bluuebunny/crossref_metadata_2025_split huggingface dataset:
Input impedance of electromagnetic bandgap resonator antennas
Authors: Sauleau Ronan , Coquet Philippe 
Published: April 2004

AbstractThe input impedance of directive electromagnetic bandgap (EBG) resonator antennas is studied theoretically and experimentally at millimeter‐wave frequencies. These antennas consist of a printed primary source illuminating a metallo‐dielectric EBG radome through a free‐space coupling region. A Fabry–Perot (FP)‐type resonator with highly reflecting metallic strip gratings is used. The variations of input impedance, resonant frequency, and return loss at resonance are investigated as functions of the thickness of the coupling region, for various topologies of (i) printed sources (single‐ and double‐layer patch antennas and arrays) and (ii) EBG cavities with a variable Q factor (that is, directivity). We also demonstrate that the coupling conditions are optimized when the resonator is fed by a relatively directive primary source (here, a 2 × 2 aperture‐coupled patch‐antenna array), rather than by a patch or a wire antenna, as is usually done. In that case, the required accuracy of the coupling region's thickness is much less stringent, which is essential from a practical point of view. These theoretical results are experimentally validated at 60 GHz through the characterization of several configurations of EBG antennas. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 369–375, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20144
Fractal Yagi antennas: Design, simulation, and fabrication
Authors: Gianvittorio John P. , Rahmat‐Samii Yahya 
Published: April 2004

AbstractMultiband elements based on the self‐similarity of fractals may have differing radiation patterns between operating bands due to the leakage of current between scales in the geometry. A multiband Sierpinski element has been designed using embedded filters to achieve similar radiation patterns over various operating bands. This multiband element is incorporated into the design of a dual‐band Yagi antenna. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 375–380, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20145
A novel tunable fiber‐optic microwave notch filter using fiber loop and cascaded fiber Bragg gratings
Authors: Chi Hao , Zhang Xianmin 
Published: April 2004

AbstractWe experimentally demonstrate a novel tunable microwave notch filter using a fiber loop and cascaded fiber Bragg gratings (FBGs), where the filter response can be easily tuned by adjusting the wavelength of the input light. The proposed notch filter is very simple to realize. The required free spectral range (FSR) of the filter can be designed by carefully controlling the written positions of the FBGs in the fiber loop. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 386–388, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20147
Analysis of rectangular‐groove waveguides using the Fourier‐transform technique
Authors: Jia Hongting , Yasumoto Kiyotoshi , Yoshitomi Kuniaki 
Published: April 2004

AbstractA rigorous and simple method for analyzing a rectangular‐groove guide using a Fourier‐transform technique, which takes the field singularities at the edge of the guide into consideration, is presented. The convergence of the solutions is very fast and the accuracy improves significantly. It is shown that a mode‐propagation constant with five‐figure accuracy is obtained by solving a 7 × 7 matrix equation. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 388–392, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20148
Effect of variation of dielectric constant of substrate on PBG in microwave region
Authors: Tiwari Manoj K. , Gupta K. K. , Gupta H. C. , Dube D. C. 
Published: April 2004

AbstractThe effects of variation of the substrate's dielectric constant and of various geometries on photonic band gap (PBG) are studied on a microstrip‐type periodic metallic structure, and the experimental findings are presented and discussed. In this study, air is chosen as the dielectric material of the substrate. A well‐defined PBG has been observed in all the above cases. The band‐gap changes in the microwave region with the variation of the substrate's dielectric constant and the geometry of the periodic metallic structure are due to characteristic impedance. The transmission loss has been found to decrease with an increase in the dielectric constant of the substrate. Thus, it is concluded that the dielectric constant combined with the characteristic impedance of the periodic structure plays an important role in the formation of PBG. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 399–403, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20152
Analytically regularized evaluation of scattering by perfectly conducting cylinders
Authors: Lucido M. , Panariello G. , Schettino F. 
Published: April 2004

AbstractThe aim of this paper is to analyze the scattering by a rectangular‐section perfectly conducting cylinder. The solution method is based on the use of the Neumann series; the problem is regularized by factorizing the right edge behavior of the current. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 410–414, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20155
Load matching in multimode microwave‐heating applicators based on the use of dielectric‐layer moulding with commercial materials
Authors: Monzó‐Cabrera J. , Escalante J. , Díaz‐Morcillo A. , Martínez‐González A. , Sánchez‐Hernández D. 
Published: April 2004

AbstractCommercial dielectric materials placed around a sample are studied as load‐matching elements for multimode microwave‐heating applicators. The dimensions of these dielectric materials are optimized with an iterative procedure in order to achieve high‐power efficiency, thus enhancing electric‐field deposition within the sample. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 414–417, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20156
Planar inverted‐F antenna with a hollow shorting cylinder for mobile phone with an embedded camera
Authors: Chien Shao‐Lun , Hsiao Fu‐Ren , Lin Yeh‐Chian , Wong Kin‐Lu 
Published: April 2004

AbstractA novel planar inverted‐F antenna (PIFA) with a large hollow shorting cylinder suitable for integration with an embedded digital camera for a mobile phone is proposed. A design example of the proposed PIFA for application in a UMTS (1920–2170 MHz) mobile phone is demonstrated. The antenna design and experimental results are presented and discussed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 418–419, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20157
Cross‐coupled hairpin filter design using high‐permittivity substrates
Authors: Hsu Cheng‐Shing , Huang Cheng‐Liang 
Published: April 2004

AbstractA four‐pole elliptic‐function bandpass filter is designed using a compact miniaturized microstrip hairpin resonator. This miniaturized hairpin resonator is realized by using a stepped‐impedance structure with parallel coupled lines. In addition, the bandpass filter is implemented using a high‐permittivity ceramic substrate. These factors result in the reduction of the filter's size. The full‐wave simulator IE3D is used to design the hairpin resonator, and to calculate the coupling coefficient of the basic coupling strictures. The responses of the fabricated filters using Al2O3 (εr = 9.7, Q × f = 350,000 GHz) and MgNb2O6 (εr = 20, Q × f = 110,000 GHz) ceramic substrates are designed at a center frequency of 2 GHz. The compact size and the performance of this class of filters are demonstrated. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 419–423, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20158
A study of waveguides filled with anisotropic metamaterials
Authors: Xu Yansheng 
Published: April 2004

AbstractIn this paper, a rectangular waveguide and a nonraditive dielectric (NRD) waveguide, filled with anisotropic negative permittivity and permeability, are studied in detail. A general condition of the existence of TE and TM modes in these waveguides is derived. The unique characteristics of these waveguides are explored. Both fully‐ and partially‐filled cases of rectangular waveguides are examined. Characteristics of NRD waveguides with anisotropic metamaterial cores are studied. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 426–431, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20160
Formation of nano‐dots of phenylazomethine dendrimers with Rhodamine 6G on mica
Authors: Satoh Norifusa , Watanabe Takeshi , Iketaki Yoshinori , Omatsu Takashige , Fujii Masaaki , Yamamoto Kimihisa 
Published: April 2004

AbstractThe phenylazomethine dendrimer (DPA) is associated with Rhodamine 6G in chloroform, which results in the chemical shift attributed to the aromatic protons of phenylazomethine being moved upfield in the 1H‐NMR spectrum by increasing the Rhodamine 6G. The shift is saturated at the ratio of 1 : 1. On the basis of the NMR analysis, the association constant K of phenylazomethine with Rhodamine 6G was determined to be 1.4 × 104 (l/mol) in CDCl3 at 20°C. The association is also confirmed by UV‐vis spectroscopy, in which the absorption around 450 and 527 nm changes during the addition of Rhodamine 6G. The fluorescence intensity of the 1 : 1 complex of Rhodamine 6G and DPA G4 is stronger than that of the solution dissolved only in Rhodamine 6G at greater than 1 mM though it is generally known that the intermolecular interaction quenches the dye fluorescence in a concentrated solution. The association of DPA G4 with Rhodamine 6G suppresses the quenching at higher concentrations. Homogenous nano‐dots were observed on mica by casting the DPA G4 complex with Rhodamine 6G, in which the height and average area were 1.5–3 nm and 1.6 × 103 nm2 (the standard deviation σ = 3.7 nm2), respectively. Copyright © 2004 John Wiley & Sons, Ltd.
Catalytic behavior of wool‐osmium tetroxide complex for asymmetric dihydroxylation of olefins
Authors: Miao Ju‐Hong , Yang Ji‐Huo , Chen Li‐Yi , Tu Bu‐Xin , Huang Mei‐Yu , Jiang Ying‐Yan 
Published: April 2004

AbstractA new chiral polymer‐metal complex, wool‐osmium tetroxide (wool‐OsO4) complex was prepared by a very simple method. This complex was found to be able to catalyze the asymmetric dihydroxylation of allylamine to (R)‐(+)‐3‐amino‐1, 2‐propanediol and allyl chloride to (S)‐(+)‐3‐chloro‐1,2‐propanediol. The optical yields amounted to 83.7 and 57.2%, and the product yields were 80.2 and 68.5% respectively. The experimental results showed that OsO4 content in the complex, reaction time, allylamine/OsO4 molar ratio and solvent all have an effect on the product and optical yields. Additionally, wool‐OsO4 complex catalyst could be reused without any remarkable change in optical catalytic activity. Copyright © 2004 John Wiley & Sons, Ltd.
Aromatic character of annelated dimethyldihydropyrenes
Authors: Aihara Jun‐ichi , Ishida Toshimasa 
Published: April 2004

AbstractMitchell and co‐workers recently estimated the order of aromaticity for dimethyldihydropyrene (DDP) nuclei in annelated derivatives using nucleus‐independent chemical shifts (NICS). We found that two graph‐theoretically defined energetic quantities, percentage topological resonance energy (% TRE) and bond resonance energy (BRE), can be used to predict readily the relative aromaticities of these hydrocarbons and their DDP nuclei, respectively. Since these quantities are not dependent on the areas of individual rings, they are better suited for estimating the degree of aromaticity. Copyright © 2004 John Wiley & Sons, Ltd.
Kinetics and mechanisms of the gas‐phase elimination of 2‐substituted primary, secondary and tertiary hydroxy groups in nitroalkanes
Authors: Domínguez Rosa María , Herize Armando , Rotinov Alexandra , Alvarez‐Aular Alvaro , Visbal Gonzalo , Chuchani Gabriel 
Published: April 2004

AbstractThe kinetics of the gas‐phase elimination of several 2‐substituted primary, secondary and tertiary hydroxy groups in nitroalkanes were determined in a static reaction system over the temperature range 220–400°C and pressure range of 29–235 Torr. The reactions, in seasoned vessels, are homogeneous and unimolecular and obey a first‐order rate law. The presence of secondary and tertiary hydroxy substituent at the 2‐position of the nitro group in nitroalkanes leads to a retro‐aldol type of decomposition. The mechanism may be rationalized in terms of a six‐membered cyclic transition state to give the corresponding aldehyde or ketone and the nitroalkane, respectively. However, some of the primary 2‐hydroxy groups in nitroalkanes undergo a dehydration process with very limited isomerization to the corresponding alkyl nitrate. The mechanism of dehydration is believed to proceed through a six‐membered rather than the already reported four‐membered cyclic transition state to give the nitroalkene and water. In the case of the primary hydroxy substituent in 2‐methyl‐2‐nitro‐1‐pentanol, the products of elimination are HNO2 gas and 3‐hydroxy‐2‐methyl‐1‐propene. This reaction is rationalized in terms of a four‐membered cyclic transition state type of mechanism. The kinetic and thermodynamic parameters of the hydroxynitroalkane substrates are presented and discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Ground‐ and excited‐state reactivity of some ketenylcarbenes
Authors: Dogaru D. , Pietri N. , Aycard J. P. , Hillebrand M. 
Published: April 2004

AbstractThe reactivity of ketenylcarbenes has been widely discussed on experimental and theoretical grounds in connection with the photochemical decomposition in cryogenic matrices of some substituted cyclobutenediones and maleic anhydrides. It was found that, although the presence of these intermediates was postulated in the decomposition mechanisms, only monofluoroketenylcarbene was experimentally evidenced and characterized by its IR spectrum. In all other cases, the experimental data revealed the formation of the corresponding cyclopropenones and, under continuing irradiation, of the alkynes. Theoretical calculations also point to their high reactivity towards the ring closure reaction. In order to gain an insight into the main factors determining the ketenylcarbene reactivity, ab initio calculations on both the ground (HF/6–31G* and MP2/6–31G*) and the first excited state (HF/6–31G*) were performed. The results indicate that the ring closure reaction is mainly determined by the electrostatic interaction between the carbene center and the Cα atom of the ketenyl group. The role of the in‐plane interaction between the molecular orbital localized on the carbene center and the first two vacant orbitals is also discussed. The excited‐state optimized geometries allow for the characterization of the excited‐state reactivity. Copyright © 2004 John Wiley & Sons, Ltd.
Correlation and prediction of critical micelle concentration using polar surface area and LFER methods
Authors: Saunders Robert A. , Platts James A. 
Published: April 2004

AbstractModels of critical micelle concentration (CMC) using two separate methods, the linear free energy relationship of Abraham and a modified polar surface area approach, are reported. Individual models are developed for anionic, non‐ionic and structurally diverse molecules, the last including many commercially important drugs such as analgesics, anaesthetics and antibiotics. Statistical analysis demonstrates the predictive accuracy of both methods, with R2 values around 0.90 throughout. A further model for the simultaneous calculation of CMC for anionic and non‐ionic surfactants was developed, giving reasonable correlations of observed vs calculated CMC. Both methods show similar patterns in regression coefficients; the most significant factor affecting a molecule's CMC is its size, with larger surfactants giving lower CMC. Strong H‐bond acidic surfactants form micelles at lower concentrations, and increasing the H‐bond basicity of a surfactant acts to raise the CMC. Copyright © 2004 John Wiley & Sons, Ltd.
Electrochemical and theoretical study of a family of fully conjugated dendritic oligomers
Authors: Osorio Gabriela , Frontana Carlos , Guadarrama Patricia , Frontana‐Uribe Bernardo A. 
Published: April 2004

AbstractNovel dendritic oligomers of β,β‐dibromo‐4‐ethynylstyrene and formyl‐4‐ethynylstyrene were electrochemically and theoretically studied in order to gain a better insight into their redox behavior. Correlations between calculated ionization and experimental oxidation potentials (anodic peak potentials) were established. The best correlation was obtained when two important effects are considered in the theoretical calculations, probing their strong influence: (a) structural re‐accommodation in the formed radical cation and (b) solvation effects. The effect of dendritic terminal groups (dibromovinyl and formyl groups) was also analyzed. A different redox behavior was observed for these two terminal groups, presumably due to a difference in their oxidation mechanisms. A global chemical transformation for the oxidation of dibromovinyl‐terminated oligomers was proposed, providing a satisfactory explanation of the electrochemical behavior within this family of compounds (presence of adsorptive phenomena). Taking these results into account, it is possible to explain how the cation‐radical species formed in these conjugated dendritic oligomers behave when cyclic voltammetry technique is applied. Copyright © 2004 John Wiley & Sons, Ltd.
Copolymers of phenylacetylene and para‐nitrophenylacetylene with nonlinear optical properties: Further insight on the conformational structure
Authors: Sone Takeyuki , D'Amato Rosaria , Mawatari Yasuteru , Tabata Masayoshi , Furlani Anita , Russo Maria Vittoria 
Published: April 2004

AbstractCopolymers of phenylacetylene (PA) and para‐nitrophenylacetylene (pNPA), named poly(PA‐co‐pNPA), were obtained in different PA/pNPA ratios and different reaction conditions with Rh(I) catalysts. The structure of the copolymers was investigated with IR, laser Raman, 1H NMR, electron spin resonance (ESR), and diffuse reflective ultraviolet–visible (DRUV) light spectroscopies. The pristine polymers had a cis–transoidal structure as the predominant conformation with some trans sequences. Detailed ESR studies supported by computer simulation and conformation analysis have suggested that the trans sequences were due to pNPA sequences and that the cis‐CC bond sequences of pNPA were associated with a stabilized cis radical formed by four to five of pNPA monomers. This particular stabilization was probably the reason for the higher reactivity of pNPA as compared with PA. These cis sequences were preferentially cleaved to generate π radicals. The compression and, to a minor extent, thermal treatment of poly(PA‐co‐pNPA) samples induced a cis‐to‐trans isomerization, leading to a trans–transoidal form with a planar zigzag structure and with a conjugation length up to n = 24 repeat units, determined by DRUV and Raman experiments. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2365–2376, 2004
Synthesis and characterization of a multiarm star polymer
Authors: Xiaoying Sun , Xiaohui Yang , Yunhang Liu , Xinling Wang 
Published: April 2004

AbstractA multiarm star polymer was synthesized through the grafting of oligo polyglycol with urethane chain end units onto the core of hyperbranched polyglycerol (HPG), which was obtained through the cationic ring‐opening polymerization of glycidol. Samples were characterized with 13C NMR, liquid chromatography/mass spectrometry, vapor pressure osmometry, and Raman spectroscopy. The degree of branching of HPG was 0.54, and the number of arms grafting onto HPG was 4. The urethane of the arms mainly reacted with the terminal hydroxy groups of HPG. The differences between the spin–spin relaxation times indicated that the terminal segments of the star were more flexible than those of the core. Grafting polyglycol polyurethane (soft segments of polyurethane is polyglycol) onto HPG improved its dimensional stability. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2356–2364, 2004
Homologous series of alkylsilylphenyl‐substituted poly (p‐phenylenevinylene)s for light‐emitting diodes
Authors: Jin Sung‐Ho , Koo Dae‐Sung , Seo Hwang‐Un , Kim Young‐Inn , Gal Yeong‐Soon , Park Dong‐Kyu 
Published: April 2004

AbstractSubstituent‐induced electroluminescence polymers—poly[2‐(2‐dimethyldodecylsilylphenyl)‐1,4‐phenylenevinylene] [(o‐R3Si)PhPPV], poly[2‐(3‐dimethyldodecylsilylphenyl)‐1,4‐phenylenevinylene] [(m‐R3Si)PhPPV], and poly[2‐(4‐dimethyldodecylsilylphenyl)‐1,4‐phenylenevinylene] [(p‐R3Si)PhPPV]—were synthesized according to the Gilch polymerization method. The band gap and spectroscopic data were tuned by the dimethyldodecylsilyl substituent being changed from the ortho position to the para position in the phenyl side group along the polymer backbone. The weight‐average molecular weights and polydispersities were 8.0–96 × 104 and 3.0–3.4, respectively. The maximum photoluminescence wavelengths for (o‐R3Si)PhPPV, (m‐R3Si)PhPPV, and (p‐R3Si)PhPPV appeared around 500–530 nm in the green emission region. Double‐layer light‐emitting diodes with an indium tin oxide/poly(3,4‐ethylenedioxythiophene)/polymer/Al configuration were fabricated with these polymers. The turn‐on voltages and the maximum brightness of (o‐R3Si)PhPPV, (m‐R3Si)PhPPV, and (p‐R3Si)PhPPV were 6.5–8.7 V and 1986–5895 cd/m2, respectively. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2347–2355, 2004
Role of protein in the primary step of the photoreaction of yellow protein
Authors: Yamada Atsushi , Ishikura Takakazu , Yamato Takahisa 
Published: April 2004

AbstractWe show the unexpectedly important role of the protein environment in the primary step of the photoreaction of the yellow protein after light illumination. The driving force of the trans‐to‐cis isomerization reaction was analyzed by a computational method. The force was separated into two different components: the term due to the protein‐chromophore interaction and the intrinsic term of the chromophore itself. As a result, we found that the contribution from the interaction term was much greater than that coming from the intrinsic term. This accounts for the efficiency of the isomerization reaction in the protein environment in contrast to that in solution environments. We then analyzed the relaxation process of the chromophore on the excited‐state energy surface and compared the process in the protein environment and that in a vacuum. Based on this analysis, we found that the bond‐selectivity of the isomerization reaction also comes from the interaction between the chromophore and the protein environment. Proteins 2004. © 2004 Wiley‐Liss, Inc.