bluuebunny/crossref_metadata_2025 huggingface dataset:
On‐line monitoring of emulsion polymerisation using conductivity measurements
Authors: Graillat Christian , Santos Alexandre , Pinto José Carlos , McKenna Timothy F.
Published: February 2004

This work investigates the feasibility of implementing conductivity measurements for the purpose of the on‐line monitoring of particle generation by following the evolution of free surfactant concentration during SDS/styrene emulsion polymerisations. The conductivity and temperature were measured on‐line during the reactant addition and reaction stages of a number of batch emulsion polymerisations. Samples were collected for off‐line analysis of particle size and conversion. Observation of the evolution of the conductivity enabled us to measure the effect of surfactant and monomer addition. The maximum size of the monomer droplets was calculated from the decrease in conductivity that represented the adsorption of surfactant molecules onto the droplet surface. The division of SDS between the particle interface and the aqueous phase was also determined giving an indication of the particle stability.
Simulation of free radical high‐pressure copolymerization in a multi‐zone autoclave reactor: compartment model investigation
Authors: Ghiass Majid , Hutchinson Robin A.
Published: February 2004

A compartment model is used to describe the complex flow of a high‐pressure ethylene copolymerization process in an industrial multi‐feed multi‐zone autoclave reactor at steady state operation conditions. To capture the imperfect mixing effects due to fresh initiator injection, each zone is considered as a set of three interconnected well mixed CSTRs with recycle streams. Volumes of the reactors and the recycle flow are adjusted to get the best fit with results of steady state well mixed analysis for each zone. Once the temperature and conversion as state variables in each reaction volume are known, the properties of polymer produced in each zone and those of final polymer can be determined. Using a realistic set of kinetic mechanisms, temperature, monomer conversion, molecular weights and short and long chain branching frequencies in each zone and at the exit point of the reactor are estimated. Some of the model results are compared with experimental data obtained for an industrial reactor.
The influence of the counter‐ion MeB(C6F5)3− and solvent effects on ethylene polymerization catalyzed by [(CpSiMe2NR)TiMe]+: a combined density functional theory and molecular mechanism study
Authors: Xu Zhitao , Vanka Kumar , Ziegler Tom
Published: February 2004

A combined density functional theory and molecular mechanism (QM/MM) method has been used to study the first (R = Me) and the second (R = propyl) insertion of the ethylene monomer into the Ti‐R bond of (CpSiMe2Nt Bu)(R)Ti‐m‐MeB(C6F5)3. The computational results, in agreement with experimental findings, show the influence of the counter‐ion and the solvent not only changes the reaction barriers, but also alters the rate‐determining step for the second ethylene propagation, from insertion to uptake. The total reaction barrier for the first ethylene propagation has been calculated to be slightly higher than that for the second ethylene propagation, in general agreement with experimental results. The total barriers in solution are 11.7 kcal/mol and 10.5 kcal/mol for the first and second ethylene insertions, respectively. These insertion barriers are comparable to the activation energy (13.3 kcal/mol) found experimentally for the same catalyst (CGC).
Dispersing behavior of recycled rubber particles
Authors: Shahidi Nima , Teymour Fouad , Arastoopour Hamid
Published: February 2004

The hydrophobic nature of recycled rubber particles presently limits their use only in non‐aqueous media. Recycled rubber particles were chemically modified by preparation of amphiphilic semi‐interpenetrating polymer networks using poly(acrylic acid) as the hydrophilic polymer. The resulting composite particles are water dispersible and suitable for various aqueous media applications.
A discretization method for computing chain length distributions
Authors: Peklak A. David , Butté Alessandro , Storti Giuseppe , Morbidelli Massimo
Published: February 2004

The method of Kumar and Ramkrishna is a numerical technique to solve population balance equations (PBEs) by discretization while preserving two moments of the distribution. When the method is used to calculate chain length distributions in polymerization reactions, the polydispersity, which depends on the first three moments of the distribution, cannot be estimated correctly. This work presents a modification of the method that allows to preserve three moments and thus calculate the polydispersity correctly, independently of the number of grid points. The modified method is applied to a model of controlled radical polymerization via RAFT and compared with the original one.
Investigating the impact of operating parameters on molecular weight distributions using functional regression
Authors: Hutchinson R.A. , McLellan P.J. , Ramsay J.O. , Sulieman H. , Bacon D.W.
Published: February 2004

Molecular weight distributions (MWDs) are inherently functional observations in which differential weight fraction is expressed as a function of chain length. Conventional approaches for analyzing and predicting MWDs include discretization and treatment as multi‐response estimation problems, characterization using moments, and detailed mechanistic modeling to predict fractions for each chain length. However, these approaches can be sensitive to loss of information, complexity and problem conditioning. An alternative is to treat the MWDs as functional observations, and to use techniques from Functional Data Analysis (FDA), notably functional regression. The objective of this paper is to develop and apply empirical modeling techniques based on functional regression for investigating the impact of operating parameters on MWDs.
Process modelling and optimization of styrene polymerization
Authors: Gao J. , Hungenberg K.D. , Penlidis A.
Published: February 2004

Polystyrene is a common commodity with thin margin, it is desirable for industry to reduce the production cost by optimizing the process and producing polystyrene with desired properties. This paper has reviewed several commonly used process optimization policies from the literature. The kinetics of styrene polymerization with mono‐ or bifunctional initiator has also be described. It has been demonstrated that by using a temperature profile combined with selective mono‐ or bifunctional initiators, one can decrease bach time while still maintaining the desired molecular weight averages. The recently developed new tetra‐functional initiator by Elf‐Atochem provides a new tool for controlling/optimization purposes. Industrial process configurations of polystyrene production has also be discussed.
Inelastic sports pricing
Authors: Fort Rodney
Published: February 2004

A recurrent finding in estimates of the gate demand for sports events is pricing in the inelastic portion of demand. With few exceptions, this finding has either been ignored or (rather poorly) explained away. In this paper, the recurrent outcome is detailed and the explanations given by past authors are discussed. Then, profit maximization theory is explored for its inelastic pricing implications. It ends up that the local TV revenue relationships between MLB teams satisfy the situation that theory predicts would generate inelastic gate pricing. This suggests two things. First, inelastic pricing is consistent with profit maximizing team behavior. Second, fuller specification of revenue functions will enhance future work in the area. Copyright © 2004 John Wiley & Sons, Ltd.
Subsidies as incentive mechanisms in sports
Authors: Fort Rodney
Published: February 2004

Applying even the most fundamental public choice principles suggests that subsidies to sports team owners will be inversely related to ticket prices. The primary aim of this paper is to demonstrate the impact of such an inverse relationship on the pricing behavior of owners. Theory shows that if either the rent or concessions/parking response by policy makers is elastic (percentage change in subsidy is greater than the percentage change in prices by teams), then the other one cannot be. A (very) cursory look at readily available NFL data lends support to the theory, at least for single‐use stadiums. The outcomes here may inform any future analysis that extends the idea into the full‐blown analysis of the politics of subsidies and for those interested in the rationing by waiting that often occurs at sports events. Copyright © 2004 John Wiley & Sons, Ltd.
Player salary share and the distribution of player earnings
Authors: Scully Gerald W.
Published: February 2004

Veteran free agency in professional team sports has led to higher average player compensation, an increase in the share of league revenues going to players, and increased dispersion in player earnings. Tests on the distributions of player salaries in the last decade reject that they are the same in the early and later years. The variance in baseball player compensation is decomposed into share and marginal revenue product effects for 1990 and 1998, and it is found that both effects contributed to the increased variance in player salaries. A simulation of the effect of universal free agency in baseball suggests a modest increase in player salary share and a drop in compensation inequality among players. Copyright © 2004 John Wiley & Sons, Ltd.
Strategic measure of competitiveness for ranked data
Authors: Rohm Andrew J. , Chatterjee Sangit , Habibullah Mohamed
Published: February 2004

This study offers a method of evaluating the stability of ranks of a data vector over time. In particular, we study improvement of a process observed over time where the data is ranked. The degree of competition at a major tennis championship (Wimbledon) as well as how trends in the level of competition have changed over time is studied. A metric for shifts in competitiveness and a new statistical methodology is proposed. The findings suggest that competitiveness at Wimbledon has been extremely high. The study offers implications for the sport of tennis as well as an approach to measuring competitive dynamics that can be applied to other contexts. Copyright © 2004 John Wiley & Sons, Ltd.
Motivating long‐term employment contracts: risk management in major league baseball
Authors: Maxcy Joel
Published: February 2004

Long‐term employment contracts have typically been modeled as mechanisms whereby workers reduce the risk of lost income with a guaranteed long‐term wage that is less than the expected spot wage. Examination of contract length among major league baseball players shows that long‐term contracts for marginal players, those for whom it would seem most logical to desire this insurance, are rarely observed. Star players, whose income levels should enable them to purchase this sort of insurance from other sources, represent the majority of long‐term contract holders. This paper presents a theoretical model showing that firms, when facing both market uncertainty and uncertainty about an employee's future productivity, have an incentive to reallocate risk with long‐term labor contracts. In such cases, a long‐term contract may be observed without a risk premium paid by the worker. The labor markets of professional sports represent this combination of market and productive uncertainty. Empirical results from major league baseball using a binary choice probit model, which corrects for sample selection bias, support the hypothesis that factors, which increase market uncertainty and reduce productive uncertainty, are consistent with the observation of long‐term contracts. Copyright © 2004 John Wiley & Sons, Ltd.
PMD and CD characterization of chirped fiber Bragg gratings employing photonic microwave technique
Authors: Yi Xiaoke , Wei Fang , Wang Yixin , Lu Chao , De Zhong Wen
Published: February 2004

We present and demonstrate experimentally a new method for measuring the polarization mode dispersion (PMD) of chirped fiber Bragg gratings. The technique can also be used to measure chromatic dispersion (CD) more accurately by eliminating the influence of PMD. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 1–2, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20026
Analytical study on variation of temperature and absorption characteristics of single‐layer radiowave absorber by irradiation electric power
Authors: Kato Masanori , Suga Ryosuke , Hashimoto Osamu , Nakamura Takayuki , Wada Kouji
Published: February 2004

In this study, the relative complex permittivity of an epoxy resinous material is measured under changes in temperature. The temperature distribution of a single‐layer radiowave absorber is analyzed using the FDTD‐HTE method with measured relative complex permittivity, and then the irradiation electric power's temperature change inside the absorber is calculated. As a result, it is observed that the temperature inside the absorber increases rapidly, so that the irradiation electric power is high, and that the temperature of the absorber increases to 170°C after the irradiation during 120 min under the irradiation electric power with 1000 W/m2. It is found that the absorption characteristics of the absorber vary rapidly when they are calculated using the abovementioned analytical result. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 3–5, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20027
Experimental demonstration of the origin of photonic bandgap creation and associated defect modes in microwave planar circuits
Authors: Saib A. , Platteborze R. , Huynen I.
Published: February 2004

This paper presents an experimental demonstration of the origin of the Photonic bandgap, using a planar dielectric substrate with a 1D finite array of rectangular holes. A microstrip of uniform width placed above the array shows a periodic variation of impedance and refractive index. The measured transmission factor of the line exhibits a strong bandgap. When the width of the microstrip periodically changes in order to keep a constant impedance along the array, the bandgap in the measured transmission totally disappears. This proves that the creation of bandgap is due to the periodic variation of impedances instead of refractive indexes. The effect of the presence of defects is also illustrated. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 5–9, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20028
Broadband multilayer active‐slot power divider
Authors: Hui S. C. , Ooi B. L. , Fong H. Y. , Wu B.
Published: February 2004

A novel multilayer broadband active‐slot power divider is proposed for the first time. As compared to the conventional active multilayer power divider7, whose 3‐dB bandwidth of small‐signal gain is typically about 40%, the overall 3‐dB bandwidth of the small‐signal gain of the proposed multilayer active‐slot power divider is about 52%. Through the modification of the T‐junction, the proposed power divider is able to provide the characteristics of balance, low loss, and broad band. The proposed device can also provide the possibility of uneven power outputs under appropriate load modifications and amplifications. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 10–12, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20029
A broadband CPW‐fed inductive slot antenna
Authors: Lin Xian‐Chang , Wang Ling‐Teng , Lai Cheng‐Liang , Liu Yu‐Seng
Published: February 2004

In this paper, a broadband coplanar waveguide (CPW)‐fed inductive slot antenna is presented. It consists of a conventional CPW inductive slot antenna and a CPW inductively coupled slot antenna in the feeding network. The experimental results provide the characteristic of excellent enhancement of impedance bandwidth (VSWR < 2). The impedance bandwidth of this broadband antenna can reach about 4.5 GHz (2.35–6.85 GHz). Details of the antenna design and experimental results are discussed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 12–14, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20030
Dielectric constant characterization using a numerical method for the microstrip ring resonator
Authors: Fang Xiangyi , Linton David , Walker Chris , Collins Brian
Published: February 2004

A new method of dielectric‐constant measurement is developed. The dielectric constant εr of RF/microwave substrate is extracted by combining the microstrip ring resonator measurement with Ansoft HFSS electromagnetic simulation software. The developed method has two advantages: (i) characterization of dielectric constant versus multiple frequency points, and (ii) compatibility with electronics design automation (EDA) software tools. This characterization method can reduce the design cycle of microwave circuits and devices. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 14–17, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20031
A simple formulation for quasistatic solutions of elliptical, cylindrical and asymmetrical coplanar strip lines
Authors: Akan Volkan , Yazgan Erdem
Published: February 2004

Simple, analytic CAD‐oriented expressions for calculating the quasistatic TEM parameters of asymmetrical coplanar strip lines (ACPS), elliptical coplanar strip lines (ECPS), and cylindrical coplanar strip lines (CCPS) using the conformal mapping method are presented. Derived expressions are accurate and very simple to use in antennas and microwave integrated circuits. Comparisons are also made between the results of this paper and ones available in the literature. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 18–21, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20032
A bandwidth‐tunable FBG filter with fixed center wavelength
Authors: Dong Xinyong , Shum P. , Ngo N. Q. , Zhao Chunliu , Yang Jianliang , Chan C. C.
Published: February 2004

A novel bandwidth‐tunable fiber Bragg grating (FBG) filter with fixed center wavelength is demonstrated. A linear tuning range of 7.8 nm (0.26–8.06 nm) for the 3‐dB bandwidth is realized in a 10‐cm‐long uniform FBG with an original 3‐dB bandwidth of 0.26 nm. Reflectivity is maintained at higher than 0.7, even as the FBG filter is tuned to the maximum bandwidth of the range. Variation of the center wavelength is less than 0.2 nm. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 22–24, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20033
An efficient design method of LTCC filters with aggressive space mapping technique
Authors: Zhao Yong‐Jiu , Yin Ying‐Zeng , Wu Ke‐Li , Wang Jie
Published: February 2004

The aggressive space mapping (ASM) algorithm is applied to the optimization design of LTCC filters. The partial element equivalent circuit (PEEC) method is utilized as a coarse model. Low‐pass and band‐pass LTCC filters are designed with HFSS and IE3D adopted as the fine models, respectively. Conductor thickness is taken into account, since it is fairly large with respect to dielectric height. Only a few instances of fine‐model simulation are needed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 24–28, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20034
Frequency up‐conversion in multimode fiber‐fed broadband wireless networks by using agile tunable laser source
Authors: Ng'oma Anthony , Tafur‐Monroy Idelfonso , Olmos Juan Jose Vegas , Koonen Ton , Khoe Gjok‐Djan
Published: February 2004

Delivery of high‐frequency carriers to remote radio access units, which are fed by multimode fibers, is demonstrated with an agile tunable laser for the first time. The phase section of the tunable laser is modulated with a low‐frequency electrical signal resulting in an up‐conversion factor greater than 20. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 28–30, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20035
Mechanically tunable, microstrip‐element waveguide filter
Authors: Tsakonas C. , Mias C.
Published: February 2004

A mechanically tunable microwave band‐stop filter, in which tunability is achieved via a movable dielectric substrate incorporating a conductive ring element is proposed. Experimental results, which are corroborated by numerical analysis, are presented that demonstrate wide tunability within the X‐band frequency range. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 30–32, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20036
A broadband folded‐slot antenna with a semi‐circular extension
Authors: Ali M. , Usaha R.
Published: February 2004

A coplanar waveguide (CPW)‐fed broadband folded‐slot antenna is proposed. Broadband operation is achieved by designing an adjacent semicircular slot to a folded‐slot antenna. A prototype antenna was fabricated on RO4003 (εr = 3.38, substrate thickness = 1.5 mm) and measured for VSWR characteristics. The antenna can operate in the 4–6‐GHz frequency range and has a bandwidth of 42.8% within 2:1 VSWR. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 32–37, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20037
Wideband T‐probe fed circular patch antenna with dipole‐like radiation patterns
Authors: Guo Yong‐Xin , Chia M. Y. W.
Published: February 2004

Experimental and simulated results for a wideband T‐probe‐fed circular patch antenna which has dipole‐like radiation patterns are presented. With an antenna thickness of ∼0.14 times the free‐space wavelength of the center operating frequency, the proposed antenna can achieve a bandwidth of ∼32% and produce dipolelike conical radiation patterns. The measured gain is in the range of 4.0–6.0 dBi in the passband. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 37–38, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20038
Broadband low‐profile cylindrical monopole antenna for 1800 MHz operation
Authors: Lai Jeng‐Wen , Tang Chia‐Luan , Fang Shyh‐Tirng , Wong Kin‐Lu
Published: February 2004

A broadband low‐profile cylindrical monopole antenna, top‐loaded with a shorted circular patch, is presented. For 1800‐MHz operation, the antenna shows a low profile of only 11 mm, corresponding to about 6.6% of the wavelength at 1800 MHz. In addition, the antenna has a wide bandwidth (larger than 20%) covering the DCS (1710–1880 MHz) and PCS (1850–1990 MHz) bands and shows very good omnidirectional radiation. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 39–40, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20039
Optical bistability in nonlinear waveguides with photonic crystals
Authors: Nóbrega K. Z. , Hernández‐Figueroa H. E.
Published: February 2004

A new way to reduce the critical power of the bistable behavior in nonlinear optical waveguides is presented. This is achieved by embedding circular photonic crystals (PCs), satisfying the Bragg condition, along a channel waveguide. Three different schemes are analyzed: PCs in the core region only, PCs in the cladding region only, and a partial fulfillment of the core with PCs. All cases presented a decreasing of the critical or threshold power. Our numerical simulations, using the finite‐element method, show the possibility to reduce up to three times the critical power, as compared to a conventional nonlinear channel waveguide. Threshold powers as low as 30 μW can be achieved. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 40–43, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20040
Edge‐based finite‐element analysis of the field patterns in V‐shaped microshield line
Authors: Lu Mai , Leonard Paul J.
Published: February 2004

In this paper, field patterns in V‐shaped microshield transmission line are calculated by using the edge‐based finite element method. The dependence of the field patterns upon the thickness of metallic signal strip and the dielectric constant of dielectric substrate is presented. The figures in this paper have important values in the design of microshield lines in microwave and millimeter‐wave integrated circuits. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 43–47, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20041
On study of a patch antenna with shorting posts
Authors: Liu Yunlin , Wang Yong , Liao Cheng , Yang Rugui
Published: February 2004

The finite‐element method (FEM) is applied to analyze a thin substrate antenna with shorting posts. The resonant frequency of this kind of antenna is studied and compared with other numerical result and experimental data. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 47–49, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20042
New and very simple CAD models for coplanar waveguide synthesis
Authors: Yildiz Celal , Turkmen Mustafa
Published: February 2004

This paper presents new, very simple, accurate closed‐form formulas obtained by using the curve‐fitting technique for coplanar waveguide synthesis. The results achieved from this work are compared to the results obtained from the quasi‐static analysis and the synthesis formulas proposed by other researchers, as well as experimental works available in the literature. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 49–53, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20043
Miniaturized multilayer hairpin bandpass filter with tunable transmission zeros
Authors: Weng Min‐Hung , Huang Tsung‐Hui , Chang Jee‐Gong , Hung Cheng‐Yuan , Dai Bun‐Tong
Published: February 2004

A miniaturized multilayer hairpin bandpass filter using tapped‐line I/O with tunable transmission zeros is designed and implemented. This structure provides additional cross‐coupling between two layers, as well as the coupling effect on the same layer. The designed filter demonstrates superior passband characteristics with a central frequency f0= 2.39 GHz, insertion loss S21= −1.45 dB and a return loss S11= −32 dB. Moreover, by combining with two layers and tapped‐line I/O structure, the filter produces two tunable transmission zeros at 2.8 GHz with −48 dB and 3.2 GHz with −43‐dB rejection that the typical elliptic function response can be easily. Experimental results of the fabricated filter measured by network analyzer agree well with the simulation results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 53–55, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20044
Spectral‐domain modeling of superconducting microstrip structures: Transmission lines and resonators
Authors: Kedar Ashutosh , Gupta K. K. , Kataria N. D.
Published: February 2004

We present a spectral‐domain analysis of thin superconducting microstrip structures in which the effects of superconducting materials, finite conductivity, and finite thickness are taken into account, using the concept of complex surface impedance. Numerical simulations showing variation of the propagation and attenuation characteristics of transmission lines and the quality factor of resonators with regard to temperature and frequency are presented. Some of the theoretical results are compared with the available data to document the validity of the approach. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 55–59, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20045
BER analysis of a packet‐based high‐speed OTDM system employing all optical routers
Authors: Ghassemlooy Z. , Gao R. , Ball P.
Published: February 2004

In an optical time‐division multiplexed (OTDM) network with all‐optical routers, system performance, that is, the bit‐error rate (BER), is limited by a number of additional noise sources due to the router. In this paper, we investigate the noise contribution due to the crosstalk and relative intensity noise (RIN) within the router, and derive an expression for the BER. We also show that the power penalty is highly dependent on the router crosstalk and RIN. Power penalty of less than 1.5 dB is achievable when the crosstalk and RIN are <−20 dB and 10−3, respectively. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 60–63, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20046
Optimization of substrate thickness in GaAs MMICs for high‐frequency applications: Using microstrip line
Authors: Thakur Jay Prakash , Pandey A. K. , Kedar Ashutosh , Gupta K. K. , Vyas H. P.
Published: February 2004

This paper presents optimization of GaAs substrate thickness for GaAs‐MMIC processes at high frequencies using a multidielectric microstrip line, that is fabricated using MMIC process. The spectral‐domain technique is used for the theoretical evaluation of the characteristic parameters of the microstrip line. The theoretical analysis is validated by the corresponding study, which was conducted using the high‐frequency structure simulator (HFSS). Some of the results are also verified with the measured results. This work is useful for inhouse optimization of substrate thickness for various GaAs‐MMIC foundries. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 63–66, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20047
Novel bandpass filter using tapered PBG cells
Authors: Yang Ru Yung , Weng Min Hung , Wu Hung Wei , Houng Mau‐Phon
Published: February 2004

A novel bandpass filter using tapered PBG cells is designed and implemented. With the tapered PBG structure inserted between the top layer of two hairpin resonators with symmetric feed‐line tapping and a ground‐plane bottom layer, the passband characteristics are excited and, moreover, a transmission zero on the higher passband edge is produced. The novel bandpass filter using tapered PBG cells demonstrates the frequency characteristics with a central frequency f0 = 2.9 GHz, a 3‐dB bandwidth (FBW) of 9%, and insertion loss S21 of −2.8 dB. Good agreement between the experimental and simulation results is obtained. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 66–68, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20048
Improved structure of a DRO for high output power and low phase noise
Authors: Ha Sung‐Jae , Ahn Chang‐Don , Lee Keun‐Taek , Hong Ui‐Seok
Published: February 2004

In this paper, a dielectric resonator oscillator (DRO) for high output power and low phase noise is proposed. Two kinds of oscillators are designed and measured in this study. The first oscillator has an improved structure for high output power and low phase noise, while the second has only the conventional structure of the oscillator with an amplifier. Measurements show the improvement of the proposed oscillator's performance, compared to that of the conventional oscillator. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 68–70, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20049
Characterization and analysis of the effects of silicon‐substrate thickness on inductor performance
Authors: Xiong Yong Zhong , Khoo Ee‐Sze , Jeung Francis Y.C.
Published: February 2004

In this paper, the effects of the thickness of silicon substrate with backside metalization on inductor performance are investigated, and the experimental results show that thinner substrate with backside metalization results in smaller inductance, lower quality factor, and slightly higher resonant frequency. For a circular spiral inductor with substrate thickness of 50 μm, the inductance L of the 8‐turn inductor would be degraded by about 22%, compared to that with substrate thickness of 150 μm; correspondingly, the quality factor Q decreases by about 16%. The measured results also show that the inductor performance with substrate thickness of 150 μm and above does not depend upon the substrate thickness. The optimization of inductor performance involves a trade‐off between the “substrate skin effect (SSE)” and thermal conductivity. It is believed that the demonstrated results will be useful for the design and packaging of RF integrated circuits (RFICs). © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 70–73, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20050
Switchable dual‐wavelength erbium‐doped fiber‐ring lasers using a fiber Bragg grating in high‐birefringence fiber
Authors: Zhao Chun‐Liu , Yang Xiufeng , Ng Jun Hong , Dong Xinyong , Guo Xin , Wang Xiaoyan , Zhou Xiaoqun , Lu Chao
Published: February 2004

A simple switchable dual‐wavelength Er‐doped fiber‐ring laser using a fiber Bragg grating (FBG) written in high‐birefringence (HiBi) fibers is proposed. Due to the two‐peak reflections with orthogonal polarizations of the FBG, the polarization hole‐burning effect in the cavity is greatly enhanced. Experimental results show that a stable dual‐wavelength laser with very close wavelength separation (0.39 nm) can be generated at room temperature. Furthermore, the FBG in the HiBi fiber offers flexibility for selection of the laser wavelength. By adjusting a polarization controller, the laser can be switched between the stable single‐ or dual‐wavelength lasing operations. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 73–75, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20051
Familial dysautonomia
Authors: Axelrod Felicia B.
Published: February 2004

Familial dysautonomia (FD) is a neurodevelopmental genetic disorder within the larger classification of hereditary sensory and autonomic neuropathies, each caused by a different genetic error. The FD gene has been identified as IKBKAP. Mutations result in tissue‐specific expression of mutant IκB kinase‐associated protein (IKAP). The genetic error probably affects development, as well as maintenance, of neurons because there is neuropathological and clinical progression. Pathological alterations consist of decreased unmyelinated and small‐fiber neurons. Clinical features reflect widespread involvement of sensory and autonomic neurons. Sensory loss includes impaired pain and temperature appreciation. Autonomic features include dysphagia, vomiting crises, blood pressure lability, and sudomotor dysfunction. Central dysfunction includes emotional lability and ataxia. With supportive treatment, prognosis has improved greatly. About 40% of patients are over age 20 years. The cause of death is usually pulmonary failure, unexplained sudden deaths, or renal failure. With the discovery of the genetic defect, definitive treatments are anticipated. Muscle Nerve 29: 352–363, 2004
Intraoperative cranial nerve monitoring
Authors: Harper C. Michel
Published: February 2004

The purpose of intraoperative monitoring is to preserve function and prevent injury to the nervous system at a time when clinical examination is not possible. Cranial nerves are delicate structures and are susceptible to damage by mechanical trauma or ischemia during intracranial and extracranial surgery. A number of reliable electrodiagnostic techniques, including nerve conduction studies, electromyography, and the recording of evoked potentials have been adapted to the study of cranial nerve function during surgery. A growing body of evidence supports the utility of intraoperative monitoring of cranial nerve nerves during selected surgical procedures. Muscle Nerve 29: 339–351, 2004
Focal myositis associated with S‐1 radiculopathy: Report of two cases
Authors: Streichenberger Nathalie , Meyronet David , Fiere Vincent , Pellissier Jean‐François , Petiot Philippe
Published: February 2004

Two cases are described of pseudotumoral calf hypertrophy after laminectomy for a compressive S‐1 radiculopathy. The serum creatine kinase (CK) level was normal or mildly elevated. T2‐weighted magnetic resonance imaging (MRI) showed calf enlargement, with an increased signal of the medial head of the gastrocnemius muscle. Electromyography revealed fibrillation potentials and positive sharp waves, but no complex repetitive discharges in the affected gastrocnemius muscle, with motor unit potentials having mixed neurogenic and myopathic features. Muscle biopsy revealed a focal myositis associated with some features of denervation. A brief course of corticosteroids was followed by remission clinically and improvement in the MRI findings. Muscle Nerve 29: 443–446, 2004
Sarcoid polyneuropathy responsive to intravenous immunoglobulin
Authors: Heaney Dominic , Geddes Jennian F. , Nagendren Kulan , Swash Michael
Published: February 2004

We describe a 38‐year‐old woman with a predominantly sensory axonal polyneuropathy in whom a nerve biopsy demonstrated sarcoid granulomas. The neuropathy did not respond to oral steroid therapy but there was a rapid and repeated response to intravenous immunoglobulin, which gradually diminished over subsequent treatments, but remained beneficial. The systemic sarcoidosis remained active. Muscle Nerve 29: 447–450, 2004
MNGIE neuropathy: Five cases mimicking chronic inflammatory demyelinating polyneuropathy
Authors: Bedlack Richard S. , Vu Tuan , Hammans Simon , Sparr Steven A. , Myers Bennett , Morgenlander Joel , Hirano Michio
Published: February 2004

We report five patients with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) who had demyelinating peripheral neuropathy. The MNGIE neuropathy had clinical and electrodiagnostic features typical of acquired, rather than inherited, etiologies. In fact, three patients were actually treated for chronic inflammatory demyelinating polyneuropathy (CIDP). We discuss findings that may help distinguish patients with MNGIE from those with CIDP. Muscle Nerve 29: 364–368, 2004
Lack of association between acetylcholine receptor ϵ polymorphisms and early‐onset myasthenia gravis
Authors: Bonifati Domenico Marco , Willcox Nick , Vincent Angela , Beeson David
Published: February 2004

A patient with mutations in the acetylcholine receptor (AChR) ϵ subunit, who subsequently developed autoimmune myasthenia gravis (MG), led us to search for ϵ AChR mutations and polymorphisms in 167 patients with early‐onset MG. No ϵ‐subunit mutations or increased incidence of exonic ϵ‐subunit polymorphisms were found. The allelic frequency of the intron polymorphism IVS11+ 20del20 was more prevalent in non–United Kingdom subjects, both patients and healthy individuals, than in United Kingdom subjects (15.8 vs. 6.2%, P = 0.0008) but not between MG patients and healthy individuals. These data provide no evidence that heteroallelic mutations or polymorphisms in the AChR ϵ subunit are involved in the development of autoimmune early‐onset MG but raise issues for future studies. Muscle Nerve 29: 436–439, 2004
Changes in characteristics of rat skeletal muscle after experimental allergic encephalomyelitis
Authors: de Haan A. , van der Vliet M.R. , Hendriks J.J.A. , Heijnen D.A.M. , Dijkstra C.D.
Published: February 2004

Experimental allergic encephalomyelitis (EAE) serves as an animal model for certain neuroinflammatory diseases of the central nervous system, in particular multiple sclerosis (MS). EAE is accompanied by transient weakness or paralysis of hind limbs. We have investigated the effect of partial and transient conduction failure in the central nervous system on skeletal muscle function. At ∼2.5 days after development of maximal clinical signs, body and medial gastrocnemius muscle mass were lower (by ∼21 and 33%, respectively; P < 0.05) in EAE rats compared with controls. Fiber cross‐sectional area was lower by 40–50% in all fiber types. Maximal force and power were substantially lower (by 58% and 73%) in EAE rats, as was the force normalized for muscle mass (35%). However, no such weakness was found when lower stimulation frequencies were used. Generation of similar submaximal forces was attributable to a slower relaxation in EAE muscles. This advantage for the EAE muscles was lost during repeated exercise. While fatigability was similar, the difference in relaxation rate between EAE and control disappeared in fatigue. Our data suggest that, as a result of central neuroinflammatory diseases, maximal performance of skeletal muscle is impaired but submaximal performance is relatively well maintained. Muscle Nerve 29: 369–375, 2004
Biopsy‐proven alpha‐glucosidase deficiency with normal lymphocyte enzyme activity
Authors: Whitaker Charles H. , Felice Kevin J. , Natowicz Marvin
Published: February 2004

Alpha‐glucosidase deficiency is a rare cause of muscle disease in adults. The diagnosis relies on recognition of the salient clinical features and determination of significantly reduced alpha‐glucosidase (GAA) activity. Lymphocytes are the usual tissue for diagnostic enzymology; discrepant results from analyses of different tissues are unusual. We report a patient with clinical, electromyographic, and biopsy findings indicative of alpha‐glucosidase deficiency whose muscle and lymphocyte enzyme results were markedly discrepant on multiple analyses. As a result, we conclude that all patients with suspected alpha‐glucosidase deficiency and a normal lymphocyte GAA assay should also have a determination of GAA activity in muscle or skin fibroblasts. Muscle Nerve 29: 440–442, 2004
Electrodiagnostic features of acute paralytic poliomyelitis associated with West Nile virus infection
Authors: Al‐Shekhlee Amer , Katirji Bashar
Published: February 2004

West Nile virus (WNV) infection is a potentially fatal disease, with meningoencephalitis being its most common neurological manifestation. Guillain–Barré syndrome (GBS) has also been described, but acute paralytic poliomyelitis has only recently been recognized. We report the clinical and electrodiagnostic findings of five patients with WNV infection, who presented with acute paralytic poliomyelitis. Three patients manifested focal asymmetrical weakness, and two had rapid ascending quadriplegia mimicking GBS. Electrodiagnostic studies during the acute illness showed normal sensory nerve action potentials, compound motor action potentials of normal or reduced amplitude, and no slowing of nerve conduction velocities. Depending on the timing of the examination, fibrillation potentials were widespread, including in those with focal weakness. Cervical magnetic resonance imaging in one patient showed abnormal T2‐weighted signals in the spinal cord gray matter. On follow‐up, signs of clinical improvement were seen in one patient, whereas two remained quadriplegic and ventilator‐dependent 5 months after the onset. This report highlights the value of the electrodiagnostic studies in the diagnosis and prognosis of focal or generalized weakness due to acute paralytic poliomyelitis associated with WNV infection. Muscle Nerve 29: 376–380, 2004
Neurotrophins improve neuromuscular transmission in the adult rat diaphragm
Authors: Mantilla Carlos B. , Zhan Wen‐Zhi , Sieck Gary C.
Published: February 2004

Neurotrophins modulate acute and sustained synaptic plasticity. In cultured Xenopus laevis neuromuscular junctions, neurotrophins improve neuromuscular transmission. Whether this influence exists at the mammalian neuromuscular junction is unknown. We hypothesized that neurotrophins improve neuromuscular transmission at neuromuscular junctions of adult rat diaphragm muscle fibers. A diaphragm muscle—phrenic nerve preparation was used to determine the effects of brain‐derived neurotrophic factor (BDNF), neurotrophin‐4 (NT‐4) and K252a [tyrosine kinase (Trk) receptor inhibitor] on the extent of neuromuscular transmission failure induced by repetitive nerve stimulation. We found significant enhancement of neuromuscular transmission with BDNF or NT‐4 treatment, whereas K252a treatment worsened neuromuscular transmission. In contrast, diaphragm muscle contractile and fatigue properties were unaffected by neurotrophin or K252a treatment. These results demonstrate that BDNF and NT‐4 improve synaptic transmission in the adult rat diaphragm muscle, likely in a Trk‐dependent fashion. Neurotrophins may constitute a novel therapeutic target to improve neuromuscular function in the diaphragm. Muscle Nerve 29: 381–386, 2004
Oxaliplatin‐induced neurotoxicity: Acute hyperexcitability and chronic neuropathy
Authors: Lehky T.J. , Leonard G.D. , Wilson R.H. , Grem J.L. , Floeter M.K.
Published: February 2004

Oxaliplatin, a platinum‐based chemotherapeutic agent, is effective in the treatment of solid tumors, particularly colorectal cancer. During and immediately following oxaliplatin infusion, patients may experience cold‐induced paresthesias, throat and jaw tightness, and occasionally focal weakness. We assessed nerve conduction studies and findings on needle electromyography of patients with metastatic colorectal cancer before and during treatment with oxaliplatin. Twenty‐two patients had follow‐up studies within 48 h following oxaliplatin infusions, and 14 patients had follow‐up studies after 3–9 treatment cycles. Repetitive compound muscle action potentials and neuromyotonic discharges were observed in the first 24–48 h following oxaliplatin infusion, but resolved by 3 weeks. After 8–9 treatment cycles, sensory nerve action potential amplitudes declined, without conduction velocity changes or neuromyotonic discharges. The acute neurological symptoms reflect a state of peripheral nerve hyperexcitability that likely represents a transient oxaliplatin‐induced channelopathy. Chronic treatment causes an axonal neuropathy similar to other platinum‐based chemotherapeutic agents. Muscle Nerve 29: 387–392, 2004
Evoked pain in the motor endplate region of the brachial biceps muscle: An experimental study
Authors: Qerama Erisela , Fuglsang‐Frederiksen Anders , Kasch Helge , Bach Flemming W. , Jensen Troels Staehelin
Published: February 2004

Spontaneous electrical activity, interpreted as motor endplate activity, has been reported at muscle trigger points. This study examined whether the motor endplate region, identified by electromyography, is more sensitive to noxious stimuli than other muscle sites. We induced pain in the brachial biceps muscles of 21 healthy subjects by injecting capsaicin (30 μg/0.1 ml) and NaCl (5%/0.2 ml) in the motor endplate region and at electrically silent muscle sites. Needle and evoked pain were measured by a visual analogue scale (VAS) (0–10) and the short form of the McGill Pain Questionnaire. The needle pain in the motor endplate region differed both in intensity and quality from that at other sites. The maximal pain after NaCl 5% was higher, and the VAS area‐under‐the‐curve for NaCl 5% and capsaicin were larger, in the motor endplate region than in other sites. A higher density of muscle nociceptors in the vicinity of the motor endplate region may account for the observed differences in pain. These findings may have clinical implications for the treatment of musculoskeletal pain conditions. Muscle Nerve 29: 393–400, 2004