bluuebunny/crossref_metadata_2025 huggingface dataset:
Endostatin gene therapy delivered by Salmonella choleraesuis in murine tumor models
Authors: Lee Che‐Hsin , Wu Chao‐Liang , Shiau Ai‐Li
Published: October 2004

Background

Some anaerobic and facultatively anaerobic bacteria have been used experimentally as anticancer agents because of their selective growth in tumors. In this study, we exploited attenuated Salmonella choleraesuis as a tumoricidal agent and a vector to deliver the endostatin gene for tumor‐targeted gene therapy.

Methods

Attenuated S. choleraesuis carrying a eukaryotic expression plasmid encoding reporter gene was used to evaluate its abilities of tumor targeting and gene delivery in three syngeneic murine tumor models. Furthermore, S. choleraesuis carrying the endostatin expression vector was administered intraperitoneally into tumor‐bearing mice, and its antitumor effect was evaluated.

Results

Systemically administered S. choleraesuis preferentially accumulated within tumors for at least 10 days, forming tumor‐to‐normal tissue ratios exceeding 1000–10 000 : 1. Transgene expression via S. choleraesuis‐mediated gene transfer also persisted for at least 10 days. Host immune responses and tumor hypoxia may influence tumor‐targeting potential of S. choleraesuis. When systemically administered into mice bearing melanomas or bladder tumors, S. choleraesuis carrying the endostatin expression vector significantly inhibited tumor growth by 40–70% and prolonged survival of the mice. Furthermore, immunohistochemical studies in the tumors revealed decreased intratumoral microvessel density, reduced expression of vascular endothelial growth factor (VEGF), and increased infiltration of CD8+ T cells.

Conclusions

These results suggest that tumor‐targeted gene therapy using S. choleraesuis carrying the endostatin expression vector, which exerts tumoricidal and antiangiogenic activities, represents a promising strategy for the treatment of solid tumors. Copyright © 2004 John Wiley & Sons, Ltd.
Inducible production of erythropoietin using intramuscular injection of block copolymer/DNA formulation
Authors: Richard Peggy , Pollard Hélène , Lanctin Caroline , Bello‐Roufaï Mahajoub , Désigaux Léa , Escande Denis , Pitard Bruno
Published: October 2004

Background

We have previously shown that intramuscular injection of plasmid DNA formulated with a non‐ionic amphiphile synthetic vector [poly(ethylene oxide)13‐poly(propylene oxide)30‐poly(ethylene oxide)13 block copolymer; PE6400] increases reporter gene expression compared with naked DNA. We have now investigated this simple non‐viral formulation for production of secreted proteins from the mouse skeletal muscle.

Methods

Plasmids encoding either constitutive human secreted alkaline phosphatase or murine erythropoietin inducible via a Tet‐on system were formulated with PE6400 and intramuscularly injected into the mouse tibial anterior muscle.

Results

PE6400/DNA formulation led to an increased amount of recombinant alkaline phosphatase secreted from skeletal muscle as compared with naked DNA. In the presence of doxycycline, a single injection of 10µg plasmid encoding inducible murine erythropoietin formulated with PE6400 significantly increased the hematocrit, whereas the same amount of DNA in the absence of PE6400 had no effect. The increase in the hematocrit was stable for 42 days. The tetracycline‐inducible promoter permitted pharmacological control of hematocrit level after DNA intramuscular injection. However, 4 months post‐injection the hematocrit returned to its pre‐injection value, even in the presence of doxycycline. This phenomenon was likely caused by an immune response against the tetracycline‐activated transcription factor.

Conclusions

Intramuscular injection of plasmid DNA formulated with PE6400 provides an efficient and simple method for secretion and production of non‐muscle proteins. Copyright © 2004 John Wiley & Sons, Ltd.
In‐situ Polymerization of Rare‐Earth Luminous PA6
Authors: Zhang Yumei , Ye Yunting , Wang Huaping
Published: October 2004

Luminous polycaprolactam (PA6), synthesized through in‐situ polymerization, is a composite of PA6 and uniformly dispersed luminous pigment. During the polymerization, it is found that as luminous pigment was added, the time of prepolycondensation was longer and the molecular weight increased by end‐group analysis. It is also indicated that there was chemical coalescence between luminous pigment and PA6 through the end‐group analysis and FTIR. From the results of DSC, it is shown that the luminous pigment had large effect on the crystal structure of the luminous PA6. The crystallinity of luminous PA6 varied with the content of the luminous pigment and the heat‐treated conditions. From the crystallization kinetics analysis, it is shown that the crystallization rate of the composites increased as luminous pigment added.
Synthesis and Characterization of β‐Poly(glucose‐amine)‐N‐(2,3‐dihydroxypropyl) Derivatives as Medical Care and Biological Joint Material. Family 2. Tri or Tetra‐Sulfated β‐Chitosan
Authors: Youn Ryu Ga , Ryual Ryu Soung , Doung Jang Hang , Uk Jo Byeong
Published: October 2004

Chitin is a natural polysaccharide by N‐acetyl‐D‐glucosamine units β(1‐4) linked. In the present work a chitosan with DA 56% and Mv 80.000 g/mol will be employed. Several techniques to obtain sulphate derivatives of chitin and to chitosan have been proposed due to the interesting biological and chemical properties of such as heparin compounds. Among others it could be mentioned their antibactericidal and metal chelating properties. In the present work a new sulfated derivatives of chitosan with potential growth regulator properties were obtained. The reaction was carried out in heterogeneous media using a commercial growth regulator ‐SO3H as sulfating agent. All derivatives were characterized by several spectroscopic techniques. In IR spectra the bands at 1240 cm−1, (S=O stretching) and 860 cm−1, corresponding to S‐O‐C symmetric stretching, are characteristic of sulphates groups. In 1H‐NMR spectra the appearance of functional group signal confirm its structure.
Acid‐Containing Tyrosine‐Derived Polycarbonates: Wettability and Surface Reactivity
Authors: Hoven Vipavee P. , Poopattanapong Adisorn , Kohn Joachim
Published: October 2004

Tyrosine‐derived polycarbonates having carboxylic acid pendant groups were characterized by water contact angle and X‐ray photoelectron spectroscopy (XPS). A pronounce decrease of receding angle as well as contact angle hysteresis as a function of acid composition strongly indicated that the acid groups are more accessible at the water/polymer interface after hydration. pH dependent contact angle confirmed an existence of carboxylic acid groups in the surface region. The receding angle transition appearing in the pH range of 4‐6 was a consequence of hydrophilicity change due to interconverting from carboxylic acid (‐COOH) to carboxylate ion (‐COO−). The surface compositions of imidazole‐labeled polymers as analyzed by XPS were consistent with the bulk stoichiometry of the polymers. Reactivity of acid groups towards chemical reaction at the surface was also investigated. The acid groups at the surface of polymers were capable of adsorbing a significant amount of calcium ion from simulated body fluid and being activated by a reaction with N‐hydroxysuccinimide.
Micromechanical Analysis of Thermoplastic – Thermoset Interphase
Authors: Vazquez‐Rodríguez J.M. , Herrera‐Franco P.J. , Gonzalez‐Chi P.I.
Published: October 2004

The interfacial shear strength of a pull out model between a thermoplastic fiber and thermoset matrix was analyzed. The method to analyze the interfacial quality in this kind of composite was Photoelasticity. The interfacial shear strength was measured localizing the isocromatic fringes. The Isochromatic fringe corresponds to the points along the specimen in which the principal stresses have the same value.
Spectroscopic Study of Di‐Imide Hydrogenation of Natural Rubber
Authors: Samran Jareerat , Phinyocheep Pranee , Daniel Philippe , Derouet Daniel , Buzare Jean‐Yves
Published: October 2004

The diimide hydrogenation of natural rubber (NR) was studied by using p‐toluenesulfonylhydrazide (TSH) as a diimide‐releasing agent. The microstructure and the percentage of hydrogenation were studied by Raman, 1H‐NMR and 13C‐NMR spectroscopic techniques. Quantitative measurements on fraction of hydrogenated part gave the results in good agreement by using these techniques. The results indicated that percent hydrogenation increased with increasing of reaction time and about 80‐85 % hydrogenation was achieved when a two‐fold excess of TSH was used. The vibrational characteristic of C=C bond of NR is strongly Raman active and noted at 1663 cm−1. The decrease of this signal was clearly observed during the progress of hydrogenation but the vibrational frequency of the cis and trans structures of the trisubstituted olefin unit of NR can not be differentiated by this technique. While 1H‐ and 13C‐NMR analysis showed that cis‐trans isomerization of carbon‐carbon unsaturation of NR occurred during hydrogenation.
Study on the Kinetics for Enzymatic Degradation of a Natural Polysaccharide, Konjac Glucomannan
Authors: Li Guangji , Qi Li , Li Aiping , Ding Rui , Zong Minhua
Published: October 2004

The enzymatic degradation of konjac glucomannan (KGM) was conducted using β‐mannanase from an alkalophilic Bacillus sp. in the aqueous medium (pH 9.0) at 30°C. The intrinsic viscosity ([η]), molecular weight (Mw) and molecular weight distribution (MWD) of the degraded KGM were measured. The mathematical relation between [η] and Mw, [η] = 5.06 × 10−4 Mw0.754, was established. The kinetic analysis reveals a dependence of the rate constant (k) on the period of reaction and the initial substrate concentration (c0) over the range of substrate concentration (1.0∼2.0%) used in this work. The results indicate that the enzymatic degradation of KGM is a complex reaction combining two reaction processes with different orders. In the initial phase of degradation k is inversely proportional to c0, which is characteristic of a zeroth‐order reaction; while in the following phase k is independent of c0, implying the degradation follows a first‐order reaction. The reactivity difference in breakable linkages of KGM, the action mechanism of an enzyme on KGM macromolecules, and the theory concerning the formation of an enzyme‐substrate complex and ‘substrate saturation’ can be used to explain such a kinetic behavior. In addition, the enzymatic degradation of KGM was also carried out using the other enzymes like β‐mannanase from a Norcardioform actinomycetes, β‐glucanase Finizym and a compound enzyme Hemicell as a biocatalyst. By comparing and analyzing the degradation processes of KGM catalyzed by four different enzymes, it can be observed that there is a two‐stage reaction with two distinct kinetic regimes over a certain range of degradation time for each of the degradation processes. These results are useful to realize controllable degradation of polysaccharides via an environmental benign process.
Investigations of Miscibility in Interpenetrated Systems of Polyurethane and Polystyrene Obtained at Room Temperature
Authors: Widmaier Jean‐Michel , Chenal Jean‐Marc
Published: October 2004

Interpenetrating polymer systems based on crosslinked polyurethane (PU) and polystyrene (PS) were prepared at room temperature by a one‐shot (in situ) method, starting from an initial homogeneous mixture of reagents via non interfering mechanisms. Both polymerizations were performed either simultaneously or one after the other. Crosslinks and/or covalent bonds between components were deliberately introduced by the addition of appropriate monomers, in order to tailor the degree of microphase separation. Depending on the formation process, transluscent or transparent films were obtained, despite the difference in refractive index of the components. The maximum of miscibility, taken as from the glass transition criterion, was obtained for sequential tightly graft interpenetrating networks.
Rheological Behavior of Spinning Dope of Multiwalled Carbon Nanotube/Polyacrylonitrile Composites
Authors: Wang Biao , Li Jianmei , Wang Huaping , Jiang Jianming , Liu Yunqi
Published: October 2004

The spinning dope of Multiwalled carbon nanotube/polyacrylonitrile composites was prepared by in‐situ polymerization in 50wt% NaSCN solution. The rheological behavior of the dope containing carbon nanotubes from 0.19wt% to 1.9wt% was investigated using rotational rheometry at 60°C.The nanotubes have diameters between 30‐50nm and lengths ranging from 6 to 10 μm. The apparent viscosity decreases with the addition of carbon nanotubes; this can be explained by the inhibition of carbon nanotubes during polymerization progress. The spinning dope containing various contents of carbon nanotubes exhibits a shear thickening effect. However, the dynamic rheological test shows there is a peak of complex viscosity with the increasing in frequency.
Mathematical Analysis of the Formation of Molecule Sizes on a Spinning Disc Reactor
Authors: Novakovic Katarina , Morris Julian , Martin Elaine
Published: October 2004

A mathematical analysis of the behaviour of the molecular weights of addition polymers during a polymerisation process is described. Spinning disc reactor (SDR) technology has been shown to yield significant improvements in terms of polymerisation rates whilst retaining close control of the molecular weights and the molecular weight distributions[1,2]. However, understanding of the kinetics of the polymerisation process on a SDR remains unresolved. One of the questions to be addressed concerns the sizes of the macromolecules preferably formed during the polymerisation process. To address this question, a mathematical analysis of the observed trends in number and weight average molecular weight, monomer concentration and polydispersity during the polymerisation process on a SDR has been undertaken. To validate the results, experimental data obtained from benzoyl peroxide initiated free radical polymerisation of styrene on a SDR[2] was used. It was concluded that most of the monomers consumed are in the growth of smaller size chains.
Preparation and Properties of Starch/Poly(vinyl alcohol) Composite Foams
Authors: Preechawong Dujdao , Peesan Manisara , Rujiravanit Ratana , Supaphol Pitt
Published: October 2004

Starch/poly(vinyl alcohol) (PVA) composite foams were prepared by baking a mixture of starch, PVA, and other ingredients in a hot mold. The effects of relative humidity, storage period, PVA content, and type and content of plasticizer (e.g. glycerol, urea, or ammonium chloride) on moisture content, water absorption, mechanical properties, and biodegradability of the as‐prepared foams were investigated. In all of the testing conditions investigated, the ultimate tensile strength was shown to be a maximum when the relative humidity was 42%RH (for a fixed storage period of 7 days) and when the storage period was 2 days (for a fixed relative humidity of 42%RH). Addition of PVA improved the ultimate strength and the elongation at break of the composite foams. An increase in the amount of added plasticizer was responsible in an increase in the percentage of elongation at break at the expense of the tensile strength of the composite foams. Resistance to water absorption of starch/PVA composites foams was found to be superior to that of pure starch foams. Lastly, enzymatic degradation tests with α‐amylase showed that addition of PVA affected a little to the enzymatic degradability of the composite foams.
Structure and Properties of Biodegradable Polymer‐Based Blends
Authors: Qiu Zhaobin , Fujinami So , Komura Motonori , Nakajima Ken , Ikehara Takayuki , Nishi Toshio
Published: October 2004

We have recently investigated the structure and properties of biodegradable polymer based blends. The biodegradable polymers studied in our work include poly(3‐hydroxybutyrate) (PHB), poly(3‐hydroxybutyrate‐hydroxyvalerate) (PHBV), poly(butylene succinate) (PBSU), poly(ethylene succinate) (PES) and poly(ϵ‐caprolactone) (PCL). The miscibility, morphology, crystallization and melting behaviour of biodegradable polymer based blends have been studied extensively, which were reviewed briefly in this manuscript.
Effects of Compositions and Processing Variables on Barrier and Mechanical Properties of Liquid Crystalline Polymer/Polyethylene Blend Films
Authors: Trongsatitkul Tatiya , Aht‐Ong Duangdao , Chinsirikul Wannee
Published: October 2004

Cast films of liquid crystalline polymer (LCP) and low density polyethylene (LDPE) blends have been produced and investigated. Effects of LCP content and processing parameters, i.e., processing temperature profile, screw speed, and post‐die drawing, on morphology and O2 barrier property are presented. Increasing processing temperature and LCP content tend to enhance aspect ratios (L/D) of the LCP dispersed phase and at the same time influencing LCP structure. These effects are clearly observed when LCP content is increased from 10 % to 30 % by wt. At high temperature profiles, LCP morphologies are presented in a more or less ‘ribbon’ or ‘tape’ like structure together with a common LCP fibrillar structure. Films of 10% and 30% LCP produced at two optimum temperature profiles show a noticeable proportion of LCP tape‐like structure and interestingly high barrier properties of ∼1.6 and 5.5 times that of the neat LDPE films. High barrier characteristics of such LCP/PE blend films are indicated by low oxygen transmission rate values. Apart from processing temperature effect, increases of screw speed result in films having smaller aspect ratios for both LCP fibers and ribbons; films also exhibit poorer barrier and mechanical properties. However, post‐die drawing clearly demonstrates a positive effect in improving aspect ratios of the LCP domains and the resulting films' moduli. Effects of post‐die drawing on enhancing films' barrier properties become more pronounced at high LCP content. By comparing with the neat LDPE film (30 μm thick) having modulus of ∼180 MPa and OTR of ∼11000 cc/m2.day, the developed LCP/PE films containing 30 wt% LCP show remarkably high modulus values of ∼1100 MPa with low OTR of ∼2000 cc/m2.day.
Effects of Epoxidation Content of ENR on Morphology and Mechanical Properties of Natural Rubber Blended PVC
Authors: Jeerupun Jarunee , Wootthikanokkhan Jatuphorn , Phinyocheep Pranee
Published: October 2004

This research work has concerned a study on toughness of PVC/natural rubber (NR) blends compatibilized with epoxidized natural rubber (ENR). The aim of this work was to investigate the effect of degree of epoxidation on morphology and mechanical properties of the blends. Epoxidized natural rubber with a variety of epoxidation contents were prepared by reacting the NR latex with formic acid and hydrogen peroxide at various chemical contents. Chemical structure and epoxidation content of epoxidized natural rubber were evaluated by FTIR and 1H‐NMR techniques. After that, three grades of ENR with epoxidation contents of 15, 25 and 42 % (by mole) were further used for blending with PVC and NR in an internal mixer at 60 rpm and at 170 °C. From tensile and impact tests, it was found that tensile elongation and impact strength of the materials remarkably increased with degree of epoxidation. On the other hand, tensile strength and modulus of the materials rarely changed with the epoxidation content. An increase in toughness of the blends with epoxidation content was related to a better molecular interaction between PVC and ENR as suggested by torque‐time curves of the materials.
Effects of Solution Concentration, Emitting Electrode Polarity, Solvent Type, and Salt Addition on Electrospun Polyamide‐6 Fibers: A Preliminary Report
Authors: Mit‐uppatham Chidchanok , Nithitanakul Manit , Supaphol Pitt
Published: October 2004

Electrospinning is a process by which ultrafine fibers which have diameters in the range of tens of nanometers to less than ten of micrometers can be produced. This process utilizes expulsion of charges as a means to very thin fiber formation. In this short report, the effects of some of the influencing solution and process parameters (i.e. solution concentration, emitting electrode polarity, solvent type, and salt addition) on morphological appearance of electrospun polyamide‐6 fibers were investigated based on visual observation of a series of scanning electron micrographs. It was found that all of the parameters studied played important roles in determining morphology and sizes of the fibers obtained.
Electrospun Non‐Woven Fabrics of Poly(ϵ‐caprolactone) and Their Biodegradation by Pure Cultures of Soil Filamentous Fungi
Authors: Ohkawa Kousaku , Kim Hakyong , Lee Keunhyung , Yamamoto Hiroyuki
Published: October 2004

The biodegradation of electrospun nano‐fibers of poly(ϵ‐caprolactone) was firstly investigated, using pure‐cultured soil filamentous fungi. In the biochemical oxygen demand test, the biodegradation of the nano‐fiber exceeded 20‐30% carbon dioxide generation. The biodegradabilities decrease with increase of the mean fiber diameter.
No global loss of neocortical neurons in parkinson's disease: A quantitative stereological study
Authors: Pedersen Kamilla M. , Marner Lisbeth , Pakkenberg Henning , Pakkenberg Bente
Published: October 2004

The global total number of neocortical neurons was estimated in 10 patients with Parkinson's disease (PD; mean age, 74.8 years; range, 68–83) and compared to 12 comparison subjects (mean age, 75.8 years; range, 70 – 84). The total mean neocortical neuron number in the patients with PD was 18.6 × 109 with a coefficient of variation (CV = SD/mean) of 0.18, which was not statistically significantly different from that of the controls (18.8 × 109; CV = 0.16; P = 0.90). In contrast to some studies reporting neocortical atrophy this was not confirmed in our study, where the mean volume of neocortex was the same in the two groups (P = 0.59). No difference was found in the volume of white matter, central gray structures, archicortex, or the ventricular system between the two groups. Most patients with PD develop cognitive disturbances with time, and this study cannot exclude that local neuron loss in specific subpopulations of neocortical neurons or cell loss in small but essential neocortical subregions may be part of the structural defects of PD. © 2004 Movement Disorder Society
High‐frequency characterization of coplanar waveguide and equivalent‐circuit modeling of interconnection for mini‐DIL package
Authors: Han Jae‐Ho , Jeong Jichai
Published: October 2004

Coplanar‐waveguide transmission line is designed and characteristic impedance, return loss, and bandwidth are obtained for a mini‐DIL package. For microwave‐circuit simulation of the package, equivalent electric‐circuit modeling of die‐attached components with wire‐bonded interconnections is done and key parasitic elements influencing the scattering performance are extracted. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 365–367, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20470
Design of reflectarrays using slotted microstrip antennas with via connecting to ground plane
Authors: Meriah S. M. , Cambiaggio E. , Bendimerad F. T. , Staraj R. , Damiano J. P.
Published: October 2004

This paper proposes a new method for designing a microstrip‐antenna reflectarray. The array is a set of slotted rectangular microstrip antennas with one or two vias connected to the ground plane. Different techniques may be used to control the phase of the reflected wave, either by adjusting the via position along the symmetry axis of the patch (which is also the E‐field direction of polarization) or by adjusting the radius of the via. The reflection coefficient in terms of via characteristics is computed by a waveguide approach (WGA) using Agilent's High‐Frequency Structure‐Simulator (HFSS) software. Three 1 × 18 elements reflectarrays in the X‐band have been designed, realized, and tested. The measured reflectarray radiation patterns show that the main‐beam steering agrees with the design requirements. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 368–370, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20471
TM010 dielectric loaded cavity resonator for microwave filter
Authors: Wang Jian , Liu Pitao , Li Ying
Published: October 2004

This paper describes a type of rectangular dielectric‐loaded cavity resonator based on TM010 mode. The resonator has an unloaded quality factor (Q) of about 10,000 and good spurious‐free performance and is suitable for the design of multiple cavity microwave filters. We present two sample filters using this kind of resonator. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 373–376, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20473
On the benefits of multifiber optical packet switch
Authors: Li Yi , Xiao Gaoxi , Ghafouri‐Shiraz H.
Published: October 2004

In this paper, we study the benefits of using multiple fibers per link in optical packet‐switched networks. The node architecture is presented and various contention resolution schemes are evaluated. Comparisons are made between the multifiber switch with a small number of wavelengths per fiber and the traditional single‐fiber switch with a large number of wavelengths per fiber. The analytical and simulation results show that although the multifiber switch cannot easily perform as well as a switch with full wavelength conversion, compared to the traditional switch, it significantly reduces the number of wavelength converters and fiber delay lines while achieving a lower packet‐loss rate. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 376–378, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20474
A method to obtain the isothermal static DC curves of microwave FET power amplifiers
Authors: Torregrosa‐Penalva G. , Asensio‐López A. , Blanco‐del‐Campo A.
Published: October 2004

This paper proposes a method to obtain the isothermal static DC curves of microwave FET power amplifiers, avoiding the use of pulsed measurements and accounting for the self‐heating problem in this type of device. The method requires the determination of the thermal resistance of the device under test and the measurement of its static DC curves under different ambient temperatures. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 378–380, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20475
Ultra‐wideband metal‐plate monopole antenna for laptop application
Authors: Wong Kin‐Lu , Chou Liang‐Che , Chen Hong‐Twu
Published: October 2004

This paper presents a study of an ultra‐wideband (UWB) metal‐plate monopole antenna applied to a laptop for wireless communications. The UWB antenna in this study is a metal‐plate monopole of an inverted‐L shape mounted at the top edge of the supporting metal frame for the laptop display. The UWB antenna shows an operating bandwidth of about 4.5 GHz (1890–6450 MHz), so that it easily cover the UMTS band (1920–2170 MHz) for mobile communication and the 2.4‐GHz (2400–2484 MHz) and 5.2/5.8‐GHz (5150–5350/5725–5875 MHz) bands for WLAN communication. That is, the UWB antenna studied is suitable for application in a laptop capable of UMTS/WLAN dual‐mode operation for wireless Internet access. The radiation characteristics for frequencies across the UMTS and WLAN bands are also presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 384–386, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20478
Beam switching and scattering analysis for a microwave hologram modeled by disk lattices with transversely modulated sizes
Authors: Zhu Wenhao , McNamara Derek A. , Shaker Jafar
Published: October 2004

The scattering from a microwave volume hologram made of layered 2D printed disk lattices is analyzed based on the dynamic interaction theory between small metallic disks and fields. The planar disk lattice has its disk size varying periodically in one direction (x) while remaining uniform in the other direction (y) to simulate a 1D holographic grating. The transmitted and reflected fields under TE plane‐wave incidence are obtained in closed form. Beam switching can be achieved with a volume hologram thus implemented and the switching angle can be controlled by the slant angle of the grating with respect to the hologram's normal. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 390–394, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20480
1 × 3 wavelength demultiplexer based on multimode interference with an index‐modulation region
Authors: Sam Y. L. , Won Y. H.
Published: October 2004

We propose a novel structure for a compact 1 × 3 wavelength demultiplexer with an index‐modulation region incorporated into a multimode interference coupler. We can have an extra output port with a simple device structure. The performance of this device has been enhanced by changing the phase within the region. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 400–403, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20482
Mutual‐coupling decomposition in antenna arrays
Authors: Letestu Y. , Mahdjoubi K. , Sharaiha A.
Published: October 2004

In this paper, a method to evaluate array patterns is presented. This method considers all the mutual‐coupling effects, and assumes that the field of an element is the sum of two distinct modes: an antenna mode and a diffraction mode. Good results are obtained for a finite linear‐dipole array. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 403–406, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20483
Fast analysis of microwave integrated circuits by use of the inner‐outer flexible GMRES‐FFT method
Authors: Mo L. , Chen R. S. , Rui P. L. , Feng X. P.
Published: October 2004

In this paper, the microstrip circuit is analyzed in terms of the mixed potential integral equation (MPIE) by using the rooftop‐function expansion and the blaze‐function testing technique. The integral equation is solved by the inner‐outer flexible generalized minimal residual fast Fourier transform (FGMRES‐FFT) method. Our numerical calculations show that the FGMRES‐FFT method can converge as high as five times faster than the generalized minimal residual‐fast Fourier transform (GMRES‐FFT) method and 16 times faster than the conjugate gradient‐fast Fourier transform (CG‐FFT) method. Some typical microstrip discontinuities are analyzed and the good results obtained demonstrate the validity of the proposed algorithm. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 409–413, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20485
Bend sensor using an embedded etched fiber Bragg grating
Authors: Yu Yong‐Sen , Zhao Zhi‐Yong , Zhuo Zhong‐Chang , Zheng Wei , Qian Ying , Zhang Yu‐Shu
Published: October 2004

We present a new bend sensor which can measure the curvature using an etched fiber Bragg grating (FBG) embedded into a beam. The reflection power of the grating detected by an optical power meter varies linearly with the curvature of the beam. This sensor is independent of temperature. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 414–417, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20486
A portable phase‐shifting interferometer with optical zoom system
Authors: Gao Zhishan , Zhu Rihong , Chen Lei , Wang Qing , He Yong , Ji Huidong
Published: October 2004

Three important parts of a portable phase‐shifting interferometer with optical zoom system are described. The first is a phase‐shifter whose driver is integrated in small size with milli‐voltage resolution and kHz dynamic‐frequency response. Second, a seed‐algorithm is proposed that some spatial points are picked up as seeds, and the wavefronts with obscuration or irregular edges can be retrieved from these seeds as they grow and spread. Third, the measurement of a corner‐cube reflector is given in detail. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 417–419, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20487
Tuning sampled nonlinearly chirped fiber Bragg gratings with adjustable chirp and fixed center wavelength
Authors: Zhao Zhiyong , Zhang Shuang , Yu Yongsen , Zhuo Zhongchang , Zhang Jian , Qian Ying , Zheng Wei , Zhang Yushu
Published: October 2004

A simple method for tuning a sampled nonlinearly chirped fiber Bragg grating (SNCFBG) without a center‐wavelength shift is demonstrated experimentally. A uniform sampled fiber Bragg grating (SFBG) is adhered on a bent plastic plate along a precalculated curve. The nonlinear chirp among the SFBG channels is tuned when a displacement is applied to the free end of the plastic plate and the central wavelength of the grating is fixed. The dispersion varies from −996.3 to −117.9 ps/nm in the center channel and the center‐wavelength shift is as small as 0.06 nm in the tuning process. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 432–434, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20493
Compact planar bandpass filter using multisection transformers
Authors: Karmakar Nemai Chandra , Ling Rita Lim Li
Published: October 2004

A novel design of multi‐section compact planar bandpass filter has been proposed. The filter uses two back to back three‐section Chebyshev impedance transformers with a coupling gap. The 15 mm by 15 mm filter resonates at 5.28 GHz and yields 6% 3 dB cutoff bandwidth. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 435–437, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20494
A wideband printed dipole antenna with optimized tapered feeding balun for ISM and FWA bands
Authors: Vasiliadis Theodore G. , Vaitsopoulos Evangelos G. , Sergiadis George D.
Published: October 2004

This paper presents a wideband printed dipole‐antenna element. The broad bandwidth is achieved by optimization of the feeding network, which is implemented as a microstrip tapered balun. The design is based on double‐sided flat‐dipole implementation. The prototype antenna exhibits a measured impedance bandwidth of 58% (VSWR < 2), operating over the entire 2.4‐GHz ISM and 3.6‐GHz FWA bands. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 437–441, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20495
Using interpolation and subvoxel modeling to calculate the power density of FDTD‐simulated electromagnetic fields
Authors: Zhao Jianxun , Wei Zhenggang
Published: October 2004

From the staggered field components provided by the finite‐difference time‐domain (FDTD) method, we use interpolation to obtain six field components at the same location and at the same time instant in order to calculate the power density (PD) of the electromagnetic field (EMF). The subvoxel modeling of the scattering object is also discussed. Comparisons indicate that the joint application of the interpolation and the subvoxel modeling effectively improves the PD precision and significantly reduces the computer memory required to implement the FDTD method. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 441–445, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20496
Shielding effectiveness of a metallic enclosure with multiple apertures
Authors: Feng Chao , Shen Zhongxiang
Published: October 2004

In this paper, we employ the hybrid finite difference–moment method to predict the shielding effectiveness (SE) of a metallic enclosure with multiple apertures. The numerical results for various aperture configurations using the hybrid technique are presented and validated. It is found that a good practice to improve the shielding effectiveness of metallic enclosures is to divide a large aperture into several smaller ones. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 447–450, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20498
A new family of microstrip open‐loop resonator filters for high‐selectivity applications
Authors: Cañete Rebenaque David , Quesada Pereira Fernando D. , Gomez Tornero Jose L. , Alvarez Melcon Alejandro , Guglielmi Marco
Published: October 2004

In this paper, the design of a novel planar narrowband microstrip filter is presented. The structure is designed and manufactured in microstrip technology, and it is formed by set of pairs of resonators of different lengths. The length of one resonator in each pair is adjusted so that a suitable odd resonance is tuned to the center frequency of the filter. The length of the other resonator is adjusted so that the next even resonance is tuned again to the center frequency of the filter. The different path of the signal in each resonator produces a cancellation of energy at a given frequency, therefore implementing a transmission zero in the insertion‐loss response of the filter. First, this paper presents a design example of a single set of resonators (basic unit cell) working at the fifth and sixth resonances. Then, two basic unit cells working at the first and second resonances are first optimized, and then they are cascaded to show how higher‐order filter responses can be implemented. The measured results confirm the theoretical predictions, and validate the new structures for high‐selectivity applications. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 450–455, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20499
Structures of new secofriedelane and friedelane acids from Calophyllum inophyllum of French Polynesia
Authors: Laure F. , Herbette G. , Faure R. , Bianchini J.P. , Raharivelomanana P. , Fogliani B.
Published: October 2004

Three new friedelane‐type triterpenoids, 3,4‐secofriedelan‐3,28‐dioic acid (1), 27‐hydroxyacetate canophyllic acid (2) and 3‐oxo‐27‐hydroxyacetate friedelan‐28‐oic acid (3), were isolated from the leaves of Calophyllum inophyllum (Clusiaceae) grown in French Polynesia. Their structures were established by the concerted application of 2D NMR techniques including gs‐COSY, gs‐HMQC and gs‐HMBC. Copyright © 2004 John Wiley & Sons, Ltd.
Influence of the cooling conditions on the temperature and crystallinity profiles generated in a sisal fiber reinforced‐polycaprolactone/starch molded part
Authors: Cyras V. P. , Stefani P. M. , Ruseckaite R. A. , Vázquez A.
Published: October 2004

In this work, we performed the simulation of the temperature and relative degree of crystallinity developed across the thickness of a sisal fiber reinforced‐polycaprolactone/starch (30%SF‐PCL/S) molded part under different cooling conditions. The non‐isothermal kinetic model of Kamal and Chu (13) was used to predict the degree of crystallinity profiles. In order to obtain the temperature profiles, the energy equation was solved by treating the composite as a continuum using mass averaged physical properties. The results indicated that for cooling at a constant wall temperature, gradient‐less crystallinity profiles for a wall temperature of 283 K and thicknesses lower than 10 mm are obtained. On the other hand, when cooling at a constant cooling rate, paired degree of crystallinity pieces can be obtained only for thicknesses lower than 2 mm. The continuum numerical approach used herein has the ability of predicting the optimal cooling cycle for manufacturing thick and crystallinity gradient‐less SF‐PCL/S parts. Polym. Compos. 25:461–469, 2004. © 2004 Society of Plastics Engineers.
Influence of polyethersulfone modification of a tetrafunctional epoxy matrix on the fracture behavior of composite laminates based on woven carbon fibers
Authors: Fernández B. , Arbelaiz A. , Diaz E. , Mondragon I.
Published: October 2004

In this study, the influence of poly(ethersulfone) (PES) as a modifying agent of a tetrafunctional epoxy matrix (TGDDM) on the mechanical behavior of composite laminates based on woven carbon fibers has been investigated. Dynamic mechanical experiments were performed on neat matrix resins and on their corresponding laminate composites. Mode‐I and Mode‐II fracture toughness tests for the bulk matrices and their composites, respectively, and also flexural and short beam shear tests (SBS) were carried out. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the morphologies obtained. A nanoscopic phase separation was obtained after PES addition, which was not able to stabilize the fracture process, leading, as a consequence, to a poor extent of improvement on fracture toughness properties. Polym. Compos. 25:480–488, 2004. © 2004 Society of Plastics Engineers.
Fatigue of fiber‐reinforced injection molded plastics. I: Stress‐lifetime data
Authors: Wyzgoski Michael G. , Krohn John A. , Novak Glen E.
Published: October 2004

Glass‐reinforced nylon 66 polyamide (PA), polybutylene terephthalate (PBT), and polycarbonate (PC) were injection molded in a ribbed plaque. Flat strips, tensile bars, and rib sections were cut from the plaque in the flow and crossflow directions and subsequently fatigue tested under both tensile and flexural loading conditions to obtain conventional fatigue S‐N (stress versus number of cycles to fail) or Wohler curves. Both the fiber alignment and the loading mode strongly influenced the resultant S‐N curve. As expected, longer fatigue life results when the imposed stress is parallel to the flow direction, which in turn parallels the predominant fiber orientation direction. Also, at the same stress level, it was observed that flexural loading resulted in a much longer fatigue life compared to tensile loading. Similar S‐N data were obtained in flexure for different geometries, such as rib or flat cross sections, as long as the local fiber orientation was similar. Attempts to use an empirical relationship to rationalize predicted fatigue data based upon tensile or breaking strength were not successful. Polym. Compos. 25:489–498, 2004. © 2004 Society of Plastics Engineers.
A dual‐scale analysis of macroscopic resin flow in vacuum assisted resin transfer molding
Authors: Kang Moon Koo , Lee Woo Il
Published: October 2004

In Vacuum Assisted Resin Transfer Molding (VARTM) where a sacrificial medium is used to facilitate the resin flow, the velocity of the resin varies drastically between inside the sacrificial medium and inside the fiber preform. Although the thickness‐to‐length ratio of a VARTM product is usually small, a 3‐D analysis is required for analyzing the lead‐lag flow in the two different media. The problem associated with the full 3‐D analysis is the CPU time. A full 3‐D numerical mesh comprising a large number of nodes requires a CPU time impractical on most computer platforms. In this study, a dual‐scale analysis technique was proposed. First, the flow analysis for the entire calculation domain was conducted in 2.5‐D. Using the results of the 2.5‐D calculation, the 3‐D analysis was performed for a small area of special concern. In some numerical examples, the local 3‐D analysis could discover an eccentric flow pattern as well as the lead‐lag flow that would inevitably be neglected in 2.5‐D simulations. The global‐local analysis technique practiced in this study can be used to analyze the intricate flow of resin through non‐uniform media in affordable CPU times. Polym. Compos. 25:510–520, 2004. © 2004 Society of Plastics Engineers.
Quasi‐static behavior of polymer composite flywheel rims
Authors: Chen Jianmin , Gowayed Yasser , Broughton Royall
Published: October 2004

In this work, the correspondence principle is used to relate quasi‐static elastic properties of composite materials to time‐dependent properties of its constituent materials (i.e., fiber and matrix). Application of Prony series combined with the multi‐data fitting method is used to enhance the efficiency of the direct inverse Laplace transform and the calculation of the time‐dependent stiffness matrix. Results show that elastic properties in directions other than fiber‐reinforcement directions have a time‐dependent character. Accelerated time‐dependent deformation studies of two flywheel rim designs for a period equivalent to 31 years show that multi‐direction reinforcement will suffer minimum change of dimension over time compared with hoop reinforcement only. Polym. Compos. 25:527–534, 2004. © 2004 Society of Plastics Engineers.
Nanocomposites of ethylene‐vinyl acetate copolymer (EVA) and organoclay prepared by twin‐screw melt extrusion
Authors: Zhang Farao , Sundararaj Uttandaraman
Published: October 2004

Preparation of nanocomposites based on ethylene‐vinyl acetate copolymer (EVA) and organoclay by melt intercalation is described in this paper. Effects of VA content, melt flow index (MFI) and maleation of EVA on melt intercalation were investigated by X‐ray diffraction. The level of intercalation into the organoclay increases greatly as VA content increases from 6 to 12 wt%, but shows minimal change from 12 to 28 wt%. For 28 wt% VA content polymers with MFI from 3 to 150, interlayer expansion exhibited a maximum at MFI = 6. Exfoliated nanocomposites were not obtained for a range of unfunctionalized EVA's of different VA content and MFI. Use of maleated EVA (MEVA) had an obvious improvement on exfoliation of the silicate layers probably due to chemical interaction between the MEVA matrix and silicate layers. FTIR results showed that the MA functionality reacts during processing. Lower clay content favored formation of an exfoliated nanocomposite structure. Exfoliated nanocomposites from MEVA exhibited higher Young's modulus and tensile strength than either pure EVA or intercalated nanocomposites from non‐maleated EVA. Polym. Compos. 25:535–542, 2004. © 2004 Society of Plastics Engineers.
UV aging of poly(propylene)/wood‐fiber composites
Authors: Seldén Ragnar , Nyström Birgitha , Långström Runar
Published: October 2004

The effect of accelerated UV‐aging on properties of PP/wood‐fiber composites has been studied. Plates containing 0, 25 and 50 wt% wood‐fibers were subjected to accelerated UV‐aging in a QUV weatherometer for up to 8 weeks. Stabilization against UV‐degradation was made by adding 3% of a UV stabilizer. The results showed that both the unfilled PP and the PP/wood‐fiber composites displayed good UV resistance with regard to mechanical properties. The color of the PP/wood‐fiber composite plates changed from brown to chalky white at the exposed area because of the formation of a thin, strongly degraded surface layer. Physical and chemical analysis of these surface layers using differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy showed that degradation of the PP matrix had occurred, leading to chemicrystallization and extensive surface cracking. A decrease in PP melting temperature was also noted, due to molecular chain scission and the formation of extraneous groups, such as carbonyls and hydroperoxides. These results indicate that the wood‐fibers act as chromophores when incorporated in the PP matrix. Increasing the fiber content from 25 to 50 wt% increases the rate of degradation of the PP matrix by approximately a factor of two. Polym. Compos. 25:543–553, 2004. © 2004 Society of Plastics Engineers.