bluuebunny/crossref_metadata_2025 huggingface dataset:
An analysis of diffractive lenses at millimeter wavelengths
Authors: Dou W. B. , Wan C.
Published: August 2002

The fields in the focal space of two types of a phase‐only diffractive lens, which is illuminated by a plane wave, are analyzed with the FDTD method and the Stratton–Chu formula. Both oblique and perpendicular incidence are considered. The diffraction efficiency is calculated. The results of experiments carried out to verify the correctness of the calculation are presented. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 396–401, 2001.
Simultaneous extrapolation of RCS in both angular and frequency domains based on AWE technique
Authors: Tong Chuangming , Hong Wei , Yuan Naichang
Published: August 2002

The radar cross section (RCS) of a target is dependent on frequency as well as angle. The method of moments (MoM) in conjunction with the asymptotic waveform evaluation (AWE) technique is applied to predict the monostatic RCS of an arbitrarily shaped two‐dimensional cylinder in both the frequency and angular domains simultaneously. The electric‐field integral equation (EFIE) of the cylinder is solved using the MoM to obtain the equivalent current on the cylinder. In the AWE technique, the equivalent current at a given frequency and angle is expanded in the desired frequency and angle band in a binomial Taylor's series. The binomial Taylor's series coefficients are then matched via the Pade approximation to a rational function. Using the rational function, the current is obtained at any frequency and angle within the interesting frequency and angular range, which is in turn used to calculate the RCS of the cylinder. The use of this method for extrapolation of the RCS has at least two significant advantages: one being the obtained RCS analytical formulas, and the other being a significant decrease in the amount of time required for modeling problems with large computational domains. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 290–293, 2002.
A gain‐clamped erbium‐doped fiber amplifier (GC–EDFA) for WDM optical packet‐switching system
Authors: Yang C. R. , Hwang H. Y. , Hong H. H.
Published: August 2002

The use of dual‐stage gain‐clamped erbium‐doped fiber amplifier (GC–EDFA) having a pump laser diode and 16‐channel wavelength‐division multiplexing (WDM) of 0.8 nm spacing in the C‐band of 1545–1560 nm wavelength was demonstrated in a burst packet‐mode optical switching system through an experimental setup. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 316–319, 2002.
Singular behavior of the Berenger and leaky‐modes series composing the 2D Green's function for the microstrip substrate
Authors: Rogier Hendrik , De Zutter Daniël
Published: August 2002

The singular behavior of the modal expansions is examined in Berenger and leaky modes for the Green's functions GA and GV of a 2D microstrip substrate. When the excitation point approaches the source point, and both are lying in the microstrip substrate, the Green's function exhibits a singularity that corresponds to the open configuration without a perfectly matched layer. This observation remains valid when one or both points are lying on the substrate–air interface, unless GA is being considered for a nonmagnetic (μr = 1) substrate. In the latter case a different singularity is obtained when both excitation point and source point are lying on the interface. That singularity is of a higher order and depends on the characteristics of the PML. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 87–93, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10244
Stable actively mode‐locked fiber‐ring laser with a large dispersion cavity
Authors: Ying Hua , Jinlong Yu , Xiaohong Ma , Yongshi Chen , Enze Yang
Published: August 2002

The performance of an actively mode‐locked fiber‐ring laser with large dispersion cavity is described. The laser output characteristics remain stable for long periods of time without external adjustment. The very stable, transform‐limited optical pulses at a repetition rate of 10 GHz were obtained successfully in this laser over wavelengths ranging from 1530 to 1556 nm. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 126–128, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10251
Corrections to “Time‐domain electric‐field integral equation with central finite difference”
Authors: Jung Baek Ho , Sarkar Tapan Kumar
Published: August 2002

Originally published Microwave Opt Technol Lett 31: 429–435, 2001 © 2002 Wiley Periodicals, Inc., 33: 148, 2002. DOI 10.1002/mop.10257
A low‐profile, bent and shorted planar monopole antenna with reduced backward radiation for mobile phones
Authors: Yeh Shih‐Huang , Chen Yen‐Yu , Wong Kin‐Lu
Published: August 2002

By bending a planar monopole into an inverted‐U shape and short‐circuiting one end to the ground, a novel low‐profile monopole antenna with reduced backward radiation is obtained. The proposed antenna is easily fed by using a capacitively coupled feed, and is suitable for applications in mobile phones for providing reduced radiation toward the user's head. A prototype of the proposed antenna for DCS operation (1710–1880 MHz) is constructed, and measured and simulated results are presented. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 146–147, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10258
A double frequency 180° lumped‐element hybrid
Authors: Giannini Franco , Scucchia Lucio
Published: August 2002

In this letter design formulas for the development of an unusual 180° hybrid working at two distinct frequencies are provided. In particular, the design formulas of a lumped‐element rat race are considered. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 247–251, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10288
Resonant frequency of a shorted circular patch with the use of a modified impedance expression for a metallic post
Authors: Chakravarty Tapas , De Asok
Published: August 2002

The accuracy of the cavity‐model analysis of a shorting post loaded circular microstrip antenna depends strongly on the exact modeling of the metallic post in the radial guide. This Letter presents an empirically generated expression for the impedance of such a post. The expression takes the edge effects into account, and its use results in a very accurate prediction of resonant frequency for all the eigenmodes of a shorting post loaded circular patch. The theoretical model is extensively compared with measured/simulated results and shows excellent agreement. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 252–256, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10290
A new microstrip patch antenna for mobile communications and bluetooth applications
Authors: Paul Binu , Mridula S. , Aanandan C. K. , Mohanan P.
Published: August 2002

A compact multiband planar octagonal‐shaped microstrip antenna simultaneously suitable for mobile communication and blue tooth application is presented. The antenna provides sufficient isolation between the two operating bands and an area reduction of ≈29 % with respect to a circular patch operating in the same band. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 285–286, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10297
Estimation of the radiation patterns of diverging/focusing type of leakywave antennas
Authors: Ohtera Isao
Published: August 2002

In this article, an extension of “field regions” to estimate simply and qualitatively the feature of the radiation patterns for the diverging/focusing systems with the inherent phase error on their aperture is discussed and applied to the curved leakywave structure. The result will be especially useful relating to the design of the curved leakywave structure in the microwave/mm‐wave applications. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 358–360, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10321
Broadband dual‐frequency coplanar probe‐fed patch antenna for GSM/DCS/PCS base stations
Authors: Chang Fa‐Shian , Wong Kin‐Lu
Published: August 2002

This article presents a novel air‐substrate patch antenna backed by a U‐shaped ground plane and excited by a coplanar probe feed for broadband dual‐frequency operation. The obtained impedance bandwidth (1:1.5 VSWR) of the antenna's lower band reaches 388 MHz (or nearly about 50% referenced to the center frequency at 787 MHz) and covers the GSM band (880–960 MHz); the upper band has a bandwidth as large as 575 MHz (or about 30% referenced to the center frequency at 1950 MHz) and covers both the DCS band (1710–1880 MHz) and the PCS band (1850–1990 MHz). Good broadside radiation characteristics for the proposed antenna have also been observed. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 370–372, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10325
Compact dual‐frequency dual‐polarized slotted microstrip patch antenna
Authors: Binoy G. S. , Aanandan C. K. , Mohanan P. , Vasudevan K.
Published: August 2002

A new design for the compact single‐feed dual‐frequency operation of a slotted square microstrip antenna is demonstrated. The antenna generates two distinct operating frequencies with different polarization planes and broad radiation characteristics. The antenna has the added advantage of an antenna size reduction as large as ∼61 and 45% in comparison to the standard rectangular patch for the above two frequencies. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 60–62, 2001.
Increasing the radiation efficiency of cellular telephones by controlling the nearby electromagnetic field around a human model
Authors: Hankui Eiji , Hashimoto Osamu
Published: August 2002

A new approach for increasing the radiation efficiency of cellular telephones, which controls the nearby magnetic field incident to a human phantom surface, has been proposed. To control the near field, a small magnetic plate is used as an electromagnetic perturbator, and it is placed near the antenna on the human side. Using the finite‐difference time‐domain (FDTD) method, it is clarified that our approach using the magnetic plate improves the radiation efficiency in practical usage (i.e., when a human phantom model is located near the antenna) by the effect of the magnetic plate, while keeping the antenna performance in the case of free space (i.e., without a human model) almost the same. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 104–107, 2001.
Comparison of path loss and time‐delay spread in regular and chaflane street corners for microcellular communications
Authors: Luis‐Rodríguez Jorge , Juan‐Llácer Leandro
Published: August 2002

A ray‐tracing model based on the application of the uniform theory of diffraction (UTD) and geometrical optics (GO) for modeling the propagation in microcellular urban scenarios has been implemented. A comparison with the simulation of published results validates our model. This model has been used to analyze some propagation characteristics (path loss and rms delay spread) in two street‐corner environments—regular and chaflane street corners. The study of the environments of the two corners shows that differences in the predictions are basically caused by the rays reflected on the walls of the chaflane corners. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 139–142, 2001.
Three‐port rectangular microstrip unequal power divider and coupler
Authors: Ray Sudhabindu , Kumar Girish
Published: August 2002

A new configuration of a three‐port rectangular microstrip power divider and coupler has been proposed. It can easily implement unequal power division of a large ratio, i.e., the power coupled to the third port can vary from −3 to −26 dB. The configuration has been analyzed using a transmission‐line model, as well as method‐of‐moments‐based software. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 219–223, 2001.
Design of a 35 GHz microstrip tapered‐array antenna with wide detection range
Authors: Lee Youngju , Jung Myoung Suk , Park Wee Sang , Choi Jae Hyun
Published: August 2002

This paper describes a microstrip array antenna designed to operate at 35 GHz, and used as a position detector of moving targets. To obtain a wide detection range, the array was arranged to have a relatively narrower beamwidth in the elevation plane compared to the beamwidth in the azimuthal plane. This was achieved by aligning the electric‐field plane of each element to the array axis. Employing a 3 dB tapered feed network, the array has a sidelobe level of less than −20 dB, while retaining a wide azimuthal beamwidth. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 276–280, 2001.
Gain‐enhanced L‐band EDFA employing a 1550 nm band ring laser
Authors: Mahdi M. A. , Ahmad H.
Published: August 2002

A unique method of upgrading a C‐band EDFA into a highly efficient L‐band EDFA is presented, incorporating a gain‐clamped amplifier (ring laser) that acts as a gain‐improving element in an unpumped erbium‐doped fiber. A gain improvement of 17.8 dB and noise figures <4.0 dB are measured for optimum settings. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 282–284, 2001.
A floating attachment mode for arbitrary wire‐to‐surface connections
Authors: Taboada J. M. , Rodríguez J. L. , Obelleiro F.
Published: August 2002

A floating attachment mode is presented here in order to improve the electromagnetic analysis of wire antennas attached to arbitrary surfaces when using the method of moments (MoM). This attachment mode overlaps the surface modes, allowing us to place the wire‐to‐surface connection at any point, independently of the surface mesh, even near or at geometrical discontinuities. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 102–105, 2001.
Distributed inductance and resistance per‐unit‐length formulas for VLSI interconnects on silicon substrate
Authors: Ymeri H. , Nauwelaers B. , Maex Karen
Published: August 2002

A new analytic model is presented (the model is based on the induced current density distribution inside silicon substrate) to calculate the frequency‐dependent distributed inductance and the associated distributed series resistance of silicon semiconducting VLSI interconnects. The validity of the proposed model has been checked by a comparison with CAD‐oriented modeling methodology in conjunction with a quasi‐TEM spectral‐domain approach. It is found that the silicon semiconducting substrate skin effect must be considered for the accurate prediction of the high‐frequency characteristics of VLSI interconnects. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 302–304, 2001.
Optical generation of microwave signals using a directly modulated semiconductor laser under modulated light injection
Authors: Seo Young‐Kwang , Kim Ajung , Kim Jung‐Tae , Choi Woo‐Young
Published: August 2002

We have experimentally demonstrated a new optical microwave signal generation scheme using semiconductor lasers in a master–slave configuration, in which both lasers are directly modulated. The sidebands of the slave laser are locked to those of the master laser by the simple control of the applied modulation power. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 369–370, 2001.
Development of a very low‐cost suspended‐substrate strip‐line configuration using nonconventional material
Authors: Karmakar Nemai Chandra
Published: August 2002

A very low‐cost suspended‐substrate strip‐line configuration is developed using packaging foam and a very thin Cu‐clad glass–epoxy laminate. The material characteristics, such as effective dielectric constant, attenuation, and loss tangent, have been determined accurately using two different transmission measurement techniques. A λ/4‐long 50 Ω transmission line is fabricated on the developed configuration, and tested successfully. The measured insertion loss is less than 0.15 dB, and the return loss is greater than 35 dB over the entire L‐band. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 413–416, 2001.
Radar target recognition using least squares estimate
Authors: Lee Joon‐Ho , Kim Hyo‐Tae
Published: August 2002

A new scheme for radar target discrimination which is independent of an aspect angle is proposed in the frequency domain. A system of linear equations is constructed using the frequency response of an unknown target and stored natural frequencies of a particular target. Whether an unknown target is a particular target or not is determined using the defined least squares estimate or the normalized estimation error. The validity of the method is shown using the method‐of‐moments (MM) frequency response. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 427–434, 2001.
Dielectric loss of multilayer coupled microstrip line using SLR formulation
Authors: Verma A. K. , Nasimuddin  , Bhupal A.
Published: August 2002

The single‐layer reduction (SLR) formulation is presented to compute the dielectric loss of even–odd modes of a multilayer coupled microstrip line. Results are compared against the results of full‐wave analysis with a maximum deviation of 2% for the wide range of parameters. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 65–67, 2001.
Research on dynamics in modulation‐doped GaAs/AlxGa1−xAs heterostructures
Authors: Li Guo‐Hui , Zhou Shi‐Ping , Xu De‐Ming
Published: August 2002

We discuss the dynamics of the forced modulation‐doped AlxGa1−xAs heterostructure device governed by the coupled differential equations, which is operative in the state far from thermodynamic equilibrium. Biased with an appropriate dc field, the system exhibits two states: spontaneous current oscillation and fixed points. Under an ac driving force imposed on a dc bias, the dynamical system shows the expected characteristics of frequency locking, quasiperiodicity, and chaos, which are sensitive to the amplitude and frequency of the external applied microwave field. In particular, the basins of attraction of both an ordinary attractor and a chaotic attractor are presented. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 93–95, 2001.
Design and fabrication of a miniature monoblock bandpass filter using high‐permittivity ceramic
Authors: Weng Min‐Hung , Liang Tsorng‐Juu , Huang Cheng‐Liang
Published: August 2002

A miniature monoblock bandpass filter with combline‐type, quarter‐wavelength, and capacitive coupling is investigated. The coupling analysis and equivalent circuit consist of the transmission lines, and lumped elements are presented to predict the filter performance. A filter design technique based on the results of the equivalent‐circuit parameters is described. A miniature monoblock bandpass filter using (Zr0.8, Sn0.2)TiO4 ceramics is fabricated at a center frequency of 1600 MHz. Excellent experimental results of the fabricated filter measured by an HP8510B network analyzer verify the design specification. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 95–97, 2001.
Optimized power dividers based on E‐plane T‐junctions
Authors: Gómez Ignacio , De Haro Leandro , Galocha Belen , Besada Jose L.
Published: August 2002

A power divider is an essential component in the design of antenna feed networks for satellite applications. Asymmetrical E‐plane T‐junctions exhibit good electrical performances and a simplified mechanical process of construction. This paper study improved structures on this baseline. These are analyzed and optimized. Two different analysis methods have been used in order to check their results. Also, the results have been verified with commercial software. Both methods are based on the GSM (general scattering matrix) and modal analysis technique. The optimization process, based on quasi‐Newton approximations, allows obtaining, for instance, a power divider with five ports (four T‐junctions cascaded) with good electrical performances. A tolerance analysis has been carried out in order to study the feasibility of power dividers. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 118–123, 2001.
Need for a cooperative study: Pulmonary langerhans cell histiocytosis and its management in adults
Authors: McClain Kenneth L. , Gonzalez Jorge Mario , Jonkers Rene , De Juli Emanuela , Egeler Maarten
Published: August 2002

Background

Pulmonary involvement with Langerhans cell histiocytosis (LCH, formerly known as histiocytosis‐X) presents as an interstitial process in children and adults either with or without symptoms. In contrast to other manifestations of LCH, most patients with pulmonary disease are adults.

Procedures

We reviewed the literature on pulmonary LCH to determine what were the clinical presentations, prognostic variables, and treatment options for this disease.

Results

Although there are spontaneous remissions, a large number of patients have progressive pulmonary deficiency and experience significant morbidity if not mortality from the disease. The efficacy of steroid versus chemotherapy in halting the process remains controversial, even if smoking is taken into consideration.

Conclusions

A multicenter study of therapy for pulmonary LCH is the obvious answer to this dilemma. We propose that interested centers organize via the Histiocyte Society to plan and execute such a trial. Med Pediatr Oncol 2002;39:35–39. © 2002 Wiley‐Liss, Inc.
Antibody formation during intravenous and intramuscular therapy with Erwinia asparaginase*
Authors: Albertsen Birgitte Klug , Schrøder Henrik , Jakobsen Preben , Avramis Vassilios I. , Müller Hans‐Joachim , Schmiegelow Kjeld , Carlsen Niels T.
Published: August 2002

Background

Determination of the frequency of antibody formation during first and second exposure to Erwinia asparaginase after i.v. and i.m. administration.

Procedure

Thirty‐nine children with newly diagnosed acute lymphoblastic leukemia (ALL) were included in this prospective study. Antibodies were determined (ELISA method) in plasma from these patients on specific days during and after therapy with 30,000 IU/m2 i.v. or i.m. every day for ten days during the induction phase (first exposure). For 19 children, antibodies were measured in plasma during and after the re‐induction phase (second exposure) following treatment with 30,000 IU/m2 i.v. or i.m. twice a week for two weeks (Mondays and Thursdays). On the same days of therapy, enzyme activity (spectrophotometric method) and the concentration of asparagine (HPLC) was determined.

Results

During the first exposure, none of the patients developed anti‐Erwinia asparaginase antibodies. During the second exposure, one patient (1 of 8 patients) treated intravenously developed antibodies, which were associated with disappearance of enzyme activity and reappearance of asparagine. Three of eleven patients developed antibodies of pharmacokinetic importance after i.m. therapy. None of the children had any clinical symptoms of hypersensitivity.

Conclusions

The formation of antibodies and subsequently altered pharmacokinetics of Erwinia asparaginase seemed to be of importance only during a second period of asparaginase therapy. Med. Pediatr. Oncol. 2002;38:310–316. © 2002 Wiley‐Liss, Inc.
A fast magnetic resonance imaging technique for children with mediastinal lymphoma: Work in progress
Authors: Wagner Maren , Kuth Rainer , Deimling Michael , Rascher Wolfgang , Rupprecht Thomas
Published: August 2002

Background

Mediastinal lymphoma often presents as a large tumor at the time of diagnosis. Usually chest X‐ray filming is the first imaging modality and it is used for routine follow‐up during the course of the disease. A new and very fast MRI technique has been developed at our center as an alternative. Results in three patients with mediastinal lymphoma during a pilot study are promising.

Procedure

After diagnosis the above patients were additionally investigated in a 0.2 T low‐field MR‐scanner by a modified true FISP sequence (see text) with an acquisition time of 3.6–4.6 sec. Follow‐up was performed by both, X‐ray filming and MRI. After diagnosis the patients, again, had both X‐ray filming and MRI investigation for follow‐up: one patient 2, one patient 3, and one patient 5 times. Images were evaluated and compared by two pediatric radiologists.

Results

Total investigation times for radiography and MRI were comparable. The tumor was better visualized by MRI on seven of nine images and gave additional information about the structure and the localization of the tumor as well as concomitant problems such as pericardial effusion.

Conclusions

True FISP MRI may prove to be a good alternative to X‐ray filming in the diagnosis and follow‐up of mediastinal lymphoma. Med Pediatr Oncol 2001;37:532–536. © 2001 Wiley‐Liss, Inc.
Distribution of the methyl radical adduct of N‐benzylidene‐1‐diethoxyphosphoryl‐1‐methylethylamine N‐oxide‐type nitrones in water–sodium dodecyl sulfate micelles: an electron paramagnetic resonance spin trapping study
Authors: Rizzi Cécile , Lauricella Robert , Bouteiller Jean‐Claude , Roubaud Valérie , Tuccio Béatrice
Published: August 2002

The behavior of the methyl radical adduct of six β‐phosphorylated nitrones in the N‐benzylidene‐1‐diethoxyphosphoryl‐1‐methylethylamine N‐oxide series in the presence of sodium dodecyl sulfate (SDS) micelles was followed by electron paramagnetic resonance spectroscopy. Except when the highly hydrophilic trap 4‐PyOPN (2) was used, all the adducts were found to partition significantly between micelles and the bulk aqueous phase. The average correlation time τ of the exchange of spin adducts between SDS micelles and water was found to be in the range 5 × 10−8—4 × 10−7 s, which is in the region of the life time of an SDS monomer in the micelle structure. In each case, the adduct affinity for the micelles has been quantified by evaluating its micelle–water distribution coefficient Kd. Copyright © 2002 John Wiley & Sons, Ltd.
General model of assignment of the relative stereochemistry in the Nicholas reaction products resulting from chiral dicobalthexacarbonyl‐1‐alkoxy‐propargylium cations
Authors: Montaña Angel M. , Cano Montserrat
Published: August 2002

The Nicholas reaction of chiral 1‐alkoxy‐dicobalthexacarbonyl‐propargylium cations with linear and/or cyclic silyl enol ethers resulted in the formation of two pairs of diastereoisomers (syn‐1, syn‐2 and anti‐1, anti‐2), depending on the relative stereochemistry of the two new stereocenters formed in the reaction products. Here, we present a model to establish the relative stereochemistry of those stereocenters on the basis of a correlation of their 1H and 13C NMR spectra, together with their conformational analysis and a study of the stereoelectronic interactions conditioning the chemical shifts and coupling constants. The importance of this method is based on its applicability to the assignment of the relative stereochemistry of non‐separable components of a diastereomeric mixture or, when diastereomers are non‐crystallizable oily products, not suitable for X‐ray diffraction analysis. Copyright © 2002 John Wiley & Sons, Ltd.
1H and 13C NMR spectral characterization of some antimalarial in vitro 2,4‐diamino‐10‐methylpyrimido[4,5‐b]‐5‐quinolone derivatives
Authors: Charris Jaime E. , Domínguez José N. , Gamboa Neira , Angel Jorge , Piña Nolberto , Guerra Mayamarú , Michelena Elba , López Simón E.
Published: August 2002

We report the 1H NMR and 13C NMR chemical shifts and J(H,H), J(H,F) and J(C,F) coupling constants of 13 2,4‐diamino‐10‐methylpyrimido[4,5‐b]‐5‐quinolone derivatives, some of them with moderate activity against Plasmodium falciparum in vitro. They were characterized and assigned on the basis of 1H, 13C and 13C–1H (short‐ and long‐range) correlated spectra. Copyright © 2002 John Wiley & Sons, Ltd.
NMR analyses of two isomeric cyclobutanes from a [2 + 2] photocycloaddition
Authors: Minter David E. , Winslow Christopher D. , Watson William H. , Bodige Satish
Published: August 2002

Complete 1H and 13C NMR assignments are reported for two isomeric cyclobutanes generated from the photochemical [2 + 2] cycloaddition of N‐methylisocarbostyril and 4‐methoxy‐3‐buten‐2‐one. The reaction is 100% regioselective and demonstrates the potential synthetic utility of de Mayo type reactions using an isocarbostyril and a stable β‐dicarbonyl enol derivative. Copyright © 2002 John Wiley & Sons, Ltd.
Structural elucidation of bipyridine helicate complexes and their precursors by NMR spectroscopy
Authors: Annunziata Rita , Benaglia Maurizio , Famulari Antonino , Raimondi Laura
Published: August 2002

1H and 13C NMR assignments of bipyridine helicate complexes and their precursor ligands were achieved using gradient‐based homo‐ and hetero‐correlated 2D experiments. The observed trends in 1H and 13C chemical shift variations [Δδ(H) and Δδ(C)], on passing from the ligands to the complexes, are accounted for on the basis of MO evaluation of atomic charges. Copyright © 2001 John Wiley & Sons, Ltd.
1H and 13C NMR assignments of 2‐oxo‐2H‐1‐benzopyran‐3‐acyl and ‐3‐amide derivatives
Authors: Martínez‐Martínez F. J. , Padilla‐Martínez I. I. , Trujillo‐Ferrara J.
Published: August 2002

1H and 13C NMR spectral data for seven 2‐oxo‐2H‐1‐benzopyran‐3‐carboxamide and two 2‐oxo‐2H‐1‐benzopyran‐3‐amide derivatives are reported. The chemical shift assignments were based on two‐dimensional experiments. Copyright © 2001 John Wiley & Sons, Ltd.
1H,117 Sn J‐HMBC spectroscopy as a tool for the determination of long‐range nJ (1H,117Sn) coupling constants in the investigation of intramolecular donor–acceptor interaction in [2‐(N,N‐dimethylaminomethyl)phenyl]stannanes
Authors: Biesemans M. , Martins J. C. , Willem R. , Lyčka A. , Růžička A. , Holeček J.
Published: August 2002

1H, 117Sn J‐HMBC spectroscopy was implemented as a tool for the determination of long range nJ(1H, 117Sn) coupling constants of [2‐(N,N‐dimethylaminomethyl)phenyl]stannanes, ArR1R2R3Sn or Ar2R1R2Sn, where R1, R2 and R3 are Ph or n‐Bu, and/or Cl or Br. It is demonstrated that coupling constants which are too small to be measured from multiplet splittings in the 1H or 117Sn spectra can be measured from the development of the sine modulation of the intensity of the 1H, 117Sn HMBC correlation peaks as a function of the incremented preparation time of the 1H,117Sn HMBC pulse sequence. It is examined whether such couplings can be used as straightforward indicators for the existence of intramolecular nitrogen–tin interactions. While some coupling constants are shown to depend on the strength of the above‐mentioned interaction, it is also demonstrated that 6J(1H,117Sn) coupling constants between the N‐methyl groups and the tin nucleus can be observed even in structures where no nitrogen–tin interactions are possible. Copyright © 2001 John Wiley & Sons, Ltd.
Complexation of selenium to (R)‐Rh2(MTPA)4: thermodynamics and stoichiometry
Authors: Duddeck Helmut , Malik Shahid , Gáti Tamás , Tóth Gábor , Choudhary Muhammad Iqbal
Published: August 2002

Variable‐temperature 1H and 77Se NMR data for 3‐phenylselenenyl‐1‐phenyl‐1‐propene (1) in the presence of Rh2(MTPA)4 (Rh*) prove that the equilibria are strongly shifted towards the adduct Rh*···1; free selenide molecules cannot be detected as long as uncomplexed rhodium atoms are available. In the case of excess Rh*, both 1 : 2 and 1 : 1 adducts (Rh* vs 1) are formed, and the latter is slightly favoured. With excess selenide, the system strongly favours the complexation of two selenide molecules (1 : 2 adduct), i.e. one at each rhodium atom. In this situation, intermolecular selenide exchange can be monitored by variable‐temperature 1H NMR spectroscopy and the energy barrier is estimated to be 54–55 kJ mol−1. Copyright © 2001 John Wiley & Sons, Ltd.
Developmentally‐regulated changes of Xist RNA levels in single preimplantation mouse embryos, as revealed by quantitative real‐time PCR
Authors: Hartshorn Cristina , Rice John E. , Wangh Lawrence J.
Published: August 2002

Xist RNA localizes to the inactive X chromosome in cells of late cleavage stage female mouse embryos (Sheardown et al., 1997: Cell 91:99–107). Fluorescence in situ hybridization (FISH), however, does not quantify the number of Xist transcripts per nucleus. We have used real‐time reverse transcription‐polymerase chain reaction (RT‐PCR) to measure Xist RNA levels in single preimplantation embryos and to establish developmental profiles in both female and male samples. The gender of each embryo was readily established based on Xist RNA levels, by counting Xist gene copies per cell, and by independent detection of the presence/absence of Sry, a Y chromosome‐specific gene. Xist expression in males was found to be very low at all stages, as suggested by FISH. In contrast, female embryos contained measurable levels of Xist mRNA starting at the late 2‐cell stage and rapidly accumulated Xist transcripts until morula stage. Xist RNA accumulation per embryo then reached a plateau, while cell division continued. We propose that during early cleavage high enough levels of Xist mRNA are transcribed to generate a pool of unbound molecules. This pool would serve to temporarily maintain X chromosome inactivation without additional transcription while the trophectoderm and inner cell mass (ICM) differentiate. The ICM would then loose the paternally imprinted pattern of X inactivation originally present in all embryonic cells. Mol. Reprod. Dev. 61:425–436, 2002. © 2002 Wiley‐Liss, Inc.
Expression of the vascular endothelial growth factor and its receptors and effects of VEGF during in vitro maturation of bovine cumulus‐oocyte complexes (COC)
Authors: Einspanier Ralf , Schönfelder Martin , Müller Karin , Stojkovic Miodrag , Kosmann Michaela , Wolf Eckhard , Schams Dieter
Published: August 2002

A complete VEGF system consisting of the ligand and two of its receptors has been detected for the first time in the bovine cumulus‐oocyte‐complex (COC). In the course of a 24 hr in vitro maturation procedure (IVM), expression of the smaller VEGF transcripts and their specific receptors flt and flk changed remarkably in a time‐dependent manner as observed by RT‐PCR. The transcript concentrations of VEGF declined within 24 hr of culture, whereas both receptor mRNAs were found enriched between 6 and 12 hr of IVM. In the follicular fluid of growing ovarian follicles, immunoreactive VEGF, measured by RIA, increased significantly, reaching highest concentrations immediately before ovulation of the oocyte. The immunohistochemical localization of VEGF in bovine COCs revealed strong signals within the cumulus cell complex clearly extending beyond the oocyte cytoplasm at the beginning of in vitro maturation. After 24 hr, IVM immunoreactive VEGF disappeared remarkably from cumulus cells and the oocyte cytoplasm. An exogenous application of VEGF at the beginning of a 24 hr IVM significantly improved cleavage rates of zygotes and their development into bovine embryos showing obvious synergistic effects in combination with FSH, when compared with untreated control embryos. In addition, the number of blastomeres in deriving blastocysts increased after VEGF supplementation. These results indicate a functional VEGF system controlling important events beside the known angiogenetic effect during in vivo and in vitro maturation of the bovine COC, possibly affecting the early embryonic viability. Mol. Reprod. Dev. 62: 29‐36, 2002. © 2002 Wiley‐Liss, Inc.
Synaptic pattern of sex complements and sperm head malformation in X‐autosome translocation carrier bulls
Authors: Basrur P.K. , Koykul W. , Baguma‐Nibasheka M. , King W.A. , Ambady S. , de León F.A. Ponce
Published: August 2002

Testicular activity and semen characteristics of bulls carrying an X‐autosome translocation t(Xp +;23q −) revealed all stages of spermatogenesis although their semen consisted of few and, exclusively, of malformed spermatozoa. Chromosome painting on metaphase spreads of their mother and synaptonemal complex analysis on these and normal bulls were carried out to test whether the location and meiotic pairing behaviour of the rearranged segments could have contributed to the sperm head malformation and oligospermia in our X‐autosome translocation (X‐AT) carrier bulls. Spermatocytes of X‐AT carriers displayed the rearranged chromosomes in a univalent‐trivalent association, with 23q − always remaining as a univalent and Xp + in synapsis with normal chromosome 23 and the Y chromosome. Chromosome painting studies to test whether the total absence of meiocytes showing a quadrivalent is due to the non‐reciprocal nature of this translocation, identified Xp sequence homology with the distal end of 23q − confirming its relocation to the terminal segment of 23q −. Our synaptonemal complex analyses also confirmed that the bovine pseudo‐autosomal region (PAR) is at the distal ends of Xq and Yp and further revealed that over 85% of spermatocytes of X‐AT carriers (and up to 13% of spermatocytes of normal bulls) sustain a Y‐axis break adjacent to the PAR. Although the exact cause of a Y‐axis break in bovine spermatocytes is not known at present, we believe that the break and possible loss of Yq in such high proportions of spermatocytes of X‐AT carriers could have contributed to the sperm head malformation and oligospermia in our X‐AT carrier bulls. Mol. Reprod. Dev. 59:67–77, 2001. © 2001 Wiley‐Liss, Inc.
Relationship between adenylate cyclase sensitivity to follitropin and FSH receptor mRNA expression in the ovary of the lizard Podarcis sicula
Authors: Borrelli Lucia , De Stasio Roberta , Parisi Elio , Filosa Silvana
Published: August 2002

In mammals, gonadal functions are regulated by two pituitary gonadotropins, follicle‐stimulating hormone (FSH) and luteinizing hormone (LH), that interact with gonadal membrane receptors to activate adenylate cyclase. In comparison to mammalian systems, in squamate reptiles a reduced amount of information exists on gonadotropins and their related receptors. This study is aimed at clarifying if, in the lizard Podarcis sicula, the ovarian sensitivity to FSH is correlated to the reproductive cycle and to the expression of membrane receptors involved in the hormone recognition. The results demonstrate that the ovarian adenylate cyclase responsiveness to FSH parallels ovarian functions, being maximal during the ovulatory period. The ovarian sensitivity to FSH is also related to oocyte growth and vitellogenesis. Northern blot analyses reveal that the FSH receptor mRNA is maximally expressed in vitellogenic oocytes during the reproductive period. These results suggest that, in lizard ovary, hormone activation of adenylate cyclase is mediated by de novo synthesis of receptors specifically involved in FSH recognition. In lizards treated in vivo with FSH during the pre‐ovulatory period, adenylate cyclase becomes refractory to further FSH stimulation 2 hr after treatment, but sensitivity to the hormone is restored after 2 weeks. Nevertheless, while the restored level of activity never exceeds that observed during the nonreproductive period, the expression level of FSH receptor mRNAs is significantly enhanced in these animals. These results suggest that in lizard the processes that regulate ovarian growth, vitellogenesis, and ovulation are controlled by a complex network of signals including gonadotropin, FSH receptor expression, and adenylate cyclase. Mol. Reprod. Dev. 62: 210–215, 2002. © 2002 Wiley‐Liss, Inc.
Maintenance of meiotic arrest in bovine oocytes in vitro using butyrolactone I: Effects on oocyte ultrastructure and nucleolus function
Authors: Fair Trudee , Hyttel Poul , Motlik Jan , Boland Maurice , Lonergan Patrick
Published: August 2002

In this study, we have shown that butyrolactone I (BL‐I), a potent inhibitor of cyclin‐dependent kinases, affects oocyte cytoplasmic morphology and nuclear function in terms of nucleolar ultrastructure and immunocytochemistry. Bovine oocytes were recovered from three classes of follicle size: 1.5–2, 2–3, and 3–6 mm. The oocytes were incubated for 40 hr with BL‐I, and subsequently processed for transmission electron microscopy or immunocytochemistry. A control group of oocytes were processed immediately upon recovery (0 hr). In general, incubation with BL‐I for 40 hr disrupted contact between cells of the cumulus oophorous and the oocyte, caused degeneration of the cortical granules and the peripheral migration of all cytoplasmic organelles. At the level of the nucleus, it induced convolution of the nuclear membrane and caused acceleration of nucleolar compaction in oocytes from follicles < 3 mm and fragmentation of nucleoli, particularly evidenced by immunocytochemistry, in oocytes from follicles > 3 mm. Furthermore, the effects appear to be more profound in fully‐grown oocytes. Mol. Reprod. Dev. 62: 375–386, 2002. © 2002 Wiley‐Liss, Inc.
Remodeling of donor nuclei, DNA‐synthesis, and ploidy of bovine cumulus cell nuclear transfer embryos: Effect of activation protocol
Authors: Alberio Ramiro , Brero Alessandro , Motlík Jan , Cremer Thomas , Wolf Eckhard , Zakhartchenko Valeri
Published: August 2002

The purpose of this study was to investigate the effects of two activation protocols on nuclear remodeling, DNA synthesis during the first cell cycle, chromosome segregation after first mitosis and development to blastocyst of embryos produced by somatic nuclear transfer. Pronuclear formation was significantly higher when activation lasted 5 hr compared to 3 hr for both ethanol–cycloheximide and ionomycin–bohemine treatment. However, the presence of a single nucleus was significantly higher in embryos activated for 3 hr in bohemine. Initiation of DNA synthesis was delayed in ethanol–cycloheximide group, however, after 12 hr labeling 100% of embryos synthesized DNA in both groups. Embryos activated with ethanol–cycloheximide developed to blastocysts at a significantly higher rate than those activated with ionomycin–bohemine. Analysis of 2‐cell embryos with DNA probes for chromosome 6, 7, and 15 by fluorescence in situ hybridization showed that at least 50% of NT embryos were of normal ploidy independent of the activation stimulus. The results presented in this study show differences between the protocols compared on the nuclear events during the first cell cycle and on the development to blastocyst. Mol. Reprod. Dev. 59: 371–379, 2001. © 2001 Wiley‐Liss, Inc.
Nuclear fragmentation characterises paraspermiogenesis in Tubifex tubifex (Annelida, Oligochaeta)
Authors: Boi S. , Fascio U. , Ferraguti M.
Published: August 2002

It is known that tubificine oligochaetes produce two types of spermatozoa: eusperm, fertilizing sperm with regular haploid DNA content; and parasperm, with a much lower DNA content, protecting and carrying the eusperm. Whereas mature spermatozoa and spermatids of the two lines are easily recognized by their morphology and DNA content, little is known about the first steps of differentiation of the two lines. This subject is addressed here in two ways: we have measured DNA content by a new method based on confocal laser microscopy and found that the total DNA content of parasperm cysts is extremely variable and equal or lower than total DNA content of eusperm cysts. Then we focused on the spermatocytes, and we found that the cells which will form paraspermatids undergo a peculiar kind of nuclear fragmentation which differ greatly from a regular cell division. During fragmentation DNA is distributed unevenly among the spermatids and this gives rise to a great and variable number of parasperm with variable DNA content. Immunocytochemical assays revealed that a proper meiotic spindle is never formed during fragmentation and that actin may play an important role in the chromatin division. Electron micrographs showed that the centrioles undergo a phenomenon of mass reproduction similar to that found in ciliated epithelia which supplies each of the numerous paraspermatids of its basal body. Mol. Reprod. Dev. 59: 442–450, 2001. © 2001 Wiley‐Liss, Inc.
Alterations of gene expression in endoderm differentiation of F9 teratocarcinoma cells
Authors: Shimada Naoka , Yamada Kazuya , Tanaka Takashi , Kawata Hiroko , Mizutani Tetsuya , Miyamoto Kaoru , Matsuzawa Tetsuro
Published: August 2002

During the endoderm differentiation of F9 mouse embryonal carcinoma cells, as induced by sodium butyrate (NaBu) or retinoic acid (RA), gene expressions of alkaline phosphatase (ALPase), pyruvate kinase (PKase) and 5′ ribonucleotide phosphohydrolase (5′‐Nase) were examined. The specific activity of ALPase was found to increase by 3.5‐fold after 48 hr treatment with NaBu. In contrast, specific activity of PKase were decreased by 63%. Northern blot analysis revealed that the elevation of ALPase activity resulted from an increase in the level of liver/bone/kidney (L/B/K)‐type ALPase mRNA and that the decrease of PKase activity was dependent on a reduction in the level of M2‐PKase mRNA. Interestingly, when NaBu was removed from the culture medium, the levels of these mRNAs reverted to their original levels after 16 h. During these processes, the specific activity of 5′‐Nase and the level of its mRNA remained unchanged. In contrast, when F9 cells were treated with RA, only the level of L/B/K‐type ALPase mRNA increased. Lastly, we examined the issue of whether an increase in the level of ALPase mRNA is dependent on the transcriptional activation of the mouse L/B/K‐type ALPase gene. Transient transfection assays using luciferase reporter constructs showed that the promoter activity increased as the result of treatment with RA but not with NaBu. Mol. Reprod. Dev. 60: 165–171, 2001. © 2001 Wiley‐Liss, Inc.
New DAPI and fish findings on egg maturation processes in related hybridogenetic and parthenogenetic Bacillus hybrids (insecta, phasmatodea)
Authors: Marescalchi Ombretta , Scali Valerio
Published: August 2002

Bacillus stick insects have proved adequate for studying a wide array of reproductive modes: sexual, parthenogenetic, hybridogenetic, androgenetic. Hybridogenetic strains (B. rossius‐grandii) were thought to discard the paternal “grandii” haploset during first meiotic division and keep the “rossius” hemiclone, whereas the clonal B. whitei (=rossius/grandii) would maintain its hybrid structure by fusing back two nonsister nuclei—each derived from previously segregated heterospecific complements—by the end of the 2nd meiotic division. New investigations on laid eggs and ovariole squashes, either DAPI stained or FISH labeled, revealed that in hybridogens the “grandii” set is excluded from the germ line prior to meiosis and that a DNA extra‐synthesis should occur to produce hemiclonal eggs after two cytologically normal meiotic divisions. On the other hand, in B. whitei eggs no genome segregation appears to occur and an intrameiotic DNA extra‐synthesis must take place to produce 2n tetrachromatidic oocytes I; these divide twice and give unreduced clonal eggs. The new findings bring hybridogenetic oogenesis of Bacillus to be coincident with that of the known hemiclonal organisms and point to an independent onset of B. whitei from hemiclonal strains. In addition, B. whitei gains a closer resemblance to B. lynceorum owing to the sharing of a cytologically identical egg maturation mechanism, of the same maternal ancestor and of peculiar chromosomal features. It is here suggested that B. lynceorum originated from the incorporation of an “atticus” genome into a B. whitei egg, according to a pathway of repeated hybridization often occurred with other polyploid hybrids. Mol. Reprod. Dev. 60: 270–276, 2001. © 2001 Wiley‐Liss, Inc.