bluuebunny/crossref_metadata_2025 huggingface dataset:
Posttraumatic stress disorder instrument wording content is associated with differences in factor structure
Authors: Elhai Jon D. , Biehn Tracey L. , Naifeh James A. , Christopher Frueh B.
Published: March 2011

The authors examined posttraumatic stress disorder (PTSD) item wording differences on the factor structure of PTSD. Nonclinical, trauma‐exposed participants were randomly assigned to complete a PTSD measure using item wording content from the PTSD Checklist (n = 182) or PTSD Symptom Scale (n = 203). Compared to the 4‐factor emotional numbing PTSD model, the 4‐factor dysphoria PTSD model fit best across groups based on smaller Bayesian information criterion (BIC) values. For PTSD Checklist participants, the numbing model's BIC was 6238.54 compared to the dysphoria model's BIC of 6156.03. For the PTSD Symptom Scale, the numbing model's BIC was 6161.38 compared to the dysphoria model's BIC of 6102.87. Groups differed on variable intercepts and residual variances. Instrument and construct implications are discussed.
THE CURRENT STATUS OF DIFFERENT AGE, DIRECT‐SEEDED REVEGETATION SITES IN AN AGRICULTURAL LANDSCAPE IN THE BURRUMBEET REGION, VICTORIA, AUSTRALIA
Authors: Florentine S. K. , Graz F. P. , Ambrose G. , O'brien L.
Published: March 2011

Many vegetation restoration works have been undertaken in Australia but only a few of those projects have been assessed for effectiveness. Revisiting earlier restoration attempts and analysing data from them is fundamental to the development of evidence‐based prescriptions for future restoration work. Therefore, this study's objectives were to (I) compare plant species composition of different age direct‐seeded revegetated sites and (II) determine the effect, if any, of different ages of revegetated sites on the natural recruitment of native plants. The study investigated four fenced restoration sites, dating from 2000, 2001, 2004 and 2005. Results showed that the density of plants surviving varied widely between plots of different ages. The highest density was found in the 2001 plot (2195·.7 stems ha−1), followed by 2000 (1877·8 stems ha−1), 2004 (197·6 stems ha−1) and 2005 (195·4 stems ha−1). An ANOVA showed that the overall amount of seed broadcast does not play a significant (p = 0·437) role in the establishment rate. Overall, Eucalyptus ovata was found to be dominant in the 2000 (794·4 ha−1) and 2001 (971 ha−1) sites. In contrast, Eucalyptus camaldulensis and Eucalyptus viminalis densities were highest in the 2004 (41 ha−1) and 2005 (60·4 ha−1) sites, respectively. PERMANOVA showed highly significant differences in the present plant composition between plots (p < 0·0001), despite similar species mixes used in sowing. Recruitment was not found in any of the sites. The least weed cover and the highest litter cover were found in the 2001 plot. A similar trend was found in the 2000 plot. In contrast, high weed cover and low litter cover were found in the 2004 and 2005 plots. Since one of the major impediments to developing better restoration strategies is the inadequate documentation of past practices, studies such as these may shed some light on how the direct‐seeded technique operates in a farm situation. Copyright © 2011 John Wiley & Sons, Ltd.
Uniaxial compression of SiO2 glass cylinders: analysis using stress‐independent material coefficients
Authors: Richter F. , Hoffmann H.‐J.
Published: March 2011

Glass cylinders made of the vitreous silica type Suprasil 1 were exposed to axial stress at nominal compressive strain rates from –10–5 to –10–2 per second in a servohydraulic press at constant temperatures ranging from 1273 K to 1648 K. Subsequently, the stress was allowed to relax. True viscoelasticity is applied for evaluation of the experimental results and closed‐form solutions demonstrate that the interpretation as a single‐element Maxwell model renders Young's modulus readily measurable along with the tensile viscosity. The significant contribution of elasticity is found to be inherent in glass even at elevated temperatures. This very distinct property did not receive general recognition before and has been neglected in the majority of earlier studies on glass upsetting. The analysis reveals that the Young's modulus decreases with a rise in temperature if the nominal strain rate is held fixed, and with a reduction in nominal strain rate at constant temperature. The viscosity can be characterized as a function of the temperature either by a Vogel‐Fulcher‐Tammann‐Hess equation or by an Arrhenian fit. The findings when fed into a FEM programme reproduce the recorded force histories quite well. However, the present study reveals that the experimental data of Young's modulus depend on the stress. The results prove unambiguously the failure of linear viscoelasticity for this particular loading case. The full implications are reserved for a subsequent publication dealing with important consequences for glass rheology.
Corrosion properties of thermal sprayed aluminium (TSA) coatings deposited by powder flame spraying
Authors: Glogović Z. , Alar V. , Kožuh Z. , Stojanović I. , Kralj S.
Published: March 2011

Thermal sprayed aluminium (TSA) coatings are widely used for the protection of steels from aqueous corrosion, including offshore structures and components that are exposed to seawater immersion, tidal and splash zone environments. In this paper, the influence of deposition parameters of aluminium coating on its corrosion properties was studied. For different application parameters of TSA coatings, the thickness, the microstructure and corrosion properties were determined. Determination of thickness was performed according to EN ISO 2064:2000 relating to the definition and determination of the thickness of metallic and other inorganic layers. Microstructure was determined using a Olympus GX50 optical microscope. The corrosion properties of the coatings were compared using an accelerated electrochemical corrosion test method. Electrochemical studies were carried out in accordance with the requirements of ASTM standard G 102 – 89. The TSA coating performance was quantified in terms of its corrosion potential and the corrosion rate, which was estimated from Tafel polarisation resistance measurements.
Load dependence of the apparent Knoop hardness of SiC ceramics in a wide range of loads
Authors: Majić M. , Ćurković L. , Ćorić D.
Published: March 2011

Silicon carbide (SiC) ceramics is a material with increasing use, due to its excellent mechanical properties, especially high hardness. In order to integrate this material into design process, we need to know its hardness as precise as possible. The Knoop hardness number (HK) is calculated using the expression: HK = α·F/d2, where F is the applied load, d is the long diagonal of the resulting 10indentation and a is the Knoop indenter geometrical constant. In this paper, the Knoop hardness of SiC ceramics was measured in the applied load range from 4.9 to 98.07 N. For some materials measured “apparent” hardness value decreases with increasing applied test load (normal indentation size effect – ISE), while for some materials measured “apparent” hardness increases with increasing applied test load (reverse indentation size effect – RISE). Obtained results show the measured hardness exhibits the ISE. In the literature several models are given for the phenomenon explanation. We used the following models: Meyer's law (F = K·dn), proportional specimen resistance – PSR (F = a1·d + a2·d2) and modified proportional specimen resistance – MPSR model (F = a0 + a1·d + a2·d2). Results of regression analysis for all applied models show they can all be used for ISE analysis. “True” hardness was determined based on the PSR and MPSR model (HKT = α·a2). The obtained results were similar. If the specimen surface is carefully prepared and the range of loads is wide, the a0 coefficient from MPSR model reaches small values and can be excluded. Therefore, for the calculation of SiC ceramics Knoop hardness, the simpler model (PSR) can be used.
Gait in SWEDDs patients: Comparison with Parkinson's disease patients and healthy controls
Authors: Mian Omar S. , Schneider Susanne A. , Schwingenschuh Petra , Bhatia Kailash P. , Day Brian L.
Published: March 2011

Patients diagnosed with Parkinson's disease on clinical grounds who subsequently turn out to have normal dopamine transporter imaging have been referred to as SWEDDs (scans without evidence of dopaminergic deficits). Despite having clinical features similar to those of Parkinson's disease, these patients seem to have different pathophysiology, prognosis, and treatment requirements. In this study we determined the similarities and differences in the gaits of SWEDDs and Parkinson's disease patients to investigate whether walking patterns can distinguish these entities. We used 3‐D motion capture to analyze the gaits of 11 SWEDDs patients (who had unilateral or asymmetric upper limb tremor with a rest component), 12 tremor‐dominant Parkinson's disease patients, and 13 healthy control participants. In common with Parkinson's disease patients, SWEDDs patients had a slow gait mainly because of a small stride length, as well as a reduced arm swing. However, several abnormal features of posture and gait in Parkinson's disease were normal in SWEDDs. Thus, SWEDDs patients had normal trunk and elbow posture, normal stride length variability, and normal bilateral step‐phase coordination, all of which were abnormal in Parkinson's disease patients. We also searched for signs of ataxic movements during normal and tandem walking, but found no evidence that ataxic gait was a general feature in SWEDDs. These findings could aid the clinician in identification of potential tremulous SWEDDs cases. © 2011 Movement Disorder Society
Coffees rich in chlorogenic acid or N‐methylpyridinium induce chemopreventive phase II‐enzymes via the Nrf2/ARE pathway in vitro and in vivo
Authors: Boettler Ute , Volz Nadine , Pahlke Gudrun , Teller Nicole , Kotyczka Christine , Somoza Veronika , Stiebitz Herbert , Bytof Gerhard , Lantz Ingo , Lang Roman , Hofmann Thomas , Marko Doris
Published: March 2011

Recently, the coffee constituents 5‐O‐caffeoylquinic acid (CGA) and N‐methylpyridinium (NMP) were identified as inducers of the Nrf2/antioxidant‐response element (ARE) detoxifying pathway under cell‐culture condition. To study the impact of CGA and NMP on the Nrf2‐activating properties of a complex coffee beverage, two different model coffees were generated by variation of the roasting conditions: a low‐roast coffee rich in CGA and a heavy‐roast low in CGA but containing high levels of NMP. Activation of the Nrf2/antioxidant‐response element pathway was monitored in vitro and in vivo.
Design of micro‐sized differential antenna for 2.4‐GHz mobile payment applications
Authors: Shen Jianghua , Lv Bo , Shen Fazhong , Huangfu Jiangtao , Ran Lixin
Published: March 2011

In this article, we propose a design and on‐board measuring approach for the realization of micro‐sized differential antennas for the 2.4‐GHz mobile payment (MP) applications. Exampled by a complete realization of a 3 × 11 mm2‐sized differential antenna driven by a commercial 2.4‐GHz transceiver integrated inside a 15 × 11 mm2‐sized micro‐SD card, such design and testing approach is described in detail. The experimental measurements of the micro‐sized antenna show that the impedance of the designed micro‐sized differential antenna well matches the complex impedance of the transceiver, and, therefore, ensure the stability of the radio frequency performance required by the MP applications. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1419–1422, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25957
Accuracy–efficiency tradeoff of temporal basis functions for time‐marching solvers
Authors: Kaur Guneet , Yilmaz Ali E.
Published: March 2011

An investigation of the impact of the temporal discretization on the marching‐on‐in‐time solution of integral equations is presented. Numerical results that quantify the efficiency–accuracy tradeoff for causal piecewise polynomial and band‐limited interpolatory functions are presented. It is observed that the former is more efficient for low to moderate accuracy levels, and the latter achieves higher, but extrapolation‐limited, accuracy levels. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1343–1348, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25960
Tunable near‐field subwavelength microwave imaging
Authors: Pochiraju Tejprakash , Malyuskin Oleksandr , Fusco Vincent
Published: March 2011

In this article, we show that a dielectric filled slot into which a capacitively loaded printed dipole antenna is inserted is capable of producing squeezing of the near electric field when excited by a cross polarized signal. Further, it is demonstrated that this effect can be used to produce a simple sensor which is capable of producing tunable subwavelength imaging of scattering objects. Results are presented which show that with commercial surface mount components subresolution of better than 0.25λ is possible across a 500 MHz bandwidth from 2.53 to 3.08 GHz with varactor tuning. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1229–1231, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25966
Design of multiwavelength DFB fiber laser with equivalent phase shifts
Authors: Jia Linghui , Yin Zuowei , Zhang Liang , Chen Xiangfei
Published: March 2011

A dual‐wavelength distributed feedback fiber laser with two equivalent phase shifts is proposed and demonstrated experimentally. By studying varied parameters of the fiber laser, which show different impacts on the lasers' characteristic, a dual‐wavelength laser of 31 pm spacing is designed and fabricated. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1453–1456, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25969
Frequency‐tunable 150W harmonic‐tuned power oscillator
Authors: Shin Suk‐Woo , Choi Jin‐Joo
Published: March 2011

In this article, a frequency‐tunable 150W harmonic‐tuned power oscillator is presented. The harmonic‐tuned power amplifier of the oscillator was designed for improving drain efficiency with a single laterally diffused metal oxide semiconductor transistor using a nonlinear harmonic balance simulation code. The oscillation frequency was tuned by a mechanical phase shifter in the delay‐line feedback loop circuit. Experimental results show that the output power and the drain efficiency of the oscillator were almost same as in the power amplifier with the same transistor and operating in the same frequency range. The measured output power and drain efficiency of the fabricated oscillator were 51.8 ± 0.6 dBm and better than 55.9%, respectively, across the 902–928 MHz band. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1459–1462, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25970
Wideband antenna with shaped beams for wireless communication indoor applications
Authors: Guo Jing‐li , Zhou Shi‐gang , Zou Yan‐lin , Liu Qi‐zhong
Published: March 2011

A wideband antenna for DCS‐1800, PCS‐1900, WCDMA/IMT‐2000, WLAN, and TD‐SCDMA indoor applications is presented. The antenna consists of two half circle shaped radiating patches, a feeding ground and a reflector ground. The coupling between two patches is considered in the design of the antenna. The two patches are fed with 90° phase difference, which leads to down‐tilted radiation patterns when the antenna is mounted on a wall. A prototype is constructed and tested. Simulated and measured results are given. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1377–1379, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25973
Performance of microstrip patch antenna on a reinforced carbon fiber composite ground plane
Authors: Mehdipour Aidin , Sebak Abdel‐Razik , Trueman Christopher W. , Rosca Iosif D. , Hoa Suong V.
Published: March 2011

The performance of a microstrip patch antenna operating against a carbon fiber composite ground plane is investigated and compared with results for a copper ground, both numerically and experimentally.An electromagnetic model (EM) of the composite antenna is developed using Microwave Studio for numerical analysis. The ground plane is made of continuous reinforced carbon fiber composite composite, which has anisotropic conductivity. The direction of the fibers in the ground plane affects the current distribution, and hence the impedance bandwidth and the matching characteristics of the antenna. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1328–1331, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25976
Wideband monopole antenna coupled with a chip‐inductor‐loaded shorted strip for LTE/WWAN mobile handset
Authors: Chen Shu‐Chuan , Wong Kin‐Lu
Published: March 2011

An eight‐band long term evolution/wireless wide area network (LTE/WWAN) mobile handset antenna using a wideband monopole antenna coupled with a chip‐inductor‐loaded shorted strip is presented. Two wide operating bands are obtained to cover the eight‐band LTE/WWAN operation in the 698–960 and 1710–2690 MHz bands. The antenna's lower band is contributed by the coupled shorted strip of length about 100 mm which is short‐circuited to the system ground plane of the mobile handset through a loaded chip inductor of 10 nH. The loaded chip inductor leads to dual‐resonant behavior of the excited resonant mode and greatly enhances the lower‐band bandwidth. The upper band is formed by a wide resonant mode generated by the wideband monopole antenna and a higher‐order resonant mode generated by the coupled shorted strip. The upper‐band bandwidth of larger than 1 GHz is hence obtained. With two wide bands obtained, the antenna can be disposed on the bottom edge of the main circuit board of the mobile handset with a small board area of 10 × 60 mm2. The specific absorption rate (SAR) values of the antenna for 1‐g head tissue are also well below the limit of 1.6 W/kg for frequencies over the operating bands. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1293–1298, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25977
A dual‐band Gysel power divider with the even‐mode input extension/stub lines
Authors: Park Myun‐Joo , Lee Byungje
Published: March 2011

A new dual‐band structure is proposed for the Gysel power divider. The proposed divider features an extension line at the input and a stub line at the opposite end, both located along the symmetry plane and operating at the even‐mode excitation of the divider. The divider is analyzed rigorously to derive the exact design equations in closed‐form formula. The design, simulation and experiments based on the proposed method confirm the dual‐band capability of the divider. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1213–1216, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25979
A high CMRR BiCMOS active combiner balun
Authors: Gautier Jean‐Luc , Temcamani Farid , Régis Myrianne , Diab Hilda
Published: March 2011

An integrated bipolar differential amplifier was optimized to have maximum common mode rejection ratio (CMRR).This amplifier was then used as combiner and splitter baluns. A prototype was fabricated using a SiGe bipolar technology. Measurements show high CMRR and good agreement with simulations. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1253–1256, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25981
Detection by using dielectric materials and generation of millimeter wave in optical‐to‐radio frequency systems connecting wavelength division multiplexing and wireless networks
Authors: Park Ki‐Hwan
Published: March 2011

A 50–60 GHz continuous wave (cw) millimeter wave (MMW) converted from optical signals was detected by using dielectric materials of various kinds for optical‐to‐radio frequency systems.The converted MMW signals were radiated inside a millimeter waveguide through dielectric materials covering either the top of an optical waveguide or the bottom of an LN substrate and detected by a detector. The detected spectral linewidth of the MMW signals was less than 1 kHz. The power of the MMW signals obtained through the only Teflon or alumina at a 50–60 GHz range was larger than that detected by the strip‐waveguide beyond 5 dBm. When copper plate was inserted between the Teflon and LN substrate, the measured MMW power was larger than that detected by a strip‐waveguide beyond 15 dBm. The power of the MMW signals obtained from the bottom of an LN substrate was larger than that detected at the top of an optical waveguide beyond 5 dBm in the same range. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1409–1413, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25986
Analysis and design of a wide band omnidirectional antenna
Authors: Jacobs Ockert B. , Odendaal J. W. , Joubert Johan
Published: March 2011

The analysis and design of an omnidirectional antenna that functions over a very broad frequency band is presented. Design guidelines for this antenna have been derived using electromagnetic analysis software. Measured results of a prototype developed according to these guidelines are presented. These results are compared to simulation results to illustrate the validity of the model used to derive the empirical design guidelines. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1352–1356, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25990
Miniaturized substrate integrated waveguide filter with complementary spiral resonator
Authors: Zhou Liang , Liu Shaobin , Gao Nan , Chen Yu , Wei Yinsheng
Published: March 2011

In this letter, the miniaturized substrate integrated waveguide (SIW) filter is proposed using a complementary spiral resonator (CSR). The CSR is based on the multiple turns SR (SRm), which was introduced in 2004 by some of the authors. CSR technique can be applied to the design of miniaturized filter by increasing electrical length. To demonstrate the idea, the miniaturized SIW filter is designed with CSR2 and CSR3, respectively. The measured central resonant frequencies are 3.25 and 2.23 GHz, which are lower than the SIW filter with complementary split‐ring resonator occurs at 5.17 GHz. Details of the experimental results compared with the simulated results are presented and discussed. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1308–1311, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25992
Design of quad‐band bandpass filter using assembled resonators
Authors: Chen Fu‐Chang , Chu Qing‐Xin
Published: March 2011

This letter presents a novel approach for designing quad‐band bandpass filter with independently controlled center frequencies.Assembled resonator constructed by a stepped impedance resonator (SIR) and a stub‐loaded SIR is employed to obtain quad‐band responses. The SIR is designed to operate at the second and fourth passbands and the stub‐loaded SIR is designed to operate at the first and third passbands. Good agreement is shown between the simulation and the measurement, the resonators are meandered to give an overall circuit size of about 21.8 × 30.2 mm2. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1305–1308, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25993
Compact quad band monopole antenna
Authors: Lin Chih‐Peng , Chang Chieh‐Hsiang , Jou Christina F.
Published: March 2011

In this article, a compact quad band monopole antenna is demonstrated. Asymmetric coplanar strip feeding is applied in the design in order to compact the size. The proposed antenna fabricated on a FR4 substrate has an overall size of 30–30 mm2. By integrating an invert‐C slot and a modified invert‐F strip into an invert‐C patch, multiple resonant frequencies can be excited at 1.1, 2.35, 3.6, and 5.4 GHz individually for global positioning system, wireless local area network, Bluetooth/ISM, and Wi‐MAX applications. The measured result has shown a good agreement with the simulation results. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1272–1276, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25994
Compact planar hexa‐band inverted‐F antenna for mobile phone application
Authors: Ma J. , Yin Y.‐Z. , Hu W. , Ren X.‐S.
Published: March 2011

This article presents a compact multiband planar inverted‐F antenna design for mobile phone applications. The proposed antenna comprises dual twisted lines, a shorting strip and an L‐shaped coupling strip. The dual twisted lines are excited by the coupling strip to generate four resonance modes around 900, 1800, 2100, and 3500 MHz and covers six bands including the global system for mobile communication 850/900 (824–894 MHz), (880–960 MHz), digital communication system (1710–1880 MHz), personal communication system (1850–1990 MHz) universal mobile telecommunication system (1920–2170 MHz) and worldwide interoperability for microwave access (3400–3600 MHz). The antenna shows a planar structure and occupies a very small‐size of 15 × 26 mm2, making it especially suit for mobile phone applications. This research performed simulation by high frequency structure simulation and CST to design and analyze the antenna, and a practical structure was fabricated and tested. The measured and simulated return loss show good agreement. Moreover, the radiation patterns and the specific absorption rate are discussed too. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1233–1236, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25996
All‐optical clocked D flip‐flop memory using a hybrid integrated S‐R latch
Authors: Reis C. , Maziotis A. , Kouloumentas C. , Stamatiadis C. , Bougioukos M. , Calabretta N. , André P. , Dionisio R. , Neto B. , Dorren H. J. S. , Avramopoulos H. , Teixeira A.
Published: March 2011

We demonstrate, by using multiple Mach‐Zehnder interferometer (MZI)‐semiconductor optical amplifier structures, an all‐optical synchronous D type flip‐flop, with high‐photonic integration capability. Experimental performance analysis shows its functional and performance feasibility and high‐switching speeds were achieved. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1201–1204, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25998
Investigation of SIW‐based planar integrated w‐band low‐phase noise Gunn harmonic oscillator
Authors: Liu Yong , Tang Xiaohong , Wu Tao
Published: March 2011

Based on the substrate integrated waveguide (SIW) technology, the influence of SIW cavity on phase noise of W‐band oscillator is studied and a novel W‐band low phase noise GaAs Gunn planar harmonic oscillator is developed in this letter. The technique of harmonic extraction from Gunn diodes and the novel SIW cavity structure with short piston, which is introduced to study the influence of SIW cavity on phase noise of oscillator, are discussed in detail. Because of the high quality factor and planar structure of the SIW cavity resonator, the oscillator is characterized by some advantages such as low phase noise, small size, low cost and planar integration. The optimal phase noise is −105.81 dBc/Hz at 1 MHz offset 92.16 GHz carrier frequency and the measured output power is more than 6.2 dBm. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1239–1242, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26002
Effect of composited‐layer AlyGa1‐yN on performances of AlGaN/GaN HEMT with unintentionally doping barrier AlxGa1‐xN
Authors: Cheng Zhi‐qun , Hu Sha , Zhou Wei‐jian , Liu Jun
Published: March 2011

A novel structure AxGa1‐xN/AlN/AlyGa1‐yN/GaN HEMT with composited‐layer and unintentionally doping barrier was designed for high linearity. The effect of two‐dimensional electron gas (2DEG) and electric field on device structure parameter is obtained from the self‐consistent solution basing on theory of semiconductor energy band and quantum well. Combining with results of theory analysis and TCAD software simulation results, the optimization structure Al0.27Ga0.73N/AlN/Al0.04Ga0.96N/GaN HEMT was proposed. And AxGa1‐xN/AlN/GaN HEMT without composited‐ layer and unintentionally doping barrier was designed together for comparison. Both devices with gate length of 0.3 μm and gate width of 200 μm were fabricated. Measured results show proposed AxGa1‐xN/AlN/AlyGa1‐yN/GaN HEMT has better performances of linearity, gain, and power added efficiency (PAE) than AxGa1‐xN/AlN/GaN HEMT. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1206–1209, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26004
Antenna representation in two‐port network scattering parameter
Authors: Prakoso Teguh , Ngah Razali , Ghassemlooy Zabih , Rahman Tharek Abdul
Published: March 2011

This paper proposes a representation of antenna in two‐port network s‐parameter, by exploiting the analogy between the antenna and a two‐port network, to produce a suitable method for evaluating antennas in system and circuit simulation. Complicated steps required by previous methods to determine an antenna‐specific equivalent‐circuit and its corresponding resistor, inductor, and capacitor values are avoided. Simulations results obtained for the circuit and system software confirms the validity of the proposed scheme. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1404–1409, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26005
Capacitance of a conductor‐backed coplanar waveguide with an upper shielding
Authors: Park Yong Bae , Park Geon Hye
Published: March 2011

In this letter, the capacitance of a conductor‐backed coplanar waveguide (CPW) with an upper shielding is investigated.An electrostatic boundary‐value problem of the conductor‐backed CPW with an upper shielding is solved using the Fourier transform, mode matching technique, and superposition. The capacitance of the conductor‐backed CPW is represented in a series and calculated in terms of the CPW geometry. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1364–1368, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26007
Optical carrier sinusoidal modulation suppressed by ultra‐long semiconductor optical amplifier gain saturation
Authors: Ribeiro Napoleão S. , Cavalcante André L. R. , Gallep Cristiano M. , Conforti Evandro
Published: March 2011

The amplitude modulated sinusoidal pattern over an optical carrier is suppressed by a deeply saturated ultra‐long semiconductor optical amplifier. The extinction‐ratio of the modulated signal is reduced from 16.8 to 3.9 dB at 15 GHz. The characterization of the amplitude modulation suppression is presented, with good results for broadband operation (15 nm at 1557 nm), high‐speed (up to 35 GHz) and high input extinction‐ratio (up to 16.8 dB). © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1286–1290, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26010
Polarization‐preserving evanescent‐mode filters
Authors: Yu Seng Yong , Bornemann Jens
Published: March 2011

Rectangular and circular waveguide evanescent‐mode filters with polarization‐preserving properties are presented. The filters are formed by inserting quadruple‐ridged resonators in a square or circular waveguide operated below cutoff. They are especially suited in applications requiring short and compact components. The numerical technique that facilitates eigenvalue and scattering parameter computations is verified against measurements. Basic design considerations are discussed, and structural dimensions are provided for two 9.5 GHz filters with 500 MHz bandwidth. Performances are validated by independent and commercially available electromagnetic software packages. Sensitivity issues for fabrication are addressed by a tolerance analysis. Fabrication accuracy is acceptable for operation in dual vertical and horizontal polarizations but is considerably more stringent for circularly polarized applications. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1435–1439, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26016
Microstrip‐fed polygon slot antenna design for WLAN applications
Authors: Sim Chow‐Yen‐Desmond , Cai Fu‐Ren
Published: March 2011

A novel microstrip‐fed polygon slot antenna with dual‐band operation for WLAN (Wireless Local Area Network) applications in the 2.4/5.2/5.8 GHz bands is proposed. The polygon slot is formed by embedding two right‐angle triangular ground patches into both upper‐corners of the rectangular slot. To allow the excitation of three resonant modes located exactly around 2.4, 5.2, and 5.8 GHz bands, besides tuning the length of the hypotenuse of the triangular ground patches, an L‐shaped slit is also loaded into the rectangular radiating element. The design of this proposed antenna via simulation is illustrated in detail, and typical experiments were performed on the fabricated prototype. From the experimental results, the lower band measured along VSWR 2:1 operates from 2.36 to 2.63 GHz, while a broad upper band from 4.98 to 6.8 GHz is also observed. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1394–1398, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26018
A novel flexible GMRES with deflated restarted for efficient solution of electromagnetic problems
Authors: Hu X. Q. , Ding D. Z. , Chen R. S.
Published: March 2011

To iterative solve large dense complex linear systems arising from electric field integral equations formulation of electromagnetic scattering problems, multilevel fast multipole algorithm (MLFMA) is built to speed up the matrix‐vector product (MVP) operations. This article presents a novel flexible generalized minimum residual with deflated restarted (FGMRES‐DR), which can greatly improve the convergence of those large dense complex linear systems. Based on physical mechanism of the scattering problems, in inner iteration of FGMRES‐DR, an iterative solution of the near‐field matrix in MLFMA is adopted. In outer iteration, deflation method which is purely algebraic is used to eliminate the influence on convergence because of the smallest eigenvalues. Numerical experiments indicate that FGMRES‐DR is very effective and can reduce the number of MVP compared with the FGMRES in large‐scale electromagnetic problems. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1360–1364, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26019
Design of dual‐band colpitts VCO by switched negative resistance shaping
Authors: Chen Ying , Mouthaan Koen
Published: March 2011

A switched negative resistance shaping technique is proposed to design a dual‐band Colpitts VCO.By making use of the Miller effect, the negative resistance of the Colpitts oscillator can be shaped with an additional switchable inductor‐capacitor (LC) resonator placed between the base and the collector of the bipolar transistor. The shaping of the negative resistance guarantees oscillation to start at only the selected resonant mode when a multimode resonator is used at the input of the Colpitts oscillator. Using the proposed technique, a dual‐band VCO is designed with center frequencies of 440 and 640 MHz. The measured continuous frequency tuning range is 15.8 and 16.3% for the lower band and the upper band, respectively. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1356–1360, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26020
Enhancement technique of insertion loss and linearity for PIN diode switches
Authors: Sun Pinping , Peng Liu , Upadhyaya Parag , Jeong Dong‐Ho , Heo Deukhyoun
Published: March 2011

Design and analysis of insertion loss and linearity enhancement technique for PIN diode RF switches are presented.Measurements show a 12.5% insertion loss improvement by optimizing anode‐to‐cathode distance, a 3.29% reduction of intrinsic resistance by choosing the octagonal shape over the square one, and a 1 dB P1dB improvement by using the new cathode biased technique. A low insertion loss and high isolation single‐pole double‐throw (SPDT) switch has been built with the proposed PIN diode. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1430–1435, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26022
Comparison of dynamic contrast‐enhanced MRI and dynamic contrast‐enhanced CT biomarkers in bladder cancer
Authors: Naish J. H. , McGrath D. M. , Bains L. J. , Passera K. , Roberts C. , Watson Y. , Cheung S. , Taylor M. B. , Logue J. P. , Buckley D. L. , Tessier J. , Young H. , Waterton J. C. , Parker G. J. M.
Published: March 2011

Dynamic contrast‐enhanced MRI (DCE‐MRI) is frequently used to provide response biomarkers in clinical trials of novel cancer therapeutics but assessment of their physiological accuracy is difficult. DCE‐CT provides an independent probe of similar pharmacokinetic processes and may be modeled in the same way as DCE‐MRI to provide purportedly equivalent physiological parameters. In this study, DCE‐MRI and DCE‐CT were directly compared in subjects with primary bladder cancer to assess the degree to which the model parameters report modeled physiology rather than artefacts of the measurement technique and to determine the interchangeability of the techniques in a clinical trial setting. The biomarker Ktrans obtained by fitting an extended version of the Kety model voxelwise to both DCE‐MRI and DCE‐CT data was in excellent agreement (mean across subjects was 0.085 ± 0.030 min−1 for DCE‐MRI and 0.087 ± 0.033 min−1 for DCE‐CT, intermodality coefficient of variation 9%). The parameter vp derived from DCE‐CT was significantly greater than that derived from DCE‐MRI (0.018 ± 0.006 compared to 0.009 ± 0.008, P = 0.0007) and ve was in reasonable agreement only for low values. The study provides evidence that the biomarker Ktrans is a robust parameter indicative of the underlying physiology and relatively independent of the method of measurement. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Fast bound pool fraction mapping using stimulated echoes
Authors: Soellinger M. , Langkammer C. , Seifert‐Held T. , Fazekas F. , Ropele S.
Published: March 2011

Magnetization transfer imaging advanced to an indispensible tool for investigating white matter changes. Quantitative magnetization transfer imaging methods allow the determination of the bound pool fraction (BPF), which is thought to be directly linked to myelin integrity. Long acquisition times and high specific absorption rates are still inhibiting broad in vivo utilization of currently available BPF mapping techniques. Herewith, a stimulated echoes amplitude modulation‐based, single‐shot echo planar imaging technique for BPF and T1 quantification is presented at 3T. It allows whole brain mapping in 10–15 min and is low in specific absorption rates. The method was validated with different concentrations of bovine serum albumin (BSA) phantoms. Intra‐ and inter‐subject variability was assessed in vivo. Phantom measurements verified linearity between bovine serum albumin concentrations and measured BPF, which was independent of T1 variations. T1 values in the phantoms correlated well with values provided by standard T1 mapping methods. Intrasubject variability was minimal and mean regional BPFs of 10 volunteers (e.g., left frontal white matter = 0.135 ± 0.003, right frontal white matter = 0.129 ± 0.006) were in line with previously published data. Assessment of interhemispheric BPF differences revealed significantly higher BPF for the left brain hemisphere. To sum up, these results suggest the proposed method useful for cross‐sectional and longitudinal studies of white matter changes in the human brain. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
31P MRSI and 1H MRS at 7 T: initial results in human breast cancer
Authors: Klomp Dennis W. J. , van de Bank Bart L. , Raaijmakers Alexander , Korteweg Mies A. , Possanzini Cecilia , Boer Vincent O. , van de Berg Cornelius A. T. , van de Bosch Maurice A. A. J. , Luijten Peter R.
Published: March 2011

This study demonstrates the feasibility of the noninvasive determination of important biomarkers of human (breast) tumor metabolism using high‐field (7‐T) MRI and MRS. 31P MRSI at this field strength was used to provide a direct method for the in vivo detection and quantification of endogenous biomarkers. These encompass phospholipid metabolism, phosphate energy metabolism and intracellular pH. A double‐tuned, dual‐element transceiver was designed with focused radiofrequency fields for unilateral breast imaging and spectroscopy tuned for optimized sensitivity at 7 T. T1‐weighted three‐dimensional MRI and 1H MRS were applied for the localization and quantification of total choline compounds. 31P MRSI was obtained within 20 min per subject and mapped in three dimensions over the breast with pixel volumes of 10 mL. The feasibility of monitoring in vivo metabolism was demonstrated in two patients with breast cancer during neoadjuvant chemotherapy, validated by ex vivo high‐resolution magic angle spinning NMR and compared with data from an age‐matched healthy volunteer. Concentrations of total choline down to 0.4 mM could be detected in the human breast in vivo. Levels of adenosine and other nucleoside triphosphates, inorganic phosphate, phosphocholine, phosphoethanolamine and their glycerol diesters detected in glandular tissue, as well as in tumor, were mapped over the entire breast. Altered levels of these compounds were observed in patients compared with an age‐matched healthy volunteer; modulation of these levels occurred in breast tumors during neoadjuvant chemotherapy. To our knowledge, this is the first comprehensive MRI and MRS study in patients with breast cancer, which reveals detailed information on the morphology and phospholipid metabolism from volumes as small as 10 mL. This endogenous metabolic information may provide a new method for the noninvasive assessment of prognostic and predictive biomarkers in breast cancer treatment. Copyright © 2011 John Wiley & Sons, Ltd.
Locating median paths on connected outerplanar graphs
Authors: Lari Isabella , Ricca Federica , Scozzari Andrea , Becker Ronald I.
Published: March 2011

In this article, we study the median path problem without length restrictions on the class of connected outerplanar graphs, assuming that weights equal to 1 are assigned to the edges of a graph G, and nonnegative weights are associated to its vertices. We provide an
$O(kn)$
time algorithm, where n is the number of vertices of G and k is the number of blocks in G. As a byproduct, when G is a biconnected outerplanar graph, we provide a linear time algorithm to find a median path between two fixed vertices of G without restrictions on the length. In the literature, we did not find polynomial time algorithms for this problem on such classes of graphs. © 2011 Wiley Periodicals, Inc. NETWORKS, 2011
Parametric maximum flow methods for minimax approximation of target quotas in biproportional apportionment
Authors: Serafini Paolo , Simeone Bruno
Published: March 2011

In this article, we study the biproportional apportionment problem, which deals with the assignment of seats to parties within regions. We consider the minimization of both the maximum absolute error and the maximum relative error of the apportioned seats with respect to target quotas. We show that this can be done polynomially through a reduction to a parametric maximum flow problem. Moreover, the maximum absolute error can be minimized in strongly polynomial time. More generally, our method can be used for computing
$\ell_{\infty}$
projections onto a flow polytope. We also address the issue of uniqueness of the solution, proposing a method based on finding unordered lexicographic minima. Our procedure is compared to other well‐known ones available in the literature. Finally we apply our procedures to the data of the 2008 Italian political elections, for which the procedure stated by the law produced an inconsistent assignment of seats. © 2011 Wiley Periodicals, Inc. NETWORKS, 2012
Synthesis of the hemoglobin‐conjugated polymer micelles by click chemistry as the oxygen carriers
Authors: Li Tai‐hang , Jing Xia‐bin , Huang Yu‐bin
Published: March 2011

Amphiphilic triblock copolymers were synthesized using MPEG, cyclic carbonic ester monomer including propargyl group (MPC) and L‐lactide (LA). These copolymers could self‐assemble into core–shell spherical micelles with propargyl groups on the surface. Azided hemoglobin (Hb) was conjugated with the micelles through click reaction to form Hb‐bearing nano‐micelles. The click reaction conditions, such as the molar ratio of sodium azide to Hb, the binding ratio of Hb to copolymers, the components of catalytic solution, the reaction temperature and time, were thoroughly investigated and optimized. The resulted nano‐micelles had 100 nm diameter with 50–60 wt% of Hb content. The Hb‐based nano‐micelles showed appropriate stability and oxygen carrying capacity, and would have the potential to be used as the new type of artificial oxygen carrier. Copyright © 2011 John Wiley & Sons, Ltd.
Properties of polymer electrolytes composed of poly(ethylene oxide) and ionic liquids according to hard and soft acids and bases theory
Authors: Tsurumaki Akiko , Kagimoto Junko , Ohno Hiroyuki
Published: March 2011

We investigated the miscibility of 12 different ionic liquids (ILs) with poly(ethylene oxide) (PEO) under excess salt conditions, using hard and soft, acids and bases (HSAB) theory. The hardness of the component ions of a series of ILs was estimated from the energy calculation of their HOMO and LUMO. ILs composed of relatively hard acids, such as imidazolium cation, and soft bases such as bis(trifluoromethanesulfonyl)imide anion, displayed excellent miscibility with PEO regardless of mixing ratio. Good miscibility implies that the ions strongly interact with PEO chains, and accordingly the ionic conductivity decreased with increasing PEO content. On the other hand, the same ionic conductivity was found regardless of mixing ratio when ILs composed of soft acid and soft base such as N‐methyl‐N‐butylpyrrolidinium bis(trifluoromethanesulfonyl)imide was mixed with PEO. These data suggest that high ionic conductivity should be supported by the micro‐phase separation of polymers and ionic liquids. Copyright © 2011 John Wiley & Sons, Ltd.
Investigation of macromolecule–metal complexes as cathode catalyst in polymer electrolyte membrane fuel cell system
Authors: Yuasa M. , Kondo T. , Mori D. , Arikawa S.
Published: March 2011

Search for non‐platinum metal catalyst as the cathode of polymer electrolyte membrane fuel cell (PEMFC) is an important subject in the recent fuel cell research. Macromolecule–metal complexes with macrocyclic ligands such as porphyrin and macromolecular ligands such as polypyrrole, all of which contain four nitrogen donors (Co‐N4 chelates) and are adsorbed on carbon, were prepared and heat‐treated in the hope that they can be an alternate to the conventional carbon‐supported platinum catalyst. Carbon‐supported cobalt (5,10,15,20‐tetraethylporphyrin) (HT‐CoTEtP/C), poly(cobalt (5‐mono(3‐thienyl)‐10,15,20‐triethylporphyrin)) (HT‐P(CoM3ThTEtP)/C), and cobalt‐(polypyrrole) (HT‐CoPPy/C) were chosen as candidate heat‐treated catalysts based on the electrocatalytic activity tests on the prepared macromolecule–metal complexes. The rotating ring‐disk method revealed that these catalysts reduce oxygen mainly with four electrons. Characterization using X‐ray photoelectron spectroscopy showed that the catalysts maintain the Co‐N4 chelate structure, strongly suggesting a major contribution of the Co‐N4 chelate to the four‐electron reduction of oxygen. Membrane electrode assemblies (MEAs) of PEMFCs were then constructed using HT‐CoTEtP/C, HT‐P(CoM3ThTEtP/C), and HT‐CoPPy/C as the cathode catalysts and the current density‐cell voltage and current density‐power density relationships were examined for the PEMFC. HT‐CoTEtP/C exhibited a much higher performance than the other macromolecule–metal complexes. Although the open circuit voltage and power density values of the PEMFCs were lower than those of the conventional carbon supported platinum catalyst, the power density per unit metal weight was almost comparable for the cobalt and platinum catalysts. Copyright © 2011 John Wiley & Sons, Ltd.