bluuebunny/crossref_metadata_2025 huggingface dataset:
Reactive processing of syndiotactic polystyrene with an epoxy/amine solvent system
Authors: Schut Jaap , Stamm Manfred , Dumon Michel , Galy Jocelyne , Gérard Jean‐François
Published: October 2003

Syndiotactic polystyrene (sPS) is a new semi‐crystalline thermoplastic which is believed to fill the price‐performance gap between engineering and commodity plastics. In order to reduce the high processing temperature of sPS (>290°C), an epoxy‐amine model system was used as a reactive solvent. Such a processing aid can be used to achieve a 50 to 500 fold lowering of the melt viscosity. When initially homogeneous solutions of sPS in a stoechiometric epoxy‐amine mixture are thermally cured, Reaction Induced Phase Separation (RIPS) takes place, leading to phase separated thermoplastic‐thermoset polymer blends. We focus our study on low (wt% sPS < 20%) and high concentration blends (wt% sPS > 60%) prepared by two processing techniques (mechanical stirring in a laboratory reactor or internal mixer/ reactive extrusion respectively). These blends have different potential interests. Low concentration blends (sPS domains in an epoxy‐amine matrix) are prepared to create new, tunable blend morphologies by choosing the nature of the phase separation process, i.e. either crystallisation followed by polymerization or polymerization followed crystallisation. High concentration blends (sPS matrix containing dispersed epoxy‐amine particles after RIPS) are prepared to facilitate the extrusion of sPS. In this case, the epoxy amine model system served as a reactive solvent. The time to the onset of RIPS is in the order of 7‐9 min for low concentration blends, while it increases to 20‐45 min for high concentration samples, as the reaction rates are substantially slowed down due to lower epoxy and amine concentrations. During the curing reaction the melting temperature of sPS in the reactive solvent mixture evolves back from a depressed value to the level of pure sPS. This indicates a change in the composition of the sPS phase, caused by (complete) phase separation upon reaction. We conclude that our epoxy amine system is suited for reactive processing of sPS, where final properties depend strongly on composition and processing conditions.
Controlled synthesis of block polyesters by reactive extrusion
Authors: Moad Graeme , Groth Andrew , O'Shea Michael S. , Rosalie Julian , Tozer Ramon D. , Peeters Gary
Published: October 2003

The synthesis of block copolyesters by combining transesterification resistant oligoesters with poly(ethylene terephthalate) is described. Critical factors in the synthesis include processing conditions (temperature), end groups and catalysts used in oligoester synthesis. It is necessary to achieve a balance between ease of incorporation/synthesis and transesterification resistance. The process is discussed with reference to poly(neopentyl isophthalate) as a representative transesterification resistant oligoester. The primary motivation for the work has been the development of higher barrier poly(ethylene terephthalate) useful for making monolayer beverage containers.
Synthesis and properties of poly(m‐carborane‐siloxane) elastomers
Authors: Patel Mogon , Swain Anthony C. , Skinner Anthony R. , Mallinson Leslie G. , Hayes Gerard F.
Published: October 2003

Organic boron polymers are of interest to AWE, and a significant improvement would be to make components from a single phase material that enables the boron content to be maximised and the elastomeric properties to be tuned to requirement. This paper is a summary of the work carried out towards the synthesis and characterisation of poly(m‐carborane‐siloxane) rubbers. These rubbers have been synthesised by the Ferric Chloride‐catalysed condensation reaction between dimethoxy‐m‐carborane terminated monomer and dichlorodimethylsilane. Phenyl modified and Phenyl‐vinyl modified variations have been synthesised in addition to the unmodified poly(m‐carborane‐siloxane) polymers. The unmodified poly(m‐carborane‐siloxane) shows some crystallinity but the modified versions are amorphous and have good elastomeric properties. Overall, the measured boron content is in close agreement to that expected from the repeat unit, suggesting the synthesised rubbers have been successfully prepared. It is also demonstrated that the carborane unit offers increased thermal stability and retention of ‘rubber‐like’ properties even after ageing at high temperature.
Impact modification of PA‐6 and PBT by epoxy‐functionalized rubbers
Authors: Lievana Emiliano , Karger‐Kocsis József
Published: October 2003

Glycidylmethacrylate (GMA) grafted apolar (ethylene/propylene/diene ‐ EPDM) and polar (acrylonitrile/butadiene ‐ NBR) rubbers were melt blended with polyamide‐6 (PA‐6) and polybutylene terephthalate (PBT). The toughness of the blends containing 5, 10 and 50 wt.% epoxy functionalized rubbers was assessed by various methods (notched Charpy, perforation impact) as a function of temperature (T=23 and −40°C). The notched Charpy tests served to deduce the fracture toughness (Kc) and energy (Gc) data. It was established that EPDM‐g‐GMA is a slightly better impact modifier than is NBR‐g‐GMA albeit the latter polar rubber is more compatible with both matrices than the less polar EPDM‐g‐GMA. This finding was traced to the difference in the glass transition temperature (Tg of NBR is higher than that of EPDM) and to the dispersion of the epoxy functionalized rubbers.
Compatibilization of PA6/rubber blends by using an oxazoline functionalized rubber
Authors: Scaffalo R. , La Mantia F.P. , Bertani R. , Sassi A.
Published: October 2003

The compatibilization of blends of polyamide 6 with a nitrile butadiene rubber has been investigated. The procedure consists of two steps: modification of the nitrile groups of the rubber into oxazoline in the melt through condensation of ethanolamine with formation of a molecule of ammonia, followed by use of the modified rubber as a compatibilizing precursor which is melt mixed with the polyamide to produce the compatibilized blend. The modification reaction has been detected by NMR analysis and a rheological, mechanical and thermomechanical characterization has been carried out on the all the blends. The results indicate that the modification reaction occurs but the conversion of nitrile into oxazoline is relatively low. Use of the modified rubber in the preparation of binary polyamide/rubber blends, leads to an increase in viscosity, which is typical of compatibilized systems, and to enhanced tensile, impact and thermomechanical properties. These phenomena can be explained by the formation of in situ rubber/polyamide copolymers that act as compatibilizers, due to the reaction between oxazoline and the end groups of the polyamide. The presence of residual low molecular compounds, from the modification or from the purification of the rubber worsens all of the properties and inhibits the compatibilizing effect of the modified rubber.
Functionalization on polyamide complex with iodide: a review
Authors: Kawaguchi Akio , Tsurutani Naoki
Published: October 2003

Application with iodinated polyamide‐6 (iodine/PA‐6 complex) is introduced for modification of structure and functionality on the polyamide. Coordination between polyiodides (In− = 3, 5, ...) and the polyamide advances rapidly and drastically within polyiodide solutions even in bulky samples of the polyamide, and responsiveness in the complex with other molecules such as water is enhanced by coordination. Such response and variation of the structure of the complex can introduce novel functionality with other molecules or ions or salts into the polyamide or hydrophilic polymers.
Influence of processing method and components molecular structure on the phase behaviour of polyethylenes/dye blends
Authors: Pucci Andrea , Ruggeri Giacomo , Cardelli Camilla , Conti Giovanni
Published: October 2003

The phase dispersion of terthiophene alkyl derivatives on different polyethylene matrices was investigated. The PE affinity toward dichroic dyes with different structure, the effect of blending process and the influence of a polyolefinic compatibilizer on the homogeneity of host‐guest blends were comparatively investigated by calorimetry, DSC and SEM analyses. For these purposes, polyethylenes with different molecular weights and densities and EVAc were used as host matrices. The polymeric compatibilizer was prepared by radical functionalization of a commercial low density polyethylene. The dichroic nature of the guest phase allowed to perform UV‐Vis measurements in polarized light on oriented blend film samples. The dyes affinity toward PE is one of the key factor in obtaining oriented polyolefinic films with high optical performances for several applications.
Quantitative analysis of functional groups in HDPE powder by DRIFT spectroscopy
Authors: Földes Enikő , Szabó Zoltán , Janecska Ákos , Nagy Gábor , Pukánszky Béla
Published: October 2003

FT‐IR spectra of ethylene homopolymers and ethylene/1‐hexene copolymers polymerized under different conditions were studied by transmission and diffuse reflection (DRIFT) spectroscopy. The absorbance spectra of film samples were compared with the DRIFT spectra of powders ground from the films. For determining the concentration of the methyl and unsaturated (vinyl, vinylidene and trans‐vinylene) groups of polyethylene powders the DRIFT spectra were calibrated by comparing the IR intensities of the corresponding bands measured by the two methods. The results proved that the effect of differences in scattering of the polymer powder originating from the irregularity of the top surface, as well as the size and shape of the particles can be eliminated by the use of a proper internal standard. Linear correlation was established between the logarithms of the normalized intensities measured in absorbance and Kubelka‐Munk units. In the case of polyethylene the selection of the internal reference band affects significantly the accuracy of the calibration due to the difference in the refractive indices of the crystalline and amorphous phases.
Reactive compatibilization of recycled low density polyethylene/butadiene rubber blends during dynamic vulcanization
Authors: Fainleib Alexander , Grigoryeva Olga , Starostenko Olga , Danilenko Inna , Bardash Lubov
Published: October 2003

For reactive compatibilization of the recycled LDPE with butadiene rubber (BR) an equal quantity of few couples of reactive polyethylene copolymer/reactive polybutadiene (1/1) were introduced into the corresponding phases before the dynamic vulcanization. The LDPE/BR thermoplastic dynamic vulcanizates (TDVs) produced using the poly(ethylene‐co‐acrylic acid), PE‐AA/polybutadiene terminated with isocyanate groups, PB‐NCO compatibilizing couple with different ratio of functional groups have demonstrated the best mechanical properties and have been characterized by X‐Ray analysis and DMTA measurements. For all of systems studied the increasing components compatibility due to the formation of the essential interface layer have been observed. The PB‐NCO modifier participates in two processes: it is co‐vulcanised with BR in rubber phase and reacts in the interface with the PE‐AA dissolved in LDPE. The amorphous phase of LDPE is dissolved by rubber phase, i.e. the morphology with dual phase continuity is formed that provides an improvement of mechanical characteristics of material obtained. The best combination of mechanical characteristics was obtained for LDPE(PE‐AA)/BR(PB‐NCO), PB‐NCO=7.5 wt.% per PB, COOH/NCO=1/1. The tensile strength and an elongation at break for these blends were 3.9 MPa and 353% and for the basic non‐compatibilized blend 3.2 MPa and 217%, relatively.
Creep relaxation and stress relaxation of PS‐HI/SEBS blends
Authors: Rek Vesna , Holjevac Grgurić Tamara , Jelčić Želimir
Published: October 2003

For the selection of the polymer materials and polymer blends for various fields of applications the stability of material under constant deformation and constant load are very important. In this paper, the copolymers high‐impact polystyrene, PS‐HI, styrene‐ethylene/buthylene‐styrene block copolymer, SEBS, and their blends PS‐HI/SEBS were investigated. The investigations were done by DMA analysis. The secondary viscoelastic functions, creep, creep modulus, stress and flexural relaxation modulus were investigated in creep and stress relaxation experiment at temperatures 25, 35, 45, 55 and 65°C during 1 h. The master curves were created by time‐temperature correspondence principle, TTC. The correlation of the secondary viscoelastic functions with time, temperature and content of the hard, PS, phase was discussed.
Processing and dynamic mechanical properties of PS‐HI/SEBS blends
Authors: Rek Vesna , Holjevac Grgurić Tamara , Jelčić Želimir
Published: October 2003

Thermoplastic elastomers have been successfully used as impact modifiers for thermoplastics. Dynamic mechanical properties and phase transitions are very important for their application. In this paper, the copolymers high‐impact polystyrene, PS‐HI, styrene‐ethylene/butylene‐styrene block copolymer, SEBS, and their blends PS‐HI/SEBS were investigated. Rheological behaviour of those samples during processing was followed by measuring the torque vs. time in the extruder Haake Record 90. The investigations were done by DMA analysis. The primary viscoelastic functions, the storage modulus, E` the loss modulus, Eˇ, and loss tangent, tgδ, were determined in the temperature range −150°C to 160°C. The correlation of the processing parameters and primary viscoelastic functions with content of the hard, PS, phase were discussed.
Study of the properties of rigid and plasticized PVC/PMMA blends
Authors: Belhaneche‐Bensemra N. , Bedda A. , Belaabed B.
Published: October 2003

The aim of this work is to study the structure‐properties relationship of rigid and plasticized PVC/PMMA blends. For that purpose, blends of variable compositions were prepared in the absence and in the presence of a plasticizer di (ethyl‐2 hexyl) phtalate or DEHP. The miscibility of the two polymers was investigated by differential scanning calorimetric analysis (DSC) and Fourier transform infrared spectroscopy. The weight loss from 30 to 600°C was investigated by thermogravimetric analysis (TGA). The thermal degradation under nitrogen at 185°C was studied and the amount of HCl released from PVC was measured by the pH method. Furthermore, the variation of mechanical properties such as tensile behavior, hardness and impact resistance was investigated for all blend compositions.
Cation‐exchange fabric prepared by electron beam‐induced graft copolymerization of binary monomer mixture
Authors: Bandar Yuliya , Kim Hong Je , Lim Yong Jin , Kravets Lyubov'
Published: October 2003

Applying the electron‐beam preirradiation method in air the cation ‐ exchange fabric (CEF) containing sulfonic acid (R‐SO3H) groups was prepared by graft copolymerization of sodium styrenesulfonate with acrylic acid onto non woven polypropylene fabric. The effect of reaction conditions on the grafting yield and reaction mechanism was examined.

The ion‐exchange properties towards Cu(II) and Co(II) ions of the CEF were investigated depending on the form of the CEF and a pH of the solution. It was found that the synthesized CEF contains both strong acid groups (R‐SO3H) and weak acid (R‐COOH) groups in almost equal proportion. The utilization of the CEF in Na+ form allows to make the best use of its ion‐exchange capacity.
Conformational aspects of segmented poly(ester‐urethanes)
Authors: Ioan S. , Cojocaru I.E. , Grigoras V.C. , Macocinschi D. , Filip D.
Published: October 2003

Segmented poly(ester‐urethanes) containing hard and soft segments, were obtained from aromatic diisocyanates with thiodiglycol or diethylene glycol as chain extenders, and poly(ethylene glycol)adipate usig a multistep polyaddition process. Transition temperatures by differential scanning calorimetry and thermo‐optical analysis were employed to characterize polyurethane materials. Changes in the conformation of these polyurethanes were analyzed also, by viscometer measurements in N,N‐dimethyl‐formamide. The obtained data revealed that the thermal curves are influenced by the soft and hard segment structures in the temperature range studied.
UV stabilising synergies between carbon black and hindered light stabilisers in linear low density polyethylene films
Authors: Horrocks A. Richard , Liu Mingguang
Published: October 2003

The combined effects of selected carbon black pigments and hindered light stabilisers (HALS) on the UV stabilities of linear low density polyethylene film have been studied under UVA and UVB fluorescent radiation sources. While the presence of HALS do not change the chemistry of film photodegradation, whether they are low or high molecular variants, their presence significantly extends film lifetime relative to the sum of the effects of carbon black and HALS individually. These lifetime extensions may be defined in terms of a synergy factor defined with respect to film time to lose a specific percentage of a tensile property, namely t20, the time to lose 20% of initial elongation‐at‐break, or the carbonyl index associated with this condition.

It is proposed that possible causes of this synergy are a result of the UV screening effect of the carbon black particles which provide lower concentrations of polymer radicals for the HALS component to interact with and/or an accompanying thermal stabilising effect by the latter as a consequence of the higher polymer local temperature during irradiation of pigmented films.
Evaluation of the fire‐retardant properties of new modifiers in unsaturated polyester resins using the cone calorimetric method
Authors: Kicko‐Walczak Ewa
Published: October 2003

An investigation of the burning behaviour of a series of unsaturated polyester resin formulations has been carried out using the Cone calorimeter technique. A complex analysis of the pyrolysis of selected glass‐reinforced polyester (GRP) laminates was made based on fire‐nonretarded, fire‐retarded and smoke suppressed compositions of unsaturated polyester resins (UPR) by the use of mixtures of zinc hydroxystannate ZnSn(OH)6, (ZHS), zinc stannate ZnSnO3 (ZS) and zinc borate or zinc molybdate. The heat release (average) rate (HRR and HRRav), time required to ignite a GRP, the mass loss rate and (average) surface extinction area (SAE and SAEav) were studied in relation to thermal irradiation power and to presence or absence of a fire retardant. The cone calorimeter is shown to enable all the stages of pyrolysis of GRP involving combustion and smoke emission to be analyzed, and confirmed the good effects of Zn/Sn systems as a fire retardant additives for UPR.
Surface modified aluminium hydroxide in flame retarded noise damping sheets
Authors: Keszei Sándor , Anna Péter , Marosi Györgi , Márton Andrea , Bertalan Györgi , Valló Ferenc
Published: October 2003

Flame retarded polyethylene compounds were prepared using a series of aluminium hydroxide of different particle size applying a milling processes and special precipitation technologies. The processability and flame retardant efficiency of the flame retarded systems were compared. The effects of various surface modifications were analysed in case of one selected type of aluminium hydroxide. A silicone terminated reactive surfactant promoted not only the processability but also the flame retardant efficiency. Noise damping sheets were prepared by simultaneous application of aluminium hydroxide and barium sulphate in an elastomer blend matrix. V0 flame retardant grade could be achieved this way accompanied with improvement in the acoustic properties and maintenance of the mechanical properties.
Surface treated cellulose fibres in flame retarded PP composites
Authors: Anna P. , Zimonyi E. , Márton A. , Szép A. , Matkó Sz. , Keszei S. , Bertalan Gy. , Marosi Gy.
Published: October 2003

Polypropylene‐based composites were prepared containing non‐treated and various treated cotton fibre and wood flakes. A correlation was observed among the fibre treatment and compounding parameters, mechanical and discoloration properties. The structural changes in fibres were demonstrated by Raman spectroscopic and DSC measurements. The possibility for forming cellulose fibre containing flame retardant composites was also investigated. The efficiency of various treatments on compounding, discoloration and mechanical properties enhance in the following order: no treatment < non ionic surfactant < reactive silicone segment containing non ionic surfactant < special silylation treatment. The best results obtained with the special silylation treatment were explained with the more organophilic character and by the thermal stability of the treated fibres. Cellulose fibre as a polyol‐charring component and ammonium‐polyphosphate together constitute a high performance intumescent flame retardant system in the PP matrix.
Use of reactive surfactants in basalt fiber reinforced polypropylene composites
Authors: Matkó Sz. , Anna P. , Marosi Gy. , Szép A. , Keszei S. , Czigány T. , Pölöskei K.
Published: October 2003

Basalt fibers, similarly to other silicate fibers, can be introduced into both thermoplastic and thermosetting polymer matrices. In this work some basalt fiber reinforced polypropylene composites were investigated. The fiber‐matrix adhesion was improved by commercial and non‐commercial maleic anhydride derivatives. The latter types, called reactive surfactants, were prepared in laboratory scale and the progress of the syntheses was determined by Raman microscopy. The additives allowed performing reactive interface modification during the compounding process. Due to the interface modification with the additives in low concentration the mechanical properties improved. The boundary layers on the surface of the reinforcing fibers were observed using scanning electron microscopy (SEM).
Analysis of multicomponent polymer systems by raman microscopy
Authors: Szép A. , Marosfői B. , Bertalan Gy. , Anna P. , Marosi Gy.
Published: October 2003

The Raman microscope is one of the most convenient instruments for analyzing the structural characteristics and changes in the interfacial region of multicomponent systems. This is confirmed by the results obtained in the field of packaging materials, nanocomposites, and basalt fibre reinforced composites. In the course of this study, the chemical character of the surface and interfacial regions were investigated and, in addition, the local characteristics of the crystallization process of the polymer matrix could be determined.
Aging of silica‐filled PDMS/PDPS copolymers in desiccating environments: a DSC and NMR study
Authors: Maxwell Robert S. , Balazs Bryan , Cohenour Rebecca , Prevedel Elizabeth
Published: October 2003

The involvement of water in the reinforcing mechanism in silica‐filled polydimethylsiloxane (PDMS) based composite systems, potentially leaves the polymer composite susceptible to mechanical property changes when exposed to desiccating environments. We have studied the effects of thermal and chemical desiccation on a silica filled PDMS/PDPS copolymer system by DSC and NMR analysis. Our results show that as the polymer was desiccated, segmental dynamics in the polymer network were reduced significantly and changes in melt heats of fusion and stress relaxation were observed. NMR 1H relaxation measurements have measured a change in 1H T2e of 30% after storage in desiccating environments longer than 1 year. The experimental data presented argue that the reduced mobility of the PDMS chains in the interfacial domain after desiccation reduced the overall, bulk, motional properties of the polymer, thus causing an effective “stiffening” of the polymer matrix.
Weak flocculation of aqueous kaolin suspensions initiating by NaCMC with different molecular weights
Authors: Li Y. , Nagy É.S. , Esmail M.N. , Hórvölgyi Z.
Published: October 2003

The present work is an investigation of the effect of NaCMC with different viscosities (molecular weights) on the stability of aqueous kaolin suspensions at pH 5‐6. The stabilizing effect of polymers was characterized by measuring the sedimentation volumes (for 2.5% kaolin suspensions) and some important rheological parameters (for 40% and 50% kaolin suspensions). In certain cases the stability of suspensions was also studied in the presence of 0.5‐1.0% NaCl. The additives were incorporated into the suspensions separately and simultaneously, as well. In certain cases the effect of mixing order of NaCMCs was also studied. The lower viscosity NaCMC was found to be a better stabilizing agent than its medium viscosity counterpart at the studied polymer concentrations (0.005‐1.0%). This was manifested in smaller sedimentation volumes and lower rheological parameters (viscosity, yield stress, degree of thixotropy and elasticity). The lower and the medium viscosity polymer were simultaneously and consecutively added in a mass ratio of 50:1 and 10:1. The resulted observation of low viscosity and yield stress, and more importantly thixotropy and elasticity, can be interpreted in terms of a “site‐blocking” type flocculation.
Application of modified wastes from phenol‐formaldehyde resin and expanded polystyrene in sewage treatment processes
Authors: Bajdur Wioletta M. , Sułkowski Wiesław W.
Published: October 2003

A solution to environmental pollution by polymer plastic wastes can be their chemical modification in to useful products. Such a new solution is the obtaining of effective flocculants for sewage treatment from chemically modified phenol‐formaldehyde resin production wastes (SE and NS novolak) and expanded polystyrene wastes. Comparative analysis of flocculation properties was performed for amino derivatives of novolak wastes, synthesized sulphonated derivatives of novolak and expanded polystyrene wastes, of standard polyacryloamide and for Praestol commercial polyelectrolyte. Amino derivatives and sulphonated derivatives of polymer plastic wastes, having properties of anionic type polyelectrolytes, exhibit good flocculation properties in purification processes of sewages with a chemical composition close to that of found in the water circulating system power plant, coal‐mine, and steel plant. Application of synthesised flocculants caused a decrease of turbidity, concentration of solved impurities and improved quality parameter of purified water. It was found that synthesised polyelectrolytes could be used in industrial water treatment processes.
On the convergence properties of the method of auxiliary sources in 2D problems with open boundaries
Authors: Papakanellos P. J. , Heretakis I. I. , Capsalis C. N.
Published: October 2003

In this paper, the convergence properties of the method of auxiliary sources (MAS) when applied to two‐dimensional (2D) problems with open boundaries are studied. Although such problems have been examined in the past, the relation of the solution errors with the sources' locations has not been reported in detail. Herein, the convergence behavior in the case of a single infinite wire above a flat ground is thoroughly examined. The dependence of the boundary‐condition errors on the number and spacing of the auxiliary sources is illustrated and general rules that govern their behavior are extracted. Finally, a few concluding remarks are outlined and their utilization for the advancement of the MAS is briefly discussed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 518–522, 2003
Fast and accurate modeling of finite‐thickness 2D‐EBG structures made by circular‐section rods
Authors: Frezza F. , Pajewski L. , Schettini G.
Published: October 2003

In this paper, electromagnetic crystals constituted by 2D arrays of dielectric rods with a circular cross section and rectangular‐lattice configuration are analyzed, and the transmission and reflection efficiencies are determined. The high convergence rate of the proposed technique is demonstrated. Results are presented for both TE and TM polarizations, showing the efficiencies as a function of physical and geometrical parameters. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 433–437, 2003
A uniplanar wideband loop‐antenna design using an alternate inverted 2D cantor set sequence
Authors: Lee G. S.
Published: October 2003

In this paper a uniplanar wideband loop antenna is presented. The proposed antenna utilizes an inverted Cantor set matrix sequence of thinning and filling, taken by turns. With a 50Ω microstrip feed, an impedance bandwidth of 2–20 GHz (VSWR < 2.5) is obtained. The experimental results of return loss and radiation patterns are presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 437–439, 2003
Novel input‐matching charts for microwave amplifier design
Authors: De Dominicis M. , Giannini F. , Limiti E. , Serino A.
Published: October 2003

The relationship between the amplifier input‐return loss (IRL) and the termination at the input of the active device is investigated and a useful expression relating the IRL to the available gain of the transistor is derived. Using such a relation, new charts for microwave amplifier design, which allow a direct tradeoff among often contrasting specifications, are generated. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 439–443, 2003
Modeling control over determination of dielectric properties by the perturbation technique
Authors: Komarov Vyacheslav V. , Yakovlev Vadim V.
Published: October 2003

An accompanying numerical simulation for obtaining field patterns, resonant frequencies, and the Q factor is proposed to evaluate the experimental conditions of complex permittivity reconstruction by the perturbation method and thereby improve its accuracy and flexibility. This approach is illustrated by analyzing the measurement of dielectric constant and the loss tangent of wet movie film in a rectangular resonator. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 443–446, 2003
Optically‐controlled solid‐state plasma leaky‐wave antenna
Authors: Grewal Gurvikram , Hanson George W.
Published: October 2003

In this paper, a 2D leaky‐wave antenna is designed for millimeter‐wave applications in the W band. We consider a method for scanning the antenna beam at a fixed frequency using optical control of the properties of a semiconductor waveguide. The analyses are done at 94 GHz using silicon, although other frequency ranges and materials are possible. Beam scanning is achieved by varying the density of an optically induced plasma, without otherwise modifying the antenna structure or changing the frequency. The steepest‐descent approximation is used to calculate the far‐field radiation pattern, where we show that the beam can be scanned over an approximately 30° range. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 450–453, 2003
A novel fractal defected ground structure and its application to the low‐pass filter
Authors: Liu Hai W. , Li Zheng F. , Sun Xiao W.
Published: October 2003

A novel fractal defected ground structure (DGS) for the microstrip line is proposed. The DGS unit lattice is realized by replacing the etched rectangular holes in ground plane with a Sierpinski carpet. The proposed fractal DGS can provide better bandgap, slow‐wave characteristics, and selectivity at cutoff than the conventional dumbbell‐shaped DGS. Furthermore, the fractal DGS is applied effectively to design a low‐pass filter (LPF). A comparison between simulation and measurement confirms the validity of the LPF configuration and design procedure. A simple structure and high‐power handling capability are obtained from the proposed LPF. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 453–456, 2003
Efficient analysis of a class of microstrip antennas using the characteristic basis function method (CBFM)
Authors: Yeo Junho , Prakash V. V. S. , Mittra Raj
Published: October 2003

This paper presents a novel approach for the efficient solution of a class of microstrip antennas using the newly introduced characteristic basis functions (CBFs) in conjunction with the method of moments (MoM). The CBFs are special types of high‐level basis functions, defined over domains that encompass a relatively large number of conventional subdomain basis functions, for example, triangular patches or rooftops. The advantages of applying the CBF method (CBFM) are illustrated by several representative examples, and the accuracy as well as the computation time are compared to those of conventional direct computation. It is demonstrated that the use of CBFs can result in significant savings in computation time, with little or no compromise in the accuracy of the solution. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 456–464, 2003
Synthesis of patch antennas loaded by inhomogeneous substrates via a combined spectral domain: Genetic algorithm approach
Authors: Bilotti F. , Vegni L. , Urbani F.
Published: October 2003

The optimized design of patch antennas with inhomogeneous loading materials is presented in this paper. The analysis and a first coarse design of the antennas is applied to a numerical tool based on the method of moments (MoM) and on a full‐wave formulation developed in the spectral domain that exploits both rigorous and asymptotic closed‐form expressions of the Green's function for a stratified integrated structure with inhomogeneous substrates. In order to match the specific prescribed requirements for the antennas, then, the optimization of the patch shape (fine design) is performed by a dedicated subroutine implementing the genetic algorithm (GA) search and integrated in the aforementioned MoM numerical tool. Some numerical results showing the capabilities of the code are finally presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 464–468, 2003
A uniplanar picosecond impulse generator based on MESFET and SRD
Authors: Miao Meng , Nguyen Cam
Published: October 2003

A new compact, low‐cost uniplanar impulse generator using coplanar waveguide structure has been designed, built, and tested. This uniplanar circuit consists of three functions: initial impulse generation, impulse amplification, and impulse compression, which are realized by a step‐recovery diode and two‐stage GaAs MESFET circuits, respectively. The impulse response has an amplitude of 2.3 V and a half‐power pulse width of 115 pS. It has larger amplitude and narrower pulse width than the impulse generated by the SRD circuit alone. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 470–472, 2003
A single‐port, dual‐frequency SSFIP antenna integrating a low‐pass filter
Authors: Zürcher J‐F.
Published: October 2003

A new, very simple concept is proposed for realizing dual‐frequency antennas with arbitrary frequency separation. This idea is based on the SSFIP antenna principle and the use of a microstrip lowpass filter. It can be easily extended to any number of frequencies by simply adding antenna elements and low‐pass filters. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 472–475, 2003
GaAs pHEMT broadband low‐noise amplifier for millimeter‐wave radiometer
Authors: Aja B. , de la Fuente M. L. , Pascual J. P. , Detratti M. , Artal E.
Published: October 2003

This paper describes a GaAs pHEMT low‐noise amplifier (LNA) in the 38–48 GHz frequency band, which has been developed for the radiometers of the ESA Planck mission. It demonstrates a stable LNA design using a potentially unstable device. The three‐stage amplifier with 0.15‐μm AlGaAs/InGaAs pHEMTs, exhibits more than 16‐dB gain and 1.8‐dB average noise figure over the entire frequency band. The minimum measured noise figure was 1.6 dB with an associated gain of 17.5 dB at 43 GHz. These results show the best noise performance demonstrated among all those reported for a broadband GaAs‐based LNA at these frequencies. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 475–479, 2003
A reliable architecture for FBG sensor systems
Authors: Peng Peng‐Chun , Chi Sien
Published: October 2003

In this paper, we present a reliable architecture for the fiber Bragg grating (FBG) sensor system. The architecture can perform a self‐healing function in the event of a fiber‐link failure. Such a self‐healing function is constructed by using a bidirectional ring topology with a linear‐cavity fiber‐laser source. The fiber laser adopted in this system can enhance the signal‐to‐noise ratio (SNR) of the entire sensing network up to 50 dB. The experimental results demonstrate the feasibility of our proposed architecture. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 479–482, 2003
Analysis of discontinuities in double‐negative (DNG) slab waveguides
Authors: Dong Hao , Wu Thomas X.
Published: October 2003

In this paper, we discuss new physical insights regarding the anomalous dispersion in the double‐negative (DNG) waveguide. Base on our analysis, the discontinuity structure of a grounded DNG slab waveguide, sandwiched between two dielectric slab waveguides, is investigated and the physical insights are also presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 483–488, 2003
Planar diversity‐loop antenna for wireless pcmcia card
Authors: Wong Kin‐Lu , Chen An‐Chia , Chang Fa‐Shian
Published: October 2003

A diversity‐loop antenna mounted vertically on a wireless PCMCIA card for WLAN operation in the 5.2‐ and 5.8‐GHz bands is presented. The diversity‐loop antenna comprises two bent metal‐strip rectangular loop elements (each having a perimeter of about one wavelength of the center operating frequency) symmetrically mounted with respect to a rectangular ground plane protruding from the system ground plane of the PCMCIA card. In addition obtaining to a wide bandwidth covering the 5.2‐ and 5.8‐GHz bands, the diversity antenna shows good isolation of less than −27 dB for the two operating ports. In addition, the measured radiation patterns of the two bent‐loop elements in general cover complementary space regions, thus making this a promising antenna for providing spatial diversity in WLAN operation. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 488–490, 2003
Microstrip coupled‐line bandpass filter with a multilayer structure
Authors: Chen Wu‐Nan , Weng Min‐Hung , Huang Tsung‐Hui , Cheng Tung‐Chieh , Dai Bun‐Tong
Published: October 2003

A microstrip coupled‐line filter with a multilayer structure is designed and implemented. This structure provides additional overlapped coupling and cross coupling between two layers, except for the coupling effect on the same layer. The designed filter demonstrates the frequency characteristics with central frequency f0 = 2.4 GHz, return loss S11 = −12.2 dB, and insertion loss S21 = −2.49 dB. Moreover, it is found that, due to a transmission zero occurring at 3.14 GHz with −45‐dB rejection, a typical elliptic‐function response can be easily obtained by the proposed structure. Experimental results of the fabricated filter measured by using a network analyzer agree well with the simulation results. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 493–495, 2003
Broadband printed quasi‐self‐complementary antenna for 5.2/5.8 GHz WLAN operation
Authors: Wong Kin‐Lu , Wu Tzuenn‐Yih , Su Saou‐Wen , Lai Jeng‐Wen
Published: October 2003

A broadband printed antenna with a quasi‐self‐complementary structure for WLAN operation in the 5.2‐ and 5.8‐GHz bands is presented. The antenna mainly comprises two radiating sections: a T‐shaped strip and a rectangular patch loaded with a T‐shaped slit. Both the T‐shaped strip and slit are of the same dimensions, thus the proposed antenna tends to be a self‐complementary structure. This antenna has a compact size of 6 × 21 mm2 and shows a wide bandwidth of about 1.5 GHz (about 4.6–6.1 GHz). Good antenna performance is obtained. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 495–496, 2003
Installed performance of printed inverted‐F antennas (IFAs) at 2.45 GHz for bluetooth and 802.11b
Authors: Flint J. A. , Vardaxoglou J. C.
Published: October 2003

Detuning is evaluated in the printed inverted‐F antenna for the 2.45‐GHz ISM band. Measurements and simulations are presented for a wooden desktop, a plastic enclosure, and an automobile body. Installed return loss differed significantly from free space and therefore near‐field and environmental‐resonance effects need to be accounted for. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 497–499, 2003
A photonics‐based wideband linearised mixer
Authors: Chan Erwin H. W. , Alameh Kamal E. , Minasian Robert A.
Published: October 2003

A new wideband linearised photonic mixer structure based on a parallel topology of two electrooptic modulators is presented. This mixer realises a high spurious free‐dynamic range (SFDR), with additional advantages of requiring only a small amount of optical power and operating over a multioctave range. Experimental results for the linearised photonic mixer demonstrate a measured receiver‐noise limited SFDR of 115 dB · Hz4/5 with a low input optical‐power requirement of only 5 mW. This offers multi‐octave high dynamic range optical frequency conversion with wideband operation. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 500–502, 2003
Dual‐port dual‐polarization stacked triangular patch antennas
Authors: Row Jeen‐Sheen , Ai Ching‐Yuan
Published: October 2003

This paper presents a design for stacked triangular patch antennas with two feeds for achieving dual‐polarized operations. The top radiating element of the stacked structure is a single‐feed, triangular, planar inverted‐F antenna (PIFA) with a V‐shaped slot, which can radiate an omnidirectional dipole‐like pattern with linear polarization at two separated frequencies. The bottom radiating element is an equilateral‐triangular microstrip patch with two shorting pins, which provides circularly polarized broadside radiation patterns. The proposed stacked structure can not only provide a compact design, but can also be easily installed. In addition, an isolation of better than −20 dB between the feed ports was obtained. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 502–505, 2003
Strong coupled microstrip tapered feedlines for the applications to filters and antennas
Authors: Han Sang‐Min , Kim Young‐Sik
Published: October 2003

In this paper, new feeding structures with strong coupling using linearly and exponentially tapered lines are proposed in order to overcome the design problems due to coupling losses and impedance mismatching. The tapered feedlines are characterized for the optimum feedline length of λg/2 and insertion losses (ILs) and fractional bandwidths (FBWs) with respect to the feeding angle. The proposed structures have been applied to BPFs and patch antennas. The experimental results show lower insertion losses and better matching properties, compared with circuits with conventional feedlines. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 505–508, 2003
Impedance characteristics of the inverted microstrip circular patch antenna
Authors: Siddiqui Jawad Y. , Guha Debatosh
Published: October 2003

A CAD model used to calculate accurately the input impedance of a probe‐fed inverted microstrip circular patch (IMCP) antenna is proposed. This alleviates the existing lacunae of design information for IMCPs. The accuracy of the proposed theory is verified experimentally for various antenna parameters and resonating modes. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 508–511, 2003
Cylindrical conformal bow‐tie microstrip antennas with small curvature radius
Authors: Niu Jun‐Wei , Zhong Shun‐Shi
Published: October 2003

In this paper, bow‐tie microstrip antennas (BMAs) conformal to cylinders with small radii are studied. One‐element BMA and two‐element BMA arrays, conformal to cylinders with small radii and finite length, are simulated and measured. Theoretical results are compared with experimental ones, showing good agreement. It is observed that not only radiation patterns are changed, but also the resonant frequency is lowered and the impedance bandwidth is reduced significantly when the cylinder's radius is decreased. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 511–514, 2003
Design of a subharmonic cascode FET mixer for an IMT‐2000 base station
Authors: Kim Jeongpyo , Choi Jaehoon
Published: October 2003

In this paper, a subharmonic cascode FET mixer is proposed to improve the isolation characteristic between the local oscillator (LO) and RF ports of an unbalanced mixer. The mixer is designed by using a single‐gate FET cascode structure and driven by the second harmonic component of the LO signal. When RF power is −30 dBm and LO power is 0 dBm, the designed mixer yields a −47.17‐dBm LO‐to‐RF leakage power level and 10‐dB conversion gain. Since the LO‐to‐RF leakage power level of the designed mixer is as good as that of a double‐balanced mixer, the subharmonic cascode FET mixer can be utilized instead. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 515–518, 2003
cDNA nucleotide sequence coding for stearoyl‐CoA desaturase and its expression in the zebrafish (Danio rerio) embryo
Authors: Hsieh S.L. , Liu R.W. , Wu C.H. , Cheng W.T. , Kuo Ching‐Ming
Published: October 2003

A cDNA sequence of stearoyl‐CoA desaturase (SCD) was determined from zebrafish (Danio rerio) and compared to the corresponding genes in several teleosts. Zebrafish SCD cDNA has a size of 1,061 bp, encodes a polypeptide of 325 amino acids, and shares 88, 85, 84, and 83% similarities with tilapia (Oreochromis mossambicus), grass carp (Ctenopharyngodon idella), common carp (Cyprinus carpio), and milkfish (Chanos chanos), respectively. This 1,061 bp sequence specifies a protein that, in common with other fatty acid desaturases, contains three histidine boxes, believed to be involved in catalysis. These observations suggested that SCD genes are highly conserved. In addition, an oligonucleotide probe complementary to zebrafish SCD mRNA was hybridized to mRNA of approximately 396 bases with Northern blot analysis. The Northern blot and RT‐PCR analyses showed that the SCD mRNA was expressed predominantly in the liver, intestine, gill, and muscle, while a lower level was found in the brain. Furthermore, we utilized whole‐mount in situ hybridization and real‐time quantitative RT‐PCR to identify expression of the zebrafish SCD gene at five different stages of development. This revealed that very high levels of transcripts were found in zebrafish at all stages during embryogenesis and early development. Mol. Reprod. Dev. 66: 325–333, 2003. © 2003 Wiley‐Liss, Inc.
Immunocytochemical localization of DJ‐1 in human male reproductive tissue
Authors: Yoshida Kaoru , Sato Yoko , Yoshiike Miki , Nozawa Shiari , Ariga Hiroyoshi , Iwamoto Teruaki
Published: October 2003

DJ‐1 was identified as an activated ras‐dependent oncogene product, and was also found to be an infertility‐related protein (contraception‐associated protein 1; CAP 1) that was reduced in rat spermatozoa treated with ornidazole, one of the endocrine disrupting substances that causes reversible infertility in rats. CAP 1 is present in spermatozoa but is not detectable in the epididymal fluid of fertile rats and appears to be shed from sperm during treatment with ornidazole. To determine the functions of DJ‐1 in the human reproductive system as a target protein of endocrine active substances, we identified the localization of DJ‐1 in human testis, epididymis, ejaculated spermatozoa, and seminal plasma. DJ‐1 was present in cells existing in the seminiferous tubules and Leydig cells. Some strong expressions were observed in Leydig cells and Sertoli cells, suggesting a relation with spermatogenesis via androgen receptor (AR). In ejaculated spermatozoa, DJ‐1 existed on the surface of the posterior part of head and the anterior part of the midpiece. DJ‐1 was also present on sperm flagella when the antibody penetrated the plasma membrane, suggesting that there are two putative roles in fertilization, one is binding to the egg, and the other is flagella movement. In contrast to previous findings, we detected DJ‐1 in seminal plasma of fertile men. These results demonstrate that DJ‐1 in human seminal plasma is not only from spermatozoa but also from the testis and epididymis. It is suggested that DJ‐1 may play an important and as yet uncharacterized role in spermatogenesis and fertilization in humans. Mol. Reprod. Dev. 66: 391–397, 2003. © 2003 Wiley‐Liss, Inc.