bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis, structure, reactions, and photoelectron spectra of new mixed sulfur‐, selenium‐ or tellurium and silicon‐ or tin‐containing heterocycles
Authors: Block Eric , Glass Richard S. , Dikarev Evgeny V. , Gruhn Nadine E. , Jin Jin , Li Bo , Lorance Edward , Zakai Uzma I. , Zhang Shao‐Zhong 
Published: July 2007

AbstractMore than 40 new 4‐ to 12‐membered ring heterocycles containing various combinations of Group 14 elements (Si and Sn) and Group 16 elements (S, Se, and Te) have been synthesized and fully characterized. Synthesis of these small‐ring as well as medium‐ring (mesocyclic) heterocycles from α, ω‐dihalides was facilitated by the presence of gem‐dialkylsilyl and gem‐dialkylstannyl groups in the precursors. Solid‐state conformations of the new ring systems have been determined by X‐ray crystallography. Oxidation of mixed S(Se, Te)/Si eight‐membered ring mesocycles as well as 1,5‐dithia‐, 1,5‐diselena‐, and 1,5‐ditelluracyclooctane with NOPF6 gave dications, which can be characterized by NMR. On treatment with nucleophiles, mesocyclic dications or the corresponding radical cations underwent ring contraction to give five‐ or six‐membered ring heterocycles. The ionization energies of the above conformationally constrained β‐disilanyl sulfides and selenides were determined by photoelectron spectroscopy. These ionization energies reflect substantial (0.53‐‐0.75 eV) orbital destabilizations. The basis for these destabilizations was investigated by theoretical calculations, which reveal geometry‐dependent interaction between sulfur or selenium lone pair orbitals and σ‐orbitals, especially Si–Si σ‐orbitals. These results suggest facile redox chemistry for these compounds and significantly extend the concept of σ‐stabilization of electron‐deficient centers. © 2007 Wiley Periodicals, Inc. 18:509–515, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20333
Perfluoroketene dithioacetals and perfluorodithiocarboxylic acid derivatives: Versatile tools for organofluorine synthesis
Authors: Portella Charles , Muzard Murielle , Bouillon Jean‐Philippe , Brulé Cédric , Grellepois Fabienne , Shermolovich Yuriy G. , Timoshenko Vadim M. , Chernega Alexander N. , Sotoca‐Usina Enrique , Parra Margarita , Gil Salvador 
Published: July 2007

AbstractPerfluoroketene dithioacetals are simple and versatile compounds that can be transformed into a large variety of trifluoromethyl derivatives, in particular aza‐ and thiaheterocycles, perhalodithiocrotonic esters, and fluorinated dithiol thiones. These unsaturated perfluorodithioesters and analogs give interesting polar cycloaddition reactions whose mechanism is strongly influenced by the fluorine substitution. This substitution plays an important role in the reactivity of saturated perfluorodithiocarboxylic acids as well. Except for the carbophilic addition of allyl Grignard reagents to perfluorocarboxamides, a domino thiophilic addition‐fluoride elimination was the main reaction process. Interestingly, a three‐step domino reaction occurs when pentafluorodithioesters are treated with allyl Grignard reagents, the third step being an effective σ[3,3] rearrangement, so that the overall reaction is a formal substitution of an allyl group for the α‐fluorine atom. 2,2‐Bis(allyl)‐3,3,3‐trifluorodithiopropanoates were prepared by performing this domino reaction twice, in a possible one‐pot procedure. © 2007 Wiley Periodicals, Inc. 18:500–508, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20346
How company and managerial characteristics influence strategic alliance adoption in the travel sector
Authors: Pansiri Jaloni 
Published: July 2007

AbstractThe purpose of this paper is to examine the role of company and executive characteristics in strategic alliance formation in the tourism sector of travel. A survey of Australian travel sector businesses was carried out and the results indicate a high level of interaction through alliances between various sectors of the Australian tourism industry. Top managers' characteristics (experience, ownership and risk‐taking attitude) were found to be influential in taking strategic decisions of whether to form alliances or not. These characteristics do not play an important role in determining the number of alliances an organisation has and their geographical location, as much as company characteristics do. The findings of this paper imply that company characteristics are important in determining alliance formation. Managers should thoroughly consider these characteristics when deciding not only to form alliances, but also the types of alliances that could help their organisations to be more competitive, given limited resources. Copyright © 2007 John Wiley & Sons, Ltd.
Evaluation of the cognitive image of a country/destination by the media during the coverage of mega‐events: the case of UEFA EURO 2004TM in Portugal
Authors: Custódio Maria João Ferreira , Gouveia Pedro M. D. C. B. 
Published: July 2007

AbstractBy reporting a study undertaken during the final stages of the European Football Championships—UEFA (Union of European Football Associations) EURO 2004TM, this paper aims to evaluate the cognitive image of a country/destination by the media during the coverage of mega‐events, which may in turn contribute to the field of tourism promotion and planning. By applying various statistical methods, it is possible not only to assess and identify the aspects which have contributed the most to the opinion‐forming of autonomous agents, but also to present empirical evidence of the influence of the organisation of this event on the image formation of the destination as a whole. Copyright © 2007 John Wiley & Sons, Ltd.
Kinetic study of oxidation of N‐(α‐methylbenzylidene) anilines by dimethyldioxirane
Authors: Nose Žiga , Kovač Franci 
Published: July 2007

AbstractA kinetic study of the oxidation of substituted N‐(α‐methylbenzylidene) anilines by dimethyldioxirane was investigated using a UV/VIS spectrophotometer. Oxaziridines and nitrones were formed as intermediates, and in the excess of dimethyldioxirane corresponding carbonyl compounds, nitrosobenzene or nitrobenzene, were formed quantitatively. The kinetic data were used in the equation for the formation of oxaziridines and nitrones as an intermediate and further oxidation to the corresponding acetophenones and nitrosobenzene. Hammett ρ values were determined for compounds p‐substituted on the aromatic ring attached to the carbon atom of the imino group, and it was found that these substituents have very little effect on the oxidation reaction. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 492–497, 2007
Effects of wildfire, salvage logging and slash treatments on soil degradation
Authors: Fernández C. , Vega J. A. , Fonturbel T. , Pérez‐Gorostiaga P. , Jiménez E. , Madrigal J. 
Published: July 2007

AbstractThe effect of wildfire and the subsequent harvesting on soil degradation was evaluated in a burned Pinus pinaster stand in Galicia (NW Spain). During the first year following a fire of moderate intensity, burned trees were not harvested and soil erosion losses, measured by sediment collection at the bottom of bordered plots, were very low. An apparently limited impact of fire on soil and reduced rainfall erosivity for this period could be responsible for that result.Salvage logging took place 13 months after fire. Three post‐fire alternatives were compared: no harvesting (standing burned trees), harvesting + windrowed slash and harvesting + slash chopping. Soil losses were even lower during the 14 months after these treatments than for the previous pre‐harvesting period. Again, low mineral soil exposition and rainfall erosivity seemed to contribute to that result.Changes in soil bulk density and soil shear strength after clearcutting and slash manipulation were small and not enough to trigger sediment yield significantly.Harvesting and logging operations apparently increased soil inhomogeneities. This degree of variability was more adequately assessed by using micro‐plot fences instead of plot fences. The percentage of soil disturbed by machinery was the variable most related with the observed minor soil losses after harvesting, at micro‐plot level. This study indicated that the combined effect of wildfire and clearcutting caused only an acceleration of soil erosion when significant exposition of mineral soil occurred after these perturbations. However, these results must be taken with caution because rain erosivity during the study was low. To delay post‐fire clearcutting until several months after the fire could reduce the impact of this forestry operation on burned soils, taking advantage of the natural mulch created by scorched leaves fall, although other issues must be taken into account. Copyright © 2007 John Wiley & Sons, Ltd.
Are they always offering the lowest price? An empirical analysis of the persistence of price dispersion in a low inflation environment
Authors: Bahadir‐Lust Sebnem , Loy Jens‐Peter , Weiss Christoph R. 
Published: July 2007

AbstractWe study the existence of price distributions and the intra‐distribution dynamics for 10 food products across 131 retail stores in Germany for a time period of 43 weeks. Based upon Varian's (1980) model of sales, we aim at investigating whether the position of stores within the cross‐sectional price distribution is persistent or changes over time (mixed‐strategy equilibrium). Our results suggest a substantial degree of price dispersion even after controlling for unobserved store heterogeneity. Despite some intra‐distribution dynamics, we find evidence for a persistence of stores in the cross‐sectional price distribution over time. Copyright © 2007 John Wiley & Sons, Ltd.
The reflection coefficient of a flared microstrip line radiating in an infinite parallel‐plate waveguide
Authors: Cruz J. L. , Gimeno B. , Navarro E. A. , Such V. 
Published: July 2007

AbstractIn this article the reflection coefficient of a tapered microstrip line radiating in an infinite parallel‐plate conducting waveguide is calculated. The reflection coefficient at the feed line is evaluated by using the aperture admittance of the horn and the scattering matrix of the continuous taper. The theoretical behavior of the aperture admittance is shown and the reflection coefficient of a microstrip horn radiating in the parallel‐plate region of a bootlace lens is measured in order to verify the model. © 1993 John Wiley & sons, Inc.
A new hybrid method of calibration for polarimetric radar cross‐section measurements
Authors: Desclos L. 
Published: July 2007

AbstractThe main problem in polarimetric measurement is to retrieve all the properties (phase and magnitude) of the scattering matrix of the studied object. In most cases the proposed techniques [1–3] are very complicated and are not adaptable to intensive applications, as in the industrial domain. The development of an original technique is proposed here. The technique is very efficient and simple to use. It is based on a modification of an existing technique developed in Reference [1]. The main advantages are the facility of placement of the targets and the fact that there is no need to know the distances between the calibration targets and the emission reception system. © 1993 John Wiley & sons, Inc.
Polarimetric analysis of an anechoic chamber in a time domain
Authors: Desclos L. , Pouliguen P. 
Published: July 2007

AbstractIn an anechoic chamber, radar cross‐section (RCS) or antenna measurements intensify the need of knowing perfectly the electromagnetic (em) behavior of the locale of treatment. So it is very important to characterize the noise in the anechoic chamber. This can be done by locating and recognizing the elements which cause the perturbation. In this article a new technique using a combination of polarimetric and time domain analyses is presented. © 1993 John Wiley & sons, Inc.
Plots with matching circles for optimizing the performance of a low‐noise amplifier
Authors: Bor Sheau‐Shong , Liu Ji‐Chyun , Lu Po‐Chiang , Chang Chung‐Chi 
Published: July 2007

AbstractPlots for optimizing the performance of LNA are presented here. From the study of the interaction between the input/output stability and the conjugate‐match conditions, four modified stability circles which are designated as matching circles are analytically developed for the input/ouptut networks. The available matching area is specified by using the modified determinations of the stability criteria. © 1993 John Wiley & sons, Inc.
Application of a banded matrix iterative approach to monte carlo simulations of scattering of waves by a random rough surface: TM case
Authors: Tsang Leung , Chan Chi H. , Sangani Haresh 
Published: July 2007

AbstractA banded matrix iterative approach is applied to study scattering of a TM incident wave from a perfectly conducting one‐dimensional random rough surface. It is much faster than the full matrix inversion approach. When compared to the Kirchoff iterative approach, it is of comparable CPU time, is more accurate, and works for cases when the Kirchoff iteration fails. © 1993 John Wiley & sons, Inc.
Nepal—an algorithm for solving the volume integral equation
Authors: Chew Weng Cho , Lu Cai‐Cheng 
Published: July 2007

AbstractA new algorithm is proposed to solve the volume integral equation whereby the scatterer is first divided into N subscatterers. Smaller problems are nested within larger problems using the Huygens equivalence principle. The resultant algorithm has reduced computational complexity whose CPU time is proportional to N1.5. © 1993 John Wiley & sons, Inc.
Polarization‐encoded optical shadow casting: Edge detection using roberts operator
Authors: Alam M. S. , Iftekharuddin K. M. , Karim M. A. 
Published: July 2007

AbstractRoberts‐operator‐based edge detection is implemented using polarization‐encoded optical shadow casting. The proposed technique yields better results than the previously reported shadow‐casting edge detectors. © 1993 John Wiley & sons, Inc.
Evolution of nonlinear guided waves along a bent planar waveguide
Authors: Chang Wen‐Ching , Liu Shuh‐Fang , Wang Way‐Seen 
Published: July 2007

AbstractOptical field propagation in a nonlinear bent slab waveguide with a Kerr‐like nonlinear cladding medium is presented. With increasing input power, the self‐focusing effect significantly disturbs the original waveguide configuration, and a nonstationary evolution behavior is found. It is shown that the onset and the direction of soliton emission are sensitive to the guiding capability of the initial waveguide. In particular, a novel result is observed when the waveguide supports more than one mode. © 1993 John Wiley & sons, Inc.
Combined effect of harmonic distortion and pulse dispersion in optical fiber transmission
Authors: Fraile‐Pelaez F. Javier , Gil‐Vazquez Fernando 
Published: July 2007

AbstractWe study the transmission of Gaussian pulses by subcarrier modulation of the laser power and obtain an analytical expression of the detected photocurrent. This result provides insight into the effects of the fiber dispersion on the transmission of AM‐modulated subcarriers. © 1993 John Wiley & sons, Inc.
Symmetrical coplanar waveguide with finite ground plane
Authors: Cai M. , Kooi P. S. , Leong M. S. , Yeo T. S. 
Published: July 2007

AbstractA symmetrical coplanar waveguide with finite ground plane (SCPW) has been analyzed. The symmetrical configuration is obtained by simply placing a dielectric substrate above a conventional finite ground plane coplanar waveguide (FCPW). The conformal mapping method is used to calculate the quasistatic effective permittivity ϵeff and characteristic impedance Z0. The SCPW has a larger ϵeff and a smaller Z0, compared with the conventional FCPW. This configuration should be useful for the design of balanced mixer circuits and for applications to the design of balanced feed lines in printed antennas. © 1993 John Wiley & sons, Inc.
Effect of a dielectric overlay on a linearly tapered slot antenna excited by a coplanar waveguide
Authors: Simons Rainee N. , Lee Richard Q. , Perl Thomas D. , Silvestro John 
Published: July 2007

AbstractA linearly tapered slot antenna (LTSA) with a dielectric overlay was experimentally investigated. The presence of dielectric overlay alters the guide wavelength of the LTSA, and thus the radiation characteristics of the antenna. Results indicate that dielectric overlay could be used to reduce the physical length and to improve the radiation characteristics of the LTSA. © 1993 John Wiley & sons, Inc.
An equivalent circuit model for multielectrode lasers: Potential devices for millimeter‐wave applications
Authors: Elkadi H. , Vilcot J. P. , Decoster D. 
Published: July 2007

AbstractStatic and dynamic behaviors of multielectrode lasers are, for the first time, studied using an equivalent circuit model. The model is based on the monomode rate equations and the Fermi integral. The potential controlled absorption in the active‐region quantum wells and its saturation are included as well as the different carrier recombination mechanisms. The model predicts a higher resonance amplitude and a ‐ 20‐dB/decade slope above resonance instead of the commonly known ‐40‐dB/decade slope for direct current modulation and consequently higher cutoff frequencies are to be expected for such structures. We also discuss briefly the impedance level of such structures as well as the different phenomena to be taken into account for a more precise representation. © 1993 John Wiley & sons, Inc.
Full guided mode expansion method and optimized sine method for analyzing optical waveguides
Authors: Wang Ye Heng 
Published: July 2007

AbstractThis article shows that the full guided mode expansion method and its limit, the optimized sine method, provide simple, fast, and accurate calculations of the propagation constant, even near the cutoff frequency. Use of a smaller scale matrix results in good agreement with previous works. © 1993 John Wiley & sons, Inc.
Optimal design of long‐haul optical soliton communication systems with lumped amplifiers
Authors: Ye Xiongyan Tang Peida 
Published: July 2007

AbstractA method of designing an optical soliton communication system with lumped amplifiers is presented in this article. The design requirements and the design procedure are discussed. An exact bit‐error‐rate expression of the system is derived. Some design examples of the optimal systems are given. © 1993 John Wiley & sons, Inc.
A theoretical and experimental study of microshield circuits
Authors: Dib Nihad I. , Drayton Rhonda F. , Katehi Linda P. B. 
Published: July 2007

AbstractA theoretical and experimental study of a new type of monolithic planar transmission line is presented. This line can operate without the need for via holes or the use of air bridges for ground equalization. Furthermore, it has shown the tendency to radiate less than the conventional coplanar waveguide (CPW) and can provide a wide range of impedances due to the many available parameters for design. The space‐domain integral equation method is used to analyze several discontinuities of the proposed line. In order to validate the theory, measurements are performed on scaled models of a specific discontinuity. The experimental and theoretical results are in good agreement. In addition, it is demonstrated that the proposed line discontinuities radiate considerably less than the corresponding coplanar waveguide ones. © 1993 John Wiley & sons, Inc.
The fresnel prism as polarization interferometer
Authors: Echarri Rodolfo 
Published: July 2007

AbstractHere we show that a Fresnel prism can be used as a polarization interferometer. A linearly polarized beam, which is incident in this interferometer, is split into two circularly polarized beams, one right and another left, which generate the interference pattern. Interposing a solution of common sugar in the incident beam, the former pattern is shifted because of the circular birefringence of the sugar. Measuring the displacement of the interference pattern, we determine the phase difference between both circular polarizations introduced by the solution. Moreover, we compare this result with that obtained by measuring the rotation power, concluding that they are in good agreement. © 1993 John Wiley & Sons, Inc.
Efficient analysis of a dielectric post in a rectangular waveguide based on the two‐dimensional FD‐TD method
Authors: And Zhang Feng , Junmei Fu 
Published: July 2007

AbstractA modified two‐dimensional FD‐TD method is used for the analysis of an H‐plane waveguide loaded with a dielectric post of arbitrary shape, size, number, and location, and the dielectric post resonances and the application of measurement of permittivity constant are discussed. The numerical results are in good agreement with data available in the literature, and the versatility of this approach is given. © 1993 John Wiley & Sons, Inc.
Analysis of uncovered two‐layer three‐coupled microstrip lines on anisotropic substrates
Authors: And Chulhun Seo , Lee Choong Woong 
Published: July 2007

AbstractGeneral expressions of the variational method are obtained for the quusistatic analysis of uncovered two‐layer three‐coupled microstrip lines. The frequency‐dependent parameter is obtained by employing the extended spectral domain in the full‐wave analysis. Accurate numerical results are presented for the line capacitances to the various widths of the first layer of two‐layer three‐coupled microstrip lines on anisotropic substrates. The propagation constants and the characteristic impedances are obtained for various frequencies. © 1993 John Wiley & Sons, Inc.
A hybrid gauss‐newton‐simulated annealing optimizer for extraction of mesfet equivalent circuit elements
Authors: Leong M. S. , Kooi P. S. , Yeo T. S. , Ooi B. L. 
Published: July 2007

AbstractA new optimizer is presented for the extraction of the small‐signal equivalent circuit elements (X) of a CaAs FET from its measured scattering (S) parameters. The approach is a combination of the damped Gauss‐Newton method, for the least‐squares fitting of the S parameters, and the random search generalized simulated annealing (GSA). Novel features of the proposed approach include (i) an improved Kondoh step‐by‐step optimization of the objective functions grouped according to their sensitivity to variation of key equivalent circuit parameters (X), and (ii) exploitation of the advantages derived from a transformation of the objective functions from scattering parameters to impedance parameters. © 1993 John Wiley & Sons, Inc.
Plane‐wave propagation in a uniaxial chiro‐omega medium
Authors: Lindell Ismo V. , Tretyakov Sergei A. , Viitanen Ari J. 
Published: July 2007

AbstractPlane‐wave propagation is considered in a medium which is a generalization of the uniaxial chiral and the uniaxial omega medium, both of which have shown properties useful for the design of electromagnetic devices. The medium is reciprocal and it can be easily realized by mixing certain metal wire elements in a host material. The resulting bianisotropic medium is isotropic in directions perpendicular to an axis in space. Wave‐number expressions are derived and numerical examples considered. © 1993 John Wiley & Sons, Inc.
Performance of MMIC components at cryogenic temperatures
Authors: Bhandari Anil , Butler Donald P. , Agarwal Krishna K. 
Published: July 2007

AbstractWe have measured the cryogenic performance of off‐the‐shelf GaAs MMIC amplifier and mixer‐converter modules from different foundries, with room‐temperature designs, without finding significant degradation in performance to 77 K. Therefore, existing MMIC modules would be suitable for hybrid microwave systems with high‐Tc superconducting transmission line filters, representing a cost savings. © 1993 John Wiley & Sons, Inc.