bluuebunny/crossref_metadata_2025 huggingface dataset:
In vivo ultra‐high‐field magnetic resonance imaging of trabecular bone microarchitecture at 7 T
Authors: Krug Roland , Carballido‐Gamio Julio , Banerjee Suchandrima , Burghardt Andrew J. , Link Thomas M. , Majumdar Sharmila
Published: March 2008

Purpose

To investigate the feasibility of 7T magnetic resonance imaging (MRI) to visualize and quantify trabecular bone structure in vivo by comparison with 3T MRI and in vivo three‐dimensional (3D) high‐resolution peripheral quantitative computed tomography (HR‐pQCT).

Materials and Methods

The distal tibiae of 10 healthy volunteers were imaged. Therefore, fully balanced steady state free precession (bSSFP) and spin‐echo (bSSSE) pulse sequences were implemented and optimized for 7T. Structural bone parameters, such as apparent bone‐volume over total‐volume fraction (app.BV/TV), apparent trabecular plate separation (app.TbSp), apparent trabecular plate thickness (app.TbTh), and apparent trabecular plate number (app.TbN), were derived.

Results

All structural trabecular bone parameters correlated well (r > 0.6) between 7T and 3T, and between 7T and HR‐pQCT (r > 0.69), with the exception of app.TbTh, which correlated modestly (r = 0.41) between field strengths and very low with HR‐pQCT (r < 0.16). Regarding absolute values, app.TbN varied only 4% between field strengths, and only 0.6% between 7T and HR‐pQCT. App.TbSp correlated best between 7T and HR‐pQCT (r = 0.89). Using bSSSE, significant smaller trabecular thickness and significant higher trabecular number were found compared to bSSFP.

Conclusion

We concluded that imaging and quantification of the trabecular bone architecture at 7T is feasible and preferably done using bSSSE. There exists great potential for ultra‐high‐field (UHF) MRI applied to trabecular bone measurements. J. Magn. Reson. Imaging 2008;27:854–859. © 2008 Wiley‐Liss, Inc.
Dynamic contrast‐enhanced quantitative perfusion measurement of the brain using T1‐weighted MRI at 3T
Authors: Larsson Henrik B.W. , Hansen Adam E. , Berg Hilde K. , Rostrup Egill , Haraldseth Olav
Published: March 2008

Purpose

To develop a method for the measurement of brain perfusion based on dynamic contrast‐enhanced T1‐weighted MR imaging.

Materials and Methods

Dynamic imaging of the first pass of a bolus of a paramagnetic contrast agent was performed using a 3T whole‐body magnet and a T1‐weighted fast field echo sequence. The input function was obtained from the internal carotid artery. An initial T1 measurement was performed in order to convert the MR signal to concentration of the contrast agent. Pixelwise and region of interest (ROI)‐based calculation of cerebral perfusion (CBF) was performed using Tikhonov's procedure of deconvolution. Seven patients with acute optic neuritis and two patients with acute stroke were investigated.

Results

The mean perfusion value for ROIs in gray matter was 62 mL/100g/min and 21 mL/100g/min in white matter in patients with acute optic neuritis. The perfusion inside the infarct core was 9 mL/100g/min in one of the stroke patients. The other stroke patient had postischemic hyperperfusion and CBF was 140 mL/100g/min.

Conclusion

Absolute values of brain perfusion can be obtained using dynamic contrast‐enhanced MRI. These values correspond to expected values from established PET methods. Furthermore, at 3T pixelwise calculation can be performed, allowing construction of CBF maps. J. Magn. Reson. Imaging 2008;27:754–762. © 2008 Wiley‐Liss, Inc.
Multiresidue method for the analysis of more than 140 pesticide residues in fruits and vegetables by gas chromatography coupled to triple quadrupole mass spectrometry
Authors: Fernández Moreno José Luis , Garrido Frenich A. , Plaza Bolaños Patricia , Martínez Vidal José Luis
Published: March 2008

A new multiresidue method has been developed and validated for the determination of more than 140 pesticide residues in cucumber and orange by gas chromatography coupled to triple quadrupole mass spectrometry (GC–QqQ‐MS/MS) in a single run of 25.50 min. The triple quadrupole (QqQ) analyzer simultaneously operated in the selected reaction monitoring (SRM) and selected ion monitoring (SIM) modes, acquiring two or three transitions per compound. Samples were extracted by the application of a single‐phase extraction of 10 g of sample with acetonitrile containing 1% of acetic acid, followed by a liquid–liquid partition formed by the addition of 4 g of MgSO4 and 1 g of NaOAc. A dispersive solid‐phase extraction (D‐SPE) with primary secondary amine (PSA) was applied to clean up the extracts. A final concentration step was included in order to increase sensitivity in the instrumental analysis. The method was properly validated in each matrix in a wide dynamic range (10–400 µg kg−1): this work relies on a new quantification strategy by the use of two calibration curves to increase the dynamic range, which permitted reduction of sample dilutions and increase in sample throughput. Recovery was studied at three concentration levels (11.5, 50.0, and 150.0 µg kg−1), yielding values in the range 70–110% with precision values, expressed as relative standard deviation (RSD), lower than 20 and 25% for the intraday and interday precision, respectively. Limits of quantification (LOQs) were established at 10 µg kg−1, the lowest maximum residue level (MRL) value set by the European Union in vegetables. The method was successfully applied to the analysis of pesticide residues in real samples from the southeastern Spain. Copyright © 2008 John Wiley & Sons, Ltd.
Studies on the heterogeneity of the carotenogenic yeast Rhodotorula mucilaginosa from Patagonia, Argentina
Authors: Libkind Diego , Gadanho Mário , Broock Maria van , Sampaio José Paulo
Published: March 2008

The yeast species Rhodotorula mucilaginosa is considered to be ubiquitous due to its world‐wide distribution in terrestrial, freshwater and marine habitats, and to its ability to colonize a large variety of substrates. In this paper we assess the phenotypic and genetic variability of environmental isolates of R. mucilaginosa collected from natural and artificial environments in Patagonia, Argentina. A total of 97 strains were studied and sorted into three groups based on MSP‐PCR fingerprinting results: A, which comprised 90% of the strains, including the type strain; and B and C which included 2 and 8% of the strains, respectively. The D1D2 sequencing did not differentiate any of the 3 groups, while ITS sequencing validated the existence of group C. This group was composed of Patagonian isolates of diverse origin. DNA‐DNA reassociation studies confirmed the existence of significant genetic differences between group C and the type strain. In this study, which is the first on the intraspecific variability of a large set of R. mucilaginosa isolates, a considerable phenotypic and genetic heterogeneity was observed, however such differences were not enough to refute co‐specificity. The study of Patagonian isolates allowed the detection of a genetically distinct group of R. mucilaginosa strains. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chemotaxis of Pseudomonas sp. to caffeine and related methylxanthines
Authors: Dash Swati Sucharita , Sailaja Nori Sri , Gummadi Sathyanarayana N.
Published: March 2008

Pseudomonas sp. isolated from soil of coffee plantation area has been shown to degrade higher concentrations of caffeine (∼15 g l–1) by N‐demethylation at a rate higher than what has been reported for any strain so far. This strain exhibits positive chemotaxis towards caffeine (1,3,7‐trimethylxanthine) in swarm plate assay and modified capillary assay in a dose dependant manner. Related methylxanthines and xanthine also act as chemoattractants for the strain with the highest relative chemotactic response (RCR) seen for xanthine. Chemotaxis in Pseudomonas sp. is possibly plasmid mediated as indicated by positive chemotaxis of plasmid transformed E. coli DH5α. The chemotactic abilities of Pseudomonas sp. combined with higher rates of degradation of caffeine can be used in the development of strategies for biodecaffeination of caffeine containing wastes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interaction between carbon and nitrogen metabolism during akinete development in the cyanobacterium Anabaena torulosa
Authors: Ahuja Gurpreet , Khattar Jasvirinder Singh , Sarma Tangirala Anjaneya
Published: March 2008

Nutrient enrichment with a nitrogen (as nitrate) or carbon (as fructose) source to unaerated diazo and photoautorophic cultures of the cyanobacterium Anabaena torulosa induced early development of akinetes with high frequency. When cultures under any mode of nutrition were aerated, akinetes were not differentiated. Unaerated cultures with nitrate nitrogen or fructose exhibited higher respiratory rates and nitrogen assimilation compared to aerated cultures. This was evidenced by increased respiratory O2 uptake and high activities of pyruvate kinase, malate dehydrogenase (NAD+), nitrogenase and nitrate reductase signifying that akinete forming unaerated cultures exhibited high carbon dissimilation and nitrogen assimilation resulting in high nitrogenous build up in the cells. Aerated, non‐akinete cultures, on the other hand, were associated with low respiratory O2 uptake, low pyruvate kinase and malate dehydrogenase (NAD+) activities, suggesting that carbon dissimilation was not favoured either in presence of nitrate or fructose. Moreover, higher activity of NADP+ linked malate dehydrogenase and lower nitrate reductase activity in aerated cultures led to a high carbon and low nitrogen content of the cells resulting in high cellular C:N ratio. The results suggest that interaction between carbon and nitrogen metabolism regulates akinete development in A. torulosa. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cooperative scattering of light and atoms in ultracold atomic gases
Authors: Uys H , Meystre P
Published: March 2008

Superradiance and coherent atomic recoil lasing are two closely related phenomena, both resulting from the cooperative scattering of light by atoms. In ultracold atomic gases below the critical temperature for Bose-Einstein condensation these processes take place with the simultaneous amplification of the atomic matter waves. We explore these phenomena by surveying some of the experimental and theoretical developments that have emerged in this field of study since the first observation of superradiant scattering from a Bose-Einstein condensate in 1999 [1].
Amplification of supercontinuum by semiconductor and Er-doped fiber optical amplifiers
Authors: Lin K-H , Lin J-H
Published: March 2008

We demonstrated selective amplification of supercontinuum ultrashort optical pulses around 1300-nm and 1550-nm bands by injecting a supercontinuum source into a semiconductor optical amplifier (SOA) and an erbium-doped fiber amplifier (EDFA), respectively. The broadband supercontinuum source was obtained by coupling femtosecond Ti:Sapphire laser pulses into a dual zero-dispersion wavelengths nonlinear photonic crystal fiber. The amplified supercontinuum has fully utilized the gain bandwidth of SOA and EDFA. However, the CW background amplified spontaneous emission increases as a result of the reflection at fiber ends to cause noisy pulse train.
Corrosion behavior of composite brake materials
Authors: Jia Xian , Ling Ruo‐Fei , Chen Da‐Lu
Published: March 2008

It is very important to study the corrosion behavior of composite brake materials for their design, manufacture, and application. In the study, one kind of composite brake material used in engineering machinery, two kinds used in automobiles, and gray cast iron HT200 were selected as tested materials. Their corrosion behavior in typical acid solution, alkali solution, salt solution, running water, and air were investigated. The results showed that some components of composite brake materials, such as iron matrix, steel fiber, and iron powder, were easily subject to corrosion in acid solution. Corrosive pitting, net‐like cracking, and breakage appeared at their corrosion surfaces, and in the solution of 3.5% NaCl, corrosive pitting took place and corrosion holes of 2–8 µm diameter formed at the corrosion surface of these components. But when brake materials were exposed to the solution of 5% NaOH, the organic binder was corroded seriously, nearly parallel cracks formed at the corrosion surface and some samples even became loose powders because the corrosion makes the binder lose its adhering function. In running water and air, the tested samples have an excellent corrosion resistance, and the composite brake material containing organic binder has a better corrosion resistance compared with other tested materials. The investigation has also indicated that the interface between ingredients easily corrodes.
Phosphorus‐Containing Sulfonated Polyimides for Proton Exchange Membranes
Authors: Çakir Mustafa , Karataş Sevim , Menceloğlu Yusuf , Kayaman‐Apohan Nilhan , Güngör Atilla
Published: March 2008

Synthesis and characterization of the novel sulfonated BAPPO monomer and its use in the synthesis of a new phosphine oxide‐based sulfonated polyimide are described. BTDA, 6FDA, and DDS were used as monomers in the polyimide synthesis. Sulfonated polyimide membranes were obtained by a solution thermal imidization method. The thermal behavior of the polymers was investigated by DSC and TGA. The morphological structure of the membranes was investigated by tapping‐mode AFM. The proton conductivities of the sulfonated polyimide increased regularly as a function of sulfonated diamine content. The conductivities are good compared to typical proton exchange membranes.

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Polyester Wire Enamels ‐ Reliable Coatings in the Wire Industry from the Beginning to Nowadays
Authors: Bhanu Vinayak A.
Published: March 2008

Electric power needs to be used with prudence. Generation and transport of electric power requires insulated wires as “primary” conductors. The insulation on bare metal consists of thermosetting polymers. This review article discusses the synthesis and applications of heat cured polyester resins that are used in “primary insulation” industry. These are commonly called polyester wire enamels and they have been the work horse of this industry for past several decades. The article focuses on the developments over the past twenty years in the polymer synthesis of these polyester resins. An attempt has been also made to briefly discuss the various curing methods and their limitations.The anticipated trends of further developments in this field of research are presented. The review is hoped to fill in the gap between the active research in this specialty area and its insuffcient coverage in the main stream polymer chemistry since most of the progress is available only in patents form.

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Leptin, adiponectin, resistin, and ghrelin – Implications for inflammatory bowel disease
Authors: Karmiris Konstantinos , Koutroubakis Ioannis E. , Kouroumalis Elias A.
Published: March 2008

Inflammatory bowel disease (IBD) is characterized by anorexia, malnutrition, altered body composition, and development of mesenteric white adipose tissue (WAT) hypertrophy. Increasing evidence suggests that adipokines synthesized either in WAT or in immune cells, are involved in these manifestations of IBD. Among adipokines leptin, adiponectin and resistin hold a fundamental role while the role of ghrelin in inflammation is not well established. Preliminary studies have shown overexpression of leptin, adiponectin, and resistin in mesenteric WAT of patients with Crohn's disease (CD) and significant alterations of circulating serum levels of these adipokines in IBD. It has also been demonstrated that intestinal inflammation causes an increase in endogenous ghrelin production. In animal models of intestinal inflammation, existing data suggest that leptin, adiponectin, and resistin are pivotal mediators of inflammation. Interesting therapeutic interventions based on these data have been suggested. A specific role for hypertrophic WAT has also been implicated in CD. Further efforts with experimental and clinical studies are needed to better understand the role of adipokines in IBD.
Prebiotics, synbiotics and inflammatory bowel disease
Authors: Steed Helen , Macfarlane George T. , Macfarlane Sandra
Published: March 2008

The normal colonic microflora is intimately involved in the aetiology of inflammatory bowel diseases (IBD) such as ulcerative colitis (UC) and Crohn's disease (CD). These conditions are often refractile to conventional treatments involving the employment of anti‐inflammatory and immunosuppressant drugs, and this has led to a search for alternative therapies based on the use of probiotics, prebiotics and synbiotics. The majority of investigations in this area have been done with probiotics, and while there is increasing interest in the abilities of prebiotics and synbiotics to control the symptoms of IBD, very few randomised controlled trials have been reported. Although the results have been variable, human and animal studies have demonstrated that in many circumstances, these functional foods can alter the composition of the colonic microbiota, reduce inflammatory processes in the gut mucosa, and have the potential to induce disease remission. More work is needed to understand the effects of prebiotics and synbiotics on microbial communities in the gut, and their interactions with the host's immune system.
Dielectric properties of silicon in terahertz wave region
Authors: Li JiuSheng , Li JianRui
Published: March 2008

By using backward‐wave oscillator system, the terahertz dielectric properties of p‐type silicon were tested in the frequency range extending from 0.68 to 0.85 THz. The refractive indices, the power absorption coefficient, and the dielectric functions of various resistivity p‐type silicons were measured and compared. The variation of the refractive index of the ultra‐resistivity silicon was less than 3%, ranging from 3.037 to 3.125, but the absorption coefficient of the ultra‐resistivity silicon showed very different frequency‐dependent behaviors, ranging from 3.25 × 10−3 cm−1 to 2.90 × 10−5 cm−1, within the investigated frequency range. The ultra‐resistivity silicon will be a good candidate material for terahertz transmission waveguide with ultra‐low loss. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1143–1146, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23313
Design of novel miniaturized fractal‐shaped branch‐line couplers
Authors: Chen Wen‐Ling , Wang Guang‐Ming
Published: March 2008

Although miniaturized and fractal‐shaped branch‐line couplers have been reported by many researchers, their operating bandwidth are narrowed and shifted greatly, thus the application of these techniques were limited. In this article, we presented an exact design technique to obtain compact and fractal‐shaped branch‐line couplers for a given frequency. As an example, novel fractal‐shaped branch‐line couplers operated at 2.4 GHz using Koch fractal shapes of different iteration orders have been designed successfully, and the designed couplers all operated at the designed frequency and achieved a maximal 81.8% size reduction. And furthermore, the operating frequency and its bandwidth are virtually unaltered. The proposed method is verified by the measurement results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1198–1201, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23316
Measurement of AC current using a superstructure fiber grating
Authors: Cheng Chin‐Hsing , Chen Ming‐Hsien , Liu Wen‐Fung
Published: March 2008

In the power industry, current must be measured for metering and protection purposes. For such measurements, this article demonstrates an optical fiber sensor using a superstructure fiber grating (SFG) to measure AC current. The sensor head is based on superstructure fiber grating encapsulated in a polymer‐half‐field metal cylinder embedded a magnetic material. The sensor detects force when it is attracted by the induced magnetic force created by the solenoid along one radial direction only and responds to an axial force on the magnetic rod attached to the round plate, creating an axial attraction on the SFG. The SFG is composed of a fiber Bragg grating (FBG) and a long period grating (LPG). Therefore, variations in attractive force and temperature cause variations in SFG center‐wavelength. Thus, the sensor can be used to measure attracting forces and temperature effects simultaneously. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1168–1171, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23317
Study on high‐temperature and high‐pressure measurement by using metal‐coated FBG
Authors: Shen Ren‐Sheng , Zhang Jin , Wang Yan , Teng Rui , Wang Ben‐Yu , Zhang Yu‐Shu , Yan Wei‐Ping , Zheng Jie , Du Guo‐Tong
Published: March 2008

Metal‐coated fiber Bragg grating (MFBG) sensor was proposed to measure high‐temperature and high‐pressure condition. Metal‐coated layer of FBG improved bonding performance between metal material substrate and sensor protected as well as prolonged the lifespan of the FBG sensor. By optimized and designed thin‐wall copper cylinder structure and soldered MFBG on this, we had measured high‐temperature and high‐pressure environments. This sensor can measure the pressure range from 0 to 40 MPa. Its correlative coefficient reached 99.95% and its sensitivity was 0.0493 nm/MPa, which was about 19 times than normal Fiber Bragg Grating. Using a thermostat, a good linearity of temperature characteristic of this structure was obtained and its correlative coefficient reached 99.904%. Temperature had been measured range from 50 to 240°C. Considering FBG intrinsic advantage, it has been applied in harsh environments such as oil‐well. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1138–1140, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23319
A quantitative study on the low frequency breakdown of EFIE
Authors: Qian Zhi Guo , Chew Weng Cho
Published: March 2008

A quantitative study is presented for the low frequency breakdown of the electric‐field integral equation (EFIE) with the Rao–Wilton–Glisson basis function. The low frequency limit is ascertained hereby. Numerical experiments validate the conclusion. The line testing method is also compared with the Galerkin testing to dispel the misconception in the literature. The study thus provides a guideline for the application of EFIE in the full‐field regime. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1159–1162, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23324
Characterization of microstrip transmission lines at IR frequencies—Modeling, fabrication and measurements
Authors: Mandviwala Tasneem A. , Lail Brian A. , Boreman Glenn D.
Published: March 2008

We report the complete characterization of microstrip lines at an infrared frequency of 28.3 THz (10.6‐μm wavelength) through modeling, fabrication, and measurement. The transmission‐line parameters of interest can not be directly measured at infrared frequencies—the only measurable quantity is the voltage response of the antenna‐coupled bolometric sensor. We validate the computational approach for transmission‐line parameters by verifying the computed and measured response of the antenna connected to microstrip lines of different lengths. This also allows us to extend these calculations to explore various configurations and identify design trends. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1232–1237, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23344
Optimization of printed ultra wide‐band antenna using microgenetic algorithm combined with FDTD
Authors: Jie Sheng , Yang Xue‐Xia , Sun Xiao‐Meng
Published: March 2008

In this article, a printed U‐type ultra wide‐band (UWB) antenna is designed for UWB communication using a microgenetic algorithm (MGA) in conjunction with the finite‐difference time‐domain (FDTD) method. A stepped microstrip configuration which improves the impedance bandwidth is optimized by using MGA and FDTD to achieve the UWB characteristics. The measured VSWR of the antenna is less than 2 from 3.1 GHz to 10.6 GHz. The proposed antenna has a good radiation characteristic by measurement and the simulated gain is between 3.3 and 6 dB. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1289–1292, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23358
A circular CPW‐fed slot antenna resonated by the circular loop for broadband circularly polarized radiation
Authors: Deng I‐Chung , Ke Qing‐Xiang , Lin Ren‐Jie , King Yueh‐Tsu
Published: March 2008

The coplanar waveguide (CPW) fed circular slot antenna, resonated by the circular loop with a narrow opening, is designed for obtaining broadband circularly polarized (CP) radiation. The length of protruded signal strip (LS) is utilized to adjust the phase difference between two orthogonal field components in the circularly polarized waves. In this design, the proposed antenna has the minimum return loss of −56.5 dB at the frequency of 2.403 GHz. The impedance and 3 dB axial‐ratio bandwidths can reach up to 740 MHz or 33.3% and 390 MHz or 16.6%, respectively. In addition, the simulated results are about as good as those of the measured ones. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1423–1426, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23359
Particle swarm optimization application to microwave circuits
Authors: Ülker Sadık
Published: March 2008

This letter presents the concept of particle swarm optimization (PSO) technique applied to two sets of microwave circuits: microstrip coupler and single shunt stub matching circuit. The PSO technique that is applied to these two set of designs is tested and compared with simulation results. The results show that PSO is an efficient method for solving these kinds of problems and can be applied for the design of microwave circuits. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1333–1336, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23369
Multilayer inphase power divider for UWB applications
Authors: Abbosh A. M.
Published: March 2008

A multilayer inphase power divider with ultra wideband behavior is presented. It has a compact size with an overall dimension of 20 mm × 30 mm. The proposed divider utilizes broadside coupling via a multilayer microstrip/slot configuration. The simulated and measured results show that the proposed device has 3.3 ± 0.3 dB insertion loss, about 20 dB return loss, and 10 dB isolation across the frequency band 3.1‐10.6 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1402–1405, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23379
A low power X‐band CMOS differential VCO
Authors: Jang Sheng‐Lyang , Huang S.‐S. , Wu Sheng‐Chien , Lee Chien‐Feng , Juang M.‐H.
Published: March 2008

This article proposes a 12 GHz low power differential voltage‐controlled oscillator (VCO) based on single‐ended Colpitts oscillators. The differential VCO uses two single‐ended Colpitts VCOs coupled by a pair of pMOS cross‐coupled transistors and a transformer inductor. The differential VCO was fabricated in the TSMC 0.18‐nm CMOS process, it oscillates from 11.46 GHz to 12.45 GHz, and the power consumption is 2.76 mW at the supply voltage of 1.2 V. The measured phase noise at 1‐MHz offset is g110.95 dBc/Hz at the oscillation frequency of 12.42 GHz. The power consumption of the VCO is 2.3 mA when the supplied voltage is 1.2 V. The figure of merit of the VCO is −188.43 dBc/Hz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1389–1392, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23388
Tunable single‐to‐dual channel wavelength conversion of picosecond pulses based on four‐wave mixing in microstructure fibers
Authors: Zhang Xia , Ren Xiaomin , Xu Yongzhao , Wang Zinan , Huang Yongqing
Published: March 2008

All optical wavelength conversion between picosecond pulses based on four‐wave mixing (FWM) is experimentally demonstrated in 80‐m dispersion‐flatted high nonlinear microstructure fibers (MF). The pulsed signal with 10‐GHz repetition rate and 1.6‐ps pulse width is used as pump wave. In the experiments, both down‐ and up‐conversion are obtained in this type of wavelength converter. Moreover, tunable single‐to‐dual channel wavelength conversion is experimentally observed. The experiment results imply that it is possible to realize tunable single‐to‐multiple channel wavelength conversion. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1453–1455, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23398
Application of the tree‐cotree splitting for improving matrix conditioning in the full‐wave finite‐element analysis of high‐speed circuits
Authors: Lee Shih‐Hao , Jin Jian‐Ming
Published: March 2008

In this study the tree‐cotree splitting technique is applied for improving the finite‐element matrix conditioning for the analysis of high‐speed circuits. A well‐known issue is that at low frequencies a full‐wave solver yields less accurate solutions and may even breakdown due to ill‐conditioned system matrices. To enhance the capability and reliability of the conventional finite element method in broadband full‐wave analyses, we apply the tree‐cotree splitting to edge elements to account for the decoupling between the electric and magnetic fields at low frequencies, which is the main reason for the low‐frequency problem. The algorithm for finding a minimum spanning tree when there exist wave ports, lumped ports, or for a PEC‐free structure are described. Besides, a model order reduction method, called the solution space projection, is applied for a fast broadband analysis. We further propose an expansion to available solution bases for a better approximation to low‐frequency fields, so that a simulation can be extended to extremely low frequencies. The application is focused on the simulation of high‐speed circuits, of which both low and high frequency characteristics are of equal importance. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1476–1481, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23403
Bent inverted‐F antenna for WLAN units
Authors: Hristov H. D. , Carrasco H. , Feick R.
Published: March 2008

We show how a wire inverted‐F antenna can be made more compact without significant alteration of its impedance and radiation characteristics. Two modified inverted‐F antennas, one in air and another with solid dielectric casing, were computer‐simulated for the 2.4‐GHz band and their input match loss and bandwidth were validated experimentally. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1505–1510, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23405
An on‐site “SAR” evaluation using interpolation and plane‐wave decomposition
Authors: Saidi F. , Lautru D. , Gati A. , Wong M. F. , Nicolas E. , Jacquin F. , Wiart J. , Fouad‐Hanna V.
Published: March 2008

Two efficient techniques are investigated for the evaluation of the human exposure to electromagnetic fields in terms of the on‐site assessment of the specific absorption rate (SAR) using interpolation techniques and plane‐wave decomposition. These methods allow evaluating, in an optimal manner, the induced electromagnetic field and the SAR in a human tissue using both the measurements and calculation resulting in the alleviation of imposed constraints on them. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1501–1505, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23406
Radiation from transversely slotted waveguide
Authors: Kim Yang H. , Eom Hyo J. , Zeong Jong W.
Published: March 2008

The problem of radiation from transversely slotted waveguides is solved by using Fourier transform and mode‐matching techniques. The solution for narrow slot widths is represented in fast convergent series. Good agreement is observed between our theory and other results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1547–1549, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23416
Collinear printed array antenna
Authors: Thomas K. George , Lenin N.
Published: March 2008

A novel high gain printed dipole array antenna for omni directional coverage is presented. The dipoles are electromagnetically fed by planar slots, formed on a 50 Ω microstrip transmission line. The impedance characteristics and radiation patterns of the antenna are analyzed numerically with finite element method and compared with the measurement. The unbalanced feed point of the antenna is fed directly with a small co‐axial cable. The antenna demonstrates good impedance and pattern bandwidth of 300 MHz from 2.25–2.55 GHz and is suitable for ISM band/WLAN operation. The optimum impedance matching can be achieved by increasing the width of the 50 Ω line around the feed point and thereby altering feed point impedance. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1582–1584, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23423
Investigation of return loss for large numbers of bonding wires by FDTD method
Authors: Chen Hsing‐Yi , Su Chieh‐Pin
Published: March 2008

The finite‐difference time domain (FDTD) model is validated first by comparing the simulation results of return losses for 1, 7, and 15 bonding wires fabricated on a test board with those obtained by the HFSS software. After checking its accuracy, the FDTD method is used to investigate the return loss for bonding wire arrays with numerous geometrical parameters. From simulation results, it is found that the return loss of bonding wires can be improved by using multiple wires placed in parallel in bonding wire arrays. It is also found that operation frequency shifts of bonding wire arrays can be achieved by changing the wire numbers in bonding wire arrays. It is also reveled that the return loss of bonding wire structures is a function of the bonding wire geometry, such as the spacing between adjacent wires, wire number, wire height above the substrate, and wire length. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1575–1579, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23425
Radiation patterns of microstrip leaky‐wave antenna with parasitic elements
Authors: Li YuanXin , Xue Quan , Yung Edward Kai‐Ning , Long YunLiang
Published: March 2008

A microstrip leaky‐wave antenna (MLWA) with parasitic elements is presented in this letter. The short MLWA is the basic element, and two microstrip patches with a short‐circuit edge worked as the parasitic elements. The main lobe scans from 66° to 42° when operating frequency increases from 5.9 to 6.9 GHz. In contrast to the conventional MLWA, the reflected wave of the short MLWA (about two wavelengths) with parasitic elements is suppressed 12 dB at 6.9 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1565–1567, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23428
An internal modified rectangular loop antenna for DVB‐H applications
Authors: Choi Il H. , Lee Jung N. , Park Jong K. , Yim Byoung J.
Published: March 2008

An internal modified rectangular loop antenna with two open stubs for digital video broadcasting‐handheld (DVB‐H) terminals is proposed. The antenna consists of the modified rectangular loop, the two open stubs, and a four element matching. We have used the meandering technique to increase the electrical length of the antenna and two open stubs for tuning the high frequency edge of the DVB‐H band. To more improve the impedance bandwidth of the DVB‐H frequency band (470–702 MHz), a four element matching circuit is used. All simulations are carried out by Ansoft HFSS software. Moreover, by fabricating the antenna, the simulations results are verified by experimental data. Good antenna performances such as radiations patterns and antenna gains over the operating frequency band have been observed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1592–1595, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23440
A novel printed dual‐monopole array with antenna selection circuit for adaptive MIMO systems
Authors: Li Zhengyi , Wang Xuan , Du Zhengwei , Gong Ke
Published: March 2008

Antenna selection is an effective method to achieve reconfigurable antenna array for adaptive MIMO systems. In this article, a novel printed dual‐monopole array with antenna selection circuit for adaptive MIMO systems is proposed. By four pin‐diodes embedded in the feeding network, the array can operate as a dual‐antenna array and also work as a single antenna while the other is terminated to a matched lumped resistor. When the array operates as a dual‐antenna array the measured bandwidths cover the UMTS band with acceptable isolation. When it works as a single antenna the measured bandwidth still covers the UMTS band. From the measured radiation patterns, it is obvious that the radiation patterns of the selected monopole change little whether the other monopole is selected or not. Accordingly, the system can achieve antenna selection scheme to adapt to the time‐varying channel conditions. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1584–1590, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23442
Study on high power single‐frequency erbium doped fiber laser for long distance communications
Authors: Wang Tianshu
Published: March 2008

To stabilize the frequency, a structure with fiber seed laser plus fiber amplifier module is designed. Using only one laser diode simultaneously pumps fiber amplifier and laser through a coupler with special ratio. Single‐frequency fiber laser with high‐output power and low‐noise is achieved. The center‐wavelength is 1550.16 nm while the 3 dB spectrum‐width of output laser is 0.08 nm and the side mode suppression ratio is 55 dB. The maximum output power exceeds 23 mW, the slope efficiency is more than 20%, and the stability is less than ±0.005 dB. A nice single‐frequency is observed and the modes adjacent to the lasing mode are completely suppressed. A 10 Gbps codes rate is used in the fiber laser transmission experiment. The signal is transmitted in 42 km without regeneration. The eye diagrams of optical transmission are measured, the performance of long‐haul transmission with high‐speed modulation is perfect. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1660–1662, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23449
Low‐cost flat metal‐plate dipole antenna for 2.4/5‐GHz WLAN operation
Authors: Su Saou‐Wen , Chou Jui‐Hung
Published: March 2008

A low‐cost, one‐piece, flat‐plate dipole antenna for dual WLAN band operation is presented. The dipole antenna is rectangular in shape with the dimensions 10 mm × 37 mm and fed by 50‐Ω mini‐coaxial cable. By cutting two L‐shaped slits in each radiating arm, two dipole arms are obtained, which form a larger dipole and a smaller dipole antennas for the 2.4‐ and 5‐GHz band operation, respectively. The dipole arms are further short‐circuited, making it possible for the antenna to be fabricated by stamping a single, flat metal plate only. The impedance bandwidth for 2.4/5‐GHz WLAN operation is with VSWR below 1.5 and good omnidirectional radiation patterns are also observed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1686–1687, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23461
Compact dual band Wilkinson power divider
Authors: Mohra Ashraf S. S.
Published: March 2008

This article presents the design of a compact Wilkinson power divider for dual applications. The design is accomplished by transforming the length and impedance of the quarter wave sections of the conventional Wilkinson power divider into dual band Π‐shaped sections. Simple design equations for basic design geometry are given. The dual band power divider geometry is analyzed using EM simulator and then realized at 1.8 and 4.775 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1678–1682, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23465
Accelerated whole‐heart 3D CSPAMM for myocardial motion quantification
Authors: Rutz Andrea K. , Ryf Salome , Plein Sven , Boesiger Peter , Kozerke Sebastian
Published: March 2008

Myocardial tissue tagging using complementary spatial modulation of magnetization (CSPAMM) allows detailed assessment of myocardial motion. To capture the complex 3D cardiac motion pattern, multiple 2D tagged slices are usually acquired in different orientations. These approaches are prone to slice misregistration and associated with long acquisition times. In this work, a fast method for acquiring 3D CSPAMM data is proposed that allows measuring deformation of the whole heart in three breath‐holds of 18 heartbeats duration each. Three acquisitions are sequentially performed with line tag preparation in each orthogonal direction. Measurement acceleration is achieved by applying localized tagging preparation and a hybrid multishot, segmented echo‐planar imaging sequence. Five healthy volunteers and five patients with myocardial infarction were measured. Midwall contours were tracked throughout the cardiac cycle with an enhanced variant of the harmonic phase (HARP) technique. Circumferential shortening at end‐systole ranged from 14.1% (base) to 20.1% (apex) in healthy subjects. Hypokinetic regions in patients corresponded well with regions exhibiting hyperenhancement after contrast injection. Time to maximum circumferential shortening varied more significantly over the left ventricle in patients than in volunteers (P < 0.01). The proposed measurement scheme was well tolerated by patients and holds considerable potential to investigate cardiac mechanics in various diseases. Magn Reson Med 59:755–763, 2008. © 2008 Wiley‐Liss, Inc.
Radial single‐shot STEAM MRI
Authors: Block Kai Tobias , Frahm Jens
Published: March 2008

Rapid MR imaging using the stimulated echo acquisition mode (STEAM) technique yields single‐shot images without any sensitivity to resonance offset effects. However, the absence of susceptibility‐induced signal voids or geometric distortions is at the expense of a somewhat lower signal‐to‐noise ratio than EPI. As a consequence, the achievable spatial resolution is limited when using conventional Fourier encoding. To overcome the problem, this study combined single‐shot STEAM MRI with radial encoding. This approach exploits the efficient undersampling properties of radial trajectories with use of a previously developed iterative image reconstruction method that compensates for the incomplete data by incorporating a priori knowledge. Experimental results for a phantom and human brain in vivo demonstrate that radial single‐shot STEAM MRI may exceed the resolution obtainable by a comparable Cartesian acquisition by a factor of four. Magn Reson Med 59:686–691, 2008. © 2008 Wiley‐Liss, Inc.
Visualization of the coherence of the principal diffusion orientation: An eigenvector‐based approach
Authors: Wang JiunJie , Lin YuChun , Wai YauYau , Liu HaoLi , Lin ChingPo , Huang YingZu
Published: March 2008

A novel method for spatially mapping anisotropy/orientation coherence of the eigenvector is presented. By using an eigenvector‐based approach, an intervoxel diffusion coherence (IVDC) index was used to quantify the coherence of the principal diffusion directions within a voxel neighborhood. This method may allow reconstruction of a whole brain map to be used for diagnostic purposes. The IVDC index is calculated by a scatter matrix‐based method in a voxel‐wise manner. A simulation was performed using two fiber populations crossing at various separation angles. We demonstrate that the IVDC index was more sensitive than fractional anisotropy (FA) to changes in separation between the fibers under a noise‐free condition. Diffusion‐tensor images of six healthy volunteers were acquired on a 3.0T MR imager. The FA, coherence index, and IVDC were then calculated. The results showed that IVDC improved the contrast in several brain areas including thalamus, middle cerebral peduncle, and pons. We therefore conclude that the IVDC index provides reliable and complementary information on water diffusion in the brain. It may be useful in white matter tractography, especially to determine the termination point of a trajectory. Magn Reson Med 59:764–770, 2008. © 2008 Wiley‐Liss, Inc.
Additive angle method for fast large‐tip‐angle RF pulse design in parallel excitation
Authors: Grissom William A. , Yip Chun‐Yu , Wright Steven M. , Fessler Jeffrey A. , Noll Douglas C.
Published: March 2008

Current methods for parallel excitation RF pulse design are based on the small‐tip‐angle approximation, which provides a computationally efficient means of pulse calculation. In general, pulses designed with those methods are inaccurate when scaled to produce large‐tip angles, and methods for large‐tipangle pulse design are more computationally demanding. This paper introduces a fast iterative method for large‐tip‐angle parallel pulse design that is formulated as a small number of Bloch equation simulations and fast small‐tip‐angle pulse designs, the results of which add to produce large‐tip‐angle pulses. Simulations and a phantom experiment demonstrate that the method is effective in designingmultidimensional large‐tip‐angle pulses of high excitation accuracy, compared to pulses designed with small‐tip‐angle methods. Magn Reson Med 59:779–787, 2008. © 2008 Wiley‐Liss, Inc.
Modification of embolic‐PVA particles with MR contrast agents
Authors: Cilliers Renee , Song Ying , Kohlmeir Ellen K. , Larson Andrew C. , Omary Reed A. , Meade Thomas J.
Published: March 2008

We report the synthesis and characterization of polyvinyl alcohol (PVA) embolic particles modified with a clinically approved magnetic resonance (MR) contrast agent. PVA particles are used during transcatheter arterial embolization (TAE) procedures and this minimally invasive technique is a widely employed treatment for inoperable tumors. The PVA particles are injected into tumor vessels and prevent blood flow which results in tumor attenuation. An accurate assessment of the endpoint of embolization is critical to successful TAE procedures. Recent reports suggest that 20% of endpoint determination of TAE procedures by angiographic techniques are erroneous. Real time, in vivo imaging of the embolic particles would overcome this limitation. The contrast‐modified PVA particles described here show an 80% decrease in T1 relaxation times compared to unmodified particles. Images of particles in capillary tubes of similar size to catheters used in TAE procedures are clearly visible by MRI. Magn Reson Med 59:898–902, 2008. © 2008 Wiley‐Liss, Inc.