bluuebunny/crossref_metadata_2025 huggingface dataset:
Broadband tunable (Cr–Cu–Au) resonator using ferrite substrate
Authors: Srivastava G. P. , Dubey Ashish , Tyagi G. S.
Published: August 2002

An X‐band, end‐coupled ring resonator has been fabricated photolithographically by depositing Cr–Cu–Au film on an LiZnTi polycrystalline ferrite substrate. Resonator characteristics have been studied by keeping it in the magnetic field, which was varied from 0 to 3.0 kG. Broadband tunability of 3.1 GHz was achieved with a minimum insertion loss of −11.17 dB when the direction of the magnetic field was changed from transverse to longitudinal to the wave propagation in coupling lines. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 161–163, 2001.
Low‐bias BAR‐mode HEAP transmitting antennas
Authors: González V. , Rodríguez J. M. , Rueda C. , Segovia D. , Rajo E. , Martin Pascual C.
Published: August 2002

This paper describes the design and construction of a BAR‐mode high‐efficiency active transmitting patch antenna (HEAP). The dimensions, shape, and location of the feeding point in the antenna are chosen to obtain an input impedance so the transistor works in the BAR mode at 1650 MHz with high collector efficiency and low bias voltage. A HEAP antenna with an efficiency of about 60%, Vcc=3 V, and EIRP=2.5 W has been developed. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 163–167, 2001.
Indoor radio‐wave propagation modeling by multilevel fast multipole algorithm
Authors: Lu C. C.
Published: August 2002

Three‐dimensional indoor radio‐wave propagation is accurately modeled by solving the volume electric‐field integral equation (VEFIE). The integral equation is discretized by the method of moments (MoM), in which the building walls, ceilings, floors, as well as any internal obstacles are represented by a collection of small volumetric cells. This discretization is capable of modeling a 3‐D room structure to fine details. The solution to the MoM matrix equation is facilitated by the multilevel fast multipole algorithm (MLFMA), which significantly reduces memory requirements and CPU time. Numerical examples are shown to demonstrate the accuracy of the solution and the capability of modeling dielectric structures of nearly realistic sizes. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 168–175, 2001.
Multilayered chiral filter response at oblique incidence
Authors: Cory Haim , Rosenhouse Isaac
Published: August 2002

The response of multilayered chiral filters is investigated at oblique incidence. It is found that there is a slight degradation with respect to the same filter operating at normal incidence. A possible application is proposed for this device: a reflector or a subreflector fed at two different frequencies by two feeds situated on each side of a multilayered chiral filter functioning as a frequency‐selective surface. The response of this device is well behaved, and is similar for TE and TM modes. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 192–195, 2001.
Dual‐frequency rectangular microstrip antenna with double π‐shaped slots
Authors: Chen Hua‐Ming , Sze Jia‐Yi , Lin Yi‐Fang , Kuo Chin‐Chun
Published: August 2002

A dual‐frequency rectangular microstrip antenna with a pair of π‐shaped narrow slots close to the nonradiating edges of the patch is experimentally studied. By varying the length and spacing of the two arms of each π‐shaped slot, the proposed antenna provides a tunable frequency ratio from about 1.03 to 1.19. Details of the antenna design and experimental results are presented and discussed. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 195–197, 2001.
Helix wire tolerances in TWT small‐signal gain prediction
Authors: D'agostino Stefano , Paoloni Claudio
Published: August 2002

Small‐signal gain is an important characteristic within the framework of overall traveling‐wave tube (TWT) performance. The fabrication tolerances can determine different performances with respect to the required ones. In this letter, an accurate evaluation of the effect of the helix wire tolerances on the TWT small‐signal gain is proposed. The study is applied to a measured five‐section TWT working in the 10–13 GHz frequency band. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 208–209, 2001.
Stacked shorted microstrip antenna for low cross polarization and wide‐band
Authors: Baligar J. S. , Revankar U. K. , Acharya K. V.
Published: August 2002

A novel structure to improve the cross‐polarization characteristics of the shorted square microstrip antenna is presented. The square‐ring patch is used as a parasitic element in the stacked position to tune the input impedance, resonant frequency, cross polarization, and bandwidth of the shorted square microstrip antenna. As a result, 11% bandwidth and better than −14.5 dB cross‐polarization levels have been achieved. The theoretical results are compared with the experimental results. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 73–75, 20.
Optimum compensating susceptance and position for quadrature directional coupler
Authors: Yu Cheng‐Cheh , Chuang Sheng‐Chieh
Published: August 2002

The optimum susceptance and position for compensation of the match and isolation performances of a quadrature directional coupler are perspicuously derived in this paper. Furthermore, various frequency responses of the coupler with either capacitive or inductive loading are given to elucidate the characteristics of a susceptance‐loaded quadrature directional coupler as well. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 90–95, 2001.
Mobile transmit diversity for base‐station antenna arrays
Authors: Kavak Adnan , Xu Guanghan
Published: August 2002

For base‐station antenna arrays operating at 1.8 GHz in urban vehicular environments, we experimentally investigate the spatial diversity provided by transmitting from the mobile terminal with two λ/2 dipole antennas that are separated by λ/2 and arranged in copolarized (CP) and cross‐polarized (XP) configurations. The results show that, in both configurations, spatial signatures observed at the antenna array associated with each antenna element of the mobile change differently, especially when nonline‐of‐sight communication exists. The relative variation of spatial signatures is larger in an XP configuration compared to a CP configuration. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 95–97, 2001.
Application of nested multigrid finite elements to two‐dimensional electromagnetic scattering
Authors: Zhu Yu , Cangellaris Andreas C.
Published: August 2002

Nested multigrid techniques are combined with the finite‐element method for the fast numerical solution of two‐dimensional electromagnetic scattering problems. The finite‐element modeling is performed on nested meshes of the same computational domain. The conjugate‐gradient method is used to solve the resultant finite‐element matrix for the finest mesh, while the multigrid method acts as the preconditioner of the iterative solver. Numerical experiments are used to demonstrate the efficiency as well as the limits of the proposed methodology. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 97–101, 2001.
Ka‐Band pulsed propagation through rain‐filled atmosphere
Authors: Maitra A. , Chowdhury A. S. , Das A.
Published: August 2002

An atmosphere of rain offers a dispersive medium for the propagation of radio signals above 10 GHz. The effect of dispersion, in terms of differential attenuation and phase dispersion, is insignificant for narrowband signals. Signals modulated with very short pulses can have a wide bandwidth over which dispersion will be appreciable, causing significant signal distortion. The propagation of pulsed signals under varying propagation conditions has been studied with the Fourier transform technique. The transfer function of the rain atmosphere is obtained using propagation models that include clear‐air effects and scattering effects due to raindrops. The carrier signal at 30 GHz is considered to be modulated by a raised‐cosine pulse with a base bandwidth of 1–3 GHz. A technique for the mitigation of pulse distortion using an FIR filter is presented to restore the distorted pulse to its original shape and position to a significant extent. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 105–109, 2001.
Theory and numerical analysis of higher order dispersion effects on ultra‐high‐speed nonlinear optical loop mirror demultiplexer
Authors: Zhang Fan , Ye Peida
Published: August 2002

The effects of higher order dispersion are analyzed for the first time in ultra‐fast signal demultiplexing using a nonlinear optical loop mirror (NOLM). The results show that performance degradation of NOLM can occur when higher order dispersion is not negligible. Therefore, a loop fiber with a higher order dispersion that is as small as possible should be chosen to realize terabit/second operation of the NOLM. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 124–127, 2001.
Erratum to “FDTD Analysis and Design of Probe‐Fed Dual‐Polarized Circular Stacked Patch Antenna”
Authors: Paul Dominique L. , Craddock Ian J. , Railton Chris J. , Fletcher Paul N. , Dean Michael
Published: August 2002

This contribution shows that the FDTD technique is an effective design tool for producing dual‐polarized circular stacked patch antennas. Computational requirements may be minimized by careful modeling of the coaxial feedline, including the use of mode filtering at the aperture plane of the antenna. The design process for an antenna at a frequency of 4.7 GHz is described, and results obtained for return loss and coupling between the two ports of the antenna and radiation patterns are presented. These are in very good agreement with experimental data. © 2001 Crown Copyright. Published with permission of the Defence Evaluation and Research Agency on behalf of the controller HMSO Microwave Opt Technol Lett 30: 145–147, 2001.
Study of distributions of modes and plane waves in reverberation chambers for the characterization of antennas in a multipath environment
Authors: Rosengren Kent , Kildal Per‐Simon
Published: August 2002

A rectangular metallic cavity is known to support a number of resonant cavity modes. Each of these modes can be described as a sum of eight plane waves incident from different angles. This paper studies how these plane waves are angularly distributed in space, which is of interest when the cavity is used to simulate multipath environment. The results show that the angular distribution in space is uniform provided that the three linear dimensions of the chamber are sufficiently large, and do not deviate too much from each other. As an example, two rectangular cavities with dimensions 1 m×0.8 m×1 m and 5.5 m×2.5 m×3.5 m are analyzed in detail, and are shown to have uniform plane‐wave distributions. We also demonstrate how the chamber geometry may be chosen in order to weight the angular plane‐wave distribution in the elevation plane. A result of the study is that we detect a 25 MHz frequency band with very few modes in a small chamber designed for use with reduced accuracy in the GSM 900 MHz band. We also propose how this chamber can be modified to obtain uniform mode distribution over this frequency band. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 386–391, 2001.
Optical regeneration using a feedforward semiconductor optical amplifier with chirp‐controlled filtering
Authors: Conforti Evandro , Gallep Cristiano M. , Bordonalli Aldário C. , Kang Sung‐Mo (Steve)
Published: August 2002

Optical pulse regeneration and reshaping using nonlinear optical pulse amplification followed by a chirp‐controlled filtering is simulated. The nonlinear amplification and chirp control are obtained by feedforward current injection in a semiconductor optical amplifier. The nonlinear amplification provides pulse regeneration, and the controlled chirp, in association with an optical frequency discriminator, can be used to optimize the shape of several Gbit/s pulse streams. The simulator model has been confirmed experimentally using eye diagram techniques. In addition, the switching action of an optical semiconductor amplifier with a dynamically arbitrarily injected current can be simulated. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 438–442, 2001.
Analysis and bandwidth enhancement of Sierpinski carpet antenna
Authors: Wong S. , Ooi B. L.
Published: August 2002

The boundary integral method coupled with the segmentation method have been used for the first time to analyze Sierpinski carpet antennas of different orders. As is evident from the close agreement between calculated and measured results for the resonant frequency and input return loss, this technique is found to predict the impedance characteristic accurately. A novel stacked microstrip Sierpinski carpet fractal antenna using a photonic bandgap structure is also presented. Compared to an ordinary microstrip fractal antenna, which has a maximum bandwidth of 2%, the proposed antenna has a higher input impedance bandwidth of about 9%. The radiation patterns of the proposed antenna are improved due to the removal of unwanted radiation caused by the surface wave. The experimental measurement results of the proposed antenna are presented in this paper. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 13–18, 2001.
Fast algorithm for matrix–vector multiply of asymmetric multilevel block‐Toeplitz matrices in 3‐D scattering
Authors: Barrowes Benjamin E. , Teixeira Fernando L. , Kong Jin A.
Published: August 2002

A newO(N log N) FFT‐based method to expedite matrix–vector multiplies involving multilevel block‐Toeplitz (MBT) matrices is presented. The method is also a minimal memory method withO(N) memory requirements because only nonredundant entries of the MBT matrix are stored. The accuracy and convergence of the method are illustrated in the calculation of the scattered field and the effective permittivity of a sphere with size parameter ka up to 5 using a volume integral formulation akin to the discrete dipole approximation. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 28–32, 2001.
Buried‐object detection using free‐space time‐domain near‐field measurements
Authors: Biju Kumar S. , Aanandan C. K. , Mathew K. T.
Published: August 2002

The detection of buried objects using time‐domain free‐space measurements was carried out in the near field. The location of a hidden object was determined from an analysis of the reflected signal. This method can be extended to detect any number of objects. Measurements were carried out in the X‐ and Ku‐bands using ordinary rectangular pyramidal horn antennas of gain ∼15 dB. The same antenna was used as the transmitter and receiver. The experimental results were compared with simulated results by applying the two‐dimensional finite‐difference time‐domain (FDTD) method, and agree well with each other. The dispersive nature of the dielectric medium was considered for the simulation. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 45–47, 2001.
Far‐field pattern calculation in body‐of‐revolution finite‐difference time‐domain (BOR–FDTD) method
Authors: Yu Wenhua , Farahat Nader , Mittra Raj
Published: August 2002

In this paper, we present a far‐field pattern calculation technique in the body‐of‐revolution finite‐difference time‐domain (BOR–FDTD) method. Because the BOR–FDTD solves two‐ and half‐dimensional problems, it has different features from the three‐dimensional FDTD method in the far‐field pattern calculation. A monopole antenna fed by a coax is used to validate the technique described in this paper. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 47–50, 2001.
Erratum to “Arrayed Helical Antennas (AHA) with Low SAR for Personal Telephone Handsets”
Authors: Hong Soo‐Won , Park Myeong‐Seok , Oh Hak‐Tae , Park Cheon‐Seok
Published: August 2002

Arrayed helical antennas (AHA) for personal telephone handsets have beendeveloped for both low‐SAR and omnidirectional radiation patterns, where the AHA has two helical antennas along the direction of the width on the top of personal telephones. A comparison of the SAR value between the AHA and a conventional helical antenna (CHA) demonstrates that the SAR value of the AHA is 35% less than that of the CHA. Good performance of the radiation patterns and the VSWR of the AHA are also shown by using the experimental measurements. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 396–397, 2002.
Survival trends of childhood cancer diagnosed during 1970–1994 in Piedmont, Italy: A report from the Childhood Cancer Registry
Authors: Pastore Guido , Mosso Maria Luisa , Carnevale Fabrizio , di Montezemolo Luca Cordero , Forni Marco , Madon Enrico , Ricardi Umberto , Terracini Benedetto , Magnani Corrado
Published: August 2002

Background

The Childhood Cancer Registry of Piedmont (CCRP) started its activity in 1967. It is population based and covers the Piedmont Region (population 4,500,000; NW Italy). This article reports on time trends in survival after a childhood cancer diagnosed during 1970–1994.

Procedure

During 1970–1994, 2,329 incident cases were registered at CCRP on the basis of histological and/or clinical information, excluding 30 cases reported only by death certificate. Histological or hematological diagnosis was available for 2,067 cases. Vital status was assessed through the offices of the town of residence. At the end of follow‐up, 1,202 cases were alive, 1,084 dead and 43 were not traceable. Survival was measured for the major diagnostic groups using both univariate and multivariate statistics.

Results

The 5‐yr survival rate for acute lymphoblastic leukemia (ALL) improved regularly from 24.7% in 1970–1974 to 81.1% in 1990–1994, for acute nonlymphoblastic leukemia (ANLL) from 0% to 38.1%, for non‐Hodgkin lymphoma (NHL) from 25.2% to 67.7%, for tumors of the central nervous system (CNS) (all types) from 33.4% to 75.9% and for Ewing tumor from 0% to 90%. Focusing on survival by period of diagnosis, the highest 5‐year survival rate was observed for children diagnosed during 1985–1989 for medulloblastoma, neuroblastoma (NB), retinoblastoma, Wilms tumor, osteosarcoma, and rhabdomyosarcoma and for children diagnosed in 1990–1994 for the remaining sites. The trend over time was statistically significant for ALL, ANLL, NHL, CNS tumors, NB, and osteosarcoma as well as for all malignancies together.

Conclusions

Population‐based survival studies are useful complements to clinical studies. Survival results in the present study are similar to those presented for other European countries and the United States. For most types of neoplasm (except CNS) survival probability appears to stabilize 5–10 years after diagnosis. Med. Pediatr. Oncol. 36:481–488, 2001. © 2001 Wiley‐Liss, Inc.
Study design and cohort characteristics of the childhood cancer survivor study: A multi‐institutional collaborative project
Authors: Robison Leslie L. , Mertens Ann C. , Boice John D. , Breslow Norman E. , Donaldson Sarah S. , Green Daniel M. , Li Frederic P. , Meadows Anna T. , Mulvihill John J. , Neglia Joseph P. , Nesbit Mark E. , Packer Roger J. , Potter John D. , Sklar Charles A. , Smith Malcolm A. , Stovall Marilyn , Strong Louise C. , Yasui Yutaka , Zeltzer Lonnie K.
Published: August 2002

Background

Increased attention has been directed toward the long‐term health outcomes of survivors of childhood cancer. To facilitate such research, a multi‐institutional consortium established the Childhood Cancer Survivor Study (CCSS), a large, diverse, and well‐characterized cohort of 5‐year survivors of childhood and adolescent cancer.

Procedure

Eligibility for the CCSS cohort included a selected group of cancer diagnoses prior to age 21 years between 1970–1986 and survival for at least 5 years.

Results

A total of 20,276 eligible subjects were identified from the 25 contributing institutions, of whom 15% are considered lost to follow‐up. Currently, 14,054 subjects (69.3% of the eligible cohort) have participated by completing a 24‐page baseline questionnaire. The distribution of first diagnoses includes leukemia (33%), lymphoma (21%), neuroblastoma (7%), CNS tumor (13%), bone tumor (8%), kidney tumor (9%), and soft‐tissue sarcoma (9%). Abstraction of medical records for chemotherapy, radiation therapy, and surgical procedures has been successfully completed for 98% of study participants. Overall, 78% received radiotherapy and 73% chemotherapy.

Conclusion

The CCSS represents the largest and most extensively characterized cohort of childhood and adolescent cancer survivors in North America. It serves as a resource for addressing important issues such as risk of second malignancies, endocrine and reproductive outcome, cardiopulmonary complications, and psychosocial implications, among this unique and ever‐growing population. Med. Pediatr. Oncol. 2002;38:229–239. © 2002 Wiley‐Liss, Inc.
Neuronal migration disorders
Authors: Gleeson Joseph G.
Published: August 2002

Neuronal migration disorders are a category of developmental brain disorders leading to cortical dysplasia. This group of disorders is characterized by defective movement of neurons from the place of origin along the lining of the lateral ventricle, to the eventual place of residence in the correct laminar position within the cerebral cortex. As a result of defective migration, affected individuals typically display mental retardation and epilepsy. Although patients with the more severe forms of these disorders often present during infancy, patients may present at any age from newborn to adulthood. The migration defect may be generalized or focal, and may be disturbed at any of several stages, leading to several distinct radiographical and clinical presentations. The human phenotypes suggests that there are at least four distinct and clinically‐important steps in cortical neuronal migration, and the identification of the responsible genes suggests that multiple cellular processes are critical for correct neuronal positioning. MRDD Research Reviews 2001;7:167–171. © 2001 Wiley‐Liss, Inc.
Simulation‐based investigation of partially parallel imaging with a linear array at high accelerations
Authors: Bankson James A. , Wright Steven M.
Published: August 2002

Partially parallel imaging strategies such as SMASH, SENSE, and PILS rely on the sensitivity distribution of phased array RF coils to reduce MRI imaging time. Using an N‐element phased array, these techniques allow maximum accelerations, L, such that L ≤ N, with acceleration defined as the factor by which scan time is reduced in comparison to traditional, fully gradient encoded acquisitions. As N increases in modern MRI facilities or using special hardware extensions, its role as the primary limitation in partially parallel imaging will be reduced and other limiting factors will become dominant. Two such factors include available SNR and the variation of sensitivity distributions with imaging depth. Simulations have been conducted to evaluate the impact of slice depth and noise on partially parallel reconstructions for the case of a square linear array of overlapped elements that are parallel to the imaging plane. Results indicate that even when sensitivity distributions are exactly known, the linear surface array can only provide high accelerations over a limited imaging depth due to changing suitability of the sensitivity distributions for partially parallel reconstruction. This work emphasizes the importance of simulations for target‐based partially parallel array design. Magn Reson Med 47:777–786, 2002. © 2002 Wiley‐Liss, Inc.
k‐Space filtering in 2D gradient‐echo breath‐hold hyperpolarized 3He MRI: Spatial resolution and signal‐to‐noise ratio considerations
Authors: Wild Jim M. , Paley Martyn N.J. , Viallon Magalie , Schreiber Wolfgang G. , van Beek Edwin J.R. , Griffiths Paul D.
Published: August 2002

In this work some of the factors that can influence the signal‐to‐noise ratio (SNR) and spatial resolution in MR images of inhaled hyperpolarized gases are systematically addressed. In particular, the effects of RF depletion of longitudinal polarization and image gradient diffusion dephasing were assessed in terms of their contribution to a k‐space filter. By means of theoretical simulations and a novel method of experimental validation using a variable transverse magnetization of the 1H signal, systematic quantitative and qualitative investigations of the effects of k‐space filtering intrinsic to imaging of hyperpolarized gas were made. A 2D gradient‐echo image is considered for a range of flip angles with centric, sequential, and half‐Fourier Cartesian phase‐encoding strategies, and the results are assessed in terms of SNR and spatial resolution in the reconstructed images. Centric phase encoding was found to give the best SNR at higher flip angles, with a trade‐off in spatial resolution compared to sequential phase encoding. A half‐Fourier approach potentially offers increased SNR through the use of higher flip angles without compromising the spatial resolution, which is comparable to that achieved with sequential encoding. Magn Reson Med 47:687–695, 2002. © 2002 Wiley‐Liss, Inc.
New approach to 3D time‐resolved angiography
Authors: Madore Bruno , Pelc Norbert J.
Published: August 2002

TRICKS is an acquisition and reconstruction method capable of generating 3D time‐resolved angiograms. Arguably, the main problem with TRICKS is the way it handles the outer regions of the k‐space matrix, leading to artifacts at the edges of blood vessels. An alternative to the data‐ processing stage of TRICKS, designed to better represent edges and small vessels, is presented here. A weakness of the new approach is an increased sensitivity to motion compared to TRICKS. Since this method can use the same data as TRICKS, a hybrid reconstruction method could conceivably be developed where the advantages of both approaches are combined. Magn Reson Med 47:1022–1025, 2002. © 2002 Wiley‐Liss, Inc.
Reliable detection of macromolecules in single‐volume 1H NMR spectra of the human brain
Authors: Seeger Uwe , Mader Irina , Nägele Thomas , Grodd Wolfgang , Lutz Otto , Klose Uwe
Published: August 2002

In short echo time proton MR spectra of the brain, resonances from macromolecules are visible. The macromolecular resonances in the 0.5–2.0 ppm region can be affected by lipid contamination arising from fat‐containing regions outside the selected volume of interest (VOI). This study demonstrates that considerable lipid contamination may remain in stimulated echo acquisition mode (STEAM) spectra even if the spoiling of unwanted coherences is sufficient and the VOI is placed 2 cm or more away from fat‐containing regions. The observed contamination was attributed to residual remote out‐of‐volume excitation, although only very small out‐of‐slice ripples of less than 0.2% of the in‐slice excitation were found in the calculated excitation profile of the RF pulses. Spatial presaturation of fat‐containing regions led to a sufficient suppression of the contamination and enabled the detection of highly reproducible macromolecular resonances. Thus, in single‐volume spectroscopy as well as in spectroscopic imaging (SI or CSI), the combination of volume selection and outer volume presaturation, each in three dimensions, is highly recommended to ensure accurate detection and reliable evaluation of even small pathological alterations in macromolecules, e.g., proteins or lipids, or other resonances in the 0.5–2.0 ppm region. Magn Reson Med 45:948–954, 2001. © 2001 Wiley‐Liss, Inc.
Quantification of the effect of water exchange in dynamic contrast MRI perfusion measurements in the brain and heart
Authors: Larsson Henrik B.W. , Rosenbaum Sverre , Fritz‐Hansen Thomas
Published: August 2002

Measurement of myocardial and brain perfusion when using exogenous contrast agents (CAs) such as gadolinium‐DTPA (Gd‐DTPA) and MRI is affected by the diffusion of water between compartments. This water exchange may have an impact on signal enhancement, or, equivalently, on the longitudinal relaxation rate, and could therefore cause a systematic error in the calculation of perfusion (F) or the perfusion‐related parameter, the unidirectional influx constant over the capillary membranes (Ki). The aim of this study was to quantify the effect of water exchange on estimated perfusion (F or Ki) by using a realistic simulation. These results were verified by in vivo studies of the heart and brain in humans. The conclusion is that water exchange between the vascular and extravascular extracellular space has no effect on Ki estimation in the myocardium when a normal dose of Gd‐DTPA is used. Water exchange can have a significant effect on perfusion estimation (F) in the brain when using Gd‐DTPA, where it acts as an intravascular contrast agent. Magn Reson Med 46:272–281, 2001. © 2001 Wiley‐Liss, Inc.
Skeletal muscle hypertrophy and anti‐atrophy effects of clenbuterol are mediated by the β2‐adrenergic receptor
Authors: Hinkle Richard T. , Hodge Karen M.B. , Cody David B. , Sheldon Russell J. , Kobilka Brian K. , Isfort Robert J.
Published: August 2002

Analyses were performed to evaluate the roles of the β1‐ and β2‐adrenergic receptors in the skeletal muscle hypertrophy and anti‐atrophy response to the β‐adrenergic agonist, clenbuterol. Treatment of wild‐type mice with clenbuterol resulted in statistically significant hypertrophy of the innervated tibialis anterior and medial gastrocnemius muscles and inhibition of denervation‐induced atrophy of these muscles. Treatment of β1‐adenergic receptor knockout mice with clenbuterol also resulted in statistically significant hypertrophy of the innervated tibialis anterior and medial gastrocnemius muscles and inhibition of denervation‐induced atrophy of these muscles. In contrast, in β2‐adrenergic receptor knockout mice and in mice lacking both the β1‐ and β2‐adrenergic receptors, clenbuterol treatment did not result in hypertrophy of the innervated tibialis anterior and medial gastrocnemius muscles, nor did it inhibit denervation‐induced atrophy in these muscles. Together these data demonstrate that the β2‐adrenergic receptor is responsible for both the skeletal muscle hypertrophy and anti‐atrophy effects of the β‐adrenergic agonist clenbuterol. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002
Cell death and apoptosis‐related proteins in muscle biopsies of sporadic amyotrophic lateral sclerosis and polyneuropathy
Authors: Schoser Benedikt G.H. , Wehling Sonja , Blottner Dieter
Published: August 2002

To investigate disease‐related differences of cell death and apoptosis in human denervation atrophy, we studied DNA fragmentation by the terminal deoxynucleotidyltransferase‐mediated dUTP‐biotin nick end labeling (TUNEL) method in 38 biopsies of clinically nonaffected and affected muscles from patients with sporadic amyotrophic lateral sclerosis (sALS), in 13 muscle biopsies from patients with chronic peripheral neuropathies, and in 8 biopsies from control subjects. In addition, expression of apoptosis‐related proteins, bax, bcl‐2, and Fas, was studied in 20 biopsies of sALS and 10 chronic peripheral neuropathies. We identified DNA cleavage in 10% of myofibers of patients and in up to 1.5% of control samples. In clinically affected muscles of ALS, a larger amount of TUNEL‐positive myofibers (mean 10.5 ± 5.9%) was detected, similar to chronic peripheral neuropathies (mean 10.0 ± 7.4%). Atrophic myofibers were immunopositive for bax, bcl‐2, and, to a weaker extent, for Fas. However, bax‐, bcl‐2‐, or Fas‐positive atrophic myofibers did not reveal consecutive DNA cleavage. Differences between sALS subgroups and chronic peripheral neuropathies were not found. In human denervation atrophy the bcl‐2/bax and the FasL/Fas systems are apparently active independently of DNA fragmentation and apoptosis. DNA fragmentation thus displays an additional reaction that is not disease‐specific at chronic stages of human denervation processes, probably recapitulating events like skeletal muscle fiber remodeling in embryonic skeletal tissue development. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1083–1089, 2001
Effects of the atypical neuroleptic clozapine on micturition parameters in anesthetized rats
Authors: Vera Pedro L. , Nadelhaft Irving
Published: August 2002

Clozapine, an atypical antipsychotic, has resulted in a number of reports of urinary disturbances in the clinical literature. We examined the effects of clozapine on urodynamic parameters in the anesthetized rat and compared the effects to those of the typical antipsychotic haloperidol and the selective D2 and D4 antagonists, raclopride and L‐745,870, respectively. Clozapine abolished high‐frequency oscillations (HFO) during the expulsion phase, and profoundly altered a number of other parameters (e.g., intercontraction interval and resting pressure). Clozapine did not affect the peak contraction pressure during cystometrograms but displayed peripheral inhibition of bladder contractions elicited by electrical stimulation of the pelvic nerve (possibly mediated via clozapine's anti‐muscarinic effects). Haloperidol had less potent effects than clozapine since it reduced the amplitude of HFO to 25% of control and also affected several other parameters but without peripheral bladder inhibition. Raclopride only resulted in a modest decrease (approximately 70% of control) in the HFO and no alteration in other parameters. L‐745,870 was effective only at highest dose tested suggesting that it might not be acting selectively at D4 receptors. Therefore, we propose that clozapine primarily interferes with the function of the external urethral sphincter. These effects can only be partly explained through antagonism of D2 receptors. Since both clozapine and haloperidol have interactions with other transmitter systems beside dopamine, we suggest that central antagonism of D2 receptors, coupled to central antagonism of another receptor system and peripheral muscarinic receptor blockade, may account for clozapine's potent effects on micturition. Neurourol. Urodynam. 20:623–639, 2001. © 2001 Wiley‐Liss, Inc.
A queuing model for due date control in a multiserver repair shop
Authors: Keizers Joris , Adan Ivo , van der Wal Jan
Published: August 2002

This paper deals with a repair shop with multiple parallel servers, which has to carry out planned overhauls. Each overhaul consists of a large number of maintenance jobs. The overhaul process is interrupted by randomly arriving emergency jobs. To control the delivery performance of the overhauls, knowledge about the overhaul makespan distribution should be available. Using a 2‐dimensional Markov model, we derive the first and second moment of the overhaul makespan analytically for the case that the repair times of all overhaul jobs are identically and exponentially distributed. For the case of nonidentical repair time distributions, an approximation is presented. Simulation shows that the makespan distribution fitted on these moments gives an excellent approximation. © John Wiley & Sons, Inc. Naval Research Logistics 48: 281–282, 2001
31P NMR spectroscopy of blood plasma: determination and quantification of phospholipid classes in patients with renal cell carcinoma
Authors: Süllentrop F. , Moka D. , Neubauer S. , Haupt G. , Engelmann U. , Hahn J. , Schicha H.
Published: August 2002

Advanced renal cell carcinoma (RCC) has a poor prognosis and is characterized by an unpredictable clinical course. The aim of this study was to assess the systemic phospholipid distribution as a possible marker of tumor stage and tumor spread beyond the kidney. To this end, the effect of renal cell carcinoma (RCC) on phospholipid concentrations in blood plasma using31P NMR spectroscopy was studied in: (a) 29 patients with RCC prior to nephrectomy; (b) 19 healthy volunteers; (c) three patients with other renal tumors (renal metastases of bronchial carcinoma and of renal pelvic carcinoma, and a benign renal tumor). Furthermore, the phospholipid concentrations of eight patients of group (a) were determined 6 months after nephrectomy, when they were in remission. We found considerable deviations in the concentrations of the lysophosphatidylcholines (LPC1, LPC2) in both male and female patients with RCC compared to healthy volunteers (male—LPC1 0.217 ± 0.062 vs 0.297 ± 0.049 mmol/l, LPC2 0.036 ± 0.014 vs 0.068 ± 0.024 mmol/l; female—LPC1 0.195 ± 0.071 vs 0.296 ± 0.044 mmol/l, LPC2 0.037 ± 0.027 vs 0.044 ± 0.014 mmol/l). In addition, female patients with RCC showed lower concentrations of phosphatidylcholines (PC; 1.409 ± 0.268 vs 1.947 ± 0.259 mmol/l). The low phospholipid concentrations normalized for patients in remission. Phospholipid concentrations were found to depend on tumor stage and metastatic spread. The deviations in phospholipid concentrations (LPC1, LPC2, PC) observed may be attributable to systemic effects caused by the tumor as well as changes in enzyme activities. Copyright © 2002 John Wiley & Sons, Ltd.
In‐vivo visualization of phagocytotic cells in rat brains after transient ischemia by USPIO
Authors: Rausch M. , Baumann D. , Neubacher U. , Rudin M.
Published: August 2002

Cerebral ischemia provokes tissue damage by two major patho‐physiological mechanisms. Direct cell necrosis is induced by diminished access of neurons and glia to essential nutrients such as glucose and oxygen leading to energy failure. A second factor of cellular loss is related to the activation of immune‐competent cells within and around the primary infarct. While granulocytes and presumably monocytes are linked to the no‐reflow phenomenon, activated microglia cells and monocytes can release cytotoxic substrates, which cause delayed cell death. As a consequence the infarct volume will increase, despite restoration of cerebral perfusion. In the past, visualization of immune competent cells was only possible by histological analysis of post‐mortem tissue. However, contrast agents based on small particles of iron oxide are known to accumulate in organs rich in cells with phagocytotic function. These particles can be tracked in vivo by MRI methods based on their relaxation properties. In the present study, the spatio‐temporal distribution of USPIO particles was monitored in a rat model of transient cerebral infarction using T1‐ and T2‐weighted MRI sequences. USPIO were detected in vessels at 24 h after administration. At later time points specific accumulation of USPIO was observed within the infarcted hemisphere, with maximal signal enhancement on day 2. Their detectability based on T1‐contrast disappeared between day 4 and day 7. Immuno‐histochemically (IHC) stains confirmed the presence of macrophages, presumably blood‐derived monocytes within areas of T1 signal enhancement. Direct visualization of iron‐burdened macrophages by IHC was only possible later than day 3 after occlusion. Copyright © 2002 John Wiley & Sons, Ltd.
Wireless ATM network architectures
Authors: Hác Anna
Published: August 2002

Emulated LAN technology supports mobile hosts in wireless ATM networks. This paper introduces virtual LAN (VLAN) services using ATM LAN emulation technology which operates on a client/server model. One of the attractive features of the VLAN is the capability to group users into a broadcast domain. The focus of this paper is the issue of supporting quality of service to mobiles in a wireless ATM network. Copyright © 2001 John Wiley & Sons, Ltd.
Network topology management in a mobile‐switch ATM network: dynamic partition algorithms
Authors: Cheng Sheng‐Tzong , Chen C. , Li C. , Chen Chia‐Mei
Published: August 2002

In this paper we propose two partition algorithms. The main policy of the algorithms is finding out the area(s) in which mobile switches congregate within a peer group. Copyright © 2002 John Wiley & Sons, Ltd.
Balanced network flows. VII. Primal‐dual algorithms
Authors: Fremuth‐Paeger Christian , Jungnickel Dieter
Published: August 2002

We discuss an adaptation of the famous primal‐dual 1‐matching algorithm to balanced network flows which can be viewed as a network flow description of capacitated matching problems. This method is endowed with a sophisticated start‐up procedure which eventually makes the algorithm strongly polynomial. We apply the primal‐dual algorithm to the shortest valid path problem with arbitrary arc lengths, and so end up with a new complexity bound for this problem. © 2002 John Wiley & Sons, Inc.
Oriented hypercubes
Authors: Fraigniaud Pierre , König Jean‐Claude , Lazard Emmanuel
Published: August 2002

In this paper, we show how to give an orientation to the edges of an hypercube so that the inducedorientedhypercube offers approximately the same communication performance as that of the original nonoriented hypercube (routing, broadcasting, connectivity, etc.), that is, we show that it is possible to construct anN‐node oriented hypercube with the same communication and computational power as that of anN‐node hypercube, although with approximately the same pin‐complexity as that of a$\sqrt{N}$‐node hypercube. © 2002 Wiley Periodicals, Inc.
File distribution in networks with multimedia storage servers
Authors: Ryoo Jeong‐dong , Panwar Shivendra S.
Published: August 2002

In this paper, we consider a problem in networks with storage servers for providing multimedia service. The design involves assigning communication link capacity, sizing the multimedia servers, and distributing different types of content at each server, while guaranteeing an upper limit on the individual end‐to‐end blocking probability. We consider alternative methods for obtaining the end‐to‐end blocking probability with low computation time and present optimization procedures to obtain an optimal solution. Under a linear cost structure, our numerical investigations consider different scenarios that might be helpful in understanding how to distribute multimedia content for a cost‐optimized solution. © 2001 John Wiley & Sons, Inc.
Postnatal cell proliferation and death in a lateralized, gender‐related, asymmetric nucleus
Authors: Holman Steve , Collado Paloma
Published: August 2002

Sexual differentiation and lateralization of neurone number in a discrete forebrain nucleus (SDApc) related to masculine vocal emission, occur contemporaneously in postnatal (P0–P15) gerbils. Stereological estimates of cell proliferation and death during SDApc organization were made by BrdU labelling and pyknosis, respectively. Results confirmed that rates of apoptosis were greater in females and lateralized in males. Immunoreactive BrdU cells, located in the SDApc at P0–P6, with low levels at P15, were not numerically different between the sexes. Only at one age, P0, in males, was a left‐right difference seen in BrdU‐immunoreactive cell numbers. Microglia, identified by isolectin immunostaining, were numerically similar to BrdU cells. We suggest that apoptosis, rather than neurogenesis, differentiates and lateralizes SDApc organization, and proliferating cells are microglia, phagocytosing debris. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 150–158, 2001
Receptor protein tyrosine phosphatases regulate retinal ganglion cell axon outgrowth in the developing Xenopus visual system
Authors: Johnson Karl G. , McKinnell Iain W. , Stoker Andrew W. , Holt Christine E.
Published: August 2002

Receptor protein tyrosine phosphatases (RPTPs) are regulators of axon outgrowth and guidance in a variety of different vertebrate and invertebrate systems. Three RPTPs, CRYP‐α, PTP‐δ, and LAR, are expressed in overlapping but distinct patterns in the developing Xenopus retina, including expression in retinal ganglion cells (RGCs) as they send axons to the tectum (Johnson KG, Holt CE. 2000. Expression of CRYP‐alpha, LAR, PTP‐delta, and PTP‐rho in the developing Xenopus visual system. Mech Dev 92:291–294). In order to examine the role of these RPTPs in visual system development, putative dominant negative RPTP mutants (CS‐CRYP‐α, CS‐PTP‐δ, and CS‐LAR) were expressed either singly or in combination in retinal cells. No effect was found on either retinal cell fate determination or on gross RGC axon guidance to the tectum. However, expression of these CS‐RPTP constructs differentially affected the rate of RGC axon outgrowth. In vivo, expression of all three CS‐RPTPs or CS‐PTP‐δ alone inhibited RGC axon outgrowth, while CS‐LAR and CS‐CRYP‐α had no significant effect. In vitro, expression of CS‐CRYP‐α enhanced neurite outgrowth, while CS‐PTP‐δ inhibited neurite outgrowth in a substrate‐dependent manner. This study provides the first in vivo evidence that RPTPs regulate retinal axon outgrowth. © 2001 John Wiley & Sons, Inc. J Neurobiol 49: 99–117, 2001
Erratum to the ‘Load stepping schemes for critical state models’ International Journal for Numerical Methods in Engineering 2001; 50:67–93
Authors: Sheng Daichao , Sloan Scott W.
Published: August 2002

The original article to which this Erratum refers was published in Interntational Journal for Numerical Methods in Engineering 2001; 50:67–93.
FFS contact searching algorithm for dynamic finite element analysis
Authors: Wang Fujun , Cheng Jiangang , Yao Zhenhan
Published: August 2002

A new contact searching algorithm for general contact systems is proposed in this paper. Due to that the smooth and accurate geometry description is crucial to the contact stress analysis, we have worked out a free‐formed‐surface (FFS) algorithm specialized to model the contacting surface with theC1boundary continuity and the exact boundary condition definition. Moreover, the geometrical description using the FFS produces those data required for determining the actual contact direction and calculating the exact contact penetration. Numerical simulation results demonstrate that our contact searching algorithm is robust and capable to simulate three‐dimensional contact problems accurately. Copyright © 2001 John Wiley & Sons, Ltd.
An Eulerian‐Lagrangian substructuring domain decomposition method for unsteady‐state advection‐diffusion equations
Authors: Wang Hong , Al‐Lawatia Mohamed
Published: August 2002

We develop an Eulerian‐Lagrangian substructuring domain decomposition method for the solution of unsteady‐state advection‐diffusion transport equations. This method reduces to an Eulerian‐Lagrangian scheme within each subdomain and to a type of Dirichlet‐Neumann algorithm at subdomain interfaces. The method generates accurate and stable solutions that are free of artifacts even if large time‐steps are used in the simulation. Numerical experiments are presented to show the strong potential of the method. © 2001 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 17:565–583, 2001
Analysis of algebraic systems arising from fourth‐order compact discretizations of convection‐diffusion equations
Authors: Gopaul Ashvin , Bhuruth Muddun
Published: August 2002

We study the properties of coefficient matrices arising from high‐order compact discretizations of convection‐diffusion problems. Asymptotic convergence factors of the convex hull of the spectrum and the field of values of the coefficient matrix for a one‐dimensional problem are derived, and the convergence factor of the convex hull of the spectrum is shown to be inadequate for predicting the convergence rate of GMRES. For a two‐dimensional constant‐coefficient problem, we derive the eigenvalues of the nine‐point matrix, and we show that the matrix is positive definite for all values of the cell‐Reynolds number. Using a recent technique for deriving analytic expressions for discrete solutions produced by the fourth‐order scheme, we show by analyzing the terms in the discrete solutions that they are oscillation‐free for all values of the cell Reynolds number. Our theoretical results support observations made through numerical experiments by other researchers on the non‐oscillatory nature of the discrete solution produced by fourth‐order compact approximations to the convection‐diffusion equation. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 155–178, 2002; DOI 10.1002/num.1041