bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral properties and time asymptotic behaviour of linear transport equations in slab geometry
Authors: Latrach Khalid , Dehici Abdelkader
Published: September 2002

The goal of this paper is to analyse some spectral properties of time‐dependent monoenergetic linear transport equation with perfect reflecting boundary conditions.It is proved that the streaming operator generates a strongly continuous group and its explicit expression is derived. This enables us to investigate in details the compactness properties of the second‐order remainder term of the Dyson–Phillips expansion for a large class of collision operators. The validity of the obtained results for perfect periodic boundary conditions is also discussed. Copyright © 2001 John Wiley & Sons, Ltd.
A rigorous modal cutoff analysis of plastic‐clad parabolic cylindrical waveguides: Maxwell's field approach
Authors: Choudhury P. K.
Published: September 2002

Using Maxwell's field equation, an analytical treatment is presented of a step‐index parabolic cylindrical waveguide. The waveguide materials are chosen such that there remains an appreciable difference between the refractive‐index values of the guiding and nonguiding regions, and a strong guidance of electromagnetic waves can perform. Moreover, the chosen materials are in use in the fabrication of low‐cost optical waveguides. The cutoff eigenvalue equation for the waveguide modes is derived under this rigorous condition. Further, no approximations for fields are used in the analysis. A comparison of the results is made with that published earlier on this problem. The analysis shows that the guide supports a fewer number of modes, which is an indication of the possible applications of these guides in optical communications and other related areas. Due to the waveguide geometry, the guide loses its well‐defined discreteness, and a kind of mode bunching is attained; the bunching tendency of modes is found to be much more prominent in this rigorous approach. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 151–156, 2001.
A conical‐pattern annular‐ring microstrip antenna with a photonic bandgap ground plane
Authors: Lin Shun‐Yun , Wong Kin‐Lu
Published: September 2002

A probe‐fed annular‐ring microstrip antenna with a photonic bandgap (PBG) ground plane operating in the higher order mode of TM21for conical‐pattern radiation is experimentally demonstrated. The antenna studied is printed on a thin FR4 substrate (relative permittivity 4.4) and, owing to the PBG ground plane used, significant improvements in the antenna performances are observed. The obtained impedance bandwidth is doubled, and the antenna gain is enhanced by about 7 dBi. Details of the experimental results are presented and discussed. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 159–161, 2001.
Analysis of microstrip discontinuity by edge‐based FEM combined with SOC technique
Authors: Chen R. S. , Wang,and D. X. , Yung Edward K. N.
Published: September 2002

In this paper, the application of the edge‐based vector finite‐element method combined with the short‐open calibration (SOC) technique to three‐dimensional microstrip discontinuity is presented. This SOC technique is directly accommodated in the FEM algorithm, and is used to truncate the computational domain. The developed FEM algorithm is applied to the modeling of microstrip discontinuities that can be segmented into two distinct sections: a static model of feedlines, and a dynamic model of circuit discontinuity. The FEM is formulated in such a way that the port voltages and currents are explicitly represented through relevant network matrices. The SOC technique is used to remove or separate unwanted parasitic errors brought by the approximation of the impressed voltage source, and also to address the problem of the resulting consistency between different simulations. Truncation of the computational domain by the SOC technique for microstrip circuits makes the iterative solvers for large‐sparse linear matrix equations from the FEM converge much faster than by perfectly matching layers (PMLs). Results for microstrip discontinuities are very well compared with available publications. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 169–174, 2001.
Four‐element TEM horn array for radiating ultra‐wideband electromagnetic pulses
Authors: Wang Jianguo , Tian Chunming , Luo Genxin , Chen Yusheng , Ge Debiao
Published: September 2002

In this paper, ultra‐wideband arrays using interconnected transverse electromagnetic (TEM) horns are studied. The paper analyzes the radiation characteristics of four‐element arrays using the finite‐difference time‐domain (FDTD) method. The computed results for arrays are compared with those for the single TEM horn and two‐element array. Some properties of the four‐element array, such as the input impedance, voltage standing‐wave ratio, and energy pattern, are presented in this paper. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 190–194, 2001.
Modeling of multiple scattering among vias in planar waveguides using Foldy–Lax equations
Authors: Tsang Leung , Chen Houfei , Huang Chung‐Chi , Jandhyala Vikram
Published: September 2002

The full‐wave solution of multiple scattering among cylindrical vias in planar waveguides is modeled by using Foldy–Lax equations. By using the equivalence principle, the coupling among traces with many vias is decomposed into interior and exterior problems. For the interior problem, the dyadic Green's function is expressed in terms of vector cylindrical waves and waveguide modes. The Foldy–Lax equations of multiple scattering among the cylindrical vias are calculated. The waveguide modes are decoupled in the Foldy–Lax equations. The scattering matrix of coupling among vias is calculated. Numerical simulations of the scattering matrix are illustrated for several hundred vias. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 201–208, 2001.
Dual‐polarized dielectric resonator antennas
Authors: Huang Chih‐Yu , Chiou Tzung‐Wern , Wong Kin‐Lu
Published: September 2002

Two feeding designs for achieving dual orthogonal linear polarization operations of dielectric resonator (DR) antennas fed by microstrip lines are demonstrated. The microstrip feedlines can be placed directly under the DR or conformal to the surface of the DR. Good dual‐polarization excitation can be obtained for the two feeding designs. Experimental results for the return loss, isolation between two feeding ports, and radiation patterns are presented and discussed. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 222–223, 2001.
Grating structures with symmetric fractionally organized gaps
Authors: Barbosa Carmem L. , Cazo Rogério M. , Hattori Haroldo T.
Published: September 2002

It is well known that grating structures with subgratings separated by small identical gaps (for example, quarter‐wavelength gaps) create a transmission window in the middle of the reflectivity spectrum. In this paper, we analyze structures with mirror symmetry with respect to their centers, but with gaps at both ends that continuously decrease toward their centers. These structures exhibit several dips in the central lobe of the reflectivity spectrum, with spectral properties (linewidths, spectral spacing between dips, etc.) dependent upon the design parameters of the subgratings (length, period, and magnitude of the modulation of the core refractive index). In a special case, the spectral separation between two dips in the main lobe can be controlled by adequately changing these parameters. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 223–229, 2001.
Simulation study of thermal effects in bistable laser diodes
Authors: Madhan M. Ganesh , Vaya P. R. , Gunasekaran N.
Published: September 2002

The effect of temperature on the hysterisis behavior, threshold current, and threshold voltage of a bistable laser diode are studied by simulating its equivalent electrical circuit, developed from the rate equations. Simulations are carried out using the circuit analysis program PSPICE. The study shows that the forward threshold current, hystersis width, and threshold voltage vary exponentially with temperature. Further, the transient temperature variation in the active region due to pulsed input is also analyzed. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 233–237, 2001.
Successful therapy of subcutaneously growing human hepatoblastoma xenografts with topotecan*
Authors: Warmann Steven W. , Fuchs Jörg , Wilkens Ludwig , Gratz Klaus Friedrich , von Schweinitz Dietrich , Mildenberger Hermann
Published: September 2002

Background

Human hepatoblastoma is an infrequent liver tumor in children. Although many hepatoblastomas can be treated adequately with well‐defined treatment regimens, problems still persist with advanced and non‐resectable tumors; in these cases, an effective chemotherapy is necessary to improve the patients' prognosis. This underlines the need for alternative anti‐tumor agents in the treatment of human hepatoblastoma. The aim of this study was to investigate the therapeutic effects of topotecan, a water‐soluble camptothecin analog (topoisomerase‐I‐antagonist), in an in vivo model of three human hepatoblastomas xenografted subcutaneously into nude mice.

Procedure

Hepatoblastoma cell suspensions from three children were transplanted subcutaneously into nude mice NMRI (nu/nu). Treatment with topotecan was initiated when the tumors reached a volume between 50 and 80 mm3. A dose of 6.6 mg/kg of topotecan were given intraperitoneally every 4 days on four occasions. The tumor volume development and α‐fetoprotein alterations were measured and statistically analyzed. After the treatment, the tumors were investigated histologically and by immunhistochemistry.

Results

There was a significant reduction of tumor growth in all treated tumor xenografts vs. untreated control groups (mean relative volume 3.1 vs. 47.4; P = 0,0015–0,0079). Serum α‐fetoprotein levels were reduced in all three cell lines, in two of them significantly (mean 44,535 kU/l vs. 228,883 kU/l; P = 0.005–0.246). Histologically, the tumor necrosis rates were higher and immunhistochemistry showed lower proliferation activities in the treated tumor xenografts vs. the control groups.

Conclusion

The data show that topotecan is an effective agent in the treatment of human hepatoblastoma xenografts. From these results, treatment with topotecan appears to be a promising alternative in the pre‐ and postoperative therapy of patients suffering from human hepatoblastoma. Med Pediatr Oncol 2001;37:449–454. © 2001 Wiley‐Liss, Inc.
Immunohistochemical detection of p53 protein expression as a prognostic indicator in Wilms tumor
Authors: Sredni Simone Treiger , de Camargo Beatriz , Lopes Luiz Fernando , Teixeira Roberto , Simpson Andrew
Published: September 2002

Background

Mutations of the tumor suppressor gene p53 are commonly found in several kinds of human cancer. In some types of neoplasms, accumulation of p53 protein has been reported to correlate with more aggressive clinical behavior. The role of p53 expression in Wilms tumors (WT) is not clear yet, but most studies have confirmed its correlation with anaplasia and advanced stage disease.

Procedure

Ninety‐seven WT were evaluated for p53 expression by immunohistochemistry in formalin‐fixed parafin‐embedded tissue and correlated with outcome. Tumors were classified as p53‐Negative (p53‐N) when no positivity was observed or only few cells showed weak positivity (0/1+) and p53‐Positive (p53‐P) when there was a diffuse and strong nuclear positivity (2+/3+).

Results

p53‐P was detected in 13 out of 97 tumors and was associated with disease relapse (39 vs.17%; P = 0.06) but not with anaplasia. Among p53‐N patients only 5% had metastatic disease compared with 31% of the p53‐P sample. (P = 0.038). Overall survival was 94% for patients with p53‐N vs. 85% for patients with p53‐P at 1 year (P = 0.34).

Conclusions

p53 expression in Wilms tumor detected by immunohistochemistry seems to be associated with advanced disease and relapse. Med Pediatr Oncol 2001;37:455–458. © 2001 Wiley‐Liss, Inc.
New approach to gridding using regularization and estimation theory
Authors: Rosenfeld Daniel
Published: September 2002

When sampling under time‐varying gradients, data is acquired over a non‐equally spaced grid in k‐space. The most computationally efficient method of reconstruction is first to interpolate the data onto a Cartesian grid, enabling the subsequent use of the inverse fast Fourier transform (IFFT). The most commonly used interpolation technique is called gridding, and is comprised of four steps: precompensation, convolution with a Kaiser‐Bessel window, IFFT, and postcompensation. Recently, the author introduced a new gridding method called Block Uniform ReSampling (BURS), which is both optimal and efficient. The interpolation coefficients are computed by solving a set of linear equations using singular value decomposition (SVD). BURS requires neither the pre‐ nor the postcompensation steps, and resamples onto an n × n grid rather than the 2n × 2n matrix required by conventional gridding. This significantly decreases the computational complexity. Several authors have reported that although the BURS algorithm is very accurate, it is also sensitive to noise. As a consequence, even in the presence of a low level of measurement noise, the resulting image is often highly contaminated with noise. In this work, the origin of the noise sensitivity is traced back to the potentially ill‐posed matrix inversion performed by BURS. Two approaches to the solution are presented. The first uses regularization theory to stabilize the inversion process. The second formulates the interpolation as an estimation problem, and employs estimation theory for the solution. The new algorithm, called rBURS, contains a regularization parameter, which is used to trade off the accuracy of the result against the signal‐to‐noise ratio (SNR). The results of the new method are compared with those obtained using conventional gridding via simulations. For the SNR performance of conventional gridding, it is shown that the rBURS algorithm exhibits equal or better accuracy. This is achieved at a decreased computational cost compared to conventional gridding. Magn Reson Med 48:193–202, 2002. © 2002 Wiley‐Liss, Inc.
Motion correction using the k‐space phase difference of orthogonal acquisitions
Authors: Welch Edward Brian , Felmlee Joel P. , Ehman Richard L. , Manduca Armando
Published: September 2002

Rigid body translations of an object in MRI create image artifacts along the phase‐encode (PE) direction in standard 2DFT imaging. If two images are acquired with swapped PE direction, it is possible to determine and correct for arbitrary in‐plane translational interview motions in both images directly from phase differences in the k‐space acquisitions by solving a large system of linear equations. For example, if one assumes two N × N 2D acquisitions with in‐plane translational interview motion, 4N unknown motions may corrupt the two images, but the phase difference at each point in k‐space yields a system of N2 equations in these 4N unknowns. If the acquisitions have orthogonal PE directions, this highly overdetermined system of equations can be solved to provide the motion records, which in turn can be used to correct the motion artifacts in each image. The theory of this orthogonal k‐space phase difference (ORKPHAD) technique is described, and results are presented for synthetic and in vivo motion‐corrupted data sets. In all cases, the data showed clear improvement of translation‐induced artifacts. These methods do not require special pulse sequences and are theoretically generalizable to partial Fourier imaging and 3D acquisitions. Magn Reson Med 48:147–156, 2002. © 2002 Wiley‐Liss, Inc.
Apparent diffusion of water, ions, and small molecules in the Xenopus oocyte is consistent with Brownian displacement
Authors: Sehy Jonathan V. , Ackerman Joseph J.H. , Neil Jeffrey J.
Published: September 2002

The incoherent displacement of water in living tissues is of considerable interest because of the widespread use of diffusion‐weighted MRI, for which image contrast is based on the water apparent diffusion coefficient (ADC). It has been hypothesized that the decrease in water ADC associated with brain injury is primarily due to a reduction in the ADC of water in the intracellular space. Xenopus oocytes permit direct measurement of ADC values for intracellular molecules, thereby providing insight into the nature of intracellular motion. In this study, the measured ADC values of small molecules and ions are shown to be primarily size‐dependent, indicating that intracellular water motion in the oocyte is mainly Brownian displacement with little or no role for cytoplasmic streaming. Further, intracellular water ADC values show no dependence on diffusion time over a broad range (3.4–100 ms), suggesting that barriers to displacement are finely spaced (≤ 2–3 μm). The water diffusion shows some small anisotropy, suggesting that the cell has structure, giving water displacement a directional preference. The calculated intracellular apparent viscosity, which reflects the combined effects of barriers to motion, intermolecular binding, and fluid phase viscosity was 2.07 ± 0.09 cP. Magn Reson Med 48:42–51, 2002. © 2002 Wiley‐Liss, Inc.
Effect of adrenergic stimulation on Rb+ uptake in normal and ischemic areas of isolated pig hearts: 87Rb MRI study
Authors: Kupriyanov V.V. , Xiang B. , Sun J. , Jilkina O.
Published: September 2002

The role of adrenergic stimulation in Rb+ uptake in normal and ischemic areas of pig hearts was investigated using an agonist (dobutamine) and an antagonist (S‐propranolol). The left anterior descending artery (LAD) in isolated pig hearts was cannulated to maintain adequate perfusion of the LAD bed (2.2–2.8 ml/min/g). Rb+ loading was initiated by switching perfusion to Rb+‐containing Krebs‐Henseleit (KH) buffer in the presence of 0.1 μM dobutamine, 0.5 μM propranolol, or no drug (control), and the LAD flow was reduced to 10% of the baseline for 120 min. The flow through the LAD was then restored to normal and the drugs were removed. In all groups the rate of Rb+ uptake obtained from serial 87Rb images was severely depressed in the ischemic anterior wall relative to that in the normal posterior wall. Dobutamine increased the rate of Rb+ uptake in the posterior wall (6.3% ± 1.4% vs. 2.5% ± 0.25% per minute in control) and did not affect the rate in the anterior wall (0.86% ± 0.40% vs. 1.14% ± 0.19% per minute in control). Propranolol did not affect Rb+ uptake in either of these areas. We conclude that the stimulation of Rb+ uptake by dobutamine is related to activation of Na+/K+ ATPase and passive Na+ influx in normal tissue. The lack of any effect of propranolol implies a low level of endogenous norepinephrine during low‐flow (LF) ischemia. Magn Reson Med 48:15–20, 2002. © 2002 Wiley‐Liss, Inc.
Multishot 3D slice‐select tailored RF pulses for MRI
Authors: Stenger V. Andrew , Boada Fernando E. , Noll Douglas C.
Published: September 2002

A multishot 3D slice‐select tailored RF pulse method is presented for the excitation of slice profiles with arbitrary resolution. This method is derived from the linearity of the small tip angle approximation, allowing for the decomposition of small tip angle tailored RF pulses into separate excitations. The final image is created by complex summation of the images acquired from the individual excitations. This technique overcomes the limitation of requiring a long pulse to excite thin slices with adequate resolution. This has implications in applications including T‐weighted functional MRI in brain regions corrupted by intravoxel dephasing artifacts due to susceptibility variations. Simulations, phantom experiments, and human brain images are presented. It is demonstrated that at most four shots of 40 ms pulse length are needed to excite a 5 mm‐thick slice in the brain with reduced susceptibility artifacts at 3T. Magn Reson Med 48:157–165, 2002. © 2002 Wiley‐Liss, Inc.
On the application of a non‐CPMG single‐shot fast spin‐echo sequence to diffusion tensor MRI of the human brain
Authors: Bastin Mark E. , Le Roux Patrick
Published: September 2002

The strong sensitivity of Carr‐Purcell‐Meiboom‐Gill (CPMG) fast spin‐echo (FSE) sequences, such as rapid acquisition with relaxation enhancement (RARE), to the phase of the prepared transverse magnetization means that artifact‐free single‐shot diffusion‐weighted images can currently only be obtained with a 30–50% reduction in the signal‐to‐noise ratio (SNR). However, this phase sensitivity and signal loss can be addressed in FSE sequences that use quadratic phase modulation of the radiofrequency (RF) refocusing pulses to generate a sustained train of stable echoes. Here the first application of such a non‐CPMG single‐shot FSE (ssFSE) sequence to diffusion tensor MR imaging (DT‐MRI) of the human brain is described. This approach provides high SNR diffusion‐weighted images that have little or no susceptibility to poor B0 magnetic field homogeneity and the strong eddy currents typically present in DT‐MRI experiments. Magn Reson Med 48:6–14, 2002. © 2002 Wiley‐Liss, Inc.
Simultaneous echo refocusing in EPI
Authors: Feinberg David A. , Reese Timothy G. , Wedeen Van J.
Published: September 2002

A method to encode multiple two‐dimensional Fourier transform (2D FT) images within a single echo train is presented. This new method, simultaneous echo refocusing (SER), is a departure from prior echo planar image (EPI) sequences which use repeated single‐shot echo trains for multislice imaging. SER simultaneously acquires multiple slices in a single‐shot echo train utilizing a shared refocusing process. The SER technique acquires data faster than conventional multislice EPI since it uses fewer gradient switchings and fewer preparation pulses such as diffusion gradients. SER introduces a new capability to simultaneously record multiple spatially separated sources of physiologic information in subsecond image acquisitions, which enables several applications that are dependent on temporal coherence in MRI data including velocity vector field mapping and brain activation mapping. Magn Reson Med 48:1–5, 2002. © 2002 Wiley‐Liss, Inc.
Numerical study of boundary conditions for solute transport through a porous medium
Authors: Peters Glen P. , Smith David W.
Published: September 2002

A transition region may be defined as a region of rapid change in medium properties about the interface between two porous media or at the interface between a porous medium and a reservoir. Modelling the transition region between different porous media can assist in the selection of the most appropriate boundary conditions for the standard advection–dispersion equation (ADE). An advantage of modelling the transition region is that it removes the need for explicitly defining boundary conditions, though boundary conditions may be recovered as limiting cases. As the width of a transition region is reduced, the solution of the transition region model (TR model) becomes equivalent to the solution of the standard ADE model with correct boundary conditions. In this paper numerical simulations using the TR model are employed to select the most appropriate boundary conditions for the standard ADE under a variety of configurations and conditions. It is shown that at the inlet boundary between a reservoir and porous medium, continuity of solute mass flux should be used as the boundary condition. At the boundary interface between two porous media both continuity of solute concentration and solute mass flux should be used. Finally, in a finite porous medium where the solute is allowed to advect freely from the exit point, both continuity of solute concentration and solute mass flux should be used as the outlet boundary condition. The findings made here are discussed with reference to a detailed review of previous relevant theoretical and experimental observations. Copyright © 2001 John Wiley & Sons, Ltd.
Dynamic response of soft poroelastic bed to linear water waves—a boundary layer correction approach
Authors: Hsieh Ping‐Cheng , Huang Liang‐Hsiung , Wang Tsan‐Wen
Published: September 2002

According to Chen et al. (Journal of Engineering Mechanics, ASCE 1997; 123(10):1041–1049.) a boundary layer exists within the porous bed and near the homogeneous‐water/porous‐bed interface when oscillatory water waves propagate over a soft poroelastic bed. This boundary layer makes the evaluation of the second kind of longitudinal wave inside the soft poroelastic bed very inaccurate. In this study, the boundary layer correction approach for the poroelastic bed is applied to the boundary value problem of linear oscillatory water waves propagating over a soft poroelastic bed. After the analyses of length scale and order of magnitude of physical variables are done, a perturbation expansion for the boundary layer correction approach based on two small parameters is proposed and solved. The solutions are carried out for the first and third kind of waves throughout the entire domain. The second kind of wave which disappears outside the boundary layer is solved systematically inside the boundary layer. The results are compared with the linear wave solutions of Huang and Song (Journal of Engineering Mechanics, ASCE 1993; 119:1003–1020.) to confirm the validity. Moreover, a simplified boundary layer correction formulation which is expected to be very useful in numerical computation is also proposed. Copyright © 2001 John Wiley & Sons, Ltd.
Generating Pareto‐optimal boundary points in multiparty negotiations using constraint proposal method
Authors: Heiskanen Pirja
Published: September 2002

In this paper a constraint proposal method is developed for computing Pareto‐optimal solutions in multiparty negotiations over continuous issues. Constraint proposal methods have been previously studied in a case where the decision set is unconstrained. Here we extend the method to situations with a constrained decision set. In the method the computation of the Pareto‐optimal solutions is decentralized so that the DMs do not have to know each others' value functions. During the procedure they have to indicate their optimal solutions on different sets of linear constraints. When the optimal solutions coincide, the common optimum is a candidate for a Pareto‐optimal point. The constraint proposal method can be used to generate either one Pareto‐optimal solution dominating the status quo solution or several Pareto‐optimal solutions. In latter case a distributive negotiation among the efficient points can be carried out afterwards. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48: 210–225, 2001
Mobility prediction and routing inad hocwireless networks
Authors: Su William , Lee Sung‐Ju , Gerla Mario
Published: September 2002

By exploiting non‐random behaviors for the mobility patterns that mobile users exhibit, we can predict the future state of network topology and perform route reconstruction proactively in a timely manner. Moreover, by using the predicted information on the network topology, we can eliminate transmissions of control packets otherwise needed to reconstruct the route and thus reduce overhead. In this paper, we propose various schemes to improve routing protocol performances by using mobility prediction. We then evaluate the effectiveness of using mobility prediction via simulation. Copyright © 2001 John Wiley & Sons, Ltd.
Enhancing TCP performance with a load‐adaptive RED mechanism
Authors: Aweya James , Ouellette Michel , Montuno Delfin Y. , Chapman Alan
Published: September 2002

This paper describes a technique for enhancing the effectiveness of RED by dynamically changing the threshold settings as the number of connections (and system load) changes. Using this technique, routers and switches can effectively control packet losses and TCP timeouts while maintaining high link utilization. Copyright © 2001 John Wiley & Sons, Ltd.
ATM test‐bed architecture for training purposes
Authors: Ahmed Rana Ejaz
Published: September 2002

Due to the recent tremendous growth in ATM products, there is a strong need for training and education for engineers working in the field of ATM networks. This paper describes the architecture of an ATM test‐bed that can be used to provide such training. Copyright © 2001 John Wiley & Sons, Ltd.
Network optimization with stochastic traffic flows
Authors: Liu Xian
Published: September 2002

Conventional management optimization models are being challenged by the evolution of electronic and optical networks and it is necessary to incorporate the stochastic effect of traffic flows into network models. This paper introduces the stochastic programming (SP) methodology to characterize the stochastic traffic. Two network models, capacity assignment and flow assignment, are proposed. One of the SP approaches, the Wait‐and‐See method, is integrated into the presented models. Simulation results are reported. Copyright © 2002 John Wiley & Sons, Ltd.
Postembryonic proliferation in the spiny lobster antennular epithelium: Rate of genesis of olfactory receptor neurons is dependent on molt stage
Authors: Harrison Paul J.H. , Cate Holly S. , Swanson Eric S. , Derby Charles D.
Published: September 2002

Olfactory systems undergo continuous growth and turnover in many animals. Many decapod crustaceans, such as lobsters and crayfish, have indeterminate growth, and in these animals, turnover of both peripheral and central components of the olfactory system occurs continuously throughout life. In this study, we examine the dynamics of olfactory receptor neuron (ORN) proliferation in the antennule of the Caribbean spiny lobster, Panulirus argus, using in vivo incorporation of the cell proliferation marker BrdU. We show that addition of ORNs occurs in a “proximal proliferation zone” (PPZ), which exists on the proximo‐lateral margin of the existing ORN population. The PPZ is spatially and temporally dynamic in that it travels as a wave in the proximal and lateral directions in the antennule. This wave results in continuous addition of ORNs throughout the molt cycle. The rate of proliferation, as measured by the size and shape of the PPZ, changes depending on the animal's molt stage. The rate is highest during premolt and lowest during intermolt. ORNs are the most prominent cell‐type produced in the PPZ, but other cell types, including glia, are also produced. Patches of proliferating epithelial cells occur immediately proximal to the PPZ, suggesting that neuronal and glial precursors reside in this region. Possible mechanisms for peripheral and central modulation of ORN development are discussed. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 51–66, 2001
RISK‐1: A novel MAPK homologue in axoplasm that is activated and retrogradely transported after nerve injury
Authors: Sung Ying Ju , Povelones Michael , Ambron Richard T.
Published: September 2002

Sensory neurons (SNs) of Aplysia are widely used to study the molecular correlates of learning. Among these is the activation of an Aplysia (ap) MAPK that phosphorylates the transcription factor apC/EBPβ. Because crushing the axons of the SNs induces changes similar to learning, we tested the hypothesis that apMAPK is a point of convergence on the pathways for learning and injury. One event in common is long‐term hyperexcitability (LTH), and LTH was induced in the SNs after intrasomatic injection of active vertebrate extracellular signal‐regulated kinase 1 (ERK1; as an apMAPK surrogate). Nerve crush activated an axoplasmic kinase at the site of injury that phosphorylated apC/EBPβ. Surprisingly, this was not apMAPK, but a kinase that was recognized by antibodies to vertebrate ERKs and to doubly phosphorylated, activated ERKs. The activated kinase was transported to the cell body and nucleus and its arrival was concurrent with an injury‐induced increase in apC/EBPβ mRNA and protein. We call this retrogradely transported kinase RISK‐1. RISK‐1 initiated the binding of apC/EBPβ to the ERE enhancer site in vitro and an increase in ERE‐binding was detected in injured neurons containing active RISK‐1. Thus, Aplysia neurons contain two MAPK homologues, one of which is a late acting retrogradely transported injury signal. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 67–79, 2001
Some observations on the l2 convergence of the additive Schwarz preconditioned GMRES method
Authors: Cai Xiao‐Chuan , Zou Jun
Published: September 2002

Additive Schwarz preconditioned GMRES is a powerful method for solving large sparse linear systems of equations on parallel computers. The algorithm is often implemented in the Euclidean norm, or the discrete l2 norm, however, the optimal convergence result is available only in the energy norm (or the equivalent Sobolev H1 norm). Very little progress has been made in the theoretical understanding of the l2 behaviour of this very successful algorithm. To add to the difficulty in developing a full l2 theory, in this note, we construct explicit examples and show that the optimal convergence of additive Schwarz preconditioned GMRES in l2 cannot be obtained using the existing GMRES theory. More precisely speaking, we show that the symmetric part of the preconditioned matrix, which plays a role in the Eisenstat–Elman–Schultz theory, has at least one negative eigenvalue, and we show that the condition number of the best possible eigenmatrix that diagonalizes the preconditioned matrix, key to the Saad–Schultz theory, is bounded from both above and below by constants multiplied by h−1/2. Here h is the finite element mesh size. The results presented in this paper are mostly negative, but we believe that the techniques used in our proofs may have wide applications in the further development of the l2 convergence theory and in other areas of domain decomposition methods. Copyright © 2002 John Wiley & Sons, Ltd.
Some recent issues in computational failure mechanics
Authors: Borst René de
Published: September 2002

An overview is given of some recent developments in computational modelling of localization and failure phenomena in solids. Cohesive‐zone models are considered as well as enrichment of continua using gradients in space and in time. The latter models are applied to static instabilities as well as to propagative instabilities. The determination of the additional parameters that emerge in gradient continua is treated and attention is paid to the spatial resolution that is necessary to properly capture bands of localized deformation. Finally, the impact is considered which imperfection patterns may have on the failure mode. Copyright © 2001 John Wiley & Sons, Ltd.
A micro–macro and parallel computational strategy for highly heterogeneous structures
Authors: Ladevèze P. , Loiseau O. , Dureisseix D.
Published: September 2002

A new micro–macro computational strategy is proposed for the analysis of structures which are described up to the micro level, such as composite structures. The description of micro and macro quantities is performed on the interface arising from the decomposition of the structure into an assembly of substructures and interfaces. A traction‐based version of the micro–macro strategy is described and the influence of the numerical parameters as well as the performance of the approach are discussed. Copyright © 2001 John Wiley & Sons, Ltd.
A calcium channel blocker nicardipine protects neurons from zinc‐induced toxicity in rat hippocampus
Authors: Demir Şerif , Bağirici Faruk , Marangoz Cafer
Published: September 2002

The neurotoxicity is an important problem in medicine. The present study was designed to investigate the changes in pyramidal cell density of rat hippocampus after intracortical zinc sulphate (ZnSO4) and calcium channel blocker nicardipine administration. Animals were divided into three groups as control, zinc and zinc+nicardipine groups. Zinc sulphate (500 µg/kg) was injected intracortically into 2 mm lateral of Bregma. The same volume of saline (2µl) was given to the rats belonging to control group. Rats in the third group, zinc + nicardipine were injected in to same injection point.

Animal groups were observed for one week. The zinc + nicardipine group received daily nicardipine (10mg/kg/day) for seven days. After a week, the rats were perfused intracardially with neutral formaline. The hippocampal sections were stained with hematoxylen‐eosine. Pyramidal cells per unit length (mm) were counted under light microscope (with 400x magnification). The density of pyramidal cell was found as follows (values presented for each group are belong to right CA1, right CA2, right CA3, left CA1, left CA2, left CA3 respectively): control groups; 126.2 ± 4.5 neuron/mm, 117.3 ± 6.2 neuron/mm, 113.6 ± 4.0 neuron/mm, 129.9 ± 4.0 neuron/mm, 129.8 ± 5.0, 127.7 ± 3.3, zinc groups; 38.3 ± 1.3 neuron/mm, 36.5 ± 1.6 neuron/mm, 34.1 ± 1.2, 35.0 ± 1.4 neuron/mm, 33.9 ± 1.5 neuron/mm, 32.9 ± 1.2 neuron/mm, zinc + nic groups; 87.9 ± 1.4 neuron/mm, 89.9 ± 3.7 neuron/mm, 82.2 ± 2.8 neuron/mm, 91.2 ± 3.8 neuron/mm, 91.9 ± 4.6 neuron/mm, 84.3 ± 4.0 neuron/mm. The differences between groups were found to be statistically significant (p < 0.001).

These results suggest that nicardipine considerably reverses the decrease in pyramidal cell density probably caused by zinc administration into the hippocampus of rat. This effect may be due to the prevention of excessive calcium influx and hence the prevention of cell loss. The results also suggest a possible therapeutic role for calcium channel blocker nicardipine in neurodegenerative diseases.
Phosphorylation and inactivation of Bad by GDNF‐activated protein kinase B/Akt in human neuroblastoma cells
Authors: Neff Frauke , Eggert Karla , Schlegel Jürgen
Published: September 2002

Here we show, that GDNF activates the endogenous phosphatidylinositol‐3′ kinase (PI3K)/proteinkinase B/Akt (PKB/Akt) signalling pathway and the mitogen activated protein kinase (MAPK) cascade in human neuroblastoma cell line SH‐SY5Y. Consistent with this finding we found a PI3K‐dependent but not MAPK‐dependent binding of phosphorylated Bad proteins to 14‐3‐3 proteins. Our data support the hypothesis that GDNF exerts its neuroprotective effects by activation of the anti‐apoptotic PI3K/Akt signalling pathway and subsequent inactivation of Bad.
Dopamine neurons heterozygous for the Nurr1‐null allele have reduced survival in vitro
Authors: Eells J.B. , Yeung S.K. , Nikodem V.M.
Published: September 2002

Although Nurr1 is essential for the differentiation of midbrain dopamine neurons, its function in mature dopamine neurons has not been determined. In order to investigate the role of Nurr1 in the survival of dopamine neurons, neurons from the mesencephalon of newborn pups heterozygous for the Nurr1‐null mutation (+/–) or wild‐type (+/+) littermates were grown in culture. Postnatal cultures revealed a significant reduction in the survival and growth of tyrosine hydroxylase immunoreactive (TH‐IR) neurons from Nurr1 +/– pups as early as 1 day in culture despite having normal TH‐IR neuron numbers in vivo. The Nurr1 +/+ and +/– TH‐IR neurons responded to treatment with forskolin, glia cell‐line derived neurotrophic factor and brain‐derived neurotrophic factor, although significantly fewer Nurr +/– TH/IR neurons survived. These data suggest that the loss of a single allele of Nurr1 significantly reduces the survival capacity of postnatal dopamine neurons in vitro without affecting normal development or differentiation.
Parameter studies of modal vibrations associated with impurity pinned dislocations in a metal single crystal
Authors: Cooke Charlie H. , Kroll John
Published: September 2002

Koehler's model [1–2] of motion for edge‐type dislocations in a metal single crystal that are pinned down by impurity atoms is studied. An exact solution can be found, which is composed of a rapidly decaying transient and a steady time‐oscillating, steady state vibration. This solution is used to improve Koehler's [1] approximation to the steady time‐oscillating steady state vibration. General parameter studies of the modes of oscillation are then performed. The present result is of some significance, because it allows insight into the behavior of crystalline solids over a wide parameter range, whereas Koehler's asymptotic approach is valid only for materials that exhibit order‐of‐magnitude variation in system parameters. © 2001 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 17: 427–439, 2001.
Convergence acceleration by varying time‐step size using Bi‐CGSTAB method for turbulent flow computation
Authors: Tsai W. B. , Lin W. W. , Chieng C.‐C.
Published: September 2002

A design of varying step size approach both in time span and spatial coordinate systems to achieve fast convergence is demonstrated in this study. This method is based on the concept of minimization of residuals by the Bi‐CGSTAB algorithm, so that the convergence can be enforced by varying the time‐step size. The numerical results show that the time‐step size determined by the proposed method improves the convergence rate for turbulent computations using advanced turbulence models in low Reynolds‐number form, and the degree of improvement increases with the degree of the complexity of the turbulence models. © 2001 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 17: 454–474, 2001.
Patient‐centered interventions
Authors: Lauver Diane R. , Ward Sandra E. , Heidrich Susan M. , Keller Mary L. , Bowers Barbara J. , Brennan Patricia Flatley , Kirchhoff Karin T. , Wells Thelma J.
Published: September 2002

Patient‐centered care is valued in nursing. However, until recently, nurse‐researchers have focused on testing the effects of standardized rather than patient‐centered interventions (PCIs). The latter are those interventions that are altered to address selected patient characteristics (e.g., beliefs, habits, or goals). PCIs have been well received, and in some studies they have been associated with improved health outcomes. In this article we describe briefly the concept patient centered, summarize the development of research on PCIs, discuss kinds of PCIs, provide examples of PCIs and how they have been derived and implemented, and raise issues for theory and future research. © 2002 Wiley Periodicals, Inc. Res Nurs Health 25:246–255, 2002
Design of high efficiency polymeric cation exchange fibers1
Authors: Dominguez Lourdes , Benak Kelly R. , Economy James
Published: September 2002

In this study, we have been exploring a new ion exchange material in the form of a fiber that could yield a number of important advantages over conventional ion exchange beads. In this approach, ion exchange fibers are prepared by 1) coating low‐cost glass fiber substrates with a polystyrene/divinylbenzene oligomer, 2) curing, and 3) sulfonating. The sulfonation process and effects of varying degrees of crosslinking were characterized through diffuse reflectance infrared spectroscopy and acid‐base neutralization titrations. Capacities of 4.7 meq/g (on a per resin basis) were easily obtained. Kinetics experiments showed the contact efficiencies of the new systems were greatly improved over the traditional beads due to greater surface associated with the film morphology and shorter diffusion lengths. This translated into an order of magnitude increase in ion exchange rate. As a result of the thin coatings, the use of solvents prior to functionalization, and preswelling of the finished product prior to end‐use were eliminated. Scanning electron microscopy was used to image the fibers and track­their mechanical integrity through various stages of­the process. Finally, repetitive regenerations proved­the long‐term stability of the spent fibers. Copyright­© 2001 John Wiley & Sons, Ltd.
Poly(imidoaryl ether)s with bulky highly fluorescent pendent groups
Authors: Meng Yuezhong , Hill Antisar R. , Hay Allan S.
Published: September 2002

Three novel aromatic imidoaryl bisphenols 6a–c with bulky groups of varying size on the pendent phenyl ring have been synthesized from 3,8‐bis(4‐hydroxyphenyl)‐­N‐phenyl‐1,2‐naphthalimide 1a. Poly(imidoaryl ether)s were synthesized in dipolar aprotic solvents by reacting the monomers with activated difluoro compounds. Glass transition temperatures (T
g) for the polymers are in the range 265.9–315.0 °C, and they exhibit a range of colors from yellow to red. The highest T
g and 5% weight loss temperature of these polymers were 315 and 496 °C, respectively. Most of the polymers are soluble in chloroform at room temperature. The UV‐vis absorption spectra of polymers 11ae, 11be and 16 were recorded in chloroform. Polymer 16 has the most intense absorption peaks (above 300 nm) at 492 and 528 nm, respectively, while the fluorescent spectrum of polymer 16 shows several peaks at 428, 539, 577 and 625 nm, respectively, when excited at 350 nm. Copyright © 2001 John Wiley & Sons, Ltd.
Degradation and 5‐fluorouracil release behavior in vitro of polycaprolactone/poly(ethylene oxide)/polylactide tri‐component copolymer† 1
Authors: Wang Shenguo , Chen Hongli , Cai Qing , Bei Jianzhong
Published: September 2002

The in vitro degradation behavior of the polyester/polyether copolymer based on polycaprolactone/poly(ethylene oxide)/polylactide (PCEL) significantly depends on the caproxyl (CL)/lactyl (LA) ratio for the same poly(ethylene oxide) (PEO) content. The PCEL copolymer with rich CL units shows the crystalline structure of PCL with a slow degradation rate, while it presents the crystalline structure of poly‐L‐lactide (PLLA) with more LA units that has a fast degradation rate. In the case of PCEL with similar CL and LA unit contents, it only exhibits the crystalline structure of PEO and the degradation rate is faster especially during the early stage of the degradation due to the rapid cleavage of the PEO. The drug release system is prepared using 5‐fluorouracil (5‐Fu) as the model drug and PCEL copolymers as the drug carriers. It is shown that the drug release rate is controlled by the composition, morphology and properties of the PCEL copolymer. In particular, the PCEL copolymer with 70% LA units displays a near zero‐order sustained release in about 60 days. Therefore, these copolymers have potential application as a controlled 5‐fluorouracil delivery system. Copyright © 2001 John Wiley & Sons, Ltd.
Compatibilized poly(ether imide)/LCP blends: drawing ability and mechanical properties of the ribbons
Authors: Vallejo F. J. , Bastida S. , Eguiazábal J. I. , Nazábal J.
Published: September 2002

The effects of the addition of polyarylate (PAr) on the drawing ability of poly(ether imide) (PEI)/Rodrun liquid‐crystalline 5000 (Ro LC5000) (Ro) blends and on the mechanical properties of their ribbons were studied. The compatibilizing effect of the PAr led to an increase in the drawing ability of the blends, as seen by the fact that the maximum Ro content compatible with the drawing process increased from 15 to 30%. This may lead to new applications in the field of gas barrier materials.

The presence of PAr also led to an increase in the adhesion between the two phases of the blends and consequent improved ductility. However, the very high modulus of elasticity and tensile strength in the direction of orientation (up to three‐fold those of the matrix) due to the less developed fibrillation were smaller than the corresponding values before compatibilization. These very large modulus of elasticity and tensile strength values and those perpendicular to the direction of orientation, which were similar to those of the matrix, led to a high anisotropy in the extruded ribbons that increased with the draw ratio (DR) and the Ro contents. The high mechanical properties of the ribbons may be used and the anisotropy diminished by layering the ribbons in, and perpendicular to, the direction of orientation, according to the expected external load. Copyright © 2002 John Wiley & Sons, Ltd.