bluuebunny/crossref_metadata_2025 huggingface dataset:
Incidence and effects of Ha‐ras codon 12 G→A transition mutations in preneoplastic lesions induced by N‐nitrosomethylbenzylamine in the rat esophagus
Authors: Liston Beth W. , Gupta Ashok , Nines Ronald , Carlton Peter S. , Kresty Laura A. , Harris Gabriel K. , Stoner Gary D.
Published: August 2002

N‐nitrosomethylbenzylamine (NMBA)–induced rat esophageal tumorigenesis is an important model for squamous cell carcinoma of the human esophagus. In this model, previous studies have shown that the GGA→GAA Ha‐ras codon 12 mutation is present in the majority of papillomas. No other Ha‐ras mutation has been identified. Studies using other models of chemical carcinogenesis suggest that Ha‐ras activation has a critical role during tumor initiation. We have used laser‐capture microdissection and polymerase chain reaction–restriction fragment length polymorphism analysis to study the role of codon 12 Ha‐ras mutation at various stages of tumor development in the rat esophagus. Our results indicate that Ha‐ras mutation was present infrequently (4.3%) in premalignant lesions. The incidence of Ha‐ras mutation was high in papillomas (57.1%), however, and 50% of papillomas expressed mutant Ha‐ras RNA message. Additionally, there was a linear trend correlating increased incidence of Ha‐ras mutation with later papilloma stage. These data suggest the role of ras activation later in neoplastic development. To evaluate the potential mechanism of action by which Ha‐ras contributes to promotion and progression in this model, we compared mRNA expression of cyclin D1 and p27 in Ha‐ras mutant and Ha‐ras normal papillomas. We found no differences in mRNA expression of either cyclin D1 or p27 between these two papilloma populations. Our data suggest an important paradigm shift for the role of ras mutations in this model of chemical carcinogenesis, indicating a functional role of Ha‐ras activation in promotion/progression and not in the initiation phase of NMBA‐induced papillomagenesis. © 2001 Wiley‐Liss, Inc.
MCDM methods in strategic planning of forestry on state‐owned lands in Finland: applications and experiences
Authors: Kangas Jyrki , Kangas Annika , Leskinen Pekka , Pykäläinen Jouni
Published: August 2002

The forests in Finland have been under intensive planning for decades. Currently, mathematical programming is widely used in planning of wood production. Today's multi‐functional forestry, however, calls for more flexible decision support methods. MCDM tools have been used in responding to fresh planning challenges. For example, the Finnish Forest and Park Service, entrusted with the care of the vast majority of state‐owned natural resources in Finland, endeavours to produce large‐scale natural resource plans satisfying the needs of both economic, social, and ecological sustainability. Participatory approach is applied in the process.

Several forestry applications of MCDM methods, particularly those making use of the AHP or the HIPRE program, have been presented. Also, the outranking methods ELECTRE and PROMETHEE have been tested. Due to the nature of forestry applications, statistical techniques for analysing uncertainties in pairwise comparisons and for utilizing interval judgement data have been developed to improve the usability of the AHP. Recently, a hybrid method called A'WOT, making use of the AHP and SWOT, was also introduced into strategic forest planning.

This paper summarizes the experiences gained in applying a MAVT and two outranking methods in connection with a participatory natural resource planning process in Finland. In addition, some results of the method development work related to application needs are briefly presented. The details of the planning cases reviewed here have previously been presented in forestry journals. The purpose of this paper is not only to show how MCDM methods have been applied in forestry, but also to discuss the usability and usefulness of MCDM methods from the viewpoint of supporting forestry decision making—and how they might further be improved. Also, some perspectives for the future development work of MCDM applications in the field of natural resource management are focused on. As a conclusion, the use of more than just one MCDM method in a single planning process is seen usually recommendable. In addition, developing hybrid MCDM methods is regarded as a potential direction for future research. Also, closer co‐operation between method developers and appliers is called for to produce more useful applications. Copyright © 2002 John Wiley & Sons, Ltd.
Relationships for modeling the performance of rectangular gas chromatographic columns
Authors: Spangler Glenn E.
Published: August 2002

Golay's theory for open tubular GC columns was recently revised for application to rectangular GC columns. The HETP was found to be the same as for open tubular columns provided the average linear velocity,ū, and the resistance‐to‐mass‐transfer‐in‐the‐gas‐phase,CM, are redefined. In this paper, a simplified expression for the average linear velocity is derived and used to fit a variety of exit flow data collected on microfabricated rectangular GC columns. Also the resistance‐to‐mass‐transfer‐in‐the‐gas‐phase is studied and the results compared to earlier relationships derived by Giddings, Chang, Myers, Davis and Caldwell, and by Golay. The three theories agree, with the present theory predicting a slightly higher value forCMfor large retention indices. The slightly higher value forCMis attributed to the geometry for the rectangular column that is better modeled with the present theory than the former theories. © 2001 John Wiley & Sons, Inc. J Micro Sep 13: 285–292, 2001
Development for the analysis of reactive oxygen species using capillary electrophoresis with laser‐induced fluorescence detection
Authors: Yu Eunah , Ban Eunmi , In Mun Kyo , Yoo Young Sook
Published: August 2002

Reactive oxygen species (ROS) have been identified as important chemical mediators that regulate signal transduction pathways. Today, the importance of ROS in pathological events has become increasingly apparent. To monitor the ROS in biological systems, various techniques such as cytochrome c peroxidase assay and malonaldialdehyde detection were developed and used clinically. However, these methods are very laborious and time‐consuming. Therefore, in this study, we developed a capillary electrophoresis (CE)‐based ROS monitoring technique using dihydrorhodamine 123 (DHR‐123). DHR‐123 is a nonfluorescent compound, and can be oxidized irreversibly and rapidly by ROS to rhodamine 123 (Rho‐123), which is a fluorescent dye. Upon detecting the amount of the fluorescence from Rho‐123, we could indirectly quantify the amount of ROS generation in biological systems. Determination of Rho‐123 was performed in an uncoated silica capillary (27 cm×75 μm i.d.) using a CE system with laser‐induced fluorescence detection. Optimum conditions for the Rho‐123 detection were 50 mM borate buffer (pH 10.0), running at 20°C, and 5 s injection. This method allowed the detection of Rho‐123 with a detection limit around 50 pM. We also applied this developed method to the analysis of intracellular ROS level in methamphetamine (MA) treated PC12 cells. © 2001 John Wiley & Sons, Inc. J Micro Sep 13: 327–331, 2001
Mobility and ionization constant of basic drugs in methanol. Application of nonaqueous background electrolytes for capillary zone electrophoresis based on a conventional pH scale
Authors: Porras Simo P. , Jyske Pentti , Riekkola Marja‐Liisa , Kenndler Ernst
Published: August 2002

The ionization constants of nine basic drugs (ethylmorphine, thebaine, codeine, levorphanol, dihydrocodeine, cocaine, alprenolol, propranolol and methamphetamine) in methanol were determined from the dependence of their mobilities on the pH* of the background electrolyte (BGE), based on a conventional pH* scale. Mobilities in the BGEs with acetate as counter ion were seemingly too low, an effect that was related to ion pair formation of the cationic analytes with acetate. After numerical correction of this effect the application of the Henderson–Hasselbalch equation enabled the calculation of the pKa* values, which were found to be between 9.3 and 11.2. These pKa* values are only 1 to 2.5 pK units higher than in pure water, which is in marked contrast to the changes observable for neutral acids. © 2001 John Wiley & Sons, Inc. J Micro Sep 13: 149–155, 2001
Identification of CS‐derived compounds formed during heat‐dispersion of CS riot control agent*†
Authors: Kluchinsky Timothy A. , Savage Paul B. , Sheely Michael V. , Thomas Richard J. , Smith Philip A.
Published: August 2002

High temperatures are frequently used to disperse 2‐chlorobenzylidene malononitrile (CS) riot control agent. We examined airborne CS degradation products heat‐dispersed together with CS from canisters of a type used by law enforcement personnel for crowd and riot control. Air contaminants derived from CS were trapped using a polytetraflouroethylene filter. Analysis was by open tubular gas chromatography coupled to mass spectrometry. Compounds observed in addition to CS included 2‐chlorobenzaldehyde, 2‐chlorobenzonitrile, quinoline, 2‐chlorobenzylcyanide, 1,2‐dicyanobenzene, 3‐(2‐chlorophenyl)propynenitrile,cisandtransisomers of 2‐chlorocinnamonitrile, 2,2‐dicyano‐3‐(2‐chlorophenyl)oxirane, 2‐chlorodihydrocinnamonitrile, benzylidenemalononitrile,cisandtransisomers of 2‐cyanocinnamonitrile, 2‐chlorobenzylmalononitrile, 3‐quinoline carbonitrile, and 3‐isoquinoline carbonitrile. © 2001 John Wiley & Sons, Inc. J Micro Sep 13: 186–190, 2001
Rent extraction, principal–agent relationships, and pricing strategies: vendor licensing during the 1996 Olympic Games in Atlanta
Authors: Allen Ralph C. , Stone Jack H.
Published: August 2002

Two‐part pricing, price‐discrimination, rent creation and extraction, principal–agent theory, and public choice perspectives on public bureaucracies are used to interpret a vendor‐license marketing arrangement and controversy arising out of the 1996 Olympic Games in Atlanta, GA. Containing features predicted by principal–agency theory, Atlanta's arrangement with its marketing agent was a response to the behavior of public bureaucracies and a low cost method of converting visitors' consumer surplus to rent, which could be extracted by the marketing agent and then by Atlanta. Atlanta's incentive to enforce vendor property rights was influenced by the nature of the game between Atlanta and prospective vendors. Copyright © 2001 John Wiley & Sons, Ltd.
Experimental study of vascularized nerve graft: Evaluation of nerve regeneration using choline acetyltransferase activity
Authors: Iwai Makoto , Tamai Susumu , Yajima Hiroshi , Kawanishi Kohichi
Published: August 2002

A comparative study of nerve regeneration was performed on vascularized nerve graft (VNG) and free nerve graft (FNG) in Fischer strain rats. A segment of the sciatic nerve with vascular pedicle of the femoral artery and vein was harvested from syngeneic donor rat for the VNG group and the sciatic nerve in the same length without vascular pedicle was harvested for the FNG group. They were transplanted to a nerve defect in the sciatic nerve of syngeneic recipient rats. At 2, 4, 6, 8, 12, 16, and 24 weeks after operation, the sciatic nerves were biopsied and processed for evaluation of choline acetyltransferase (CAT) activity, histological studies, and measurement of wet weight of the muscle innervated by the sciatic nerve. Electrophysiological evaluation of the grafted nerve was also performed before sacrifice. The average CAT activity in the distal to the distal suture site was 383 cpm in VNG and 361 cpm in FNG at 2 weeks; 6,189 cpm in VNG and 2,264 cpm in FNG at 4 weeks; and 11,299 cpm in VNG and 9,424 cpm in FNG at 6 weeks postoperatively. The value of the VNG group was statistically higher than that of the FNG group at 4 weeks postoperatively. Electrophysiological and histological findings also suggested that nerve regeneration in the VNG group was superior to that in the FNG group during the same period. However, there was no significant difference between the two groups after 6 weeks postoperatively in any of the evaluations. The CAT measurement was useful in the experiments, because it was highly sensitive and reproducible. © 2001 Wiley‐Liss, Inc. MICROSURGERY 24:43–51 2001
Muscle free flaps with full‐thickness skin grafting: Improved contour over traditional musculocutaneous free flaps
Authors: Chang James , Jones Neil
Published: August 2002

Occasionally, the aesthetic contour of a musculocutaneous flap can be improved by using the skin paddle as a full‐thickness skin graft to cover the free muscle flap. In three patients, traditional musculocutaneous free flap coverage of wounds would have resulted in excess soft tissue bulk. To optimize final contour, the subcutaneous tissue was excised, and the skin replaced as a full‐thickness skin graft. Problems with postoperative flap monitoring and skin graft take were not encountered. This technique offers the microsurgeon a simple method to optimize the aesthetic results of composite free tissue transfer. © 2001 Wiley‐Liss, Inc. MICROSURGERY 21:70–73 2001
Modified sleeve anastomosis for reconstruction of the hepatic artery in rat liver transplantation
Authors: Li Jun , Dahmen Uta , Dirsch Olaf , Shen Kai , Gu Yanli , Broelsch Christoph Erich
Published: August 2002

End‐to‐end sleeve anastomosis between a donor common hepatic artery and a recipient proper hepatic artery was proven to be the most physiological and simple method for hepatic rearterialization in rat liver transplantation. Current technical variants of the sleeve technique, however, are hampered by the high rate of bleeding from the anastomotic site. This report deals with a technical modification which inhibits postoperative bleeding efficiently. The procedure consisted of a guiding suture, as previously described in other technical variants, and a modified fixing suture. Instead of using a single stitch to fix the feeding vessel with the receiving vessel, a running suture between the edge of the donor common hepatic artery and the adventitia of the recipient proper hepatic artery was performed to avoid a possible backflow. The patency rate of 91% was as high as reported by others using a sleeve technique, which was also reflected in the histomorphological picture, being indistinguishable from normal liver histology. This technical modification simplified the procedure of reconstructing the hepatic artery and could contribute to a wider use of the arterialized liver transplantation model in rats. © 2002 Wiley‐Liss, Inc. MICROSURGERY 22:62–68 2002
Basic aspects of geopotential field approximation from satellite‐to‐satellite tracking data
Authors: Freeden W. , Michel V.
Published: August 2002

The satellite‐to‐satellite tracking (SST) problems are characterized from mathematical point of view. Uniqueness results are formulated. Moreover, the basic relations are developed between (scalar) approximation of the earth's gravitational potential by ‘scalar basis systems’ and (vectorial) approximation of the gravitational field by ‘vectorial basis systems’. Finally, the mathematical justification is given for approximating the external geopotential field by finite linear combinations of certain gradient fields (for example, gradient fields of multi‐poles) consistent to a given set of SST data. Copyright © 2001 John Wiley & Sons, Ltd.
Exchange of conserved quantities, shock loci and Riemann problems
Authors: Sever Michael
Published: August 2002

Systems of conservation laws admitting extensions, such as entropy density/flux functions, generate related systems obtained by exchanging the extension with one of the constituent equations. Often if not always, the smooth solutions of the two systems coincide, and weak solutions of one system containing only small discontinuities are approximate weak solutions of the other. The adiabatic approximation for the Euler system illustrates the utility of this procedure.

Such an exchange of conserved quantities preserves hyperbolicity and genuine non‐linearity in the sense of Lax. On the other hand, the topological structure of the shock locus of a point in phase space and the solvability of Riemann problems in the large can be strongly affected. A discussion of when and how this occurs is given here.

In this paper the exchange of conserved quantities is conveniently described by a simple homotopy in an extended version of the usual ‘symmetric variables’. A dynamical system in phase space is constructed, the trajectories of which describe the Hugoniot locus of a fixed point in phase space at each state of the homotopy. The appearance of critical points for this dynamical system is identified with the alteration of the topological structure of the Hugoniot locus by the exchange of conserved quantities. Copyright © 2001 John Wiley & Sons, Ltd.
Generalized factorization for N×N Daniele–Khrapkov matrix functions
Authors: Câmara M. C. , dos Santos A. F. , Manojlović N.
Published: August 2002

A generalization to N×N of the 2×2 Daniele–Khrapkov class of matrix‐valued functions is proposed. This class retains some of the features of the 2×2 Daniele–Khrapkov class, in particular, the presence of certain square‐root functions in its definition. Functions of this class appear in the study of finite‐dimensional integrable systems. The paper concentrates on giving the main properties of the class, using them to outline a method for the study of the Wiener–Hopf factorization of the symbols of this class. This is done through examples that are completely worked out. One of these examples corresponds to a particular case of the motion of a symmetric rigid body with a fixed point (Lagrange top). Copyright © 2001 John Wiley & Sons, Ltd.
Reliable solution of an elasto–plastic torsion problem
Authors: Hlaváček Ivan
Published: August 2002

A variational inequality with uncertain coefficients, which are given in certain bounded intervals, is considered. The inequality corresponds to a torsion problem of an elasto–plastic orthotropic bar, when employing the Haar–Kármán principle. Two maximization problems with respect to the admissible coefficients are formulated. The solvability of continuous and approximate problems is proven and a convergence analysis is presented. Copyright © 2001 John Wiley & Sons, Ltd.
A critical look at the kinematic‐wave theory for sedimentation–consolidation processes in closed vessels
Authors: Bürger R. , Kunik M.
Published: August 2002

The two‐phase flow of a flocculated suspension in a closed settling vessel with inclined walls is investigated within a consistent extension of the kinematic wave theory to sedimentation processes with compression. Wall boundary conditions are used to spatially derive one‐dimensional field equations for planar flows and flows which are symmetric with respect to the vertical axis. We analyse the special cases of a conical vessel and a roof‐shaped vessel. The case of a small initial time and a large time for the final consolidation state leads to explicit expressions for the flow fields, which constitute an important test of the theory. The resulting initial‐boundary value problems are well posed and can be solved numerically by a simple adaptation of one of the newly developed numerical schemes for strongly degenerate convection‐diffusion problems. However, from a physical point of view, both the analytical and numerical results reveal a deficiency of the general field equations. In particular, the strongly reduced form of the linear momentum balance turns out to be an oversimplification. Included in our discussion as a special case are the Kynch theory and the well‐known analyses of sedimentation in vessels with inclined walls within the framework of kinematic waves, which exhibit the same shortcomings. In order to formulate consistent boundary conditions for both phases in a closed vessel and in order to predict boundary layers in the presence of inclined walls, viscosity terms should be taken into account. Copyright © 2001 John Wiley & Sons, Ltd.
Non‐linear initial boundary value problems of hyperbolic–parabolic type. A general investigation of admissible couplings between systems of higher order. Part 2: abstract quasilinear theory
Authors: Ebenfeld Stefan
Published: August 2002

This is the second part of an article that is devoted to the theory of non‐linear initial boundary value problems. We consider coupled systems where each system is of higher order and of hyperbolic or parabolic type.

Our goal is to characterize systematically all admissible couplings between systems of higher order and different type.

By an admissible coupling we mean a condition that guarantees the existence, uniqueness and regularity of solutions to the respective initial boundary value problem.

In part 1, we develop the underlying theory of linear hyperbolic and parabolic initial boundary value problems. Testing the PDEs with suitable functions we obtain a priori estimates for the respective solutions. In particular, we make use of the regularity theory for linear elliptic boundary value problems that was previously developed by the author. In part 2 at hand, we prove the local in time existence, uniqueness and regularity of solutions to the quasilinear initial boundary value problem (3.4) using the so‐called energy method. In the above sense the regularity assumptions (A6) and (A7) about the coefficients and right‐hand sides define the admissible couplings. In part 3, we extend the results of part 2 to non‐linear initial boundary value problems. In particular, the assumptions about the respective parameters correspond to the previous regularity assumptions and hence define the admissible couplings now. Moreover, we exploit the assumptions about the respective parameters for the case of two coupled systems. Copyright © 2002 John Wiley & Sons, Ltd.
An optimal shape design formulation for inhomogeneous dam problems
Authors: Chakib Abdelkrim , Ghemires Touria , Nachaoui Abdeljalil
Published: August 2002

In this paper, the flow problem of incompressible liquid through an inhomogeneous porous medium (say dam), with permeability allowing parametrization of the free boundary by a graph of continuous unidimensional function, is considered. We propose a new formulation on an optimal shape design problem. We show the existence of a solution of the optimal shape design problem. The finite element method is used to obtain numerical results which show the efficiency of the proposed approach. Copyright © 2002 John Wiley & Sons, Ltd.
Volterra series analysis of MMIC active baluns in HEMT technology
Authors: Reina‐Tosina Javier , Crespo Carlos , Alonso José I. , Pérez Félix
Published: August 2002

In this paper, two active‐balun structures based in a differential pair are proposed for the LO and output port of a double‐balanced mixer. A Volterra series approach based on an appropriate nonlinear model for active devices is followed to analyze the baluns, and closed‐form expressions are obtained for the evaluation of the gain and IMD. Criteria for the selection of design parameters are proposed. Results have been compared with alternative nonlinear circuit analysis methods, showing a good correspondence. An MMIC was implemented with HEMTs, demonstrating a good performance up to 10 GHz with a low LO level and power consumption. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 272–277, 2001.
Frequency tuning of a dual‐band dual‐feed PIFA antenna for future mobile communications
Authors: Karmakar Nemai C. , Heng Lee Chin , Teong Chew Boon
Published: August 2002

A dual‐band dual‐feed planar inverted‐F antenna (PIFA) is tuned with its physical parameters. It is demonstrated that the corner truncation of the patch is less sensitive to the resonant frequency than the patch lengths, but the corner truncation has no adverse effect on the radiation characteristics of the PIFA. This new technique yields quicker convergence of design frequency than the conventional patch length only tuning. Both theoretical and measured results of the input return loss and radiation patterns are presented. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 345–349, 2001.
Admittance parameter and unilateral power‐gain evaluation of GaN MESFET for microwave circuit applications
Authors: Singh Adarsh , Bose Srikanta , Gupta Mridula , Gupta R. S.
Published: August 2002

The admittance parameters and unilateral power gain of a nonself‐aligned GaN MESFET incorporating the parasitic elements along with gate‐length modulation are evaluated analytically in the present model. The cutoff frequency of the maximum available gain and the maximum frequency of oscillation are also determined in the model. For a GaN MESFET (4 μm×100 μm), the maximum frequency of oscillation is obtained to be about 2 GHz at zero gate bias. Using the present model, a unilateral power gain of 18 dB is predicted for the device. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 387–393, 2001.
Linear transmitter for a frequency‐hopping system using an adaptive predistortion linearizer
Authors: Kang Kyeongwon , Lee Sangseol
Published: August 2002

We have designed a linear power amplifier for a VHF frequency‐hopping (FH) transmitter using an adaptive predistortion linearizer. We employed an analog polynomial linearizer as a predistorter. In the predistortion linearizer, the recursive least squares (RLS) algorithm is employed for the optimization process to minimize the errors between the predistorter and postdistorter output signals. The experimental results of the FH transmitter demonstrate that the spectral spreading is reduced by 10 dB. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 457–460, 2001.
Finite elements and evolution programs for the CAD of broadband rectangular‐waveguideH‐plane matched loads
Authors: Monge F. J. , Esteban J. , Zapata J.
Published: August 2002

A full‐wave CAD tool has been implemented for the design ofH‐plane rectangular‐waveguide passive circuits. The software is based on the finite‐element method and evolution programs. The tool has been employed for the design of a load, optimized for both miniaturization and robustness with respect to fabrication tolerances. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 491–494, 2001.
Global modeling approach for prematched multifinger FET
Authors: Cetiner B. A. , Coccioli R. , Housmand B. , De Flaviis Franco , Itoh T.
Published: August 2002

A scalable lumped‐element equivalent circuit of a prematched, multifinger FET cell is proposed. The model is derived using a global modeling approach that exploits both circuit and full‐wave analysis, accounting for phase delay along gate and drain manifolds. The availability of such a model is useful to perform fast performance analysis and optimization of the prematching network. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 174–178, 2002.
Propagation characteristics of a plane wave in an unbounded nonlocal omega medium
Authors: Laforgia Michela , Toscano Alessandro , Vegni Lucio
Published: August 2002

In this paper, we derive the main propagation characteristics and the polarization properties of plane waves propagating inside a nonlocal bianisotropic medium. An original condition of circular polarizability is also derived and studied. The nonlocal omega medium can, in principle, be thought of as a spreading of a large number of nonlocal omega elements in an otherwise simple isotropic dielectric host medium. A nonlocal omega element is an electrically conducting microstructure having its stem parallel to the electric field at a given point, and its loop axis parallel to the magnetic field at another point that is somewhat displaced from the first along the direction of the wave propagation. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 183–186, 2002.
A new approach to standard Schwarz–Christoffel formula calculations
Authors: Costamagna Eugenio
Published: August 2002

A new approach to the computation of the Schwarz–Christoffel formula is presented, which was suggested by previous experience with various algorithms. It exploits the similarity between actual and image polygon geometries to implement singularity cancellations in a simple, yet effective way. Some results are presented for significant mapping examples, and they are briefly discussed. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 196–199, 2002.
Microstrip line on ground plane with closely spaced perforations—fringe fields and formulas by synthetic asymptote
Authors: Chow Y. L. , Wan K. L. , Sarkar T. K. , Kolundzija B.
Published: August 2002

Accurate CAD formulas of a microstrip line on a ground plane with periodic perforations, closely spaced and at quasistatic frequencies, are derived (error <5%) for applications in multilayer circuits such as an LTCC package. By a novel technique of a synthetic asymptote, the formula has just one arbitrary constant and two separate fringe‐field terms, from the strip and from the perforation. The separation gives clear physical insights into the effects of fringe fields on both the capacitance and inductance. One insight is that the effective dielectric constant may be made to rise above the actual dielectric constant of the substrate with perforation. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 201–204, 2002.
A new characteristic impedance perturbation method for finding attenuation constants
Authors: Changhong Liang , Long Li
Published: August 2002

A new characteristic impedance perturbation method for finding the attenuation constant α of transmission lines is presented, which not only clarifies some unclear concepts and applied limitations of the Wheeler incremental inductance rule, but which also can be extended to the TM mode transmission line in some cases. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 243–245, 2002.
Experimental investigations of microwave absorber with FSS embedded in carbon fiber composite
Authors: Sha Yanan , Jose K. A. , Neo C. P. , Varadan Vijay K.
Published: August 2002

In this paper, we present the experimental results of microwave absorbers with a frequency‐selective surface (FSS) embedded in an impedance‐graded carbon fiber (CF) composite. Samples with different FSS patterns embedded in CF composites are fabricated, and experiments are carried out to find the effects of embedded FSSs. It is found that both the FSS pattern and its location in the composite are critical for the reflection property of the sample. The results are compared with the theoretical predictions using the microgenetic algorithm (MGA), and are in good agreement. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 245–249, 2002.
Broadband T and shunt‐stub‐shaped microstrip‐fed slot antenna backed by a ground plane
Authors: Jang Yong‐Woong
Published: August 2002

In this letter, we experimentally study a T and a shunt‐stub‐shaped microstrip‐fed slot antenna backed by a ground plane. The proposed antenna has a frequency bandwidth of approximately 54% forS11≤−10 dB, centered around 2.5 GHz, with relatively good pattern characteristics. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 278–280, 2002.
A technique for the fast raster‐scanned motion of a small window for millimeter‐wave image acquisition
Authors: Soto José , Dávila J. A.
Published: August 2002

Here, we propose a technique that utilizes a Nipkow disk and an integrating sphere for the fast acquisition of millimeter‐wave images. This technique has the potential for quietly achieving video frame rates. A demonstration of the principle is made in the optical region. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 32: 440–442, 2002.
Null‐forming synthesis for cylindrical patch arrays
Authors: Niemand P. , Joubert J. , Odendaal J. W.
Published: August 2002

A synthesis method is modified to synthesize patterns with multiple nulls in an otherwise omnidirectional pattern for cylindrical microstrip patch arrays. The directive radiation pattern of a cylindrical microstrip patch is incorporated into the synthesis procedure. The effect of the number of array elements and interelement spacing is investigated. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 32: 442–446, 2002.
Fiber‐optic microdisplacement sensor based on diffraction grating
Authors: Das K. K. , Alam M. S.
Published: August 2002

A new multimode‐fiber‐based microdisplacement sensor using a diffraction grating component is proposed. An analytical model is presented for the proposed technique. The performance of the proposed technique is verified via computer simulation and experimentation. The experimental results agree quite well with the theoretical model. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 32: 446–449, 2002.
Broadband property and time‐domain application of general transmission‐line equations on microstrip low‐pass filter
Authors: Zhong Xiaolong , Liu Yaowu , Mei Kenneth K.
Published: August 2002

General transmission‐line equations based on the theory of differential equations [1] were introduced in [2] and [3]. The equations' dispersion characteristic of a microstrip low‐pass filter is studied. The parameters L, C, α, and β of general transmission‐line equations are found to be almost invariant to frequency in the passband of the microstrip low‐pass filter. By restoring current and voltage distributions with the use of equations in both frequency and time domains, the broadband property of these equations on the microstrip low‐pass filter is evident. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 123–126, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10250
Microstrip‐fed cavity‐backed slot antennas
Authors: Li Quan , Shen Zhongxiang , Teo Peng Thian
Published: August 2002

Two types of cavity‐backed slot (CBS) antennas fed by a microstrip line and operating at 5.8 GHz are described in this letter. One is a broadband linearly polarized CBS antenna, which can provide 34% bandwidth for a 10‐dB return loss. The other is a circularly polarized dual T‐shape CBS, which has 4% bandwidth for a 3‐dB axial ratio and a 15% bandwidth for a 10‐dB return loss. The simulated and measured results of both antennas are in good agreement. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 229–233, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10283
Analysis and design of cylindrical MICs with the use of a unified nonuniform cylindrical FDTD algorithm
Authors: Shen Guoqiang , Zhou Guoxiang , Chen Yinchao
Published: August 2002

In this Letter a unified nonuniform cylindrical finite‐difference–time‐domain (NU‐CFDTD) algorithm is utilized for the analysis and design of cylindrical millimeter‐wave integrated circuits (CMICs). It is shown that the algorithm is efficient in coding and flexible in treating various materials and discontinuities without adding computational resources compared with the traditional FDTD method. A visual mesh generator, CylinMesh, is developed to generate nonuniform meshes and input parameter files for practical cylindrical MIC analysis and design. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 256–262, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10291
Evaluation of polarization diversity schemes using dipole antennas
Authors: Kar Mohua , Wahid Parveen
Published: August 2002

This Letter presents analytical comparisons of properties such as output signal‐to‐interference‐plus‐noise‐ratios (SINR), correlation coefficients (ρe) and mean effective gains (MEG) for a H/V cross‐dipole scheme and a ± 45° slant dipole scheme. These polarization schemes, combined with space diversity, provide good results useful for wireless communications applications. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 277–284, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10296
Characterization of the radio wave propagation over mixed land–sea paths with the use of the forward‐backward method
Authors: López Jesús Alberto , Pino Marcos Rodríguez , Obelleiro Fernando
Published: August 2002

The objective of this Letter is to study the propagation over a nonhomogeneous surface composed of land and sea. To tackle this study, an integral‐equation (IE) formulation plus impedance boundary conditions (IBCs) are used. In order to solve the problem raised, an efficient algorithm based on the method of moments (MoM) is employed. Numerical results show that the field strength over a mixed‐path terrain, beyond the coastline, is larger or smaller than the one over a homogeneous surface, depending on the receiver height. Besides the reception height, the effect is characterized by other parameters, such as the transmitter antenna height, the surface geometry, the frequency, and the electrical properties of the soil. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 287–292, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10298
Practical double‐channel variable polarization system with short switching time
Authors: Che Wenquan , Sha Kan , Yung Edward K. N. , Wen Junding
Published: August 2002

The design consideration of a double‐channel variable polarization system is investigated in this Letter, and the important components in the system are introduced. In addition, the experimental results of several components and indexes of the system are presented: the polarization switching time of the double‐channel variable polarization system is 3 μs; the peak and average power capability are 14 kW and 80 W, respectively; the polarization isolation is 20 dB; the ellipticity is 1 dB. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 292–294, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10299
Highly decoupled planar dipoles in an air waveguide backed by a perfect‐magnetic‐conductor plate above the earth
Authors: Je Do‐Heung , Ra Jung‐Woong
Published: August 2002

Two planar dipoles inside an air waveguide backed by a perfect‐magnetic‐conducting (PMC) plane are suggested as a highly isolating transmitting‐and‐receiving subsurface continuous‐wave‐radar antenna. Its coupling mechanism is shown to be the contributions of the evanescent lateral wave and the leaky wave. A design finding the optimum frequency and its bandwidth yielding the minimum mutual coupling less than −60 dB is shown. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 303–306, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10302
Microwave noise performance of metamorphic InP/In0.53Ga0.47As/InP DHBT on GaAs substrates
Authors: Xiong Yong Zhong , Ng Geok‐Ing , Wang Hong , Fu Jeffrey S.
Published: August 2002

The microwave noise performances of metamorphic (MM) InP/In0.53Ga0.47As/InP double‐heterojunction bipolar transistors (DHBTs) on GaAs substrate are investigated for the first time. The noise figures and associated gains of the device with an emitter size of 5 × 5 μm2are studied in the frequency range of 2–10 GHz. The variations of minimum noise figure at different collector currents are presented. At 2 GHz, the best minimum noise figure (FMIN)of 2.1 dB with an associated gain(GASS) of 12.7 dB have been achieved atVCE= 1.5 V andIC= 0.3 mA (1.2 kA/cm2). For comparable size and current density, these results show noise performance comparable to those of reported lattice‐matched InP HBT at lower frequency (∼2 GHz).© 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 306–308, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10303
Computation of radar cross section of jet engine inlets
Authors: Liu Jian , Dunn Eric , Baldensperger Pierre , Jin Jian‐Ming
Published: August 2002

The finite element‐boundary integral (FE‐BI) method was used to calculate the radar cross section (RCS) of jet engine inlet geometries. Comparisons of numerical results with measurements are shown to demonstrate the capability of the method. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 322–325, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10309
Compact dual‐frequency PIFA with a chip‐inductor‐loaded rectangular spiral strip
Authors: Yeh Shih‐Huang , Wong Kin‐Lu
Published: August 2002

By loading a chip inductor of suitable inductance (about 12 nH or less) to a planar inverted‐F antenna (PIFA) with a shorted rectangular spiral strip, the frequency ratio of the antenna's first two resonant frequencies can be controlled, which makes dual‐frequency operation with a desired frequency ratio easy to achieve. In addition, with the use of a shorted rectangular spiral strip, the proposed PIFA, has compact dimensions for a fixed dual‐frequency operation. Design examples of the proposed PIFA with a compact size of 7.2 × 10 × 26 mm3 to achieve dual‐frequency operation at about 900 and 1800 MHz are presented. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 394–397, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10333
Distributed sources on coplanar waveguides: Application to photomixers for THz local oscillators
Authors: Pasqualini Davide , Neto Andrea , Wyss Rolf A.
Published: August 2002

An electromagnetic model and a design of a photomixer‐based local oscillator for THz frequencies is presented. The theoretical investigation is on the nature of the fields excited in the coplanar waveguide (CPW) by impressed distributed sources. On this basis a CPW and antenna design is presented to optimize the radiated output power given the photoinduced rf currents. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 430–435, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10342
Influence of randomly varying birefringence on dark soliton transmission and its suppression
Authors: Li Hong , Huang Dexiu
Published: August 2002

The influence of randomly varying birefringence on dark soliton transmission is investigated by numerical simulation. The results show that randomly varying birefringence leads to a soliton frequency shift, causes radiation waves, and disrupts the stability of dark soliton transmission. The splitting of a soliton pulse may appear because of the strong randomly varying birefringence. Nonlinear gain can be used to effectively suppress the influence. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 107–109, 2001.
Optical time‐spreading/frequency‐hopping differential OOK–CDMA system
Authors: Wan Sheng Peng , Hu Yu
Published: August 2002

A new optical time‐spreading/frequency‐hopping differential CDMA (TS/FH CDMA) system is proposed in this paper. It uses new codes called prime/OOC codes as address codes. Fast optical frequency hopping and large capacity can be implemented with the system. By assigning two orthogonal codes for one user, and using these two codes to encode 1 and 0, respectively, the receiver can use differential detection. If they are balanced well between the 1‐branch and 0‐branch, the proposed system can effectively abate multiaccess interference (MAI), background noise, detector noise such as dark current, leakage current, and thermal noise, etc. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 125–128, 2001.
An accurate computation of Green's functions for multilayered media in the near‐field region
Authors: Abdelmageed Alaa K. , Mohsen Adel A. K.
Published: August 2002

The discrete complex image method is one of the most efficient techniques used to evaluate the Green's functions of multilayered media. The usual extraction of surface waves may limit the validity of this method in the near‐field region. The aim of this work is to handle this problem such that the representation is valid for all field regions. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 130–131, 2001.
Conical dielectric resonator antennas excited by a coaxial probe
Authors: Kishk Ahmed A. , Glisson A. W. , Yin Yan
Published: August 2002

Dielectric resonator antennas of conical shapes are experimentally examined. The dielectric cone resides above a ground plane, and is excited by a coaxial probe. Two configurations of the cone are tested: one with the wide base placed on the ground plane, and the other with the cone inverted on the ground plane. Results show that the inverted cone achieves a wider bandwidth. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 160–161, 2001.
Low‐loss wideband microwave coaxial bias T
Authors: Möttönen V. S. , Piironen P. , Räisänen A. V.
Published: August 2002

A low‐loss and well‐matched wideband microwave coaxial bias T is presented. A simple structure makes the bias T easy and low cost to design and fabricate. Test results demonstrate the excellent performance of the bias T. The measured return loss is better than 30 dB, and the insertion loss is close to 0.1 dB over awide frequency range. The 0.5 dB insertion loss bandwidth is 3–16 GHz. Furthermore, the RF isolation is more than 30 dB. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 236–238, 2001.
Application of adaptive basis functions for a diagonal moment‐matrix solution of two‐dimensional field problems—TE case
Authors: Waller Marsellas L. , Rao Sadasiva M.
Published: August 2002

In this work, we present the application of specially constructed adaptive basis functions to generate a diagonal matrix in the method‐of‐moments solution procedure for the calculation of a scattered electromagnetic field from arbitrarily shaped two‐dimensional cylinders excited by a transverse electric incident electromagnetic wave. Several numerical examples are also presented to validate the new method. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 270–273, 2001.
Simplified calculations on some common passive microwave networks
Authors: Hallbjörner Paul
Published: August 2002

Calculating the required line impedances for a specified performance on passive microwave networks like directional couplers and power dividers/combiners is a well‐known problem. A simple method is presented that uses the net power flow in the transmission lines of the network, together with power conservation at the intersections. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 285–288, 2001.
A comparison of dual‐band spur‐line printed antennas for handheld terminals
Authors: Martínez‐González Antonio , Sánchez‐Aguilar Ma. Angeles , Martínez‐Vazquez Marta , Sánchez‐Hernández David
Published: August 2002

Recent breakthroughs in mobile phone technology are focusing on new techniques that allow the compact integration of dual‐band printed antennas into handsets with an increase in their inherent narrow bandwidth. In this letter, novel rectangular, circular, triangular, hexagonal, and bow‐tie‐shaped spur‐line dual‐band printed structures have been designed, measured, and compared. Although a second resonant frequency is obtained, it has been clearly made evident that spur‐line filter techniques are unable to obtain broad‐bandwidth elements, unless they can be combined with other methods. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 205–207, 2001.
A push–pull digital optical switch (DOS) in polymer using truncated‐structural X‐branches (TSXB)
Authors: Pandit M. K. , Chan H. P. , Chiang K. S. , Ghosh S. , Das A. K.
Published: August 2002

We report the design and simulation performance of a digital push–pull switch based on a wide‐angle, asymmetric X‐junction that we recently proposed (truncated‐structural X‐branch). At a full‐branching angle of 1.2°, the crosstalk and (straight‐port) transmission at the zero‐voltage state were −19 and −0.92 dB, respectively. In the switched state, they are −17.45 and −1.06 dB, respectively. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 208–211, 2001.