bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analytical analysis of a rectangular shielded multilayer coupled coplanar waveguide
Authors: Shan Zhiyong , Zhang Yanhua , Zhou Xilang , Yao Ji 
Published: April 2004

AbstractThe closed‐form expressions for calculating the quasi‐static parameters of a rectangular shielded multilayer coupled coplanar waveguide (RSMCCPW) are presented. Expressions of the odd‐ and even‐mode characteristic impedances, which can provide accurate and fast calculations, are derived by using conformal‐mapping techniques. The numerical results are obtained and compared with those available in the literature for similar unshielded structures. Good agreement between the results is observed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 392–395, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20149
A low‐profile broadband 16‐mm‐diameter post‐type monopole antenna ceiling‐mounted in a building
Authors: Jang Yong‐Woong , Go Hyun‐Chull 
Published: April 2004

AbstractThis paper experimentally presents a low‐profile broadband post‐type monopole antenna. The characteristics of the antenna are highly dependent on the design parameters (Rm, hm, hfl, and Rg). Instead of a wire monopole, the proposed antenna is made of a 16‐mm‐diameter aluminum post that is ceiling‐mounted in a building. This is due to the low‐radiation resistance in the usable band. The post‐type element is used to enhance the impedance matching. The experimental impedance bandwidth obtained is approximately 67.9% (1.9824–3.5534 GHz) for a VSWR of less than 2.0. The impedance bandwidth covers multiband operations for mobile and satellite communication. We also present the measured radiation patterns and gain characteristics of the proposed antenna. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 395–397, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20150
High‐gain broadband patch antenna with a cavity ground for 5‐GHz WLAN operation
Authors: Su Saou‐Wen , Wong Kin‐Lu , Cheng Yuan‐Tung , Chen Wen‐Shyang 
Published: April 2004

AbstractA novel broadband patch antenna with an equilateral‐triangular cavity ground for achieving enhanced antenna gain over a large bandwidth is presented. A constructed prototype covering the 5.2/5.8‐GHz (5150–5350/5725–5875 GHz) WLAN bands and showing a high antenna‐gain level of about 9.8 dBi is demonstrated. Across the operating band, the prototype also shows good radiation characteristics with reduced cross‐polarization and backward radiation. Details of the proposed antenna design and obtained experimental results are presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 397–399, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20151
Efficient analysis of L‐probe coupled patch antenna arrays mounted on a finite conducting cylinder
Authors: Cao Xiangyu , Li Pei , Luk K. M. , Liang Changhong , Gao Jun 
Published: April 2004

AbstractThe radiation pattern of an L‐probe coupled patch‐antenna array mounted on a finite conducting cylinder is accurately and efficiently computed by the electric‐field integral equation (EFIE) in conjunction with the method of moments (MoM) and Galerkin's testing procedure. The effects of different dimensions of the cylinder on the radiation characteristics are studied, including beamwidth, sidelobe, and backlobe. The results are useful for designing wideband smart‐antenna arrays for future mobile‐communication systems. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 403–407, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20153
Analysis of Raman amplifiers' transient effects and TDM‐pumped Raman amplifiers using the finite‐difference method
Authors: Wei Huai , Tong Zhi , Wang Muguang , Jian Shuisheng 
Published: April 2004

AbstractWe propose a novel method to analyze Raman amplifiers (RAs) by solving difference equations. This method is highly convenient for analysis of the transient effects of Raman amplifiers under dynamic conditions. Some properties of time‐division multiplexing (TDM)‐pumped RAs are analyzed theoretically. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 407–410, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20154
Novel combined MOD‐P multiband antenna structures inspired by fractal geometries
Authors: Soler Jordi , Garcia Daniel , Puente Carles , Anguera Jaume 
Published: April 2004

AbstractA novel set of multiband antenna structures, which combine different geometries based on fractal elements, are presented. The new combined radiating elements profit from the multifrequency properties of the noncombined geometries, thus providing a mechanism to adjust the antenna parameters. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 423–426, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20159
Hydrogenation of aldehydes catalyzed by kieselguhr‐supported carboxymethylcellulose‐nickel complex
Authors: Zhou De‐Jun , Zhou Da‐Qing , Cui Xiao‐Hua , Wang Fu‐Ming , Huang Mei‐Yu , Jiang Ying‐Yan 
Published: April 2004

AbstractA new kieselguhr‐supported carboxymethylcellulose‐nickel complex (Kie‐CMC‐Ni) has been prepared by a simple method, which has been found to catalyze the hydrogenation of benzaldehyde, valeraldehyde and isobutyraldehyde to the corresponding alcohols in high yield (100, 92 and 86% respectively). The catalyst could be reused without obvious loss of its catalytic activity. Copyright © 2004 John Wiley & Sons, Ltd.
1,3,2‐Dioxaborines as potential components in advanced materials—a theoretical study on electron affinity
Authors: Fabian Jürgen , Hartmann Horst 
Published: April 2004

Abstract1,3,2‐Dioxaborines with fluorine and other substituents at boron were calculated by first‐principles methods based on density functional theory (DFT: B3‐LYP) or many‐body perturbation theory at the second order [MBPT(2): MP2]. 1,3,2‐Dioxaborines are derivatives of 1,3‐dicarbonyl compounds also known as 1,3‐diketoborates. According to quantum chemical calculations, 2,2‐difluoro‐1,3,2‐dioxaborines are of puckered structure with a low barrier to inversion. The calculated charge distribution does not reflect well the traditional formula description. The boron atom carries a positive rather than a negative charge. Some compounds have a pronounced zwitterionic character accompanied by relatively high dipole moments. The calculated positive electron affinities (EAs) classify 1,3,2‐dioxaborines as organic electron‐acceptor compounds. Depending on the type of substitution, the EAs vary between about 0.5 and 3.5 eV (DFT calculations). The EAs of various substituted 1,3,2‐dioxaborines are of the same order of magnitude as those of quinones and close to electron affinities of strong organic acceptor compounds such as tetracyanoethylene (TCNE). Numerical predictions are verified by comparison with EAs of a series of well‐known medium‐sized organic compounds studied experimentally and theoretically at the same level of theory. In good agreement with results reported for other series of compounds, the average absolute error between theoretical and experimental EAs was 0.19 eV. Because of the ability of 3,5‐diaryl‐2,2‐difluoro‐1,3,2‐dioxaboranes to fluoresce efficiently and to accept electrons easily, these compounds are potential candidates for future applications. Copyright © 2004 John Wiley & Sons, Ltd.
Effects of non‐ionic and mixed non‐ionic–cationic micelles on the rate of aqueous cleavages of phenyl benzoate and phenyl salicylate in alkaline medium
Authors: Khan M. Niyaz , Ismail Emran 
Published: April 2004

AbstractPseudo‐first‐order rate constants (kobs) for the hydrolysis of phenyl salicylate (PSH) and phenyl benzoate (PB) in the alkaline medium show a monotonic decrease with the increase in [C16E20]T (total concentration of Brij 58) at constant [CH3CN] and [NaOH]. This micellar effect is explained in terms of the pseudophase model of micelles. These results show a characteristic difference between the effects of [C16E20]T and previously published effects of [C12E23]T (total concentration of Brij 35) on the rates of aqueous cleavage of PSH and PB at [CnEm]T/[NaOH]≥∼3. The values of kobs, obtained at different [C16E20]T in the presence of a constant amount of CTABr, follow the empirical relationship kobs=(k0+θK[C16E20]T)/(1+K[C16E20]T), where θ and K are empirical parameters. The values of θ are not affected whereas the values of K decrease with increase in [CTABr]T in a mixed C16E20–CTABr micellar system. The values of θ at different [CTABr]T show that θ>k0 for hydrolysis of PSH and θ<k0 for hydrolysis of PB in the presence of 0.01 M NaOH. The effects of [CTABr]T on K and θ are explained in terms of the pseudophase model of micelles coupled with the empirical relationship KS=KS0/(1+KC16E20/S[C16E20]T). Copyright © 2004 John Wiley & Sons, Ltd.
Racemization and hydrolysis of (S)‐naproxen 2,2,2‐trifluoroethyl ester in non‐polar solvents by strong neutral bases: implication for ion‐pair kinetic basicity and hydrolysis
Authors: Lin Han‐Yuan , Lay Eddy , Wen Wen‐Yen , Dewi Hamza , Cheng Yu‐Chi , Tsai Shau‐Wei 
Published: April 2004

AbstractBy using strong neutral bases as catalyst, a detailed investigation of the racemization of (S)‐naproxen 2,2,2‐trifluoroethyl ester was conducted in the non‐polar solvents isooctane, cyclohexane and n‐hexane. The second‐order interconversion constant $k^*_{\rm int}$ as representing the ion‐pair kinetic basicity in isooctane was first estimated and correlated with the equilibrium ion‐pair basicity pKip in tetrahydrofuran, giving slopes of 0.768 and 0.689 for non‐phosphazene and phosphazene bases, respectively, in the Brønsted correlations. The result was further compared with that for (S)‐naproxen 2,2,2‐trifluoroethyl thioester, showing about a 1–2 orders of magnitude enhancement of $k^*_{\rm int}$ for the corresponding thio‐containing analogue. A smaller influence of non‐polar solvents (i.e. isooctane, n‐hexane and cyclohexane) on $k^*_{\rm int}$ was found. Kinetic analysis of the racemization and hydrolysis of (S)‐naproxen 2,2,2‐trifluoroethyl ester in isooctane and n‐hexane containing 7‐methyl‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene and water suggests nucleophilic hydrolysis by the base, where the breakdown of tetrahedral intermediates IR1 and IS1 is the rate‐limiting step and the hydrolysis constant khy is in proportion to the product of base and ion‐pair concentrations. Copyright © 2004 John Wiley & Sons, Ltd.
Conformations of N,N‐diethyl‐β‐alanine and β‐alanine as a function of solvent
Authors: Piro Nicholas A. , Stein Robin S. , Roberts John D. 
Published: April 2004

AbstractConformational equilibria of N,N‐diethyl‐β‐alanine were estimated from vicinal proton–proton coupling constants between the CH2CH2 group in protic and aprotic solvents of different polarities. β‐Alanine was similarly studied in dimethyl sulfoxide (DMSO). In general, the results for both substances correspond fairly well with those reported earlier for β‐alanine in neutral and acidic aqueous solutions. There appeared to be little conformational preference for N,N‐diethyl‐β‐alanine in any of the solvents used, ranging from water to dichloromethane. The exception was a moderate preference (66–73%) for the trans conformer displayed by the conjugate base of N,N‐diethyl‐β‐alanine in all of the solvents studied. Copyright © 2004 John Wiley & Sons, Ltd.
Influence of solvent viscosity on the rate of hydrolysis of dipeptides by carboxypeptidase Y
Authors: Kanosue Yoshifumi , Kojima Satoshi , Ohkata Katsuo 
Published: April 2004

AbstractThe influence of solvent viscosity on the rate of enzymatic hydrolysis of a series of dipeptides (Z‐Phe‐Gly, Z‐Phe‐Sar, Z‐Phe‐Ala, Z‐Phe‐NMeAla, Z‐Phe‐Aib and Z‐Phe‐Pro) by carboxypeptidase Y was investigated. The effect of solvent viscosity on the enzymatic hydrolysis revealed that whereas all kcat values decreased with viscosity, those of the N‐alkyl peptides decreased more than those of the N‐H peptides. The kinetic behaviour implies the involvement of conformational changes of the enzyme in terms of the ‘induced‐fit’ process. Copyright © 2004 John Wiley & Sons, Ltd.
Copolycondensation of various compositions of isophthalic acid and terephthalic acid with hydroquinones or bisphenols by tosyl chloride/dimethylformamide/pyridine
Authors: Higashi Fukuji , Takakura Tomohiro , Sumi Yasuyuki 
Published: April 2004

AbstractThe polycondensation of isophthalic acid (IPA)/terephthalic acid (TPA) with aromatic diols by tosyl chloride/dimethylformamide/pyridine in solution was examined through changes in the IPA/TPA compositions, the kinds of dihydroxyl components, the periods of their addition, and the reaction temperatures. The reaction proceeded favorably at IPA/TPA ratios of 70/30 to 50/50, similarly to an earlier report on the interfacial reaction. The effects of the compositions were significant in the reactions with monosubstituted hydroquinones. The results were examined from distributions of the resulting oligomers prepared at a reaction extent of 0.7, determined by gel permeation chromatography. The reaction producing better results exhibited distributions closer to the theoretical ones. The period of addition also favorably affected the distributions as well as the results of the polycondensation. These results were attributed to the change in the reaction method, in which the diols reacted with the aggregates that formed from the activated IPA and TPA. The change was likely caused by the degree of association of IPA and TPA in the aggregates, on the basis of melting points and IR spectra of mixtures of dimethyl esters of IPA and TPA prepared by the quenching of the aggregates with methanol. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2321–2328, 2004
Novel conducting polymer poly[bis(phenylamino)disulfide]: Synthesis, characterization, and properties
Authors: Su Yu‐Zhi , Niu Yong‐Ping , Xiao Yi‐Zhi , Xiao Min , Liang Zhao‐Xi , Gong Ke‐Cheng 
Published: April 2004

AbstractA bis(phenylamino)disulfide was prepared through the reaction of S2Cl2 with aniline, and its configuration was confirmed with elemental analysis, Fourier transform infrared (FTIR), Fourier transform Raman (FT‐Raman), and 1H NMR spectroscopy. A novel conducting polymer, poly[bis(phenylamino)disulfide] (PPAD), was synthesized from bis(phenylamino)disulfide by both chemical and electrochemical polymerization. The structure of this polymer, in which the side‐chain disulfide bonds were linked to the nitrogen atoms of the main‐chain polyaniline, was characterized with FTIR, FT‐Raman, gel permeation chromatography, electron spectroscopy, and X‐ray photoelectron spectroscopy. A four‐probe measurement revealed that the electrical conductivity of PPAD was 1.8 × 10−2 to 2.1 × 10−3 S cm−1, depending on the doping agents and the pH of the medium for either chemical synthesis or electrochemical synthesis. The conductivity, molecular weight, and spectroscopic properties of the polymer, in comparison with those of polyaniline, showed decreases in the polaron delocalization, structural order, and doping level of the main chain because of the steric hindrance of side‐chain SS bonds. The cyclic voltammograms of the polymer and the monomer showed that the redox reactions (doping/undoping processes) of the main chain (π‐conjugated system) occurred in almost the same potential range of −0.3 to 0.3 V versus an Ag/AgCl (saturated KCl) electrode as that of thiol (thiolate anion)/disulfide of the side chain in PPAD; the bond cleavage (reduction) and formation (oxidation) reactions of the disulfide bond in the polymer became easier and more reversible than those of the monomer. These results suggested that this conducting organodisulfide polymer might be a candidate material for energy‐storage devices such as lithium secondary batteries, proton‐exchange batteries, and electrochemical capacitors. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2329–2339, 2004
A general clustering approach with application to the Miyazawa–Jernigan potentials for amino acids
Authors: Esteve J.G. , Falceto F. 
Published: April 2004

AbstractIn this article, we address the problem of classification of amino acids. Starting from the Miyazawa–Jernigan matrix obtained from the relative positions of amino acids in the crystal structure of globular proteins, we develop a fully unsupervised method of classification for the amino acids. The method is based in the subdominant ultrametric associated to the distance induced by the Miyazawa–Jernigan matrix and the maximum likelihood principle to determine the cluster structure. We obtain a classification consistent with the five groups used in the literature, although with some peculiarities. We also show the stability of our results against changes of the method used to classify the amino acids. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Molecular dynamics simulations of structural changes during procaspase 3 activation
Authors: Piana Stefano , Rothlisberger Ursula 
Published: April 2004

AbstractMolecular dynamics (MD) simulations of the structural rearrangements on the pathway leading to procaspase 3 activation are presented. A retrostructural approach is used to build procaspase 3 from mature caspase 3. The peptide bond that is cleaved during enzyme maturation is gradually reformed during the MD simulation and the most relevant structural changes that occur as a consequence are analyzed. The main structural features that characterize this procaspase 3 model are compared with the available X‐ray structure of procaspase 7 as the only zymogen structure that has been crystallised so far. The MD simulations indicate that in the free caspase 3, the flexible selectivity loop is already preorganized to accomodate the substrate. Such a preorganization is not present in either monomeric caspase 3 or in the procaspase 3 dimer, indicating that the structure of the selectivity loop is highly sensitive to perturbations. Proteins 2004;55:000–000. © 2004 Wiley‐Liss, Inc.
Theoretical study of the ligand–CYP2B4 complexes: Effect of structure on binding free energies and heme spin state
Authors: Harris Danni L. , Park Jin‐Young , Gruenke Larry , Waskell Lucy 
Published: April 2004

AbstractThe molecular origins of temperature‐dependent ligand‐binding affinities and ligand‐induced heme spin state conversion have been investigated using free energy analysis and DFT calculations for substrates and inhibitors of cytochrome P450 2B4 (CYP2B4), employing models of CYP2B4 based on CYP2C5(3LVdH)/CYP2C9 crystal structures, and the results compared with experiment. DFT calculations indicate that large heme–ligand interactions (ca. −15 kcal/mol) are required for inducing a high to low spin heme transition, which is correlated with large molecular electrostatic potentials (∼−45 kcal/mol) at the ligand heteroatom. While type II ligands often contain oxygen and nitrogen heteroatoms that ligate heme iron, DFT results indicate that BP and MF heme complexes, with weak substrate–heme interactions (ca. −2 kcal/mol), and modest MEPS minima (>−35 kcal/mol) are high spin. In contrast, heme complexes of the CYP2B4 inhibitor, 4PI, the product of benzphetamine metabolism, DMBP, and water are low spin, have substantial heme–ligand interaction energies (<−15 kcal/mol) and deep MEPS minima (<−45 kcal/mol) near their heteroatoms. MMPBSA analysis of MD trajectories were made to estimate binding free energies of these ligands at the heme binding site of CYP2B4. In order to initially assess the realism of this approach, the binding free energy of 4PI inhibitor was computed and found to be a reasonable agreement with experiment: −7.7 kcal/mol [−7.2 kcal/mol (experiment)]. BP was determined to be a good substrate [−6.3 kcal/mol (with heme–ligand water), −7.3 kcal/mol (without ligand water)/−5.8 kcal/mol (experiment)], whereas the binding of MF was negligible, with only marginal binding binding free energy of −1.7 kcal/mol with 2‐MF bound [−3.8 kcal/mol (experiment)], both with and without retained heme–ligand water. Analysis of the free energy components reveal that hydrophobic/nonpolar contributions account for approximately 90% of the total binding free energy of these substrates and are the source of their differential and temperature‐dependent CYP2B4 binding. The results indicate the underlying origins of the experimentally observed differential binding affinities of BP and MF, and indicate the plausibility of the use of models derived from moderate sequence identity templates in conjunction with approximate free energy methods in the estimation of ligand‐P450 binding affinities. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Direct measure of functional importance visualized atom‐by‐atom for photoactive yellow protein: Application to photoisomerization reaction
Authors: Yamada Atsushi , Ishikura Takakazu , Yamato Takahisa 
Published: April 2004

AbstractPhotoreceptor proteins serve as efficient nano‐machines for the photoenergy conversion and the photosignal transduction of living organisms. For instance, the photoactive yellow protein derived from a halophilic bacterium has the p‐coumaric acid chromophore, which undergoes an ultrafast photoisomerization reaction after light illumination. To understand the structure‐function relationship at the atomic level, we used a computational method to find functionally important atoms for the photoisomerization reaction of the photoactive yellow protein. In the present study, a “direct” measure of the functional significance was quantitatively evaluated for each atom by calculating the partial atomic driving force for the photoisomerization reaction. As a result, we revealed the reaction mechanism in which the specific role of each functionally important atom has been well characterized in a systematic manner. In addition, we observed that this mechanism is strongly conserved during the thermal fluctuation of the photoactive yellow protein. We compared the experimental data of fluorescence decay constant of several different mutants and the present analysis. As a result, we found that the reaction rate constant is decreased when a large positive driving force is missing. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Irreversible formation of intermediate BSA oligomers requires and induces conformational changes
Authors: Vaiana S.M. , Emanuele A. , Palma‐Vittorelli M.B. , Palma M.U. 
Published: April 2004

AbstractUnderstanding the relation between protein conformational changes and aggregation, and the physical mechanisms leading to such processes, is of primary importance, due to its direct relation to a vast class of severe pathologies. Growing evidence also suggests that oligomeric intermediates, which may occur early in the aggregation pathway, can be themselves pathogenic. The possible cytotoxicity of oligomers of non‐disease‐associated proteins adds generality to such suggestion and to the interest of studies of oligomer formation. Here we study the early stages of aggregation of Bovine Serum Albumin (BSA), a non pathogenic protein which has proved to be a useful model system. Dynamic light scattering and circular dichroism measurements in kinetic experiments following step‐wise temperature rises, show that the “intermediate” form, which initiates large‐scale aggregation, is the result of structural and conformational changes and concurrent formation of oligomers, of average size in the range of 100–200 Å. Two distinct thresholds are observed. Beyond the first one oligomerization starts and causes partial irreversibility of conformational changes. Beyond the second threshold, additional secondary structural changes occurring in proteins being recruited progress on the same time scale of oligomerization. The concurrent behavior causes a mutual stabilization of oligomerization, and of structural and conformational changes, evidenced by a progressive increase of their irreversibility. This process interaction appears to be pivotal in producing irreversible oligomers. Proteins 2004;9999:000–000. © 2004 Wiley‐Liss, Inc.