bluuebunny/crossref_metadata_2025 huggingface dataset:
Ring‐opening polymerizations for the synthesis of sequence‐controlled copolymers
Authors: Cho Iwhan
Published: July 2003

Various prestructured cyclic monomers were synthesized and polymerized to construct the copolymers of controlled mer sequence. Substituted 8‐, 10‐ and 12‐membered cyclic olefins were polymerized by ROMP catalyst, i.e., W(OAr)2Cl4/Et4Pb. Those polymers obtained were the alternating terpolymers of butadiene and vinyl monomers. Cyclic monomers with mesogenic groups as substituents were prepared and polymerized successfully. The resulting polymers were highly liquid crystalline exhibiting rather lower transition temperatures than their monomeric analogs.
Structure‐property correlation of light‐emitting polymers containing alternating phenylene and thienylene/bithienylene repeating units
Authors: Xu Jingmei , Chan Hardy S.O. , Ng S.C.
Published: July 2003

A number of series of fluorescent and conducting polymers containing alternating 3‐functionalized thienylene/ bithienylene and phenylene/ pyridyl/ biphenylene units were synthesized from a number of central symmetric high oligomers and characterized using UV‐Vis, photoluminescence, conductivity measurement, thermal analysis, electrochemistry, XRD and XPS. Structural variation of the polymers was realized by both side chain and polymer backbone modifications. Close structure‐property correlation of the polymers was observed. This paper mainly reports the results of two families of them, those substituted by alkyl pendant chains and electro‐withdrawing and donating groups.
Constructing robust crew schedules with bicriteria optimization
Authors: Ehrgott Matthias , Ryan David M.
Published: July 2003

Optimization‐based computer systems are used by many airlines to solve crew planning problems by constructing minimal cost tours of duty. However, today airlines do not only require cost effective solutions, but are also very interested in robust solutions. A more robust solution is understood to be one where disruptions in the schedule (due to delays) are less likely to be propagated into the future, causing delays of subsequent flights. Current scheduling systems based solely on cost do not automatically provide robust solutions.

These considerations lead to a multiobjective framework, as the maximization of robustness will be in conflict with the minimization of cost. For example crew changing aircraft within a duty period is discouraged if inadequate ground time is provided. We develop a bicriteria optimization framework to generate Pareto optimal schedules for the domestic airline. A Pareto optimal schedule is one which does not allow an improvement in cost and robustness at the same time.

We developed a method to solve the bicriteria problem, implemented it and tested it with actual airline data. Our results show that considerable gain in robustness can be achieved with a small increase in cost. The additional cost is mainly due to an increase in overnights, which allows for a reduction of the number of aircraft changes. Copyright © 2003 John Wiley & Sons, Ltd.
An interactive fuzzy satisficing method for multiobjective stochastic linear programming problems using chance constrained conditions
Authors: Sakawa Masatoshi , Kato Kosuke
Published: July 2003

Two major approaches to deal with randomness or ambiguity involved in mathematical programming problems have been developed. They are stochastic programming approaches and fuzzy programming approaches. In this paper, we focus on multiobjective linear programming problems with random variable coefficients in objective functions and/or constraints. Using chance constrained programming techniques, the stochastic programming problems are transformed into deterministic ones. As a fusion of stochastic approaches and fuzzy ones, after determining the fuzzy goals of the decision maker, interactive fuzzy satisficing methods to derive a satisficing solution for the decision maker by updating the reference membership levels is presented. Copyright © 2003 John Wiley & Sons, Ltd.
Application of GIS and multicriteria evaluation in locating sustainable boundary between the tunari National Park and Cochabamba City (Bolivia)
Authors: Sharifi M.A. , van den Toorn W. , Rico A. , Emmanuel M.
Published: July 2003

Increased population growth and urbanization, has caused increase in demand for land around the city of Cochabamba, which has led to encroachment into the National Park and the construction of illegal settlements. This has created a number of problems, some of which are the direct consequences of the new settlements in the ‘Tunari’ foothills. These settlements constitute a threat to the environment and people because of their location in flood risk and aquifer recharge areas. In response to this problem the city authorities are considering relocating the boundary between the National Park and the city. This study has focused on the design and evaluation of alternative locations for a sustainable boundary between the north of ‘Cochabamba City’ and the southern boundary of the ‘Tunari National Park’. In this process, a rational and systematic approach of collaborative‐decision‐making, supported by geographical information systems (GIS) and multicriteria evaluation (MCE) has been employed and evaluated. Copyright © 2003 John Wiley & Sons, Ltd.
A multidimensional framework for financial–economic decisions
Authors: Hallerbach Winfried , Spronk Jaap
Published: July 2003

Most financial–economic decisions are made consciously, with a clear and constant drive to ‘good’, ‘better’ or even ‘optimal’ decisions. Nevertheless, many decisions in practice do not earn these qualifications, despite the availability of financial economic theory, decision sciences and ample resources. We plea for the development of a multidimensional framework to support financial economic decision processes. Our aim is to achieve a better integration of available theory and decision technologies. We sketch (a) what the framework should look like, (b) what elements of the framework already exist and which not, and (c) how the MCDA community can co‐operate in its development. Copyright © 2003 John Wiley & Sons, Ltd.
The effect of offset patch on the broadband characteristics of an electromagnetically coupled patch antenna
Authors: Chung Kwok L. , Mohan Ananda S.
Published: July 2003

In this paper, we investigate the effect of the offset patch and layer misalignments on the broadband characteristics of a two‐layer, electromagnetically coupled, stacked patch antenna with airgap at the X‐band. Linear and angular displacements of the parasitic patch on the dielectric layer are considered for the experimental study. The measured results show very robust impedance characteristics of the proposed antenna element against layer misalignment. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 345–348, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11056
An improved analysis of one‐dimensional PBG structure using the ADI‐FDTD method
Authors: Tang Wei , Jiao Pei‐Nan , Li Le‐Wei , Li Qing‐Liang , Wu Zhen‐Sen
Published: July 2003

In this paper, an improved finite‐difference time‐domain (FDTD) algorithm is proposed in order to eliminate the restraint by the Courant–Friedrich–Levy condition. The new algorithm is developed based on an alternating‐direction implicit (ADI) approach. In this method, the conventional time step is divided into two time sub‐steps and each of their difference errors can be remedied. It thus has a high efficiency in the case when a long time is spent to reach a stable status, and this situation usually appears in periodical structures such as PBG structures. A numerical example of one‐dimensional (1D) PBG materials is considered to demonstrate the availability and efficiency of this scheme. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 348–352, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11057
Genetic algorithm optimization of a multisectional corrugated conical horn antenna
Authors: Yang Dooyeong , Chung You Chung , Haupt Randy
Published: July 2003

This paper presents the design of a wideband corrugated multisectional conical horn using a genetic algorithm (GA). The GA optimizes the length, flare angle, and first slot depth of each section of the horn in order to match the admittance, reduce the voltage standing wave ratio (VSWR) of the horn, and generate the desired pattern. A VSWR of less than 1.6 is obtained over the frequency range 11–18 GHz. The optimized multisectional conical horn antenna has four sections, is less than 7λ long, and has very low sidelobe levels. The ratio between ratio between the co‐polarization and the cross‐polarization patterns is greater than 60 dB. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 352–356, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11058
Novel phase shift line in feedforward circuit using photonic bandgap
Authors: Seo Chulhun
Published: July 2003

In this paper, a phase shifter with a shifting photonic bandgap (PBG) cell is designed and fabricated in the main loop of a linear feedforward circuit. A portion of the PBG cell is designed for phase shift in the tuning phase. The shifting PBG cell has been applied in the feedforward main loop in order to cancel the main two‐tone signals. The complete cancellation of the main signal is obtained in the main signal loop of a linear power amplifier. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 357–359, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11059
Transmitting and receiving wide‐band signals using reciprocity
Authors: Ji Zhong , Sarkar Tapan K. , Jung Baek Ho
Published: July 2003

In this paper, we present a method based on reciprocity which can transmit and receive a baseband wide‐bandwidth signal without distortion. The time‐domain combined field integral equation (TD‐CFIE) is used to get the simulation results. Numerical results are presented, which show the validity of the presented methodology. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 359–362, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11060
Cost‐effective fabrication of a phase mask by direct etching of the laser‐interference grating on fused silica substrate
Authors: Lu Ying‐Tsung , Chen Yung‐Hsin , Chi Sien
Published: July 2003

A simple and cost‐effective method to manufacture a phase mask with high diffraction efficiency for deep UV application is proposed. The deep rectangular grating fabricated by using laser interference is etched directly into a fused silica substrate, instead of the dielectric coating on a substrate (done in a previous method). Using the metal layer on a dielectric layer for masking in the deep, dry etching process is also unnecessary in our technique. A fabricated rectangular grating with high diffraction efficiency is presented in this paper. We also demonstrate the fabrication processes and show the optimum parameters for our proposed technology. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 362–365, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11061
Non‐reciprocal couplers using distributed amplifier topology
Authors: Parkinson Graham , Paul Dipak K.
Published: July 2003

A distributed amplifier circuit can be adapted to form a non‐reciprocal four‐port coupler, which can be integrated in an MMIC such as an MMIC feedforward linearizer. This paper illustrates, by simulation, the potential for these couplers. Control of the coupling factor is discussed and the boundary of realisable circuit components is studied. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 366–368, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11062
Advanced modeling of semiconductor lasers based on quantum Boltzmann equations
Authors: Wartak M. S. , Weetman P.
Published: July 2003

In this paper, we briefly describe the development of an advanced model of semiconductor lasers. Wigner functions and quantum Boltzmann equations were used to formulate the model. Our aim is to improve upon the presently used drift‐diffusion‐based models. Basic laser characteristics, such as power spectrum and current across the structure of a single quantum well, have been determined. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 369–371, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11063
Parasitic resistance and polarization‐dependent polynomial‐based non‐linear analytical charge‐control model for AlGaN/GaN MODFET for microwave frequency applications
Authors: Korwal Manju , Haldar S. , Gupta Mridula , Gupta R. S.
Published: July 2003

A simple and compact non‐linear analytical charge control model for the AlmGa1−mN/GaN MODFET is developed. This model incorporates the effect of parasitic resistances Rs and Rd, fermi potential (EF)‐variation with sheet‐carrier concentration ns, and the charge induced in 2D electron gases (2‐DEG) due to the highly dominant effects of spontaneous and piezoelectric polarization at the heterojunction of the MODFET. Extrinsic current‐voltage characteristics show good agreement with experimental data and closed‐form expressions for transconductance, drain conductance, and unit current‐gain cutoff frequency are obtained. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 371–378, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11064
A C‐band injection‐locked balanced oscillator for direct‐conversion QPSK modulation applications
Authors: Wen Guangjun , Xie Fuzhen , Shen Zhongxiang , Law Choilook , Li Jiayin , Ge Peng
Published: July 2003

A novel quadrature phase shift keying (QPSK) modulation method for RF signal is proposed in this paper. An injection‐locked balanced oscillator (ILBO) operating in the 5.8‐GHz ISM band is developed to demonstrate the approach using a hybrid integrated microwave‐circuit technique. The developed ILBO shows a free‐running performance with anti‐phase outputs of −0.33 dBm at 5.8 GHz under dc bias of 1.183 V and 7.2 mA, total DC‐to‐RF efficiency of 21.8%, and phase noise of −114.85 dBc/Hz at 100‐kHz offset. In the locked state by a 5.8‐GHz injection signal of −23.0 dBm, the device achieved a locking bandwidth of 39 MHz from 5.7806–5.8196 GHz with a 22.5‐dB locking gain, and acquired an output signal phase variation of up to 178° by altering the bias. Four different phase‐state RF signals were obtained from the ILBO by combining the injection‐locking phase‐modulation scheme with a balanced oscillator topology of anti‐phase outputs. As a consequence, the ILBO with a single‐polar double‐throw switch can function as a direct‐conversion QPSK modulator by modulating both the oscillator and switch bias. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 378–381, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11065
Performance of planar four‐element array of single‐fed circularly polarized dielectric resonator antenna
Authors: Kishk Ahmed A.
Published: July 2003

A single‐fed circularly polarized dielectric resonator antenna is analyzed numerically. The element is a perturbed rectangular dielectric resonator excited by a coaxial probe and is used in a four‐element planar array. Different arrangements and excitations for the elements are used to study their effect on the circular polarization bandwidth. The circular polarization (cp) bandwidth for the sequential rotation feeding is found to be the best method and the broadside radiation cp is frequency independent. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 381–384, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11066
Parameter extraction of a base‐collector equivalent circuit model for SiGe heterojunction bipolar transistors
Authors: Lee Seonghearn
Published: July 2003

By deriving new Z‐parameter equations, accurate extraction is performed to determine all base‐collector model parameters in a SiGe heterojunction bipolar transistor (HBT) equivalent circuit directly from measured S parameters, without any test structure and geometric calculation. The calculated power and current gains are in good agreement with the measured gains, thus verifying the accuracy of the extraction. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 384–387, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11067
A novel ion concentration measurement method using a PBG cell
Authors: Lin Huang‐Cuang , Liu Chin‐Hsiang , Tsao Shyh‐Lin
Published: July 2003

A novel ion concentration in liquid detection measurement method is proposed. This new technique uses an improved low pass filter (LPF) photonic band gap (PBG) cell structure, which is laid out on board a printed circuit (PCB). This paper demonstrates how the method can be applied to measure the concentration of CuSO4with the advantage of low cost. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 387–389, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11068
PAE improvement and compensation of small‐signal gain drift due to temperature on power amplifiers through active biasing
Authors: Torregrosa‐Penalva Germán , Asensio‐López Alberto , Ortega‐González F. Javier , Blanco‐del‐Campo Álvaro
Published: July 2003

Power millimetre‐wave band transmitters are commonly formed by a chain of MESFET or HEMT GaAs MMIC power amplifiers. Under large‐signal conditions the reverse gate output current, which appears at the gate port of those devices due to drain‐gate breakdown mechanisms, causes a drop in the power amplifier's power added efficiency (PAE) figure, thus affecting the entire transmitter reliability. Additionally, it is desirable to obtain a stable performance from the transmitters for different ambient temperatures. In particular, millimetre‐wave wireless systems, such as the local multipoint distribution system (LMDS), require constant small signal gain for a wide range of temperatures. In this paper, an active bias network is used to compensate for both effects. The performance of the active bias network is shown to be superior, in terms of the power amplifier's PAE and the compensation of the power amplifier's small signal gain drifts due to temperature, to a conventional resistive divider when used for biasing the power amplifier. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 389–392, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11069
Surface‐wave propagation along a metamaterial slab
Authors: Cory H. , Barger A.
Published: July 2003

Surface‐wave propagation along a metamaterial slab with negative permittivity and permeability is analyzed. The dispersion relations are determined for the TM and TE (odd and even) modes. The Brillouin diagrams are drawn and show that, for odd modes after cutoff, there is an initial frequency range for which there are two possible propagation coefficients. All the even modes exhibit the same behaviour except the first one. In this case a band‐pass region appears, suggesting that the device could be used as a filter. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 392–395, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11070
Contention resolution by shared wavelength converters and fiber delay lines in an optical packet switch
Authors: Yi Li , Ghafouri‐Shiraz H.
Published: July 2003

Contention resolution techniques greatly affect the architecture and performance of an optical packet switch (OPS). Fiber delay lines (FDLs) and wavelength converters which can resolve the contention problem and provide acceptable performance, have been demonstrated in many OPS designs. However, the large hardware volume of the optical components limits the integration and scalability of the OPS system. In this paper, we propose a design that can efficiently utilize the wavelength converters and use a very limited number of FDLs. The performance of the proposed design has been evaluated by simulation. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 395–398, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11071
Narrow flat metal‐plate antenna for dual‐band WLAN operation
Authors: Fang Chi‐Yin , Tung Hao‐Chun , Su Saou‐Wen , Wong Kin‐Lu
Published: July 2003

A novel dual‐band antenna made of a narrow, rectangular, flat metal plate for wireless local area network (WLAN) operation in the 2.4‐ and 5.2‐GHz bands is presented. The antenna comprises a larger radiating arm, a smaller radiating arm, and a shorting portion. The larger and smaller radiating arms control a lower resonant mode at about 2.4 GHz and an upper resonant mode at about 5.2 GHz, respectively, and are connected to each other through the shorting portion. The antenna is easily excited by using a 50Ω mini coaxial line and shows good antenna performance. The proposed antenna design is described and experimentally studied. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 398–400, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11072
Genetically engineered multiband high‐impedance frequency selective surfaces
Authors: Kern Douglas J. , Werner Douglas H. , Wilhelm Michael J. , Church Kenneth H.
Published: July 2003

A methodology is presented for the design synthesis of metamaterials that act as thin multifrequency artificial magnetic conductors. These structures are realized by placing a frequency‐selective surface above a conventional prefect electric conductor, separated by a thin dielectric layer. The frequency‐selective surface design is optimized using a micro‐genetic algorithm to operate at multiple, narrow frequency bands. Two examples of genetically engineered multiband high‐impedance frequency‐selective surfaces (that is, artificial magnetic conductors) are presented and discussed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 400–403, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11073
Near fields evaluated with the wave concept iterative procedure method for an E‐polarisation plane wave scattered by cylindrical strips
Authors: Raveu N. , Vuong T. P. , Terrasse I. , Piau G.‐P. , Baudrand H.
Published: July 2003

The wave concept iterative procedure (WCIP), already improved for planar circuits, is developed in this paper for cylindrical structures. The WCIP method has been applied with success to the scattering of an E‐polarisation plane wave on cylindrical strips. The results are in good agreement with previous works in the literature, and the calculation time involved is quite reasonable. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 403–406, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11074
Flexible polymer light‐emitting devices based on ruthenium complexes
Authors: Wang Tzyy‐Jiann , Chen Chiu‐Hui , Chang Shu‐Mei , Tzeng Yih‐Jing , Chao Yu‐Chou
Published: July 2003

Polymer light‐emitting devices (PLED) using ruthenium complexes doped in the polymer blend of PVK and PBD on the flexible substrate are presented. The effects of dye‐doping concentration and polymer blend thickness on the device performance are discussed. By using ruthenium complexes, the flexible PLED exhibits improved color purity and device stability. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 406–409, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11075
Determination of conductor loss of multilayer‐coupled microstrip lines for CAD application
Authors: Verma A. K. , Nasimuddin
Published: July 2003

By modifying and adopting the incremental inductance rule, in association with the variational method in the Fourier domain, and using the single layer (SLR) formulation, we present a fast and accurate method to compute the conductor loss of a multilayer‐coupled microstrip line with and without shield. The accuracy of the method has been tested against several full‐wave methods. The conductor loss of many useful structures is compared. The method is valid for conductor thickness t > 1.11 skin depth. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 409–415, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11076
Compact combined antenna with dual dipolar‐type radiation
Authors: Delaveaud C. , Brocheton C.
Published: July 2003

Two dipolar radiating sources have been combined in a compact structure to provide a dual orthogonal omnidirectional coverage. A dual‐port antenna configuration using this concept has been designed to operate at I.S.M. 2.4‐GHz frequency band. Experimental results concerning S parameters and radiation characteristics are compared to simulation results. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 415–418, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11077
A semivectorial method for the modeling of photonic crystal fibers
Authors: De Francisco C. A. , Borges B. V. , Romero M. A.
Published: July 2003

This paper presents a versatile finite‐difference‐based method, formulated in terms of the simultaneous over‐relaxation (SOR) technique, for the modeling of photonic crystal fibers. The dispersion characteristics of such fibers are obtained and the results are compared with previously published data with excellent agreement. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 418–421, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11078
A new aperture‐coupled patch antenna
Authors: Cheng C. H. , Li K. , Tang K. F. , Matsui T.
Published: July 2003

A new aperture‐coupled patch antenna is presented, in which the patch is surrounded by a conductor ground and the sides of the dielectric substrate are covered with conductor walls. The antenna was investigated numerically and experimentally. Result shows that the antenna has a bandwidth of about 28% (for |S11| ≤ −10 dB) centered at 10 GHz and an average gain of about 7.4 dBi over the operating frequency range, which are better than that of a conventional aperture‐coupled patch with the same parameters. At the same time, the antenna maintains a good radiation pattern. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 422–423, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11079
Simulated annealing algorithm applied in optimum design of optical thin‐film filters
Authors: Huang H. C. , Hsu M. H. , Chen K. L. , Huang J. F.
Published: July 2003

This method shows the superiority of designing DWDM filters by using the idea of simulated annealing algorithm. By applying this method, the spectral transmittance and reflectance curves of these filters all effectively achieve their desired optical performances. Although the design procedure is concentrated on 1550‐nm band, in general, this method can be applied to arbitrary frequency bands. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 423–428, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11080
3D near‐field model for uniform slanted fiber gratings
Authors: Jáuregui C. , Cobo A. , López‐Higuera J. M.
Published: July 2003

A 3D near‐field model for a uniform slanted fiber Bragg grating (FBG) is presented. This model, based on antenna theory, allows for the calculation of the radiated near field in the space surrounding a fiber that contains a tilted uniform fiber Bragg grating. Radiation patterns can also be obtained. The model has been successfully checked via experiments. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 428–432, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11081
Novel radical‐responsive MRI contrast agent based on paramagnetic liposomes
Authors: Gløgård Christian , Stensrud Gry , Aime Silvio
Published: July 2003

A novel, radical responsive MRI contrast agent based on a gadolinium chelate conjugated to a liposome through a disulfide linker was synthesized, with the aim of pursuing the in vivo mapping of radicals. The liposome was prepared by incorporating a thiol‐activated phospholipid, which was subsequently reacted with a gadolinium chelate containing a free thiol group. The long reorientational motion of the supramolecular adduct endows the paramagnetic agent with a relaxivity significantly higher than that of the free complex. The disulfide bond represents a radical‐sensitive moiety and a large decrease in contrast efficacy (T1 relaxivity) is shown upon its cleavage. A preliminary assessment of the system was made by means of in vitro gamma‐irradiation and thiol–disulfide bond exchange with dithiothreitol. Both methods showed a clear dose‐dependent decrease in T1‐relaxivity. Copyright © 2003 John Wiley & Sons, Ltd.
Structural analysis of 3‐α‐acetyl‐20(29)‐lupene‐24‐oic acid, a novel pentacyclic triterpene isolated from the gum resin of Boswellia serrata, by NMR spectroscopy
Authors: Belsner Klaus , Büchele Berthold , Werz Udo , Simmet Thomas
Published: July 2003

3α‐Acetyl‐20(29)‐lupene‐24‐oic acid (1) was isolated from the gum resin of Boswellia serrata. Its presence evidently suggests, that the oxidosqualene triterpene pathway of Boswellia serrata closely resembles the biosynthetic route already found in other plants. Complete 1H and 13C spectral assignments were derived from 1D and 2D NMR spectra. This is the first compound with the lupene backbone combining a 3α‐hydroxy or 3α‐acetyl group with the 24‐carboxyl group, a configuration which is typical of the classical boswellic acids. Copyright © 2003 John Wiley & Sons, Ltd.
Structural determination and complete NMR spectral assignments of a new diterpenoid obtained from triptonide by biotransformation
Authors: Ning Lili , Jiang Xiaomei , Ye Min , Guo Hongzhu , Bi Kaishun , Guo Dean
Published: July 2003

A new diterpenoid, 12β,13α‐dihydroxytriptonide, was obtained from the transformed culture of triptonide by Catharanthus roseus cell suspension cultures. The complete 1H and 13C NMR assignments of the compound were carried out by using DEPT, COSY, HSQC, g‐HMBC and NOESY techniques. Copyright © 2003 John Wiley & Sons, Ltd.
Complete assignments of 1H and 13C NMR resonances of oleanolic acid, 18α‐oleanolic acid, ursolic acid and their 11‐oxo derivatives
Authors: Seebacher Werner , Simic Nebojsa , Weis Robert , Saf Robert , Kunert Olaf
Published: July 2003

Complete assignments of 1H and 13C NMR chemical shifts for oleanolic acid, 18α‐oleanolic acid, ursolic acid and their 11‐oxo derivatives based on 1H, 13C, 2D DQF‐COSY, NOESY, HSQC, HMBC and HSQC‐TOCSY experiments were achieved. Copyright © 2003 John Wiley & Sons, Ltd.
Influence of the C—H· · ·N intramolecular interaction on the spatial structures and 1H and 13C NMR parameters of heteroaryl vinyl ethers and sulfides
Authors: Afonin Andrei V. , Ushakov Igor A. , Kuznetsova Svetlana Yu. , Andriyankova Lyudmila V.
Published: July 2003

A complete analysis of the 1H and 13C spectra of the representative series of heteroaryl vinyl ethers and sulfides and heteroaryl styryl sulfides was carried out. The electronic and spatial structures of these compounds are discussed. It was shown that the C—H· · ·N intramolecular interactions in the investigated molecules influence significantly the spectral parameters and the conformational equilibrium. Copyright © 2003 John Wiley & Sons, Ltd.
NMR spectroscopy as a tool to investigate the degradation of aromatic compounds by a Pseudomonas putida strain
Authors: Bertini I. , Provenzani A. , Viezzoli M. S. , Pieper D. H. , Timmis K. N.
Published: July 2003

Pseudomonas putida strain KT2442, harbouring the pWW0 TOL plasmid, was grown with a number of different homologous aromatic acids as carbon sources. Small samples of liquid culture supernatant were collected and directly analysed by 2D NMR spectroscopy. In all cases similar compounds with olefinic signals were observed to accumulate. To elucidate the structures of these compounds, 2D NMR experiments with 500 and 600 MHz spectrometers equipped with a CryoProbe (Bruker BioSpin) were performed on samples obtained from a culture growing on 4‐methylbenzoate and, for 13C spectroscopy, on 13C‐labelled 4‐methylbenzoate. In all cases a 1,2‐dihydroxycyclohexa‐3,5‐diene‐carboxylate derivative was identified. The use of this technique helped us to identify easily some metabolites that were released into the solution by bacteria and to follow their secretion as a function of time. The high sensitivity of the present approach allowed a clear and rapid acquisition of spectra, notwithstanding the low concentration of the compounds. The benefits of introducing the use of NMR cryoprobes to perform metabolic pathway studies is demonstrated. Copyright © 2003 John Wiley & Sons, Ltd.
Assignment of chemical shifts in benzohydroxamic acid and structure of its silylated derivatives by 15N enrichment
Authors: Schraml Jan , Blechta Vratislav , Soukupová Ludmila , Karban Jindřich , Mindl Jaromír
Published: July 2003

15N isotopic enrichment was necessary for the unequivocal assignment of the 1H NMR lines to the protons in the NH–OH fragment of benzohydroxamic acid, BHXA, C6H5CONHOH, in dry dimethyl sulfoxide solutions. The assignment [δ(NH) = 11.21, δ(OH) = 9.01, 1J(15N,1H) = 102.2 Hz, 2J(15N,1H) <1.5 Hz], which is opposite to that used by other authors, confirms the assignment extended to BHXA by Brown and co‐workers from the spectra of acetohydroxamic acid. The enrichment allowed also assignment of the 29Si lines in the spectra of disilylated benzohydroxamic acid, (Z)‐tert‐butyldimethylsilyl N‐tert‐butyldimethylsilyloxybenzoimidate (2) and (Z)‐tert‐butyldiphenylsilyl N‐tert‐butyldiphenylsilyloxybenzoimidate (3), and confirmed structure of the monosilylated products, N‐tert‐butyldiphenylsilyloxybenzamide (4) and N‐tert‐butyldiphenylsilyloxy benzoimidic acid (5). Copyright © 2003 John Wiley & Sons, Ltd.
Multinuclear magnetic resonance, electrospray ionization time‐of‐flight mass spectral and molecular modelling characterization of lithocholic acid amide esters with various nitrogen heterocycles
Authors: Virtanen Elina , Tamminen Jari , Haapala Mervi , Mänttäri Pia , Kauppinen Reijo , Kolehmainen Erkki
Published: July 2003

1H, 13C and 15N NMR and electrospray ionization time‐of‐flight mass spectrometric characterizations of five lithocholate esters of piperazine diamides are described. Two of them are cholaphane‐type cyclic structures esterified with 2,2′‐bipyridine‐4,4 ′ ‐ and pyridine‐2,6‐dicarboxylic acid and the other three esters are open structures comprising two or four lithocholyl residues. The conformational preferences of the dimeric congeners were examined by using molecular modelling and variable‐temperature 1H NMR techniques. Copyright © 2003 John Wiley & Sons, Ltd.
Use of natural abundance 15N DEPT NMR to investigate curing of urea–formaldehyde resin in the presence of wood fibers
Authors: Gill B. D. , Manley‐Harris M. , Thomson R. A.
Published: July 2003

Natural abundance 15N NMR using a DEPT pulse sequence was employed to follow the curing of urea–formaldehyde resin in the presence of wood fiber, fiber extracts and acid or base. The advantages of 15N NMR, large range chemical shifts, simplification of spectra and lack of interference by additives, can be exploited. The disadvantages of low sensitivity and long relaxation delays are offset by using a cross‐polarization technique. Copyright © 2003 John Wiley & Sons, Ltd.
15N NMR spectra of some 3‐substituted 4(1H)‐quinolinones and their 1‐methyl derivatives
Authors: Zięba Andrzej , Maślankiewicz Andrzej , Milata Viktor , Sitkowski Jerzy
Published: July 2003

15N NMR spectral data for 3‐substituted (chloro, bromo, acetyl, carboxy, carboethoxy, methylsulfanyl, methylsulfinyl, N,N‐dimethylsulfamoyl, nitro) 4(1H)‐quinolinones and their 1‐methyl derivatives are presented. Copyright © 2003 John Wiley & Sons, Ltd.
Detailed assignments of 1H and 13C NMR spectral data of 14 cyclopentane derivatives
Authors: Constantino Mauricio Gomes , Júnior Valdemar Lacerda , da Silva Gil Valdo José
Published: July 2003

Detailed assignments of 1H and 13C NMR spectral data for 14 cyclopentane derivatives are reported. The assignments are based on 1D 1H and 13C NMR and on 2D shift‐correlated [1H, 13C‐HMQC], J‐resolved and NOEDIF experiments. Copyright © 2003 John Wiley & Sons, Ltd.
Assignment of the major and minor components of gentamicin for evaluation of batches
Authors: Deubner Ralph , Schollmayer Curd , Wienen Frank , Holzgrabe Ulrike
Published: July 2003

The antibiotic agent gentamicin sulfate is a mixture of several structurally very similar aminoglycosides. The major components of gentamicin are gentamicin C1, C1a, C2 and C2a. These major components were separated by means of column chromatography. The 1H and 13C NMR spectra of the free bases and the corresponding sulfates were assigned using HMQC, HMBC and selective TOCSY experiments. Additionally, the 1H and 13C NMR spectra of the sulfates and hydrochlorides, respectively, of the minor components were assigned. The full assignment of all components of gentamicin is necessary for the quantitative analysis of batches of gentamicin. By means of coupled liquid chromatography–NMR, several different batches were studied, revealing different compositions of batches from various sources. Copyright © 2003 John Wiley & Sons, Ltd.
Gradient‐enhanced one‐dimensional pulse schemes for quaternary and methylene carbon detection
Authors: Nagana Gowda G. A.
Published: July 2003

Gradient‐enhanced pulse schemes are presented for the detection of quaternary and methylene carbons. The new pulse schemes permit the detection of quaternary and methylene (—CH2) carbons or CH2 carbons alone from a single experiment. Efficient suppression of CH and CH3 carbons in all the pulse schemes is achieved by creating their antiphase magnetization and then dephasing using gradients. In the pulse schemes for detection of only CH2 carbons, the quaternary carbons are also suppressed either by dephasing using gradients or by rendering them unobservable by retaining in longitudinal order. The experimental results of the gradient pulse schemes are demonstrated on cholesteryl acetate and cyclosporin A. These one‐dimensional techniques, because of their simplicity and the ease of performing the experiments, can be important for routine chemical applications. Copyright © 2003 John Wiley & Sons, Ltd.
NMR and EPR studies of the reaction of nucleophilic addition of (bi)sulfite to the nitrone spin trap DMPO
Authors: Potapenko Dmitrii I. , Bagryanskaya Elena G. , Reznikov Vladimir V. , Clanton Thomas L. , Khramtsov Valery V.
Published: July 2003

The reaction of the nitrone spin trap 5,5‐dimethylpyrroline‐N‐oxide (DMPO) with sodium (bi)sulfite in aqueous solutions was investigated using NMR and EPR techniques. Reversible nucleophilic addition of (bi)sulfite anions to the double bond of DMPO was observed, resulting in the formation of the hydroxylamine derivative 1‐hydroxy‐5,5‐dimethylpyrrolidine‐2‐sulfonic acid, with characteristic 1H and 13C NMR spectra. The reaction mechanism was suggested and corresponding equilibrium constants determined. The mild oxidation of the hydroxylamine results in the formation of an EPR‐detected spectrum identical with that for the DMPO adduct with sulfur trioxide anion radical. The latter demonstrates that a non‐radical addition reaction of (bi)sulfite with DMPO may contribute to the EPR detection of SO3−• radical. This possibility must be taken into account in spin trapping analysis of sulfite radical. Copyright © 2003 John Wiley & Sons, Ltd.
Quindolinocryptotackieine: the elucidation of a novel indoloquinoline alkaloid structure through the use of computer‐assisted structure elucidation and 2D NMR
Authors: Blinov Kirill , Elyashberg Mikhail , Martirosian Eduard R. , Molodtsov Sergey G. , Williams Antony J. , Tackie Albert N. , Sharaf Maged M. H. , Schiff Paul L. , Crouch Ronald C. , Martin Gary E. , Hadden Chad E. , Guido Jane E. , Mills Kent A.
Published: July 2003

Numerous indoloquinoline alkaloid structures have been identified from extracts of the West African plant Cryptolepis sanguinolenta. Recently, through the use of 2D NMR methods and cryogenic NMR probe technology in conjunction with computer‐assisted structure elucidation (CASE) methods, the structures of some chemical degradation products of this family of alkaloids have also been reported. We now report the characterization of a novel indoloquinoline dimeric alkaloid, quindolinocryptotackieine, through the extensive utilization of CASE methods. The NMR data presented here were collected over a decade earlier before the elucidation of the structure was possible, since manual analysis did not present a conclusive structure, whereas CASE produced a series of structures from which the structure could be verified. The original mass spectrometric (MS) data collected for the sample were problematic. Contemporary MS data were instead recollected from remaining small quantities of this alkaloid using modern instrumentation. The re‐collected data gave a usable molecular ion and several key fragment ions that were diagnostically useful. Copyright © 2003 John Wiley & Sons, Ltd.
Isolation and characterization of a Tie2 kinase inhibitory sulfated triterpenoid from a green alga of the Tuemoya genus: complete assignment of the 1H and 13C spectra of a sulfated triterpenoid Tie2 kinase inhibitor
Authors: Clement Jason A. , Zhou Bing‐Nan , Johnson Randall K. , Kingston David G. I.
Published: July 2003

Bioassay‐guided fractionation of an extract of a Tuemoya sp., using an assay for inhibitors of the enzyme Tie2 kinase, afforded a mixture of the sulfated cycloartanol triterpenoids 1 and 2. We report the full 1H and 13C NMR spectral assignments for 1 and the 13C NMR spectral assignments for 2. Copyright © 2003 John Wiley & Sons, Ltd.
Conformational study of fosinopril sodium in solution using NMR and molecular modeling
Authors: Liu Songbai , Shi Yanhong , Zhang Qingwen , Song Guoqiang
Published: July 2003

Two conformers of fosinopril sodium in methanol were unambiguously established using 2D NMR methods and variable‐temperature NMR experiments. Differences in their conformational structure were shown to be related to the rotational energy barrier about the amide bond and hydrophobic interaction. The relationship between the 3D structure and activity is discussed. It is suggested that the trans‐conformer may be more biologically active owing to its stacking structure and strong hydrophobic interaction and the cis‐conformer could be more easily hydrolyzed because of its extended structure. Copyright © 2003 John Wiley & Sons, Ltd.
Back analysis of model parameters in geotechnical engineering by means of soft computing
Authors: Pichler B. , Lackner R. , Mang H. A.
Published: July 2003

In this paper, a parameter identification (PI) method for determination of unknown model parameters in geotechnical engineering is proposed. It is based on measurement data provided by the construction site. Model parameters for finite element (FE) analyses are identified such that the results of these calculations agree with the available measurement data as well as possible. For determination of the unknown model parameters, use of an artificial neural network (ANN) is proposed. The network is trained to approximate the results of FE simulations. A genetic algorithm (GA) uses the trained ANN to provide an estimate of optimal model parameters which, finally, has to be assessed by an additional FE analysis. The presented mode of PI renders back analysis of model parameters feasible even for large‐scale models as used in geotechnical engineering. The advantages of theoretical developments concerning both the structure and the training of the ANN are illustrated by the identification of material properties from experimental data. Finally, the performance of the proposed PI method is demonstrated by two problems taken from geotechnical engineering. The impact of back analysis on the actual construction process is outlined. Copyright © 2003 John Wiley & Sons, Ltd.
Development of the DYNA3D simulation code with automated fracture procedure for brick elements
Authors: Tabiei Ala , Wu Jin
Published: July 2003

Numerical simulation of cracked structures is an important aspect in structural safety assessment. In recent years, there has been an increasing rate of development of numerical codes for modelling fracture procedure. The subject of this investigation is implementing automated fracture models in the DYNA3D non‐linear explicit finite element code to simulate pseudo 3D crack growth procedure. The implemented models have the capabilities of simulating automatic crack propagation without user intervention. The implementation is carried on solid elements. The methodology of implementing fracture models is described. An element deletion‐and‐replacement remeshing procedure is proposed for updating the explicit geometric description of evolving cracks. Fracture parameters such as stress intensity factors, energy release rates and crack tip opening angle are evaluated. The maximum circumferential stress criterion is used to predict the direction of crack advancement. Seven crack problems are presented to verify the effectiveness of the methodology. Mesh sensitivity and loading rate effects are studied in the validation of the presented procedure. Copyright © 2003 John Wiley & Sons, Ltd.
Fast direct solution of the Helmholtz equation with a perfectly matched layer or an absorbing boundary condition
Authors: Heikkola Erkki , Rossi Tuomo , Toivanen Jari
Published: July 2003

We consider the efficient numerical solution of the Helmholtz equation in a rectangular domain with a perfectly matched layer (PML) or an absorbing boundary condition (ABC). Standard bilinear (trilinear) finite‐element discretization on an orthogonal mesh leads to a separable system of linear equations for which we describe a cyclic reduction‐type fast direct solver. We present numerical studies to estimate the reflection of waves caused by an absorbing boundary and a PML, and we optimize certain parameters of the layer to minimize the reflection. Copyright © 2003 John Wiley & Sons, Ltd.
A variant of the subspace iteration algorithm for generalized eigenproblems
Authors: Rajendran S. , Liew K. M.
Published: July 2003

A variant of the subspace iteration algorithm for the generalized eigenproblem, Kp= λMp, is proposed. The algorithm does not require the computation of the projected stiffness matrix, and hence, the projected eigenproblem turns out to be a standard eigenproblem as against the generalized eigenproblem of the classical algorithm. This results in appreciable saving in the number of operations of the Rayleigh–Ritz step and hence the solution time, particularly when a large number of eigenvalues are to be computed. The numerical experiments suggest that the proposed algorithm can yield a saving in solution time of up to 28% for certain eigenproblems. Copyright © 2003 John Wiley & Sons, Ltd.