bluuebunny/crossref_metadata_2025 huggingface dataset:
Three‐Dimensional Structure of Olefinic Thermoplastic Elastomer Blends Using Electron Tomography
Authors: Sengupta Pratip , Noordermeer Jacques W. M.
Published: March 2005

Summary: The present communication reports the first use of electron tomography in reconstructing the three‐dimensional morphology in thermoplastic elastomer blends. The blends investigated were dynamically vulcanized blends of ethylene‐propylene‐diene (EPDM) rubber/poly(propylene)/oil and polystyrene‐block‐(ethylene‐co‐butylene)‐block‐polystyrene (SEBS)/poly(propylene)/oil. An easy identification of blend morphology could be carried out at blend compositions, where conventional transmission electron microscopic imaging gives misleading information. This technique gives a higher resolution than any other microscopic technique, and is applicable to blends with dispersed as well as co‐continuous morphologies.

Example of a tomographic model of partially co‐continuous SEBS phases in a SEBS/PP/oil thermoplastic blend. Only the contours of the SEBS phase are shown.

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Example of a tomographic model of partially co‐continuous SEBS phases in a SEBS/PP/oil thermoplastic blend. Only the contours of the SEBS phase are shown.
NMR Analysis and Regiochemical Structure of Some Selectively 13C‐Enriched Poly(propylene)s
Authors: Zambelli Adolfo , Csok Zsolt , Sessa Irene
Published: March 2005

Summary: The regiochemical structures of poly(propylene)s obtained in the presence of three single‐site catalysts, Cp*Ti(CH3)3 + B(C6F5)3 (I + III), CpTi(CH3)3 + B(C6F5)3 (II + III), and VCl4 + anisole + Al(C2H5)2Cl (V + A), are investigated by 13C NMR analysis. Polymer 1, obtained in the presence of I + III is, seemingly, fully regioregular, while, surprisingly, polymer 2, obtained in the presence of II + III, appears to be alternating sequence of primary and secondary regioblocks, very much like polymer 3, obtained in the presence of V + A. The stereochemical structure of the polymer obtained in the presence of I + III is in excellent agreement with a Bernoullian statistical model of the stereoselective propagation, while those of the other two polymers possibly require a Coleman‐Fox model.

13C NMR spectra of 10%‐enriched poly[(2‐13C)propylene], 1′ and 2′, prepared under the conditions reported in Table 1 for the corresponding poly(propylene)s, 1 and 2. The resonances of the tertiary carbons are diagnostic of the regioblock structure of sample 2′.

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13C NMR spectra of 10%‐enriched poly[(2‐13C)propylene], 1′ and 2′, prepared under the conditions reported in Table 1 for the corresponding poly(propylene)s, 1 and 2. The resonances of the tertiary carbons are diagnostic of the regioblock structure of sample 2′.
Highly‐Ordered Hybrid Organic‐Inorganic Isoporous Membranes from Polymer Modified Nanoparticles
Authors: Nyström Daniel , Antoni Per , Malmström Eva , Johansson Mats , Whittaker Michael , Hult Anders
Published: March 2005

Summary: Organic‐inorganic hybrid materials consisting of nanosized silica particles with surface grafted PS or PS‐b‐PMMA were synthesized using ATRP. These hybrid materials were used in the fabrication of highly‐ordered isoporous membranes. Optical characterization revealed that the membranes consisted of hexagonally ordered pores of uniform size. The combination of an open pore structure and high surface area makes isoporous membranes into materials of high interest in fields as biotechnology and photonics.

Image from optical microscope of hybrid nanoparticle membrane of SiO2‐g‐PS with hexagonally‐ordered pores.

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Image from optical microscope of hybrid nanoparticle membrane of SiO2‐g‐PS with hexagonally‐ordered pores.
Gelation Studies, 3
Authors: Richter Sven , Brand Torsten , Berger Stefan
Published: March 2005

Summary:The sol‐gel transition of one thermoreversible gelling mixture made of xanthan gum and locust bean gum has been studied by using in situ time‐resolved dynamic light scattering (DLS) and measuring the spin‐lattice relaxation timeT1of several protons. A critical dynamical behavior was observed near the sol‐gel transition, which is characterized by the presence of power‐law spectra over four decades of the delay time in the time‐intensity correlation functiong2(t)−1 ∼ t−μat 48 °C. The increase inT1with increasing temperature becomes steeper at 50 °C indicating a significant change in the local mobility of one anomeric proton of the xanthan side chain and the anomeric protons of the locust bean gum mannose backbone.

Temperature dependence of the spin‐lattice relaxation timeT1for the equatorial anomeric proton of the mannopyranosic unit located next to the main chain of the xanthan.

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Temperature dependence of the spin‐lattice relaxation timeT1for the equatorial anomeric proton of the mannopyranosic unit located next to the main chain of the xanthan.
Combining Atom Transfer Radical Polymerization and Click Chemistry: A Versatile Method for the Preparation of End‐Functional Polymers
Authors: Lutz Jean‐François , Börner Hans G. , Weichenhan Katja
Published: March 2005

Summary: The bromine chain ends of well‐defined polystyrene ($\overline M _{\rm n}$ = 2 700 g · mol−1, $\overline M _{\rm w} /\overline M _{\rm n}$ = 1.11) prepared using ATRP were successfully transformed into various functional end groups (ω‐hydroxy, ω‐carboxyl and ω‐methyl‐vinyl) by a two‐step pathway: (1) substitution of the bromine terminal atom by an azide function and (2) 1,3‐dipolar cycloaddition of the terminal azide and functional alkynes (propargyl alcohol, propiolic acid and 2‐methyl‐1‐buten‐3‐yne). The “click” cycloaddition was catalyzed efficiently by the system copper bromide/4,4′‐di‐(5‐nonyl)‐2,2′‐bipyridine. In all cases, 1H NMR spectra indicated quantitative transformation of the chain ends of polystyrene into the desired function.

Preparation of well‐defined functional polymers possessing diverse chain‐end functionalities by the combination of atom transfer radical polymerization and click chemistry.

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Preparation of well‐defined functional polymers possessing diverse chain‐end functionalities by the combination of atom transfer radical polymerization and click chemistry.
Monte Carlo Technique to Simulate Amide Interchange Reactions, 3
Authors: Liu Zhen Hong , Wang Chao Sheng , Wang Xia Qin , Huang Nan Xun , Filippini‐Fantoni Roberto
Published: March 2005

Summary: Influence of amide interchange reactions of polyamide 6 (PA6) on its molecular weight distribution (MWD) was analyzed using a kinetic Monte Carlo simulation method, by which two reaction systems with different types of initial non‐equilibrium distributions, monodisperse and bimodal distribution, were investigated. The simulation results indicate that initial deviations from equilibrium MWD are rapidly relaxed to an equilibrium one, which approaches the most probable MWD proposed by Flory. The reaction time to reach the equilibrium MWD decreases with an increase in reaction temperature. The simulated polydispersity index data suggest that about 0.3 interchanges per segment are sufficient to equilibrate the non‐equilibrium systems, consistent with the results reported by Jo et al. on ester interchange reactions of poly(ethylene terephthalate) (PET).

Variation of polydispersity index Q with interchange reaction time at different reaction temperatures for an initial monodisperse distribution.

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Variation of polydispersity index Q with interchange reaction time at different reaction temperatures for an initial monodisperse distribution.
A Mathematical Model for the Longest Ethylene Sequence Distribution of Random Ethylene Copolymers
Authors: Gemoets Frederik , Hagen Henk
Published: March 2005

Summary: In the first step to model Crystaf® curves, a mathematical expression ψ has been derived to describe the longest ethylene sequence (LES) distribution of random binary (e.g., ethylene/α‐olefin) copolymer chains. Based on this expression, a method Ψpolymer has been developed to describe the LES‐distribution of random copolymers. Comparisons of the LES‐distribution of a random copolymer with polydispersity of 2, as calculated by Ψpolymer, with Monte Carlo simulation and with a method previously described in literature show that the derived mathematical expression ψ is correct. This model allows for the description of the crystallizing temperature‐distribution of polymers using the reported relation between crystallizing temperature and LES. It will also hold if the crystallizing temperature of a chain would depend on other chain properties next to its LES. Exactly this latter prospect will favor the use of the mathematical expression derived in this report, above the ones from the literature.

LES weight‐distribution of a random copolymer, calculated by Ψpolymer and by a Monte Carlo simulation.

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LES weight‐distribution of a random copolymer, calculated by Ψpolymer and by a Monte Carlo simulation.
Model Bridging Effects of Asymmetrical Triblock Copolymers
Authors: Peng Changjun , Li Jiankang , Liu Honglai , Hu Ying
Published: March 2005

Summary: We have performed Monte Carlo simulations to study the bridging of symmetrical or asymmetrical triblock copolymers confined between two similar or different solid surfaces based on a simple lattice model. The influence of the molecular structure, surface separation, adsorption energy, chain composition, and the chain concentration on the fractions of chains with bridge, loop and dangling configurations are reported in detail. The results show that the largest bridging fraction is given only when symmetrical triblock copolymers are confined between two parallel surfaces with the same adsorption energy. The bridge fraction is decreased so long as the asymmetry of the copolymers or the difference between the two surfaces is enhanced. It was found also that the bridging fraction increases as the adsorption energy increases. The bridging fraction Ωbridge under different separations, Lz, can be expressed as $\Omega _{{\rm bridge}} = A(1 - L_z /L_{z.\max } )^\alpha $ in various situations. On the other hand, by introducing a symmetry index ν, the influence of molecular structure of copolymers on the bridges can be illustrated approximately by a relation $(1 - \Omega _{{\rm b,asym}} /\Omega _{{\rm b,symm}} ) = B(1 - \nu )^\zeta $ when the two surfaces are similar and the adsorption energy is not too high. Combining the two expressions, data of the bridge fractions for copolymers of different symmetries confined between surfaces with different separations can be described with a single equation, which, in some occasion, can be used for prediction.

Influence of molecular structure on the bridging fraction for ${\rm A}_{r_{{\rm A1}} } {\rm B}_{{\rm 40}} {\rm A}_{r_{{\rm A2}} }$.

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Influence of molecular structure on the bridging fraction for ${\rm A}_{r_{{\rm A1}} } {\rm B}_{{\rm 40}} {\rm A}_{r_{{\rm A2}} }$.
Diagnosis of Impurity Levels in a Copolymerization Process
Authors: Lou Shijin , Duever Thomas A. , Budman Hector M.
Published: March 2005

Summary: This work investigates a fault diagnosis problem in the copolymerization process of styrene and methyl methacrylate (STY/MMA). Two topics are discussed in this paper: the system observability and optimal experimental design (OED) to reduce fault misclassification. Lack of observability has been found to be one of the major causes of misclassification in fault diagnosis, which is not remediable by any means other than including the right measurements necessary for the observability. In this work, the system observability has been studied through simulation analysis. Then, two new experimental design methods are proposed to train the projection pursuit regression (PPR) algorithm for fault diagnosis purpose. The new design methods, referred to as Gaussian probability design and Fuzzy boundary design, are compared to a conventional factorial design, to evaluate their performance for the problem under study. The Gaussian probability design is based on the calculation of the probability of an experimental data point near a class boundary belonging to a specific class. The Fuzzy boundary design is based on a bootstrapping technique used in part for the learning process in developing neural network models. It investigates the insufficiency of training data based on the identification of class boundaries by a group of models, such as PPR models. Both Gaussian probability design and Fuzzy boundary design methods automatically search for the sparseness of the training data, and provide guidelines to include pairs of training data on two sides of a class boundary in the areas where the data density is the lowest. The proposed design methods outperform a conventional factorial design by reducing the fault misclassification more effectively with the same amount of additional training data.

Testing data in the process measurement space of temperature vs. conversion.

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Testing data in the process measurement space of temperature vs. conversion.
Advanced Computational Strategies for Modelling the Evolution of Full Molecular Weight Distributions Formed During Multiarmed (Star) Polymerisations
Authors: Chaffey‐Millar Hugh , Busch Markus , Davis Thomas P. , Stenzel Martina H. , Barner‐Kowollik Christopher
Published: March 2005

Summary: A novel computational strategy is described for the simulation of star polymerisations, allowing for the computation of full molecular weight distributions (MWDs). Whilst the strategy is applicable to a broad range of techniques for the synthesis of star polymers, the focus of the current study is the simulation of MWDs arising from a reversible addition fragmentation chain transfer (RAFT), R‐group approach star polymerisation. In this synthetic methodology, the arms of the star grow from a central, polyfunctional moiety, which is formed initially as the refragmenting R‐group of a polyfunctional RAFT agent. This synthetic methodology produces polymers with complex MWDs and the current simulation strategy is able to account for the features of such complex MWDs. The strategy involves a kinetic model which describes the reactions of a single arm of a star, the kinetics of which are implemented and simulated using the PREDICI® program package. The MWDs resulting from this simulation of single arms are then processed with an algorithm we describe, to generate a full MWD of stars. The algorithm is applicable to stars with an arbitrary number of arms. The kinetic model and subsequent algorithmic processing techniques are described in detail. A simulation has been parameterised using rate coefficients and densities for a 2,2′‐azoisobutyronitrile (AIBN) initiated, bulk polymerisation of styrene at 60 °C. A number of kinetic parameters have been varied over large ranges. Conversion normalised simulations were performed, leading to information regarding star arm length, polydispersity index (PDI) and the fraction of living arms. These screening processes provided a rigorous test for the kinetic model and also insight into the conditions, which lead to optimal star formation. Finally, full MWDs are simulated for several RAFT agent/initiator ratios as well as for stars with a varying number of arms.

Full MWDs from a star with 1, 2, 4, 6 and 8 arms.

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Full MWDs from a star with 1, 2, 4, 6 and 8 arms.
A paracrine signal mediates the cell transformation response to low dose gamma radiation in JB6 cells
Authors: Weber Thomas J. , Siegel Robert W. , Markillie Lye M. , Chrisler William B. , Lei Xingye C. , Colburn Nancy H.
Published: March 2005

The carcinogenic response to radiation is complex and may involve adaptive cellular responses as well as a bystander effect mediated by paracrine or intercellular signaling activities. Using a newly developed co‐culture model we have examined whether low dose gamma radiation induces the transformation of JB6 mouse epidermal cells as well as non‐irradiated bystander cells. Cell transformation response is defined as the acquisition of anchorage‐independent growth properties and is quantified by counting colonies on soft agar. Exposure of JB6 cells to low dose (2–20 cGy) gamma radiation resulted in an approximate 1.9 ± 0.1 and 2.8 ± 0.5‐fold increase in cell transformation response when cells were seeded at 1 × 104 or 1 × 105 cells/dish, relative to respective sham exposed controls. We developed a co‐culture model where sham exposed or irradiated JB6 cells were mixed with non‐irradiated JB6 cells that had been stably transfected with the enhanced yellow fluorescent protein (EYFP) to enable the distinction of fluorescent bystander‐specific colonies. A significant increase in the number of bystander‐specific colonies was observed in co‐culture with 10 cGy irradiated JB6 cells (224 ± 9), relative to the number of bystander‐specific colonies arising in co‐culture with sham exposed JB6 cells (55 ± 16). Our results indicate that low dose radiation induces the transformation of JB6 cells and that a soluble paracrine factor that is secreted by irradiated cells induces the transformation of non‐irradiated bystander cells. © 2005 Wiley‐Liss, Inc.
Double‐blind, placebo‐controlled, unforced titration parallel trial of quetiapine for dopaminergic‐induced hallucinations in Parkinson's disease
Authors: Ondo William G. , Tintner Ron , Dat Voung Kevin , Lai Dejian , Ringholz George
Published: March 2005

We completed a single site, double‐blind, placebo‐controlled, parallel design study of quetiapine for hallucinations in PD. Thirty‐one subjects with PD and prominent visual hallucinations and Mini‐Mental State Examination score >21 were randomly assigned in a 2:1 drug to placebo ratio, up to 200 mg daily of quetiapine or matching placebo given in two doses. They were seen at 3 weeks (100 mg/day) and 12 weeks (200 mg/day, with optional dose reduction). Evaluation included the Unified Parkinson's Disease Rating Scale (UPDRS), the Baylor PD Hallucination Questionnaire, and a battery of neuropsychological tests. The demographics between subjects randomized to drug (n = 21) vs. placebo (n = 10) were similar. The final dose of active drug was 200 (n = 11), 150 (n = 2), 100 (n = 3), and 75 (n = 1) mg per day. All placebo subjects were on the equivalent of 200 mg per day. The UPDRS Activities of Daily Living and Motor scores did not significantly change compared to placebo. Compared to placebo, there were no significant changes in our hallucination questionnaire, the Brief Psychiatric Rating Scale (BPRS), or question 12 (hallucination item) of the BPRS. There were no significant changes on any of the neuropsychological measures. Adverse events on drug included sedation (n = 9), but no drug‐related adverse events precipitated discontinuation and none were rated as serious. Quetiapine, up to 200 mg daily, was well tolerated and did not worsen UPDRS scores; however, there was no significant improvement in psychosis rating scales compared to placebo. Larger doses of drug and greater sample sizes might be considered in future studies. © 2005 Movement Disorder Society
Power reflectance measurements of metal meshes and grids using a quasi‐optical resonator
Authors: Kapilevich B. , Gover A. , Eliran A.
Published: March 2005

This paper presents a novel approach developed for the measurement of the power reflectance of metal meshes and wire grids using a quasi‐optical resonator. It is based on the reconstruction of a grid's reflectance from the resonance curve of a quasi‐optical resonator. The model of the resonator loaded by a mesh has been developed to provide direct reconstruction of its reflectance. A comparison of the measured results with data obtained in free‐space measurements has shown good agreement. Examples of reflectance measurements of both conventional and twin‐shaped meshes are presented to illustrate the technique suggested. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 185–188, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20765
Band‐notched ultra‐wideband circular‐disk monopole antenna with an arc‐shaped slot
Authors: Wong Kin‐Lu , Chi Yun‐Wen , Su Chih‐Ming , Chang Fa‐Shian
Published: March 2005

By embedding a simple arc‐shaped slot in a circular‐disk monopole antenna, an ultra‐wideband (UWB, 3.1–10.6 GHz) operation with a controlled notched frequency band can be obtained. The arc‐shaped slot is placed close to the boundary of the circular‐disk monopole and has a length of about one‐half wavelength of the desired notched frequency. The proposed slotted circular‐disk monopole antenna showing UWB operation with a notched frequency band for rejecting the 5.8‐GHz WLAN band is demonstrated. The effects of the dimensions of the arc‐shaped slot on the notched frequency band are also analyzed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 188–191, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20766
On the estimation of scattering from convex conducting cylinders
Authors: Chumachenko Vitaliy P.
Published: March 2005

A novel approach for estimating the high‐frequency field scattered by a convex conducting cylinder is proposed. The theory is based on the locality property of short‐wave scattering and considers the curvature of the target and the shadow‐side currents. The approach is more accurate than the physical optics (PO) approximation and requires PO‐comparable computational costs. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 191–194, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20767
Design and signal‐integrity analysis of a backplane for high‐speed digital systems
Authors: Zhang Hua , Hong Wei , Wang Yuanqing , Wang Wei , Hu Jinsong , Wang Haiming , Yang Guangqi , Zhang Nianzu , Cui Tiejun
Published: March 2005

The design of a backplane in high‐speed digital systems is presented, with an emphasis on systematic analysis of the signal integrity using full‐wave electromagnetic methods when the system carries high‐speed digital signals. The simulation and measurement results in both the frequency and time domains are presented for a high‐speed digital‐circuit demo system at the data rate of 500 M/bs, and are in good agreement. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 194–199, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20768
A new look at FDTD excitation sources
Authors: Su Tao , Yu Wenhua , Mittra Raj
Published: March 2005

In FDTD simulations, the excitation sources can be divided into two categories: (i) the displacement‐current source, which is generated by a time‐varying electric field; (ii) the induced‐current source, which exists in the lossy material. Currently, the latter source is the popular choice in most FDTD simulations. However, there are two problems with the use of this source: the time signal shape at the observation points is different from that of the input pulse, and an artificial DC component is introduced into the solution that prevents the solution from converging to zero. The objective of this paper is to investigate these excitation sources and to clarify some concepts in FDTD simulations. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 203–207, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20770
Nonradiative dielectric waveguide embedded in metamaterial with negative permittivity or permeability
Authors: Yang Ping , Li Duochuan , Wu Ke
Published: March 2005

A nonradiative dielectric waveguide (NRD) embedded in a metamaterial with negative permittivity or permeability is proposed and theoretically characterized in this work. This dielectric waveguide structure is inherently nonradiating at bends and discontinuities, since metamaterials with negative permittivity or permeability cannot support any propagating modes. The waveguide supports hybrid longitudinal section magnetic (LSM) and longitudinal section electric (LSE) modes. It is demonstrated that the LSM11 mode is the lowest‐order mode when the waveguide dimensions are properly designed. The theoretical results indicate that this guided‐wave structure is able to narrowly confine electromagnetic fields within the core dielectric strip, thus exhibiting nonradiating properties. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 207–210, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20771
CPW feed to rectangular DRA
Authors: Ghosh Bratin , Antar Yahia M. M. , Petosa Aldo , Ittipiboon Apisak
Published: March 2005

Characteristics of uniplanar feed topologies for the dielectric resonator antenna (DRA) based on the CPW are presented. The dual‐resonance characteristics of the capacitive feed are discussed. A comparison of the CPW capacitive, square‐loop, and inductive feeds shows that the real‐estate requirements and radiation patterns are strongly influenced by the feed type. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 210–216, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20772
Phase‐noise measurement of free‐running microwave voltage‐controlled oscillators
Authors: Ng Hoi‐Yee , Tsang Kim‐Fung , Yuen Chung‐Ming
Published: March 2005

This paper reports an efficient method to measure the phase noise of free‐running microwave voltage‐controlled oscillators using a general‐purpose spectrum analyzer. The system tracks the frequency drifting signal by using a charge pump phase‐locked loop. The measurements taken on a 1.9‐GHz oscillator demonstrates the system accuracy. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 216–217, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20773
3D scalar FDTD method for waveguides with circular symmetry
Authors: Lu Changgui , Cui Yiping
Published: March 2005

A 3D scalar finite‐difference time‐domain (FDTD) method in cylindrical coordinates is formulated in order to analyze the wave propagation in circularly symmetric waveguides. The 2nd‐order Mur's absorbing boundary condition (ABC) is provided as well. This method can be used to simulate the propagation and coupling between the modes in a multimode waveguide structure. An isotropic point source propagating in either a symmetric medium or multimode step‐index fiber and a plane‐source propagation in multimode fiber are simulated in this paper. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 218–221, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20774
Miniaturization of hairpin bandpass filters using high‐permittivity substrate
Authors: Huang Cheng‐Liang , Hsu Cheng‐Hsing , Tsai Chih‐Ming
Published: March 2005

The miniaturization of hairpin bandpass filters by employing two high‐permittivity ceramic substrates (with respective dielectric constants of 9.7 and 20) are investigated. Microwave dielectric ceramics with high permittivity are commonly applied in several microwave communication components. With the advantages of compact size, high‐permittivity ceramics can be used as the substrate for bandpass filters. Moreover, the fundamental characteristics of newly developed compact stepped‐impedance hairpin resonators with parallel coupled lines have also been described and applied to the design of bandpass filters. In this paper, the designed mixed‐coupled structures are simulated using an IE3D simulator. The responses of the fabricated filters using Al2O3(εr= 9.7,Q×f= 350000 GHz) and MgNb2O6(εr= 20,Q×f= 110000 GHz) ceramic substrates are designed at a center frequency of 2 GHz. The compact size and performance of this class of filters are demonstrated. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 222–225, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20776
Wideband quarter‐wave patch antenna with a single‐layer capacitive feed on a finite ground plane
Authors: Joubert J. , Odendaal J. W.
Published: March 2005

The design and radiation characteristics of a wideband quarter‐wave patch with a single‐layer capacitive feed are presented. The E‐plane radiation pattern of the antenna is shown to be very dependent on the size of the ground plane, and the results for two extreme cases are obtained in order to illustrate this effect. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 225–227, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20777
L‐strip‐fed wideband rectangular dielectric resonator antenna
Authors: Menon Sreedevi K. , Lethakumary B. , Bijumon P. V. , Sebastian M. T. , Mohanan P.
Published: March 2005

In this paper, the advantages of using L‐shaped microstrip feed to excite a rectangular dielectric resonator antenna (DRA) by electromagnetic coupling are presented. This feeding technique enhances the bandwidth and gain of the antenna without affecting its size. The experimental results are validated using Fidelity software based on the finite‐difference time‐domain (FDTD) method. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 227–228, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20778
Application of active electromagnetic bandgaps to the design of tunable resonators in CPW technology
Authors: Gil I. , Bonache J. , García‐García J. , Martín F.
Published: March 2005

Capacitively coupled resonators with wide tuning range have been proposed in coplanar waveguide (CPW) technology, based on the concept of electromagnetic bandgaps (EBGs). By loading the resonator with shunt‐connected varactor diodes, the phase velocity of the line and, hence, the resonant frequency of the structure can be electrically controlled. Due to the slow‐wave effect related to the presence of the varactors, a certain level of miniaturization is also achieved. Moreover, the frequency‐selective properties of EBGs are used to reject the first spurious frequency of the resonators. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 229–232, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20779
Mode‐converting vacuum windows in circular waveguides: Analysis and synthesis in the case of axially symmetric modes
Authors: Tkachenko V.I. , Yashina N.P.
Published: March 2005

A rigorous mathematical model of electromagnetic‐wave scattering by a complicated axially symmetric resonator‐type junction in a circular waveguide is developed. The efficiency, accuracy, and stability of the solution and its numerical implementation provide a robust numerical tool for the synthesis of the waveguide unit with required characteristics. Extensive numerical experiments result in the design of a matching vacuum window possessing the features of an H02 ⇒ H01 mode converter. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 233–237, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20780
Analysis of parallel coupled‐line bandpass filters using a ground‐plane aperture
Authors: Zhang Zhenyu , Guo Yong‐Xin , Ong Ling Chuen , Chia M. Y. W.
Published: March 2005

Parallel coupled‐line bandpass filters using the ground‐aperture technique are analyzed in this paper. A design guide and design curves for this kind of coupled‐line bandpass filter on commonly used high‐ and low‐permittivity substrates are presented. Based on the proposed design curves, two sample bandpass‐filter configurations are designed. The design is simulated using Ansoft HFSS and validated by the measurements. Good agreement between the simulated and measured responses is obtained. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 237–240, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20781
Characteristic parameters for CPWs on a very thin dielectric layer
Authors: Zhao Ji‐Xiang
Published: March 2005

In this paper, approximate analytical expressions for characteristic parameters of CPWs on a very thin dielectric layer are given. The “crowding phenomenon” that occurs during the process of conformal mapping is overcome. Combining these expressions with the partial‐capacitance method, the characteristic parameters for CPWs on a multidielectric layered substrate are computed and are found to agree well with the test data. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 240–241, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20783
A K‐band inverted microstripline‐fed linear tapered slot antenna and its 16‐element E‐plane array
Authors: Wu Chen
Published: March 2005

An inverted microstripline‐fed linear tapered slot antenna element and a design of its 16‐element E‐plane array are presented in this paper. The element is designed using the finite‐difference time‐domain (FDTD) method. The calculated results show that it has a wide‐impedance bandwidth in the K‐band. To investigate the E‐plane array, the return loss at each element input port, the couplings among elements, and the array's radiation patterns are obtained using the FDTD method. Using a unique three‐piece assembled structure, the array is fabricated and tested experimentally. The measured results show that it has a wide bandwidth and antenna efficiency. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 241–246, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20784
Temperature dependence of light polarization in active erbium‐doped fiber
Authors: Quintela M. A. , Madruga F. J. , López‐Amo M. , López‐Higuera J. M.
Published: March 2005

Experimental results on the temperature dependence of the polarization state of the amplified optical signal between 0°C and 50°C are reported in this paper for an erbium‐doped fiber amplifier. The instabilities of the polarization state decrease with increasing temperature when pumped at 1480 nm. The rates are reported. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 246–249, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20785
Diode large‐signal characteristics measurement for high‐power rectennas
Authors: Xu Junshu , Xu Changlong , Xu Deming , Yang Xuexia
Published: March 2005

In this paper, an Agilent 8722ES Network Analyzer with option 085 is configured to directly measure the diode large‐signal characteristics. A set of smart microstrip calibration standards corresponding to this measurement system is also designed. Using the measured nonlinear equivalent‐circuit parameters of the diode, a matching circuit is designed to improve the power conversion efficiency from RF to DC, at an input power level of 90 mw and 200Ω load, and a maximum conversion efficiency of 70% was achieved at frequency of 9.75 GHz. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 249–251, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20786
A class of novel compact filters with quasi‐hairpin structure using stepped‐impedance resonators
Authors: Liao Shry‐Sann , Chen Hsien‐Ku , Liao Hsien‐Yuan , Chang Yin‐Cheng
Published: March 2005

A class of novel compact filters with quasi‐hairpin structure using stepped‐impedance resonators (SIRs) is presented. The SIR open stub is used as the loaded structure for the filter design with the merit of small size and sharp transition band (TB). Additionally, these filters achieve sharp TB for lowpass filters (LPFs) and improved selectivity for bandpass filters (BPFs) at 2.45 GHz. All of the filters retain the dimensions of the circuit by more than 60%, as compared to the conventional one. These filters are very useful for applications in wireless‐communication systems. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 251–255, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20787
Simulation, fabrication and testing of a left‐handed microstrip coupler
Authors: Tan Y. S. , Rao X. S. , Chen L. F. , Tan C. Y. , Ong C. K.
Published: March 2005

A broadband left‐handed parallel‐line microstrip coupler is implemented by both electromagnetic simulation and actual fabrication. The circuit dimensions are smaller and more compact than those in previous studies and a thinner Duroid substrate of thickness h = 0.635 mm is used. Parametric studies were performed using IE3D, and fabrication was done via a Quick Circuit 7000 prototyping machine. The network‐analyser measurements indicate broad bandwidth coupling in the 6.5–7.7‐Ghz region. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 255–258, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20788
Applications of the Z‐Y T‐chart for nonreciprocal stub tuners
Authors: Torrungrueng D. , Thimaporn C.
Published: March 2005

Impedance matching is a part of the design process for a microwave system to achieve the maximum power delivered to the load. In this paper, nonreciprocal single‐stub and double‐stub matching networks are studied graphically using a generalized Smith chart, called the T‐chart, developed for nonreciprocal transmission lines. The stubs can be connected in series or in parallel with the main feed line. Basic procedures and concepts for nonreciprocal stub tuners are similar to those of reciprocal ones. It is found out that the “forbidden region” for double‐stub shunt tuners, where the load cannot be matched, is independent of the phase angle ϕ of associated characteristic impedances of nonreciprocal transmission lines. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 259–262, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20789
Computer‐aided numerical characterization and experimental studies for high‐power operation of IMPATT oscillators
Authors: Kar Subar
Published: March 2005

A computer‐aided numerical characterization is done for oscillator properties on the basis of large‐signal modeling of IMPATT diodes supported by experimental studies, in order to select suitable parameters for high‐power operation of IMPATT oscillators. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 262–265, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20790
An internal ultra‐wideband metal‐plate monopole antenna for UMTS/WLAN dual‐mode mobile phone
Authors: Hsiao Fu‐Ren , Wong Kin‐Lu
Published: March 2005

A novel compact ultra‐wideband (UWB) metal‐plate monopole antenna for mobile‐phone applications is presented. The antenna is easily fabricated from a single metal plate and is suitable to be embedded within the casing of a mobile phone as an internal antenna. Further, the antenna shows a wide operating bandwidth of about 6 GHz (about 1.9–7.9 GHz), which makes it easily cover the UMTS band (1920–2170 MHz) for mobile communications and the 2.4‐GHz (2400–2484 MHz) and 5.2/5.8‐GHz (5150–5350/5725–5875 MHz) bands for WLAN communications. That is, the antenna is suitable for application in a UMTS/WLAN dual‐mode mobile phone. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 265–268, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20791
Research on highly Yb3+‐doped passive mode‐locked fiber ring laser
Authors: Xiu‐Jiang Huang , Zhan Sui , Yong‐Zhi Liu , Ming‐Zhong Li , Hong‐Huan Lin , Jian‐Jun Wang , Xin Li , De‐Shuang Zhao , Hai‐Yan Chen
Published: March 2005

Theoretical and experimental results on the self‐starting passive mode‐locked Yb fiber‐ring laser generating short pulse are reported. The relations between the laser‐cavity parameters and mode‐locked pulse characteristics are discussed. 980‐nm LD‐pumped laser is used as the pump source and high‐concentration Yb3+‐doped fiber is adopted as the gain medium. Using the nonlinear polarization rotation (NPR) effect of the fiber, a self‐starting stable mode‐locked pulse is obtained, with a center wavelength of 1046 nm, a 3‐dB bandwidth of 6.01 nm, and a 20‐dB bandwidth of 16 nm. The mode‐locked threshold power is 150 mW and output power is 26 mW with a 20‐MHz repetition rate. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 269–270, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20792
Metastatic malignant melanoma presenting as pancytopenia in a three‐year‐old boy
Authors: Spiller Susan E. , Hawkins Douglas S. , Finn Laura S. , Sze Raymond W. , Sybert Virginia
Published: March 2005

Malignant melanoma is rare in childhood and has never been reported to cause pancytopenia due to bone marrow metastases in a child. We report a 3‐year‐old boy with a large congenital melanocytic nevus who presented with bone pain and pancytopenia due to diffuse bone and bone marrow infiltration with metastatic melanoma without an identifiable primary site. Despite treatment with imatinib mesylate there was no response and the patient died with progressive disease. This case illustrates an unusual presentation of bone marrow failure secondary to malignant melanoma in a young child with symptomatic metastatic marrow infiltration, a rarely reported site of melanoma involvement in adults or children. Pediatr Blood Cancer 2005; 45:60–63. © 2005 Wiley‐Liss, Inc.
Main chain thermotropic liquid crystalline polyurethanes containing biphenyl mesogens based on novel AB‐type self‐polycondensation route: FT‐IR and XRD studies
Authors: Ranganathan T. , Bhoje Gowd E. , Ramesh C. , Kumar Anil
Published: March 2005

The detailed mesophasic characterization of main chain liquid crystalline polyurethanes containing biphenyl mesogen, which were synthesized by the novel AB‐type self‐polycondensation approach, was carried out by using Differential Scanning Calorimetry (DSC), Polarized Optical Microscopy (POM), variable temperature X‐ray Diffraction (XRD), and Fourier Transform Infrared (FT‐IR) spectroscopic studies. The type of mesophase present in these polymers was identified to be the smectic A phase by POM and XRD studies. The smectic layer thickness was found to increase as the length of the spacer increased. The effect of temperature on the hydrogen bonding was analyzed by FT‐IR studies. The curve‐fitting analysis of the NH stretching and CO stretching modes of vibrations indicated a gradual decrease in hydrogen bonding during the transition from the crystalline state to the mesophase. The mesophase to isotropic liquid transition was then accompanied by the complete disappearance of the hydrogen bonding. The biphenyl bands also showed changes during phase transitions due to the coupling of biphenyl vibration modes with the urethane linkage attached to it. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1903–1912, 2005
Characterization of ring‐opening polymerization of genipin and pH‐dependent cross‐linking reactions between chitosan and genipin
Authors: Mi Fwu‐Long , Shyu Shin‐Shing , Peng Chih‐Kang
Published: March 2005

In this study, a novel chitosan‐based polymeric network was synthesized by crosslinking with a naturally occurring crosslinking agent—genipin. The results showed that the crosslinking reactions were pH‐dependent. Under basic conditions, genipin underwent a ring‐opening polymerization prior to crosslinking with chitosan. The crosslink bridges consisted of polymerized genipin macromers or oligomers (7 ∼ 88 monomer units). This ring‐opening polymerization of genipin was initiated by extracting proton from the hydroxyl groups at C‐1 of deoxyloganin aglycone, followed by opening the dihydropyran ring to conduct an aldol condensation. At neutral and acidic conditions, genipin reacted with primary amino groups on chitosan to form heterocyclic amines. The heterocyclic amines were further associated to form crosslinked networks with short chains of dimmer, trimer, and tetramer bridges. An accompanied reaction of nucleophilic substitution of the ester group on genipin by the primary amine group on chitosan would occur in the presence of an acid catalysis. The extent in which chitosan gels crosslinked with genipin was significantly dependent on the crosslinking pH values: 39.9 ± 3.8% at pH 5.0, 96.0 ± 1.9% at pH 7.4, 45.4 ± 1.8% at pH 9.0, and 1.4 ± 1.0% at pH 13.6 (n = 5, p < 0.05). Owing to the different crosslinking extents and different chain lengths of crosslink bridges, the genipin‐crosslinked chitosan gels showed significant difference in their swelling capability and their resistance against enzymatic hydrolysis, depending on the pH conditions for crosslinking. These results indicated a direct relationship between the mode of crosslinking reaction, and the swelling and enzymatic hydrolysis properties of the genipin‐crosslinked chitosan gels. The ring‐opening polymerization of genipin and the pH‐dependent crosslinking reactions may provide a novel way for the preparation and exploitation of chitosan‐based gels for biomedical applications. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1985–2000, 2005
Reversible addition–fragmentation chain transfer polymerization of methyl methacrylate in suspension
Authors: Biasutti John D. , Davis Thomas P. , Lucien Frank P. , Heuts Johan P. A.
Published: March 2005

The reversible addition–fragmentation chain transfer polymerization of methyl methacrylate mediated by 2‐cyanoprop‐2‐yl dithiobenzoate (CPDB) in bulk (60 and 70 °C) and suspension (70 °C) was studied, and in both polymerization systems, a good control of the molecular weight and polydispersity was observed. Stable suspension polymerizations were carried out over a range of CPDB concentrations, and with increasing CPDB concentration, the particle size and polydispersity index of the produced polymer decreased. The former was ascribed to the lower viscosities of the monomer and polymer droplets at low conversions, which caused easier breakup with the applied shear stresses. Lower polydispersity indices at higher CPDB concentrations were probably caused by a diminished gel effect, which was observed at lower CPDB concentrations at high conversions, causing a broadening of the molecular weight distribution. The livingness of the polymers formed in suspension was proven by successful chain extensions with methyl methacrylate, styrene, and 2‐hydroxyethyl methacrylate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2001–2012, 2005
Synthesis of poly(arylene thioether)s from protected dithiols and aromatic difluorides with an organic base
Authors: In Insik , Kim Sang Youl
Published: March 2005

Aromatic poly(arylene thioether)s were synthesized from N‐propyl‐S‐carbamate‐protected aromatic dithiols and aromatic difluorides. The deprotection of the protected dithiols with an organic base such as 1,8‐diazabicyclo[5.4.0]‐7‐undecene at room temperature and subsequent polymerization with the difluoride monomers at 120 °C in N‐methyl‐2‐pyrrolidinone produced high molecular weight polymers with intrinsic viscosities as high as 0.45 dL/g. The use of organic bases instead of inorganic bases for the generation of thiophenoxide nucleophile was a convenient way of avoiding metallic impurities in the synthesis of the poly(arylene thioether)s through a nucleophilic aromatic substitution reaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2021–2027, 2005
Alkali metal salt‐catalyzed aldol addition of dimethylsilyl enolate on a polyether structure
Authors: Yamamoto Shin‐Ichi , Morita Hidehiko , Hayashi Sachika , Moriya Osamu
Published: March 2005

The aldol addition of dimethylsilyl enolates to aldehydes with alkali metal salt catalysts was examined. Several kinds of polyether derivatives were employed as solid solvents without a liquid one. In the presence of the polymer (Gr) obtained from poly(ethylene glycol) methyl ether methacrylate (PEGMA) or the crosslinked derivatives (GLs) from PEGMA, the aldol addition proceeded efficiently and yielded the product. The effective catalyst was lithium bromide for Gr and potassium bromide for GLs. The crosslinked polyether GLs were easily separated from the reaction mixture by simple filtration, which was preferable to simplifying the treatments of the reaction. The results demonstrated that the presence of polyether structures provided a favorable reaction environment and enabled the reaction under solvent‐free conditions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2075–2084, 2005