bluuebunny/crossref_metadata_2025 huggingface dataset:
Silyl thioacetals: Versatile building blocks for organic synthesis
Authors: Schaumann Ernst
Published: July 2007

Silyl thioacetals have been shown to allow entry into the chemistry of silyl(arythio) carbenes. Moreover, silyl thioacetals are successful reaction components in the homo‐Peterson cyclopropane synthesis, and, via 1,4‐silyl migration, in the domino synthesis of larger carbocyclic and of heterocyclic rings. Finally, the application of thioacetal‐based silyl migration in the synthesis of acyclic systems is discussed. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:600–608, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20344
Dieldrin elicits a widespread DNA repair and antioxidative response in mouse brain
Authors: Sava Vasyl , Velasquez Adriana , Song Shijie , Sanchez‐Ramos Juan
Published: July 2007

Dieldrin is an organochlorine pesticide that is toxic for monoaminergic neurons. This study was designed to test the hypothesis that a weak DNA repair response to dieldrin by nigrostriatal dopaminergic (DA) neurons results in depletion of striatal DA. The activity of the mammalian base excision repair enzyme oxyguanosine glycosylase was utilized as the index of DNA repair. Other measures of oxidative stress were also studied, including the regional distribution of lipid peroxidation and superoxide dismutase (SOD) activity. The effects of acute and slow infusion of dieldrin on striatal DA levels were biphasic with a transient initial depression followed by increases beyond normal steady‐state levels. Dieldrin administration caused a global oxidative stress evidenced by increased levels of lipid peroxidation in all brain regions, an effect consistent with its capacity to affect mitochondrial bioenergetics. Dieldrin also elicited strong antioxidative and DNA repair responses across the entire mouse brain. Although mitochondrial SOD was not as increased in midbrain as it was in other regions following a cumulative dose of 24 mg/kg, this response, along with the robust DNA repair response, appeared to be sufficient to protect potentially vulnerable DA neurons from cytotoxicity. However, the long‐term consequences of chronic low‐dose dieldrin exposure remain to be studied, especially in light of the concept of “slow excitotoxicity,'' which postulates that even a mild bioenergetic compromise can over time result in the demise of neurons. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:125–135, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20165
Catechin as an antioxidant in liver mitochondrial toxicity: Inhibition of tamoxifen‐Induced protein oxidation and lipid peroxidation
Authors: Tabassum Heena , Parvez Suhel , Rehman Hasibur , Banerjee Basu Dev , Raisuddin Sheikh
Published: July 2007

Tamoxifen (TAM) is a nonsteroidal triphenylethylene antiestrogenic drug widely used in the treatment and prevention of breast cancer. TAM brings about a collapse of the mitochondrial membrane potential. It acts both as an uncoupling agent and as a powerful inhibitor of mitochondrial electron transport chain. The effect of catechin pretreatment on the mitochondrial toxicity of TAM was studied in liver mitochondria of Swiss albino mice. TAM treatment caused a significant increase in the mitochondrial lipid peroxidation (LPO) and the protein carbonyls (PCs). It also caused a significant increase in superoxide radical production. Pretreatment of mice with catechin (40 mg/kg) showed significant protection as demonstrated by marked attenuation of increased oxidative stress parameters such LPO, PCs, and superoxide production. It also restored the decreased nonenzymatic and enzymatic antioxidants of mitochondria. The inhibitory effect of catechin on TAM‐induced oxidative damage suggests that it may have potential benefits in prevention of human diseases where reactive oxygen species have some role as causative agents. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:110–117, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20167
Oxidative stress and damage in liver, but not in brain, of fischer 344 rats subjected to dietary iron supplementation with lipid‐soluble [(3,5,5‐trimethylhexanoyl)ferrocene]
Authors: Lykkesfeldt Jens , Morgan Evan , Christen Stephan , Skovgaard Lene Theil , Moos Torben
Published: July 2007

Accumulation of iron probably predisposes the aging brain to progressive neuronal loss. We examined various markers of oxidative stress and damage in the brain and liver of 3‐ and 24‐month‐old rats following supplementation with the lipophilic iron derivative {(3,5,5‐trimethylhexanoyl)ferrocene} (TMHF), which is capable of crossing the blood–brain barrier. At both ages, iron concentration increased markedly in the liver but failed to increase in the brain. In the liver of TMHF‐treated young rats, levels of α‐ and γ‐tocopherols and glutathione (GSH) were also higher. In contrast, the brain displayed unaltered levels of the tocopherols and GSH. Malondialdehyde (MDA) level was also higher in the cerebrospinal fluid (CSF) and the liver but not in the brain. In old rats, the absence of an increase in iron concentration in the brain was reflected by unaltered concentrations of GSH, tocopherols, and MDA as compared to that in untreated rats. In the aging liver, concentrations of GSH and MDA increased with TMHF treatment. Morphological studies revealed unaltered levels of iron, ferritin, heme oxygenase‐1 (HO‐1), nitrotyrosine (NT), or MDA in the brains of both young and old rats treated with TMHF. In contrast, TMHF treatment increased the level of HO‐1 in Kupffer cells, NT in hepatic endothelial cells, and MDA and ferritin in hepatocytes. Although these results demonstrated an increase in the biochemical markers of oxidative stress and damage in response to increasing concentrations of iron in the liver, they also demonstrated that the brain is well protected against dietary iron overload by using iron in a lipid‐soluble formulation. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:145–155, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20170
Toxicities induced in cultured cells exposed to zearalenone: Apoptosis or mutagenesis?
Authors: Ayed‐Boussema Imen , Ouanes Zouhour , Bacha Hassen , Abid Salwa
Published: July 2007

Zearalenone (ZEN) is a fusarotoxin produced mainly by Fusarium graminearum in temperate and warm countries. ZEN has several adverse effects on humans and animals. It has a strong estrogenic activity associated with hyperestrogenism and leads to several physiological alterations in the reproductive tract. Even though the mutagenic and genotoxic proprieties of ZEN have been described recently, its molecular mechanisms of action are not completely understood. The aim of this study was to determine the involvement of other possible mechanisms in ZEN‐induced toxicities. Each of the following toxicities, cytotoxicity, cell cycle perturbation, genotoxicity, and mutagenicity, was monitored in Vero cells exposed to ZEN. Our results showed that ZEN‐reduced cell viability correlated to cell cycle perturbation–induced DNA fragmentation, resulting in DNA‐laddering patterns on agar gel electrophoresis. This observation is consistent with apoptosis, which was confirmed by induction of apoptotic bodies. Moreover, ZEN induced in a concentration‐dependant manner the formation of micronuclei and chromosome aberrations. This apparent contradiction between the apoptotic and mutagenic effects of ZEN can be explained by the modification of normal cellular regulation inducing apoptotic or antiapoptotic factors resulting from a lack of or an incorrect DNA‐reparation in relation to cell exposure to the toxin. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:136–144, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20171
Race, language, and mental evolution in Darwin's descent of man
Authors: Alter Stephen G.
Published: July 2007

Charles Darwin was notoriously ambiguous in his remarks about the relationship between human evolution and biological race. He stressed the original unity of the races, yet he also helped to popularize the notion of a racial hierarchy filling the gaps between the highest anthropoids and civilized Europeans. A focus on Darwin's explanation of how humans initially evolved, however, shows that he mainly stressed not hierarchy but a version of humanity's original mental unity. In his book The Descent of Man, Darwin emphasized a substantial degree of mental development (including the incipient use of language) in the early, monogenetic phase of human evolution. This development, he argued, necessarily came before primeval man's numerical increase, geographic dispersion, and racial diversification, because only thus could one explain how that group was able to spread at the expense of rival ape‐like populations. This scenario stood opposed to a new evolutionary polygenism formulated in the wake of Darwin's Origin of Species by his ostensible supporters Alfred Russel Wallace and Ernst Haeckel. Darwin judged this outlook inadequate to the task of explaining humanity's emergence. © 2007 Wiley Periodicals, Inc.
Francis bacon's behavioral psychology
Authors: Macdonald Paul S.
Published: July 2007

Francis Bacon offers two accounts of the nature and function of the human mind: one is a medical‐physical account of the composition and operation of spirits specific to human beings, the other is a behavioral account of the character and activities of individual persons. The medical‐physical account is a run‐of‐the‐mill version of the late Renaissance model of elemental constituents and humoral temperaments. The other, less well‐known, behavioral account represents an unusual position in early modern philosophy. This theory espouses a form of behavioral psychology according to which (a) supposed mental properties are “hidden forms” best described in dispositional terms, (b) the true character of an individual can be discovered in his observable behavior, and (c) an “informed” understanding of these properties permits the prediction and control of human behavior. Both of Bacon's theories of human nature fall under his general notion of systematic science: his medical‐physical theory of vital spirits is theoretical natural philosophy and his behavioral theory of disposition and expression is operative natural philosophy. Because natural philosophy as a whole is “the inquiry of causes and the production of effects,” knowledge of human nature falls under the same two‐part definition. It is an inquisition of forms that pertains to the patterns of minute motions in the vital spirits and the production of effects that pertains both to the way these hidden motions produce behavioral effects and to the way in which a skillful agent is able to produce desired effects in other persons' behavior. © 2007 Wiley Periodicals, Inc.
Measurement of signal‐to‐noise ratios in MR images: Influence of multichannel coils, parallel imaging, and reconstruction filters
Authors: Dietrich Olaf , Raya José G. , Reeder Scott B. , Reiser Maximilian F. , Schoenberg Stefan O.
Published: July 2007

Purpose

To evaluate the validity of different approaches to determine the signal‐to‐noise ratio (SNR) in MRI experiments with multi‐element surface coils, parallel imaging, and different reconstruction filters.

Materials and Methods

Four different approaches of SNR calculation were compared in phantom measurements and in vivo based on: 1) the pixel‐by‐pixel standard deviation (SD) in multiple repeated acquisitions; 2) the signal statistics in a difference image; and 3) and 4) the statistics in two separate regions of a single image employing either the mean value or the SD of background noise. Different receiver coil systems (with one and eight channels), acquisitions with and without parallel imaging, and five different reconstruction filters were compared.

Results

Averaged over all phantom measurements, the deviations from the reference value provided by the multiple‐acquisitions method are 2.7% (SD 1.6%) for the difference method, 37.7% (25.9%) for the evaluation of the mean value of background noise, and 34.0% (38.1%) for the evaluation of the SD of background noise.

Conclusion

The conventionally determined SNR based on separate signal and noise regions in a single image will in general not agree with the true SNR measured in images after the application of certain reconstruction filters, multichannel reconstruction, or parallel imaging. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Balanced steady‐state free precession vs. segmented fast low‐angle shot for the evaluation of ventricular volumes, mass, and function at 3 Tesla
Authors: Grothues Frank , Boenigk Hagen , Graessner Joachim , Kanowski Martin , Klein Helmut U.
Published: July 2007

Purpose

To compare balanced steady‐state free precession (SSFP) and segmented fast low angle shot (FLASH) for quantification of left and right ventricular volumes and function and for left ventricular mass at high field (3 Tesla).

Materials and Methods

A total of 33 patients (19 male, mean age 54 years) with various forms of heart disease underwent ventricular function studies using cine SSFP and FLASH sequences with identical slice orientations.

Results

Using SSFP, left ventricular end‐diastolic (+10 mL [4.7%], P < 0.001) and end‐systolic volumes (+9 mL [6.1%], P < 0.001) measured larger whereas mass was considerably smaller (–23 g [–12.9%], P < 0.001) and ejection fraction (–1% [–3.2%], P < 0.01) marginally smaller. Right ventricular end‐diastolic (+4 mL [2.6%], P = 0.001) and end‐systolic volumes (+4 mL [5.1%], P < 0.01) were also larger, but no significant difference for right ventricular ejection fraction (P = 0.05) was found.

Conclusion

Similar to previous results at 1.5 Tesla, at high magnetic field the cine SSFP technique led to discrete but significantly higher ventricular volume measurements and to a significantly smaller measurement of left ventricular mass in patients. The effect on left and right ventricular ejection fraction was minor, although the difference remained significant for the left ventricle. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Inflammatory myofibroblastic tumors in the liver: MRI of two immunohistochemically‐verified cases
Authors: Yu Jeong‐Sik , Park Chanil , Kim Joo Hee , Chung Jae‐Joon , Kim Ki Whang
Published: July 2007

In immunohistochemically‐proven hepatic inflammatory myofibroblastic tumors, MRI revealed layered patterns of contrast enhancement during dynamic imaging, consisting of outer hypovascular rind and inner hypervascular stroma and mimicking the imaging features of pyogenic organized abscess with deficient central necrosis in four lesions in two patients. For the outer hypovascular rind, T2‐weighted images showed hyperintensity, suggesting immature fibrosis corresponding to the area of arterial hypovascularity and delayed contrast enhancement. The patients' favorable clinical course and imaging findings reflected the benign nature of these lesions, from an infectious origin, despite the phenotypic expression of myofibroblastic proliferation in the hypervascular stroma containing chronic inflammatory cells. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Angiotensin converting enzyme inhibition of fish protein hydrolysates prepared from alkaline‐aided channel catfish protein isolate
Authors: Theodore Ann E , Kristinsson Hordur G
Published: July 2007

Peptides derived from aquatic animals have been shown to have inhibitory activity against angiotensin converting enzyme (ACE), which is a key enzyme behind elevated blood pressure. In this study a catfish protein isolate was prepared and hydrolyzed to 5%, 15% and 30% degrees of hydrolysis (% DH) and soluble peptides separated from the total hydrolysate. The hydrolysate and its soluble peptide fraction were studied separately. Increased hydrolysis produced smaller peptides, with the smallest peptides remaining in the soluble fraction. Both hydrolysates and its soluble fraction had high ACE inhibition activities, from 70% to 90.6%, depending on fraction and % DH. Results suggested that there is not a simple relationship between average peptide size and extent of % DH and ACE inactivation, but clearly the soluble fraction of the hydrolysate, containing the smallest peptides, is responsible for most of the ACE inhibition activity of the hydrolysate. Hydrolysates prepared from a pure and uniform catfish protein isolate substrate do therefore show a potential for ACE inhibition and may find use as bioactive ingredients. Copyright © 2007 Society of Chemical Industry
A new shallow water model with polynomial dependence on depth
Authors: Rodríguez José M. , Taboada‐Vázquez Raquel
Published: July 2007

In this paper, we study two‐dimensional Euler equations in a domain with small depth. With this aim, we introduce a small non‐dimensional parameter ε related to the depth and we use asymptotic analysis to study what happens when ε becomes small.

We obtain a model for ε small that, after coming back to the original domain, gives us a shallow water model that considers the possibility of a non‐constant bottom, and the horizontal velocity has a dependence onzintroduced by the vorticity when it is not zero. This represents an interesting novelty with respect to shallow water models found in the literature. We stand out that we do not need to makea prioriassumptions about velocity or pressure behaviour to obtain the model.

The new model is able to approximate the solutions to Euler equations with dependence onz(reobtaining the same velocities profile), whereas the classic model just obtains the average velocity. Copyright © 2007 John Wiley & Sons, Ltd.
The effect of parasitic components of GaAs FETs on high‐frequency gain
Authors: Seo Youngseok , Kim Bumman , Park Wee Sang
Published: July 2007

Parasitic component effects on the gain of GaAs FETs are described. Numerical simulation shows that the frequency range of the unstable region (K < 1) of an FET decreases as gate resistance, drain resistance, or source inductance increases, and as source resistance decreases. The increase of gate or drain resistance does not affect MSG but does reduce MAG. The increase of source inductance or resistance reduces MSG and MAG. The Mag degradation is due to the decrease of |y21/y12| for the source resistance and the increase of K for the other parasitics. These findings should be helpful in the design and analysis of microwave GaAs FETS. © 1993 John Wiley & sons, Inc.
A CG‐FFHT method for the scattering solution of axisymmetric inhomogeneous media
Authors: Liu Qing‐Huo , Chew Weng Cho
Published: July 2007

We propose a new technique to solve the integral equation for wave scattering by an axisymmetric inhomogeneity using the conjugate gradient (CG) method together with the fast Fourier‐Hankel transforms (FFHT). The method uses fast Hankel transform (FHT) and fast Fourier transform (FFT) requiring only O(N log N) floatingpoint operations per iteration and O(N) storage. © 1993 John Wiley & sons, Inc.
Spectral‐domain moment‐method analysis of coplanar microstrip parasitic subarrays
Authors: Chen Wei , Lee Kai‐Fong , Lee R. Q.
Published: July 2007

Coplanar subarrays consisting of one fed patch and two or more parasitic patches are studied using spectral‐domain full‐wave analysis and the moment method. Results are given for three‐element linear subarrays and the five‐patch cross. © 1993 John Wiley & sons, Inc.
Conditions of perfect absorption for a single‐layer electromagnetic‐wave absorber under oblique incidence
Authors: Liang C. H. , Zhao X. Y.
Published: July 2007

The conditions for perfect absorption under oblique incidence in a single‐layer homogeneous absorber backed by a perfectly conducting plate are derived in this article. The cases corresponding to the two types of polarization of the incidence‐wave, perpendicular polarization (TE) and parallel polarization (TM), are discussed, respectively. Some conclusions and curves are given. © 1993 John Wiley & sons, Inc.
A coaxial test fixture for characterizing low‐impedance microwave two‐terminal devices
Authors: Monahan Gregory P. , Morris Arthur S. , Steer Michael B.
Published: July 2007

A technique using a coaxial diode test fixture for the mount‐independent characterization of potentially unstable two‐terminal devices is presented. A standard three‐terminal calibration procedure using reference packages is used to calibrate to the surface of the packaged device. The test fixture is designed to present a low, nonresonant impedance to the device so that measurement resolution is enhanced. The characterization of an IMPATT diode is presented as an example. © 1993 John Wiley & sons, Inc.
On the time‐domain response of microstrip dipoles embedded in a low‐loss grounded dielectric slab
Authors: Cicchetti Renato
Published: July 2007

A space‐time analysis of the field radiated from microstrip dipoles embedded in a low‐loss grounded dielectric slab is proposed. The analysis is based on the dyadic Green's function method. The radiation mechanism as well as the structure electrical and geometrical parameters influencing the radiation phenomenon are analyzed. Design guidelines to reduce the amplitude of the radiated field, or its distortion, are suggested. © 1993 John Wiley & sons, Inc.
Evolution of a stokes wave pumped by an elementary soliton propagating in optical fibers
Authors: Zhao Y. , Yang S. W. , Tu B. F.
Published: July 2007

The production of a Stokes wave due to a Raman effect pumped by an elementary soliton propagating in optical fibers is studied analytically and numerically. The approximated analytical results show that cross‐phase modulation results in the added periodical amplification of the Stokes wave, and the maximum amplification distance exists due to the soliton pump fiber loss. The numerical results show that the smaller the pulse walk off, the greater the effect of the energy transfer from the soliton to the Stokes wave. © 1993 John Wiley & sons, Inc.
Application of filter theory in the design of twas based on FETS with different gate widths
Authors: Paoloni Claudio , Kosslowsky Stefan
Published: July 2007

A generalized approach for the design of traveling wave amplifiers will be presented. Compared to conventional methods our procedure introduces filter techniques in the TWA design. The main advantage is an improved input and output VSWR of the circuit. A complete amplifier design based on available technological process parameters will be demonstrated. The introduction of normalized parameters and charts results in a process‐independent applicability of the method. The method is well matched to the facilities of MMIC design since the demand for FETs with different gate widths can be satisfied easily. © 1993 John Wiley & sons, Inc.
Electromagnetic far‐field pattern modeling for an active microstrip antenna module
Authors: McDowall D. S. , Fusco V. F.
Published: July 2007

The far field of an active antenna module comprising a MESFET device with microstrip element terminations is modeled using a large‐signal harmonic balance technique and discrete two‐dimensional equivalents of the planar circuit elements. Simulated results are presented for comparison with the measured performance of the real antenna. © 1993 John Wiley & sons, Inc.
Detection of longitudinal electromagnetic fields in AIR
Authors: Giakos George C. , Ishii T. Koryu
Published: July 2007

By means of a small square loop antenna and an electric probe it was possible to detect significant longitudinal components of magnetic and electric fields, respectively, in the far zone in the air. Unique features of this observation are the abundance and the slow variation with radial distance of the detected longitudinal electromagnetic field components which seem to decay at a rate much slower than 1/r2. © 1993 John Wiley & sons, Inc.
Three‐dimensional nanometer structures
Authors: Chou Chih‐Chung , Gregory Don A.
Published: July 2007

Three‐dimensional (3D) structures in the nanometer range are difficult to create by conventional planar approaches. Having this capability would extend the variety of nanodevices, increase the device unit volume density dramatically, and approach a more completely miniaturized and integrated version of practical device systems. Such systems would be an advantage in signal processing because of low energy consumption and improved measurement resolution. © 1993 John Wiley & sons, Inc.
Scattering by thin lossy dielectric plates‐a finite‐difference time‐domain approach
Authors: Boonzaaier J. J. , Pistorius C. W. I.
Published: July 2007

This Letter discusses the computation of scattering by thin lossy nondispersive dielectrics using the finite‐difference time‐domain (FD‐TD) method. The time‐domain relationship between the electric fields normal to a lossy material boundary is used in a “smart cell” approach which allows the thickness of the dielectric to be less than the spatial grid size. These results are compared to the “brute force” FD‐TD approach. © 1993 John Wiley & sons, Inc.
Directivity versus element spacing for a scanning array
Authors: Zimmerman M. , Lee R. Q.
Published: July 2007

It is well known that for linear array antennas with isotropic elements, the directive gain depends upon the spacing between the elements. However, this relationship is not as well documented for planar arrays or arrays with medium gain elements, such as micro‐strip patches, particularly in scanned cases. In this article, linear, rectangular, and hexagonal arrays with both isotropic elements and medium gain elements are examined. © 1993 John Wiley & sons, Inc.
Slot synchronization in optical‐fiber ppm systems with gaussian‐type received pulse shapes
Authors: Cryan R. A. , Elmirghani J. M. H. , Clayton F. M.
Published: July 2007

The problem of determining the precise slot boundaries is an essential one in optical‐fiber pulse position modulation (PPM) systems due to the temporal nature of the format. Here we present an original spectral characterization of the PPM process and establish the requirements to realize a discrete spectral slot rate component. In particular we show that this component is independent of the modulation index and data probability distribution. The dependence of the component on pulse shapes is investigated and examined for the important class of dispersed Gaussian‐type pulse shapes normally associated with optical‐fiber transmission. Original practical results, measured on a 128‐slot PPM system, are presented and shown to be in agreement with the theoretical predictions to within 1 dB. © 1993 John Wiley & Sons, Inc.
The theory of chiroferrite waveguides
Authors: Shen Zhongxiang
Published: July 2007

The eigenvalue problem for the determination of propagation modes in a waveguide filled with a homogeneous chiroferrite medium is formulated. As an illustrative example the circular chiroferrite waveguide is analyzed, and the corresponding dispersion relations and diagrams are obtained. © 1993 John Wiley & Sons, Inc.
Broadband slant linearly polarized biconical antenna
Authors: Lakshminarayana D. , Prasad R. V. Hara , Mutiny T. G. K.
Published: July 2007

A broadband biconical antenna with a slant linear polarizer operating over 2‐26 GHz has been designed, fabricated, and tested. The antenna has yielded a nominal VSWR of less than 3.0 and an omni deviation of within ±3.0 dB. This antenna is highly compact and hence will find applications in systems where space requirements are very stringent. © 1993 John Wiley & Sons, Inc.
A generalized eigenvalue method for fdtd analyses
Authors: Ko Wai Lee , Aksun M. Irsadi , Mittra Raj
Published: July 2007

In this article we apply the generalized eigenvalue method (GEM) to extract the complex exponentials from a truncated time record computed by the finite‐difference time‐domain (FDTD) code for analyzing microwave integrated circuits. To obtain accurate scattering parameters without further FDTD computations, the truncated FDTD time record is efficiently extended into the future by summing the complex exponentials with complex coefficients determined by the least‐squares method. Numerical GEM results with fewer poles are shown to be in good agreement with those obtained by the Prony method with a large number of poles. © 1993 John Wiley & Sons, Inc.
Irradiance analysis for indoor point‐to‐point and quasidiffuse infrared channels
Authors: Gabiola Francisco J. , Betancor Manuel J. , Santamaría Asunción , Polo Angel , López‐Hernández Francisco J.
Published: July 2007

This article deals with the calculation of the irradiance produced by an optical system made up of a lens and a nonpunctual optical source with generalized Lambertian profile (cosn ð). This calculus can be applied to predict the size and power distribution of the irradiated area in point‐to‐point and quasidiffuse channels. Theoretical results are in good agreement with experimental measurements. © 1993 John Wiley & Sons, Inc.
A comparison of nonlinear behavior between matrix and distributed amplifiers
Authors: D'agostino S. , Massenzio M.
Published: July 2007

In this article we present the nonlinear simulations of a matrix amplifier and compare its power‐handling capabilities to those of a two‐stage distributed amplifier. The simulations confirm our hypothesis of better performances of the matrix over the usual distributed topology both in higher output power level and lesser harmonic distortion. The somewhat larger number of active devices, as compared with other topologies, makes the matrix topology particularly well suited for monolithic implementation. © 1993 John Wiley & Sons, Inc.
Longitudinal slots in dielectric‐filled rectangular waveguides
Authors: Rengarajan Sembiam R. , Steinbeck Michael
Published: July 2007

A longitudinal radiating slot cut in a broad wall of a dielectric filled rectangular waveguide is analyzed rigorously. Pertinent coupled integral equations for the aperture electric field of a thick wall slot are solved by the method of moments. Numerical results are presented for the slot characteristics over a range of permittivity values of the dielectric. Shunt admittance representation is found to be poor for higher values of the dielectric permittivity. © 1993 John Wiley & Sons, Inc.
Coplanar waveguide low‐pass filter using open circuit stubs
Authors: Kanamaluru Sridhar , Li Ming‐Yi , Chang Kai
Published: July 2007

A five‐element Chebyshev low‐pass filter having high roll off, built using coplanar waveguide open circuit stubs for the capacitive elements, is investigated. Passband ripple within 1.5 dB and a stop‐band rejection of more than 45 dB is achieved. Comparison of the predicted and experimentally measured results is presented and the agreement is good. © 1993 John Wiley & Sons, Inc.
Using engineered tbcco step edge junctions as microwave mixers
Authors: Fenzi N. O. , Aidnik D. L. , Soares E. R. , Bourne L. C. , Cardona A. H. , Rohlfing S. M.
Published: July 2007

A method for characterizing the noise and conversion loss performance of high‐temperature superconductor (HTS) nonlinear components is described. Data on conversion loss and noise figure for step edge junctions (SEJs) manufactured on HTS is presented and discussed. © 1993 John Wiley & Sons, Inc.
Effects of chirality admittance on the propagating modes in a parallel‐plate waveguide partially filled with a chiral slab
Authors: Toscano Alessandro , Vegni Lucio
Published: July 2007

The field distributions and cutoff equation of the propagating modes in chiral parallel‐plate waveguide are derived and the effects of chirality admittance on the cutoff wavelengths of the fundamental hybrid modes are examined. The results show that the cutoff wavelengths of the fundamental hybrid modes are approximately proportional to ζc, and that in chiral parallel‐plate waveguides, the longitudinal components of electric and magnetic fields are always coupled as in the chirowaveguide, etc.; TE, TM, or TEM modes cannot be supported. © 1993 John Wiley & Sons, Inc.
Analysis of the electro‐optic effect in anisotropic crystals with 2‐mm AND 3‐m point group symmetry using a first‐order perturbation technique
Authors: Faria J. A. Brandao
Published: July 2007

The results of a recently proposed perturbation approach are successfully applied to the analysis of the Pockels effect in some representative electro‐optic crystals, namely, potassium niobate and lithium niobate crystals. © 1993 John Wiley & Sons, Inc.
New three‐configuration fet deembedding method
Authors: Gerard H. , Mouquet Y.
Published: July 2007

We have developed a new de‐embedding method for III‐V VET chips designed without a via hole. This method makes accurate measurement of access wire inductances and pad capacitances possible, without the need for any simplifying assumptions regarding the equivalent circuit [1] or additional scaling developments [2]. © 1993 John Wiley & Sons, Inc.
Proposal of all‐optical shuffle multihop networks with dedicated and shared channels
Authors: Camarda P. , D'orazio A. , Nuovo M. M. , Matera F. , Settembre M.
Published: July 2007

In this work we show how to implement all‐optical shuffle multihop networks with network interface units presenting a general value of inputs and outputs and taking into consideration both dedicated and shared channels.
Full nonlinear analysis of near‐carrier noise in discriminator‐stabilized microwave oscillators
Authors: Rizzoli Vittorio , Mastri Franco , Masotti Diego , Neri Andrea
Published: July 2007

The Letter demonstrates the application of modern nonlinear CAD techniques based on the harmonic‐balance method to the computation of near‐carrier noise in microwave oscillators stabilized by a discriminator‐based feedback loop. Oscillator noise is described as being generated by two basic mechanisms: a fundamental‐frequency jitter due to noise‐induced frequency modulation of the carrier, and a phase jitter due to the superposition on the carrier of upper and lower noise sidebands generated by frequency conversion in the nonlinear devices. The numerical analysis is fully general purpose and can be applied to oscillator topologies of arbitrary complexity in a straightforward way. The simulation technique is applied to an ultra‐low‐noise discriminator‐stabilized dielectric‐resonator oscillator, and is shown to exactly predict the measured noise performance of the real circuit.
Multimode operation of antenna integrated microwave quantumwell‐diode oscillator
Authors: Rydberg A. , Forsgren M. , Brugger H. , Landgraf B. , Willander M.
Published: July 2007

Theoretical and experimental results for QW‐diode oscillators integrated with a rectangular microstrip antenna, forming an active antenna, are reported. Multimode operation is demonstrated for the active antenna, with an equivalent isotropic radiated power (EIRP) of 0.73 mW for the antenna TM01 mode, at 810 MHz. © 1994 John Wiley & Sons, Inc.
Nonlinear optical microwave interactions in microstrip linear resonators in GaAs
Authors: Kwark Bongsin , Yeh Chun‐Liang , Ho Chien‐Hsun , Weichold Mark H. , Chang Kal , Taylor Henry F.
Published: July 2007

A new optoelectronic mixer parametric amplifier has been fabricated in semiinsulating GaAs using a microstrip linear resonator structure with photoconductive gaps. Schottky contacts were used to produce nonlinear response characteristics, which were characterized with optical and microwave excitations. Harmonic frequencies were optically generated up to 14.6 GHz by illuminating the photoconductive gap with a GaAlAs laser diode modulated near the fundamental resonant frequency of 4.9 GHz. An optical input at frequency frf was mixed with a microwave input at fLO to obtain sum and difference frequencies fLO ± frf. Parametric amplification of the optical input of up to 29 dB was obtained. © 1994 John Wiley & Sons, Inc.
A recursive LU decomposition algorithm
Authors: Twig Yigal , Kastner Raphael
Published: July 2007

A recursive LU decomposition scheme extends the capabilities of nonrecursive algorithms for the reduction of computation time when geometrical modifications are made to a precomputed scatterer. Significant savings are achieved for cases of many different attachments, or when the initial scatterer is amenable to a particular efficient solution. © 1994 John Wiley & Sons, Inc.
On the existence condition for bistability in a one‐coupler optical fiber ring resonator by using degenerate two‐wave mixing
Authors: Ja Y. H.
Published: July 2007

The existence condition for bistability, B2G > 1, in a one‐coupler single‐mode optical fiber ring resonator using two different all‐fiber schemes of degenerate two‐wave mixing (DTWM) is studied in detail. It is shown that the existence condition for bistability is in general a necessary condition only, not a sufficient condition for the occurrence of the DTWM bistability. © 1994 John Wiley & Sons, Inc.
Mixing properties of a 20‐GHz‐bandwidth 1.5‐μm MQW DFB laser in Ku and Ka bands
Authors: Mathoorasing D. , Kazmierski C. , Blez M. , Ougazzaden A. , Mircea A.
Published: July 2007

Investigation of microwave mixing properties of MQW DFB lasers in the millimeter‐wave domain showed efficient conversion loss for both analog and digital signals. Conversion losses as low as 3, 7.5, and 14 dB have been found for a 5‐GHz local oscillator around the second, third, and fourth (20.95 GHz) harmonic frequencies, respectively. © 1994 John Wiley & Sons, Inc.
Improved computational efficiency for the FDTD method
Authors: Zhao Ping‐Ya , Wu Chen , Litva John
Published: July 2007

In this short article we present a new fast finite‐difference timedomain (FDTD) method. Producing exactly the same solution to Maxwell's equations as Yee's classic FDTD method, the fast FDTD method offers up to a 50% reduction in the number of multiplications, which is a very important indicator of the computational complexity of an algorithm. Mathematical analysis and computer simulations are given in the article. © 1994 John Wiley & Sons, Inc.
Characteristics of a rectangular microstrip patch antenna with protecting spaced dielectric superstrate
Authors: Afzalzadeh Reza , Karekar R. N.
Published: July 2007

A dielectric protecting superstate with spacing on the order of one wavelength from the rectangular microstrip patch antenna and of thickness up to about half a wavelength shows very small variation in resonance frequency (fr) and reflection coefficient (Γ). Effects of the same on radiation pattern (RP) includes drastic changes in beamwidths. By use of the spaced superstate the patch can be protected without the need to redesign parameters like frand Γ. © 1994 John Wiley & Sons, Inc.
Determination of excitation voltages of a slotted waveguide array
Authors: Narasimhan M. S. , Rao R. Sriharl , Jayakumar Immanuel
Published: July 2007

A technique for determination of excitation voltages of a linear waveguide slotted array from its measured radiation pattern is described in this Letter. Only the measured far‐field amplitude pattern is used for calculating the slot excitation voltages using FFT algorithm. © 1994 John Wiley & Sons, Inc.
Harmonic and intermodulation performance of nonlinear optical directional couplers
Authors: Abuelma'attl Muhammad Taher
Published: July 2007

A Fourier‐series model describing the input‐output characteristic of nonlinear optical directional couplers is presented. Using this model, closed‐form expressions are obtained for the harmonic and intermodulation performance of nonlinear optical directional couplers excited by multisinusoidal signals. © 1994 John Wiley & Sons, Inc.
The modified equivalent surface current for biisotropic media
Authors: Rong Yu
Published: July 2007

The concept of the modified equivalent surface current is introduced for an electromagnetic field in a homogeneous and biisotropic region. © 1994 John Wiley & Sons, Inc.
PulsedI‐Vcharacterization and noise measurements for an accurate hbt large‐signal model
Authors: Dlenot Jean‐Marc , Plana Robert , Gayral Michel , Graffeull Jacques
Published: July 2007

The various model parameters involved in an HBT large‐signal model based on the Ebers‐Moll topology have been extracted from noise measurements, pulsed I‐V characterizations, and S‐parameter measurements. Using this model a good correlation has been established between the estimated and measured output power variations versus the input power of a GaAlAs/GaAs HBT. © 1994 John Wiley & Sons, Inc.
New architecture for selfrouting photonic ATM switching with self‐synchronization and optically processed control
Authors: Zhang Jian‐Guo
Published: July 2007

A new architecture is presented to optically self‐route photonic ATM switching. Two wavelengths are used to carry clock‐data and address signals, respectively. This allows to independent processing of both signals at each switching mode; so the complexity of optical routing controllers is reduced while the reliability of address decoding is improved. © 1994 John Wiley & Sons, Inc.
Study of tunneling time in tunneling BI‐quantum‐well and resonant tuneling barrier structures
Authors: Sugiyama Yoshihiro , Inata Tsuguo , Tackeuchi Atsushi , Nakata Yoshiaki , Nakamura Satoshi , Muto Shunichi
Published: July 2007

We studied the electron tunneling time in tunneling bi‐quantum‐well and resonant tunneling burrier structures with a pump‐probe photo‐luminescence system using optical mixing. The tunneling time decreased as the temperature increased, which is attributed to electrons in an exciton state thermalizing into free electrons having a faster tunneling time. © 1994 John Wiley & Sons, Inc.
Theoretical and experimental studies of electric‐field‐induced refractive index change in quantum‐film, ‐wire, and ‐box structures
Authors: Ravikumar K. G. , Aizawa T. , Shimomura K. , Kikugawa T. , Asada M. , Aral S. , Suematsu Y. , Yamauchi R.
Published: July 2007

In this article we report theoretical as well as experimental studies of the electric‐field‐induced refractive index change in InGaAs/InP quantum‐well structures, viz., quantum‐film, quantum‐wire, and quantum‐box structures. The refractive index change, easily measured using a Mach‐Zehnder interferometer setup, was around 1%, 4%, and 7% in quantum film, quantum wire, and quantum box, respectively, in the longer‐wavelength region corresponding to the positive refractive index change peak. Moreover, we will discuss that the refractive index change dependency on the polarization of incident light in a quantum film can be controlled by introducing suitable tensile strain in it. It was found that for a well width of 11 nm, 0.3% tensile strain should be induced to obtain polarization‐independent refractive index change. © 1994 John Wiley & Sons, Inc.
Flip‐chip lnAlAs/lnGaAs superlattice avalanche photodiodes with back‐illuminated structures
Authors: Hanatani Shoichi , Nakamura Hitoshi , Tanaka Shigehisa , Ido Tatemi , Notsu Chiaki
Published: July 2007

A transparent InAlAs/InGaAs superlattice (SL) multiplication layer at a wavelength of 1.55 μm was realized by using quantum‐size effect. Using this SL, flip‐chip separate absorption and multiplication InAlAs/InGaAs SL avalanche photodiodes with back‐illuminated structures were demonstrated. A dark current lower than 2 μA at a multiplication factor of 10, a large gain‐bandwidth product of 110 GHz, and a wide bandwidth of 12 GHz were obtained at the wavelength of 1.55 μM. © 1994 John Wiley & Sons. Inc.
Multiple‐quantum‐well optical modulators and their monolithic integration with DFB lasers for optical‐fiber communications (invited paper)
Authors: Wakita Koichi , Kotaka Isamu
Published: July 2007

High‐speed, low‐driving‐voltage operation of multiple‐quantum‐well (MQW) external modulators based on the quantum‐confinement Stark effect (QCSE) operating at long wavelengths are reviewed. We discuss the design and characteristics of ultrafast intensity and phase MQW modulators that have been developed by our group and we compare them with those of other material systems and structures based on a defined figure of merit for external modulators. In addition, we discuss a new integrated light source that enables external modulation of an in‐plane DFB laser to reduce wavelength chirping and coupling loss with a laser and a modulator. Finally, we describe new applications for optical soliton pulse generation using the above intensity modulator. © 1994 John Wiley & Sons, Inc.
High‐speed modulation of GaAs/AlGaAs multiple‐quantum‐well (MQW) asymmetric Fabry‐Perot (ASFP) reflection modulator
Authors: Nawaz M. , Olsen Borgar T. , MaCilvaney K.
Published: July 2007

We report the high‐frequency performance of GaAs/AlGaAs multiple‐quantum‐well‐ (MQW‐) based asymmetric Fabry‐Perot (ASFP) reflection modulator. The measured frequency response bandwidth of the modulator was ∼600 MHz at an applied voltage of only 5 V at a wavelength of ∼854 nm. The differential contrast of the modulator was 4.0 at an applied voltage of 12.5 at a wavelength of 863 nm. © 1994 John Wiley & Sons, Inc.
High‐power 0.98‐μm strained‐layer quantum‐well lasers with InGaP cladding
Authors: Ijichi Tetsuro , Ohkubo Michio , Iketani Akira , Kikuta Toshio
Published: July 2007

Recent progress on InGaAs/GaAs strained‐layer quantum‐well lasers using InGaP cladding are reported. The 0.98‐, 1.02‐, and 1.06‐μm polyimide buried ridge waveguide lasers fabricated by using selective chemical etching are applicable to high‐power use. Further, employing InGaAsP layers lattice matched to GaAs enables the realization of GRIN‐SCH lasers, which is expected to be a technique to improve the laser characteristics. © 1994 John Wiley & Sons, Inc.
High‐efficiency InGaAs/InGaAsP compressively strained multiple‐quantum‐well laser diode
Authors: Ogita Shouichi , Kobayashi Hirohiko , Higashi Toshio , Okazaki Niro , Aoki Osamu , Soda Haruhisa
Published: July 2007

The characteristics of the InGaAs/InGaAsP compressively strained multiple‐quantum‐well laser diodes with thin wells were studied experimentally to realize the pumping laser diode for the optical‐fiber amplifier. High external quantum efficiency and comparatively low threshold current density were obtained when the thickness of the well was reduced to less than 2 nm. It was also found that the characteristic temperature depends only on the optical confinement to the wells when the optical confinement factor is smaller than 1.5%. Output power as high as 210 mW was demonstrated in the coated sample with the optimized well structure. © 1994 John Wiley & Sons, Inc.
Extremely low power penalty in 2.5‐Gb/S transmission experiment using 1.55‐μm MQW‐DFB lasers with optimized QW number
Authors: Kawano M. , Aoyagi T. , Watanabe H. , Takiguchi T. , Nakajima Y. , Takemoto A. , Hirano R.
Published: July 2007

For 1.55‐μm MQW‐DFB lasers, the dependence of transmission characteristics under 2.5‐Gb/s modulation on the number of wells is investigated experimentally and theoretically. The fiber length is 70 km and the total dispersion is 1470 ps/nm. Extremely low power penalty of 1.3 dB is obtained for a 12‐well laser with large differential gain of 7.1 × 10−16 cm2. © 1994 John Wiley & Sons, Inc.
Application of the 2D finiteelement/boundary‐element method to scattering from coated aerofoils
Authors: Meyer F. J. C. , Davidson D. B.
Published: July 2007

A two‐dimensional solver combining the finite‐element method (FEM) with the boundary‐element method (BEM) has been implemented and results have previously been compared to analytical solutions using canonical problems. The code has now been applied to predict scattering from electromagnetically larger, inhomogeneous, and lossy objects of more complex shape, including a coated aerofoil, and the results are compared to analytical as well as experimental data. The cross sections modeled were up to 15 wavelengths in Size. © 1994 John Wiley & Sons, Inc.
A C‐band microstrip varactor‐tuned reflection phase shifter employing UHF general‐purpose diodes
Authors: Brewster B. D. , Robertson I. D.
Published: July 2007

A 4‐GHz phase shifter based on a hybrid coupler terminated with reverse‐biased UHF general‐purpose diodes is shown capable of providing excellent tuning responses, adequate for noncritical applications. The assembly demonstrates that considerable component specijcation relaxation can be implemented for low microwave frequencies. © I994 John Wiley & Sons, Inc.