichi , Tago Hisao , Asada Takashi , Shigeta Masahiro , Iwamoto Toshihiko , Takita Masashi , Arimoto Itaru , Koma Hiroshi , Ohbayashi Toshio
Published: April 2008

Background/Aims: A 24-week, randomized, parallel-group, double-blind placebo-controlled study was conducted to evaluate the efficacy and tolerability of donepezil in severe Alzheimer’s disease (AD). Methods: Patients with severe AD (Mini-Mental State Examination score 1–12; modified Hachinski Ischemic Score ≤6; Functional Assessment Staging ≧6) were enrolled in this study in Japan. A total of 325 patients were randomized to donepezil 5 mg/day (n = 110), donepezil 10 mg/day (n = 103) or placebo (n = 112). Primary outcome measures were change from baseline to endpoint in the Severe Impairment Battery (SIB) and Clinician’s Interview-Based Impression of Change-plus caregiver input (CIBIC-plus) at the endpoint visit. Results: Donepezil 5 mg/day and 10 mg/day were significantly superior to placebo on the SIB, with a least-squares mean treatment difference of 6.7 and 9.0, respectively (p < 0.001 compared with placebo). CIBIC-plus analyses showed significant differences in favor of donepezil 10 mg/day over placebo at endpoint (p = 0.003). A statistically significant dose-response relationship was demonstrated with the SIB and CIBIC-plus. Donepezil was well tolerated. Conclusion: This study confirmed the effectiveness of donepezil 10 mg/day in patients with severe AD and demonstrated a significant dose-response relationship. Donepezil at dosages of both 5 mg/day and 10 mg/day is safe and well tolerated in Japanese patients with severe AD.