bluuebunny/crossref_metadata_2025 huggingface dataset:
High temporal resolution functional MRI using parallel echo volumar imaging
Authors: Rabrait Cécile , Ciuciu Philippe , Ribés Alejandro , Poupon Cyril , Le Roux Patrick , Dehaine‐Lambertz Ghislaine , Le Bihan D. , Lethimonnier F.
Published: March 2008

Purpose

To combine parallel imaging with 3D single‐shot acquisition (echo volumar imaging, EVI) in order to acquire high temporal resolution volumar functional MRI (fMRI) data.

Materials and Methods

An improved EVI sequence was associated with parallel acquisition and field of view reduction in order to acquire a large brain volume in 200 msec. Temporal stability and functional sensitivity were increased through optimization of all imaging parameters and Tikhonov regularization of parallel reconstruction. Two human volunteers were scanned with parallel EVI in a 1.5T whole‐body MR system, while submitted to a slow event‐related auditory paradigm.

Results

Thanks to parallel acquisition, the EVI volumes display a low level of geometric distortions and signal losses. After removal of low‐frequency drifts and physiological artifacts, activations were detected in the temporal lobes of both volunteers and voxelwise hemodynamic response functions (HRF) could be computed. On these HRF different habituation behaviors in response to sentence repetition could be identified.

Conclusion

This work demonstrates the feasibility of high temporal resolution 3D fMRI with parallel EVI. Combined with advanced estimation tools, this acquisition method should prove useful to measure neural activity timing differences or study the nonlinearities and nonstationarities of the BOLD response. J. Magn. Reson. Imaging 2008;27:744–753. © 2008 Wiley‐Liss, Inc.
Mass spectrometric analysis of the marine lipophilic biotoxins pectenotoxin‐2 and okadaic acid by four different types of mass spectrometers
Authors: Gerssen Arjen , Mulder Patrick , van Rhijn Hans , de Boer Jacob
Published: March 2008

The performances of four different mass spectrometers [triple‐quadrupole (TQ), time‐of‐flight (ToF), quadrupole ToF (Q‐ToF) and ion trap (IT)] for the detection of the marine lipophilic toxins pectenotoxin‐2 (PTX2) and okadaic acid (OA) were investigated. The spectral data obtained with the different mass spectrometric analyzers were used to propose fragmentation schemes for PTX2 in the positive electrospray mode and for OA in the negative electrospray mode. TQ data were used to obtain product ions, while ToF and Q‐ToF‐MS produced accurate mass data of the precursor ion and product ions, respectively. IT data provided a better understanding of the fragmentation pathways using MSn experiments. With respect to analytical performance, all four mass analyzers showed a good linearity (R2 > 0.97) and repeatability (CV < 20%). Detection limits (LoDs) (S/N = 3) were the lowest on triple‐quad MS: 12.2 and 2.9 pg on‐column for PTX2 and OA, respectively. Copyright © 2008 John Wiley & Sons, Ltd.
Genetic diversity of endophytic bacteria which could be find in the apoplastic sap of the medullary parenchym of the stem of healthy sugarcane plants
Authors: Velázquez Encarna , Rojas Marcia , Lorite María José , Rivas Raúl , Zurdo‐Piñeiro José Luis , Heydrich Mayra , Bedmar Eulogio J.
Published: March 2008

The genetic diversity of 29 endophytic bacterial strains isolated from apoplastic sap of the medullary parenchym of the stem of healthy sugarcane plants grown in Cuba was analysed by Two Primers‐Ramdom Amplified Polymorphic DNA fingerprinting (TP‐RAPD) and 16S rRNA gene sequencing. The strains were distributed into 17 groups on the basis of their TP‐RAPD patterns, and a representative strain from each group was subjected to 16S rRNA gene sequencing. Analysis of these sequences showed that the isolates belong to a wide variety of phylogenetic groups being closely related to species of genera Bacillus and Staphylococcus from Firmicutes, Microbacterium, Micrococcus and Kokuria from Actinobacteria, Rhizobium and Gluconacetobacter from α ‐Proteobacteria, Comamonas and Xanthomonas from β ‐Proteobacteria, and Acinetobacter and Pantoea from γ ‐Proteobacteria. These results show the complexity of the bacterial populations present in inner tissues of sugarcane, and indicate the interest and relevance of the studies on microbial diversity to improve our knowledge on the plant endophytic bacterial communities. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of iron and chelator on siderophore production in Frankia strains nodulating Hippophae salicifolia D. Don
Authors: Singh Anju , Mishra Arun Kumar , Singh Satya Shila , Sarma Hridip Kumar , Shukla Ekta
Published: March 2008

Effect of iron and chelator on the growth and siderophore production in the ten newly Frankia strains isolated from the root nodules of Hippophae salicifolia D. Don and the two reference strains were studied. Growth of the strains was greatly affected when grown in the iron and EDTA deprived conditions. All the strains were capable of producing both the hydroxamate and catecholate type siderophore that was detected using the Csaky and Arnow assays. Production of siderophore was enhanced in the EDTA replenish condition in contrast to the iron supplemented medium suggesting that EDTA reduces the availability of other free metals and hence creates the stress condition for which the secretion of siderophore is enhanced. A decrease in siderophore production was observed with an increase in iron concentration. Strains HsIi2 and HsIi10 were found to be producing more siderophore than the other strains. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Removal of chromium (VI) through biosorption by the Pseudomonas spp. isolated from tannery effluent
Authors: Srivastava Jatin , Chandra Harish , Tripathi Kirti , Naraian Ram , Sahu Ranjeev K
Published: March 2008

Heavy metal contamination of the rivers is a world wide environmental problem and its removal is a great challenge. Kanpur and Unnao two closely located districts of Uttar Pradesh India are known for their leather industries. The tanneries release their treated effluent in the near by water ways containing Cr metal that eventually merges with the river Ganges. Untreated tannery effluent contains 2.673 ± 0.32 to 3.268 ± 0.73 mg l–1 Cr. Microbes were isolated, keeping the natural selection in the view, from the tannery effluent since microbes present in the effluent exposed to the various types of stresses and metal stress is one of them. Investigations include the exposure of higher concentrations of Cr(VI) 1.0 to 4.0 mg l–1 to the bacteria (presumably the Pseudomonas spp.) predominant on the agar plate. The short termed study (72 h) of biosorption showed significant reduction of metal in the media especially in the higher concentrations with a value from 1.0 ± 0.02, 2.0 ± 0.01, 3.0 ± 0, and 4.0 ± 0.09 at zero h to 0.873 ± 0.55, 1.840 ± 1.31, 2.780 ± 0.03 and 3.502 ± 0.68 at 72 h respectively. The biosorption of metal show in the present study that the naturally occurring microbes have enough potential to mitigate the excessive contamination of their surroundings and can be used to reduce the metal concentrations in aqueous solutions in a specific time frame. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of farnesol on the morphogenesis of Aspergillus niger
Authors: Lorek Justine , Pöggeler Stefanie , Weide Mirko R. , Breves Roland , Bockmühl Dirk P.
Published: March 2008

Farnesol was the first quorum‐sensing regulator to be found in eukaryotic cells. In Candida albicans, a dimorphic fungal human pathogen, farnesol blocks the yeast‐to‐filamentous growth transition. Here we show that in Aspergillus niger farnesol acts as an inhibitor of conidiation: Colonies grown on media containing farnesol were unable to develop conidia. Although farnesol treated A. niger cultures exhibited a colony morphology resembling the “fluffy” phenotype of A. nidulans, which is caused by a hyperactive G‐protein/cAMP pathway, the intracellular level of cAMP in A. niger mycelia grown in presence of farnesol is greatly diminished. Furthermore, whereas inhibiting adenylyl cyclase led to a farnesol‐like effect, the addition of external cAMP inhibited conidiation without causing a “fluffy” phenotype. This suggests that the mechanisms regulating conidiation in A. niger and A. nidulans are different. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Translational research: Whither the ORS?
Authors: Jacobs Joshua J.
Published: March 2008

There is a hue and cry from the public, policy makers and funding agencies about the primacy of research translation. The federal government has responded with the NIH Roadmap for Medical Research initiative. It is proposed that the Orthopaedic Research Society (ORS) initiate its own translational roadmap along themes that parallel the NIH Roadmap: the formation of interdisciplinary teams; the focus on specific musculoskeletal diseases; cross disciplinary education in essential translational research skills; fostering translational career pathways; and providing critical fora for translational research interactions–a “translational interface.” By its very structure, the ORS is an organization that is uniquely poised to help its members respond to the demands for research translation. The roadmap outlined around these five themes is intended to make the ORS even more relevant in our professional lives and to transform the ORS into an organization that is a true catalyst for improving the musculoskeletal health of the public. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:737–740, 2008
Semipreparative chiral supercritical fluid chromatography in the fractionation of lansoprazole and two related antiulcer drugs enantiomers
Authors: Toribio Laura , del Nozal María J. , Bernal Yagüe L. , Alonso Cristina , Jiménez Juan J.
Published: March 2008

The semipreparative chiral separation of lansoprazole and two related compounds (pantoprazole and rabeprazole) using supercritical fluid chromatography (SFC) is presented in this work. Different loads were evaluated in order to obtain high enantiomeric purities and production rates. The volumes injected were 1, 2 and 4 mL. The concentrations of the racemic mixtures were 3 and 6 g/L for lansoprazole and 1.5 g/L for pantoprazole and rabeprazole. In all the cases, the recoveries, for a purity higher than 99.9%, were better for the second eluted enantiomer than for the first one. This fact conditioned the production rate of the first eluted enantiomer that, considering a fixed purity, was always lower than that obtained for the other one. In the case of lansoprazole it was possible to obtain 0.025 and 0.090 mg/min of the first and second eluted enantiomer, respectively, with an enantiomeric purity of 99.9%. For rabeprazole enantiomers 0.037 and 0.062 mg/min, and in the case of pantoprazole the results were better (0.062 and 0.122 mg/min) due to the higher resolution.
Extraction of carotenoids and chlorophyll from microalgae with supercritical carbon dioxide and ethanol as cosolvent
Authors: Macías‐Sánchez Ma Dolores , Mantell Serrano Casimiro , Rodríguez Rodríguez Miguel , Martínez de la Ossa Enrique , Lubián Luís M. , Montero Olimpio
Published: March 2008

The extraction of carotenoids and chlorophylls using carbon dioxide modified with ethanol as a cosolvent is an alternative to solvent extraction because it provides a high‐speed extraction process. In the study described here, carotenoid and chlorophyll extraction with supercritical CO2 + ethanol was explored using freeze‐dried powders of three microalgae (Nannochloropsis gaditana, Synechococcus sp. and Dunaliella salina) as the raw materials. The operation conditions were as follows: pressures of 200, 300, 400 and 500 bar, temperatures of 40, 50 and 60°C. Analysis of the extracts was performed by measuring the absorbance and by using empirical correlations. The results demonstrate that it is necessary to work at a temperature of 50–60°C and a pressure range of 300–500 bar, depending on the type of microalgae, in order to obtain the highest yield of pigments. The best carotenoid/chlorophyll ratios were obtained by using supercritical fluid extraction + cosolvent instead of using conventional extraction. The higher selectivity of the former process should facilitate the separation and purification of the two extracted pigments.
Lasing characteristics of a CW Tm:LuAG laser with a set of double cavity
Authors: Wu C T , Ju Y L , Wang Z G , Li Y F , Ma H Y , Wang Y Z
Published: March 2008

Lasing characteristics of a CW Tm:LuAG with a set of double cavity is presented in this letter. As the air gap etalon keeping at 342 μm, the highest output power reaches 107.8 mW when the totally input pump power is 1.95 W. The output center wavelength is 2027.0 nm. A single longitude mode output power of 17.1 mW is obtained when incident pump power is 855.1 mW. With the changing of DC voltage on the Piezoelectric Transducer (PZT) holding the output coupler, the reflection of the effective mirror changes correspondingly. The oscillating wavelength shifts from 2022 nm to 2031 nm. To our knowledge, this work is the first time to investigate the double cavity design in Tm:LuAG to achieve single longitude mode and tuning oscillation wavelength output laser.
Organ pipes and tin pest
Authors: Eckert A.
Published: March 2008

This article introduces various aspects of a diploma thesis on the theme of ‘tin pest in organ pipes’ submitted to the Fachhochschule in Cologne. One aspect concerns the difference between corrosion and tin pest in organ pipes, another explains the polymorphous property of tin. This is followed by a report on the research and documentation on 12 suspected cases of tin pest. A case of tin pest in an alloy of tin and lead in an Estonian organ receives particular attention, not least because hitherto it has often been assumed that tin pest could only occur in pure tin. Finally, the necessary conditions for an occurrence of tin pest are discussed as well as recommendations on treating organ pipes which have been damaged by tin pest.
Ring‐Opening Metathesis Polymerization of Amino Acid‐Functionalized Norbornene Diamide Monomers: Polymerization Behavior and Chiral Recognition Ability of the Polymers
Authors: Sutthasupa Sutthira , Sanda Fumio , Masuda Toshio
Published: March 2008

Amino acid‐derived novel norbornene monomers were synthesized and polymerized with ruthenium catalysts. The polymerization rates were affected by the stereo structure of the monomers; exo,exo‐NBL underwent ROMP faster to give the polymers in higher yields than the endo,exo‐counterpart. The Grubbs 2nd generation catalyst was the most effective for the amino acid‐based monomers. A polymer gel was synthesized by the copolymerization of exo,exo‐NBL with 2.5 mol‐% of bifunctional norbornene monomer. The gel adsorbed larger amounts of (R)‐phenylalaninol and N‐(benzyloxycarbonyl)alanine than those of the (S)‐isomers.

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The Effect of PEG Crystallization on the Morphology of PEG/Peptide Block Copolymers Containing Amyloid β‐Peptide Fragments
Authors: Krysmann Marta J. , Funari Sérgio S. , Canetta Elisabetta , Hamley Ian W.
Published: March 2008

Ordered nanostructures are observed in the melt and solid state for a series of three peptide/PEG conjugates containing fragments of amyloid β‐peptides. These are conjugated to PEG with $\overline M _{\rm n}$ = 3 300 g · mol−1 and a melting temperature Tm = 45–50 °C. The morphology at room temperature is examined by AFM and POM. This shows spherulite formation for the weakly fibrillizing KLVFF‐PEG sample but fibril formation for FFKLVFF‐PEG. The fibrillization tendency of the latter is enhanced by multiple phenylalanine residues. Simultaneous SAXS and WAXS was used to investigate the morphology as a function of temperature. The secondary structure is probed by FTIR.

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Engineering Polymer Informatics: Towards the Computer‐Aided Design of Polymers
Authors: Adams Nico , Murray‐Rust Peter
Published: March 2008

The computer‐aided design of polymers is one of the holy grails of modern chemical informatics and of significant interest for a number of communities in polymer science. This paper outlines a vision for the in silico design of polymers and presents an information model based on modern semantic web technologies, thus laying the foundations for achieving the vision.

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Intramolecular Click Cycloaddition: An Efficient Room‐Temperature Route towards Bioconjugable Polymeric Nanoparticles
Authors: de Luzuriaga Alaitz Ruiz , Ormategui Nerea , Grande Hans J. , Odriozola Ibon , Pomposo José A. , Loinaz Iraida
Published: March 2008

A highly efficient room‐temperature synthetic route to bioconjugable polymeric nanoparticles in the 5–20 nm size range based on single‐chain intramolecular click cycloaddition is described. It is illustrated by preparing single‐chain cross‐linked polymeric NPs from poly[MMA‐co‐(3‐azidopropyl methacrylate)‐co‐(3‐trimethylsilyl‐propyn‐1‐yl methacrylate)] terpolymers using a one‐pot procedure and a continuous addition technique. For polymeric NPs with an excess of azide groups, aminoacid/PMMA NPs were easily obtained by performing a second click reaction with propargyl glycine. This versatile and general method opens the way to the synthesis of other kinds of polymeric and bioconjugated NPs beyond those reported in this communication.

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Synthesis of Near‐Infrared Responsive Gold Nanorod/PNIPAAm Core/Shell Nanohybrids via Surface Initiated ATRP for Smart Drug Delivery
Authors: Wei Qingshan , Ji Jian , Shen Jiacong
Published: March 2008

Nanosized near infrared (NIR) responsive nanohybrids are synthesized by surface‐initiated atom transfer radical polymerization (SI‐ATRP) of N‐isopropylacrylamide (NIPAAm) on gold nanorods (Au NRs). Transmission electron microscopy images demonstrate that the nanohybrids have a clear core/shell structure. Temperature‐variable 1H NMR spectroscopy, quasi‐elastic light scattering (QELS), UV‐vis spectroscopy, and laser irradiation prove that the nanohybrids are both temperature and NIR responsive. Norvancomycin (NVan) loading and release experiments show that the drug release rate can be modulated by NIR irradiation. Such an intelligent drug‐delivery system might find applications in non‐invasive controlled drug release in future.

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Poly(phenylethylnorbornene)s and their Hydrogenated Derivatives
Authors: Bishop John P. , Register Richard A.
Published: March 2008

Ring‐opening metathesis polymerization (ROMP) was used to synthesize novel ring‐opened poly[5‐(2‐phenylethylnorbornene)]. Hydrogenation can produce two different saturated derivatives, with the phenyl groups either preserved or saturated to cyclohexyl groups. These two different hydrogenated products allowed us to compare the effect of replacing the pendant phenyl groups with cyclohexyl groups on properties such as the glass transition temperature (Tg). We found that Tg decreased by only 2 °C (from 28 to 26 °C) upon replacement of the phenyl groups. This contrasts with the effect of saturating the phenyl groups in the addition polymer of 5‐(2‐phenylethylnorbornene), where the Tg increased by 34 °C, from 215 to 249 °C, a remarkable difference in magnitude and direction compared with the ROMP polymers.

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Triband branch line coupler using double‐Lorentz transmission lines
Authors: Lee Hanseung , Nam Sangwook
Published: March 2008

The concept of double‐Lorentz (DL) transmission lines (TL) provides two additional degrees of freedom in realizing triband microwave devices. The triband operation is accomplished by the flexible phase slope characteristic of the DL TL with the frequency. In this article, the theory, design procedure, and implementation of the triband quarter‐wave (λ/4) DL TL are presented. Moreover, the triband λ/4 open‐circuit stub and triband branch‐line coupler (BLC) are introduced for the application of mobile TV service. The simulated and measured results of these triband components are also presented. The λ/4 DL TL open‐circuit stub demonstrates insertion loss larger than 17 dB at each target band. The triband BLC has S‐parameters of output larger than −4.569 dB, return losses larger than 14 dB, isolations larger than 15 dB, phase differences of output 90° ± 5° at each target band. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1174–1177, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23311
Segmented analysis of a finite planar ridged tapered slot antenna array for wideband phased array
Authors: Kim Junyeon , So Joonho , Jang Won , Cheon Changyul
Published: March 2008

The segmented analysis method of a finite planar ridged tapered slot antenna (RTSA) array is presented to develop a wideband phased array with a triangular lattice. The RTSA array is segmented into two‐parts with a feeder and the arrays of tapered slot antenna (TSA) and these scattering parameters are analyzed respectively. This proposed method gives the merit of a great reduction of computational cost. To verify the advantage of this method, we build the numerical model of only one feeder and dual polarized arrays of TSA with 10 × 12 elements. The measured results of the fabricated array meet the design goals of 3:1 bandwidth, scan volume of ±45°, active VSWR (AVSWR) below 3:1. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1140–1143, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23314
Miniaturized quadrature hybrid coupler using high impedance lines
Authors: Mandal Mrinal Kanti , Velidi Vamsi Krishna , Bhattacharya Amitabha , Sanyal Subrata
Published: March 2008

In this article, a new configuration has been proposed for miniaturization of a branch‐line 90° hybrid coupler. The present coupler is obtained by replacing the low impedance series arms of a conventional coupler by their equivalent parallel high impedance lines. This arrangement facilitates meandering, used to realize a compact geometry. The main advantage of the proposed coupler is that it has approximately the same bandwidth as that of a conventional one. A prototype coupler area is 45.3% of that of a conventional branch‐line coupler. The design is validated by full‐wave electromagnetic simulation and measurement. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1135–1137, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23320
New bandwidth enhancement and multiresonance technique for microstrip patch antenna
Authors: Kumar Patra Pradyumna , Pattnaik S. S. , Devi Swapna , Vidyasagar Ch. , Sastry G. V. R. S. , Bakward K. M.
Published: March 2008

The quality factor, bandwidth, and efficiency are antenna's figures of merit and these are interrelated. There is no typical method that gives full freedom to optimize these independently. Here we proposed a novel and new method to optimize bandwidth with respect to radiation quality factor Qr. Slicing a substrate into two thin layers substrate, an impedance bandwidth of 12% is achieved while reducing the volume by 44.5%. The technique proposed shows that instead of single thick substrate, if two thin substrates are used, an enhancement of impedance bandwidth takes place while maintaining high antenna gain and radiation efficiency. This is a new and novel technique for bandwidth enhancement in microstrip patch antenna and is quite different from stacked antenna. In this article, we sliced a substrate into two thin substrates each of 1‐mm thick to achieve a bandwidth of 12% and radiation efficiency of 80.5549 with an overall volume reduction of 44.5%. While a single substrate of thickness 2.5 mm which is more than the total thickness of the discussed structure gives only 5% bandwidth for same antenna dimensions. The proposed structure will find potential application in MIMO antenna system due to its volume reduction and other enhanced features. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1162–1165, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23323
A second‐order dual‐band bandpass filter using a dual‐band admittance inverter
Authors: Zhang Hualiang , Chen Kevin J.
Published: March 2008

In this article, a second‐order dual‐band bandpass filter is designed. The filter consists of two dual‐band resonators connected by a dual‐band admittance inverter. The dual‐band resonator unit is made of two shunt stubs that coordinately produce two resonances. A novel dual‐band quarter‐wavelength line acts as the admittance inverter, providing suitable admittance transformations. To verify the design concept, a filter working at 2 and 5 GHz is devised and fabricated on Rogers' RO3006 printed circuit boards. In addition, the dual‐band filter is connected with a bandstop filter to suppress the unwanted spurious response. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1184–1187, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23326
Bandpass multitap microwave photonic filter with a round‐trip configuration
Authors: Ning G. , Shum P. , Aditya S. , Cheng Linghao , Dong H.
Published: March 2008

We propose a novel bandpass microwave photonic multitap filter configuration using a section of Hi‐Bi fiber in a round‐trip configuration. The configuration makes use of a chirped FBG both as a mirror and a dispersive device. Measured results are presented to show a two‐tap and three‐tap filter response, with a notch rejection greater than 35 dB and tunability of the level of secondary sidelobes by adjusting a polarization controller. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1181–1184, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23330
Reconstruction of the shape and location of arbitrary homogeneous objects using sequentially incidences
Authors: Khalaj‐Amirhosseini M. , Hodjat‐Kashani F. , Kamarei M.
Published: March 2008

In this study, a new approach is introduced to reconstruct the location and shape of arbitrary homogeneous scatterers (conductors and lossy or lossless dielectrics) with arbitrary contrast. First, the induction current is reconstructed for radiation of each transmitter. Then, the amplitude of all reconstructed induction currents are summed with each other as a suitable function to estimate the location and shape of the scatterers. The performance of the introduced procedure is verified using some examples. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1248–1251, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23334
Internal multiband loop antenna for GSM/DCS/PCS/UMTS operation in the small‐size mobile device
Authors: Lin Chun‐I , Wong Kin‐Lu
Published: March 2008

An internal multiband loop antenna suitable for application in the small‐size mobile device (groundplane length 50 mm only) is presented. Along the loop strip of the antenna, it is configured to have two symmetric meandered sections and a central widened section. With the configured loop strip, three resonant loop modes (0.5‐, 1.0‐, and 1.5‐wavelength loop modes) can be excited to form two wide operating bands centered at about 900 and 1900 MHz for GSM/DCS/PCS/UMTS operation in the small‐size mobile device. In addition, the loop antenna along with the short ground plane studied here shows near‐omnidirectional radiation patterns in the azimuthal plane for frequencies over the antenna's two wide operating bands, which is different from conventional internal mobile phone antennas and is advantageous for practical applications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1279–1285, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23337
Actively and passively excited sinusoidal microstrip and PCB strip antennas operating at K and millimeter‐wave bands
Authors: Salman A. O. , Cetinkaya H. , Vertiy A. A.
Published: March 2008

Actively and passively excited sinusoidal wire structure is applied to the PCB strip and microstrip structures successfully at K and millimeter‐wave frequency bands. Antenna dimensions are reduced till the half value, and more rigid structure is also obtained than the sinusoidal wire antennas by this way. Actively excited PCB sinusoidal antennas are investigated at these high frequencies and passively excited ones are introduced in the literature for the first time in this study. Transversely polarized broadside radiation is obtained for both types of antenna. The measured field patterns are compared with the calculated and simulated ones. The calculated patterns, phase velocity, and attenuation constants of investigated antennas are calculated by a written MATLAB code based the analytical approach. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1302–1308, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23347
Flexible multi‐T‐shaped monopole antenna for broadband operation
Authors: Jung Jinwoo , Lee Hyeonjin , Lim Yeongseog
Published: March 2008

A novel broadband multi‐T‐shaped monopole antenna is presented. The proposed antenna has a broadband impedance bandwidth of 32.9%, which covers PCS, UMTS, WiBro, and WLAN bands. For frequencies over the operating bands, the proposed antenna displays omni‐directional radiation patterns. The proposed antenna has compact dimensions of 14 mm × 14 mm. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1251–1253, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23355
High‐frequency characterization of packaging network in TO‐CAN photodiode modules
Authors: Zhu N. H. , Wen J. M. , Zhang S. J.
Published: March 2008

A simple method for analyzing the effects of TO packaging network on the high‐frequency response of photodiode modules is presented. This method is established based on the relations of the scattering parameters of the packaging network, photodiode chip, and module. It is shown that the results obtained by this method agree well with those obtained by the conventional comparison method. The proposed method is much more convenient since only the electrical domain measurements are required. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1219–1223, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23356
Compact dual‐band bandpass filter using stepped impedance resonators
Authors: Xu He‐Ming , Xiao Zhong‐Yin , Hu Hong‐Hong
Published: March 2008

A new dual‐band bandpass filter (BPF) for 2.4/5.2 GHz WLAN systems using two‐stepped impedance resonators is presented. With new properly coupled structure, this filter appears very compact and easy to be fabricated. Measured results show that this BPF has low insertion loss of 0.3 dB at 2.4 GHz and 0.7 dB at 5.2 GHz, and wide fractional bandwidths of 30% for the first band and 17% for the second band, respectively. Measured results are in good agreement with the simulated ones. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1292–1294, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23357
MIMO capacity dependence on realistic cross‐polarization and branch power ratios
Authors: Landon David , Furse Cynthia
Published: March 2008

The dependence of channel capacity on cross‐polarization and the branch power ratio is established over a wide range of both realistic and idealized values. An existing empirical model is adjusted to avoid self‐contradictory results for cross‐coupled, but uncorrelated energy. Typical ranges are highlighted for realistic channel measurements from the literature, and extreme cases are identified. The value of a peak capacity measure is established and compared with the outage and average capacities. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1384–1388, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23360
Parasitic coupled T‐shaped microstrip patch antenna
Authors: Neog D. K. , Pattnaik S. S.
Published: March 2008

A parasitic‐coupled T‐shaped microstrip patch antenna is discussed in this article. The T‐shaped microstrip patch antenna gives dual band resonant frequency on a thin substrate. The two resonant frequencies are within the 3 dB bandwidth that shows wide bandwidth. The experimental result is in good agreement with the calculated result. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1339–1341, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23363
A 60 GHz multiport front‐end architecture with integrated phased antenna array
Authors: Moldovan E. , Tatu S. O. , Affes S.
Published: March 2008

A new front‐end architecture dedicated to 60 GHz high‐speed short‐range communications is proposed. Multiport circuits based on hybrid couplers are intensively used for both phased antenna array and down‐conversion. The front‐end, integrated in planar technology on ceramic substrate, use several IF quadrature conversion circuits, corresponding to multiple directions of arrival. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1371–1376, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23367
Low‐profile wideband MIMO antenna with suppressing mutual coupling between two antennas
Authors: Kim Ilkyu , won Jung Chang , Kim Yongjin , eil Kim Young
Published: March 2008

A planar wideband multi‐input multi‐output (MIMO) antenna for small mobile devices is introduced. The proposed MIMO antenna system made up with two identical antennas operates in 2.3–5.9 GHz, which corresponds to Wibro 802.11a, 802.11b and Mobile WiMax 802.11n bands. The enhanced performance is obtained by placing antennas uniquely to suppress mutual coupling and utilizing supplemental structure to miniaturize the size of the antennas. The proposed antenna system is useful in wideband MIMO system, especially embedded in small mobile devices. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1336–1339, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23368
Analysis of the double negative metamaterials using FDTD
Authors: Fu Jia‐Hui , Meng Fan‐Yi , Yang Guo‐Hui , Wu Qun
Published: March 2008

Using the finite‐difference time‐domain method models ideal Drude of DNG metamaterials. The Z‐transform is applied to model the Drude model that materials characterized by frequency dispersive behavior. Thus, we certificate the DNG metamaterials and its unique characteristics such as negative refraction, convergence, back‐wave, phase compensation and verify the existence of DNG Metamaterials. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1411–1414, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23371
Design and implementation of capacitive coupled‐line structure bandstop filters
Authors: Her Man‐Long , Hsu Ming‐Wei , Ko Wen , Wang Yu‐Lin , Wang Kuo‐Ming , Wang Chia‐An , Hsu Chou‐Jung
Published: March 2008

In this article, we propose and design bandstop filters with capacitive coupled‐line structure. The coupled‐line structure has small area, wide bandwidth, and steep insertion loss response. In simulation, we used Serenade and Sonnet EM simulation tools to analyze the characteristics of filters. In circuit implementation, we selected FR‐4 substrates. We used coupled‐lines on capacitive coupling bandstop filters to reduce the size about 58% and to create two attenuated poles for increasing bandwidth. First we derived the relation between the odd‐mode and even‐mode impedance theoretically. Then, we applied EM software tools to choose a proper coupling distance to implement circuit layout. Finally, the measured results were compared with the simulated results, and we found that coupled‐lines can effectively improve the reduction size of the filters. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1363–1368, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23374
Design of a compact CPW‐fed UHF RFID tag antenna for metallic objects
Authors: Um Youngman , Kim Uisheon , Choi Jaehoon
Published: March 2008

A compact CPW‐fed UHF RFID tag antenna for metallic objects is proposed. It is less sensitive to the size of metallic objects and has a low profile and a long reading distance. The antenna consists of shorting walls, CPW feed line, a tag IC, and a radiating patch with Ishaped slits. The overall dimensions of the antenna are 55 mm × 26 mm ×2.2 mm. The tag IC has an input impedance of 43 ‐ j800 Ω at 915 MHz. When the antenna is mounted on 200 mm × 200 mm, 400 mm × 400 mm, and 600 mm × 600 mm planar metallic plates, the maximum reading distances are 5.1, 5, and 4.5 m, respectively. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1439–1443, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23378
Theoretical analysis and numerical verification of waveguide‐type directional coupler constructed into thin double‐layer dielectric substrate
Authors: Che Wenquan , Xu Lei , Dong Shiwei , Russer Peter
Published: March 2008

The waveguide‐type directional couplers constructed into double‐layer thin dielectric substrates have been investigated in this article. Based on coupling theory, the theoretical formulas of coupling factor and isolation for directional couplers with two different coupling structures have been derived. Good agreement between calculation and numerical simulations can be observed well, demonstrating the validity and accuracy of our formulas. These theoretical formulas are expected to find possible applications in the design of integrated direction couplers in LTCC or multilayer PCB technologies. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1397–1402, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23380
A miniaturized patch antenna at 2.4 GHz using uni‐planar compact photonic band gap structure
Authors: Eldek Abdelnasser A.
Published: March 2008

This article presents a miniaturized patch antenna for wireless applications at 2.4 GHz. A conventional microstrip‐fed patch antenna is firstly designed to operate close to 10 GHz. Then, the antenna is modified to operate at lower frequency without changing the antenna dimensions. First, the ground plane is replaced with a uniplanar‐compact‐photonic‐band‐gap (UC‐PBG) structure. Then, a backed conductor is placed close to the UC‐PBG and connected to it through four vias. These two modifications are utilized to decrease the lower operating frequency of the antenna from 9.7 to 2.42 GHz. Thus, a 75% size reduction factor is obtained. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1360–1363, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23381
Erratum: Application of new tools for the FDTD analysis of UWB antennas on dielectric substrates
Authors: Capoglu Ilker R. , Smith Glenn S.
Published: March 2008

New techniques are described for the FDTD analysis of radiating structures mounted on infinite planar dielectric substrates. These techniques are the near‐field‐to‐far‐field transform and the totalfield/scattered‐field boundary, or the plane‐wave injector. For demonstrating the use of these techniques, a practical ultra‐wideband antenna on an ungrounded dielectric substrate is analyzed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1447–1451, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23392
Design of novel miniaturized and high quality Sierpinski square resonators
Authors: Weng Min‐Hang , Chang Lin‐Shen , Chen Wei‐Yu , Hung Cheng‐Yuan , Yang Ru‐Yuan
Published: March 2008

In this article, miniaturized fractal‐shaped Sierpinski square resonators are presented. As the order of the Sierpinski square resonator increases, the resonant frequency decreases quickly and quality factor is enhanced. A high quality resonator based on the 3rd order Sierpinski square was fabricated on commercial substrate of RT/Duroid 5880 and measured using a network analyzer. The design procedure and limitation are clearly discussed in detail in this article. Measured results also have a good agreement with the simulated results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1469–1471, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23393
Application of the preconditioned GMRES to the Crank‐Nicolson finite‐difference time‐domain algorithm for 3D full‐wave analysis of planar circuits
Authors: Yang Y. , Fan Z. H. , Ding D. Z. , Liu S. B.
Published: March 2008

The increase of the time step size significantly deteriorates the property of the coefficient matrix generated from the Crank‐Nicolson finite‐difference time‐domain (CN‐FDTD) method. As a result, the convergence of classical iterative methods, such as generalized minimal residual method (GMRES) would be substantially slowed down. To address this issue, this article mainly concerns efficient computation of this large sparse linear equations using preconditioned generalized minimal residual (PGMRES) method. Some typical preconditioning techniques, such as the Jacobi preconditioner, the sparse approximate inverse (SAI) preconditioner, and the symmetric successive over‐relaxation (SSOR) preconditioner, are introduced to accelerate the convergence of the GMRES iterative method. Numerical simulation shows that the SSOR preconditioned GMRES method can reach convergence five times faster than GMRES for some typical structures. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1458–1463, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23396
An improved small‐signal equivalent circuit model for 4H‐SIC power mesfets
Authors: Xu Yuehang , Guo Yunchuan , Xu Ruimin , Yan Bo , Wu Yunqiu
Published: March 2008

The frequency‐dependence of parasitic resistances (Rs and Rd) for 4H‐SiC power MESFETs is empirical modeled by adding two disperse parameters based on conventional small‐signal equivalent circuit (CSEC). And a new extraction procedure for the modified SEC parameters is also proposed. The calculated S‐parameters using the modified SEC model (MSEC) fit the measured ones very well up to 20 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1455–1458, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23397
Reduced‐size microstrip four‐pole bandpass filter using two‐layer structure with quarter‐wavelength resonators and open stub inverters
Authors: Djaiz Azzeddine , Denidni Tayeb A. , Boutayeb Halim
Published: March 2008

A new miniature microstrip four‐pole bandpass filter using a two‐layer structure with quarter‐wavelength resonators and open stub inverters is proposed. The coupling between the resonators in the two layers is achieved via a slot etched on a common ground plane located between the layers. The open stub inverters are used to increase the selectivity of the filter and to avoid connection to ground plane that is generally required for quarter‐wavelength resonators of bandpass filter. A four‐pole bandpass filter with elliptic‐type performance is designed and tested at 2.45 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1485–1487, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23401
Printed‐circuit filters for wireless dual‐ and triple‐band applications
Authors: Rambabu K. , Tan Adrian E. C. , Chia Michael Y. W. , Bornemann Jens
Published: March 2008

Simple dual‐ and triple‐band printed‐circuit filters for wireless applications are presented. By using a single dual‐behavior resonator for each individual band, two transmission zeros between passbands are obtained, thus providing high levels of rejection. Moreover, there is no limit on the ratio of highest to lowest passband. Several measured prototype performances show very good agreement with computations. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1495–1497, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23408
Microstrip band rejection filter using open loop resonator
Authors: Jitha B. , Bybi P. C. , Aanandan C. K. , Mohanan P.
Published: March 2008

Design of a compact microstrip band reject filter is proposed. The device consists of an Open Loop Rectangular Resonator (OLRR) coupled to a microstrip line. The transmission line has a U‐bend which enhances the coupling with the OLRR element and reduces the size of the filter. The filter can be made tunable by mounting variable capacitance to the system. Simulated and experimental results are presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1550–1551, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23415
Millimeter‐wave low‐loss transmission lines and resonators in standard 0.18‐μm CMOS technology
Authors: Lin Shui‐Yang , Yang Li‐Wu , Sun Xiao‐Wei
Published: March 2008

Design methodologies of CMOS transmission lines (T‐lines) and resonators at millimeter‐wave frequencies are presented. Three different T‐lines including thin film microstrip line, coplanar waveguide, coplanar waveguide with ground, are designed and fabricated in standard 0.18‐μm CMOS technology. After on‐wafer testing to 40 GHz and SLOT de‐embedding calibration, their S‐parameters are extracted and analyzed. To achieve a small size, meandering quarter‐wavelength line resonator and stepped impedance resonator resonating near 30 GHz are designed, with their Q‐factor of 12 and 10.5, respectively. A good agreement between the predicted and measured results has been observed up to 40 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1579–1582, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23424
MEMS based reconfigurable dual band antenna
Authors: Gupta R. K. , Sharma U. C. , Sayanu P. , Kumar G.
Published: March 2008

In this study, a novel MEMS technology based reconfigurable dual band monopole antenna implementing RF‐MEMS switch is proposed for satellite communications applications. The prototyped Dual band antenna is designed, fabricated, and tested. The proposed antenna is fabricated on Quartz and high receptivity silicon (HRS) using an ideal MEMS switch. The antenna structure consists of two elements—one element couples weakly to other element in OFF state while in ON state it couples strongly. This electromagnetic coupling, through a MEMS switch, gives rise to reconfigurable dual band antenna. The measured VSWR < 2 at 3.7–4.2 GHz frequency band when the switch is OFF, while in the ON state's VSWR < 2 at 5.9–6.4 GHz frequency band. The measured VSWR and radiation patterns indicate the suitability of this antenna for satellite applications. The fabricated switch exhibits an isolation of more than 40 dB while its insertion loss is <0.3 dB in the frequency range of interest. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1570–1575, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23426
A novel radiation pattern reconfigurable microstrip antenna for wide‐angle scanning application in phased antenna array
Authors: Ouyang Jun , Yang Feng , Yang Shiwen
Published: March 2008

This article presents a novel pattern reconfigurable microstrip antenna that operates in 3 GHz. The antenna pattern can be transformed in between two situations. The two patterns can cover the area from −70° to +70°. Specifically, this radiation pattern reconfigurable microstrip antenna has potential applications in phased antenna arrays in wide‐angle scanning. Measured results of the proposed antenna are provided. The future work about improving the operating bandwidth is also discussed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1539–1540, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23429