bluuebunny/crossref_metadata_2025 huggingface dataset:
Wideband omnidirectional L‐shaped monopole antenna for a wireless USB dongle
Authors: Su Saou‐Wen , Chen Austin , Liu Yung‐Tao
Published: January 2007

A new omnidirectional monopole antenna well suited to application in a wireless universal serial bus dongle for wideband operation is presented. The antenna is an L‐shaped metal‐plate monopole antenna consisting of a rectangular monopole element and a matching portion. The antenna is suitable to be mounted at the top region of a host dongle as a concealed antenna and can provide a very wide operating bandwidth of larger than 6.8 GHz (∼3.4–10.2 GHz). In addition, omnidirectional radiation is obtained for frequencies across the operating bandwidth. Effects of the system ground‐plane length on the antenna's impedance and radiation characteristics are also analyzed. Details of the proposed antenna are described, and a prototype of the design example is constructed and studied. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 625–628, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22217
A novel compact broadband 5–35 GHz balun
Authors: Chramiec Jerzy , Janiczak Bogdan J. , Kitliński Marek
Published: January 2007

In this paper, operating principle and modeling procedure of a new, compact, planar balun aimed at microwave and millimeter‐wave applications have been described. The structure of balun involves microstrip line‐symmetrical slotline‐bilateral slotline transitions with a novel version of multibranch broadband slotline stub. The designed experimental balun circuit covering the C‐ to K‐band frequency range clearly demonstrates the advantages of the design. Requirements resulting from balun application to doubly balanced circuits or as antenna feeder have been taken into account. In both cases, very satisfactory operation of the device in the frequency range of 5–35 GHz has been obtained in circuit manufactured on a layered low‐loss low‐permittivity dielectric substrate, with external dimensions of 7 × 8 mm2. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 622–625, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22218
Internal low‐profile metal‐plate monopole antenna for DTV portable multimedia player applications
Authors: Yu Yeon‐Sik , Jeon Seung‐Gil , Park Hoon , Seo Dong‐Hyun , Choi Jae‐Hoon
Published: January 2007

A low‐profile metal‐plate monopole antenna for mobile handset operating over Digital‐TV (DTV; 470–850 MHz) frequency band is proposed. The antenna consists of a folded rectangular patch and two slits, and has a small volume of 65 × 25 × 5 mm3. The measured return loss for the proposed antenna at DTV frequency band is better than 10 dB. The antenna has omni‐directional or monopole‐like radiation patterns, with good antenna gain even for such a compact size. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 593–595, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22219
A new configuration to improve the active loop technique for transistor large signal characterization in the Ka band
Authors: Yattoun Ismail , Peden Alain
Published: January 2007

This article presents a new configuration to improve the conventional active loop technique with pre‐matching. This reduces the power requirements of the loop amplifier when synthesizing high reflection coefficient for high power transistors. The active loop technique is very efficient in characterizing power transistors but the output power of the loop amplifier can be a strong limitation as it can exhibit non‐linear behavior when high power is needed. The proposed new configuration improves the active loop capabilities as it allows a larger reflection coefficient to be synthesized with higher linearity of the loop amplifier. Theoretical results show the interest of the new active loop and experimental measurements in the Ka band validate the linear behavior improvement of the active loop for high reflection coefficients. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 589–593, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22220
Orthogonally proximity‐coupled patch antenna for a passive RFID tag on metallic surfaces
Authors: Son Hae‐Won , Choi Gil‐Young
Published: January 2007

A new wideband rectangular patch antenna for radio frequency identification tags mountable on metallic surfaces is presented. An orthogonally proximity‐coupled feed structure, in which the direction of the microstrip feedline is orthogonal to that of the resonant length of the radiating patch, is explored to perform simple and wideband impedance matching between an antenna and a tag chip without any additional matching networks. The proposed antenna has wideband characteristics and good cross‐polarization, which are validated by simulations and measurements. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 715–717, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22222
A new CPW‐fed half‐loop antenna
Authors: Sun Jwo‐Shiun , Lee Yi‐Chieh , Wang Chuan‐Jyun
Published: January 2007

A novel and simple structure for a CPW‐fed half‐loop antenna is presented. The proposed antenna covered the ultra‐wideband bandwidth (3.1–10.6 GHz) to even higher band (∼20 GHz) for VSWR <2. Tapered slot structure and half‐loop antenna exhibited high band and low band, respectively. The measured results are in fairly good agreements with those of simulated ones. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 684–686, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22223
Internal GSM/DCS dual‐band open‐loop antenna for laptop application
Authors: Kuo Cheng‐Hao , Wong Kin‐Lu , Chang Fa‐Shian
Published: January 2007

A novel open‐loop antenna with a coupled‐line gap for application as an internal laptop antenna for GSM/DCS dual‐band operation is presented. Owing to the use of the coupled‐line gap, the proposed antenna can operate both as a half‐wavelength loop structure at 900 MHz and a one‐wavelength loop structure at 1800 MHz. The antenna is easily printed on a dielectric substrate with a low cost and is then integrated to the supporting metal frame of the laptop display to achieve a compact size of 9 mm in height and 70 mm in length, making it very promising to be embedded within the casing of the laptop as an internal antenna. Design considerations of the proposed antenna are described, and experimental and simulation results of the constructed prototype are presented. Effects of the coupled‐line gap on the dual‐band operation of the proposed antenna are also analyzed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 680–684, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22224
A 30‐GHz 10‐dB low noise amplifier using standard 0.18‐μm CMOS technology
Authors: Tu Hsin‐Lung , Yang Tsung‐Yu , Liang Kung‐Hao , Chiou Hwann‐Kaeo
Published: January 2007

A three‐stage 30‐GHz low noise amplifier (LNA) was designed and fabricated in a standard 0.18‐μm CMOS technology. The LNA has demonstrated a 10‐dB gain and a minimum noise figure of 5.2 dB at 30 GHz. The achieved input 1‐dB compression point (IP1 dB) and third order intercept point (IP3) are −7 and +2.5 dBm, with total current of 16 mA from a 1.5‐V power supply. To the author's knowledge, the LNA shows the best overall performances ever reported in standard 0.18‐μm CMOS process. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 647–649, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22226
Novel Wilkinson power divider based on left‐handed transmission lines
Authors: Li JiuSheng , Zou YongZhuo
Published: January 2007

In this paper, a novel Wilkinson power divider utilizing left‐handed transmission lines (LHTLs) is presented. The proposed device was fabricated by using the lumped L–C (−λ/4) LHTLs instead of the right‐handed transmission lines branch arms of the conventional Wilkinson power divider. Both the measured and simulated results show that the designed power divider has a wide bandwidth of return loss and isolation, and its size is 50% smaller than conventional Wilkinson power dividers. The measured results are good well with the simulated ones. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 712–715, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22227
End‐fed modified planar dipole antenna for DTV signal reception
Authors: Chi Yun‐Wen , Wong Kin‐Lu , Yeh Shih‐Huang
Published: January 2007

A novel end‐fed modified planar dipole antenna for digital television (DTV) signal reception in the 470–806 MHz band is presented. The antenna is of a narrow rectangular shape (10 mm wide and 235 mm long) and is printed on a dielectric substrate. The antenna comprises a step‐shaped radiating strip (arm 1) and a narrow rectangular radiating strip (arm 2), both separated by an L‐shaped feed gap whose one open end located at the shorter edge or end edge of the antenna. Across this open end of the L‐shaped feed gap, the antenna can be excited to provide a wide bandwidth (2.5:1 VSWR) of larger than 50%, which is much wider than that of a corresponding conventional center‐fed dipole antenna and allows the proposed antenna easily cover the 470–806 MHz band for DTV signal reception. In addition, over the operating band, the radiation performance of the proposed antenna is similar to that of the conventional center‐fed dipole antenna. The proposed end‐fed modified planar dipole antenna is studied in detail in this paper. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 676–680, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22229
Design of microstrip dual‐band bandpass filter with controllable bandwidth
Authors: Guan Xuehui , Ma Zhewang , Cai Peng , Anada Tetsuo , Hagiwara Gen
Published: January 2007

A dual‐band microstrip bandpass filter with controllable bandwidth is proposed by using new dual‐band resonators. The resonator consists of a pair of shunt open stubs, including a stepped‐impedance open stub. The open stubs produce three transmission zeros, which result in sharp attenuations near the passbands, and large isolations between the two passbands. Design formulas of this type of filters are provided. A dual‐band bandpass filter operating at 2.4 and 5.2 GHz is designed and tested, and the measured characteristics agree well with the theoretical simulations. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 740–742, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22232
RF MEMS asymmetric capacitive switch with high‐isolation at selected low‐microwave frequency
Authors: Qian Jiangyuan , Chang Hung‐Pin , Cetiner Bedri A. , Bachman Mark , De Flaviis Franco , Li G.P.
Published: January 2007

An asymmetric RF microelectromechanical systems (MEMS) capacitive switch with a novel architecture employing mode switching from a coplanar waveguide (CPW) mode to a coupled slotline (CSL) mode is reported for selected frequency within the 2–10 GHz low microwave frequency range. An additional metal‐insulator‐metal (MIM) capacitor is introduced on one end of the switch membrane as a tuning capacitor. The signal line of CSL is used as a tuning inductor. These two tuning elements together can improve the isolation of a regular capacitive RF MEMS switch by about 20 dB at the induced additional low resonant frequency ranging from 2 to 10 GHz. The measurements of the fabricated asymmetric switch demonstrated excellent isolation improvements. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 702–706, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22235
Miniaturized optical fiber Bragg grating sensor interrogator based on echelle diffractive gratings
Authors: Xiao Gaozhi , Sun Fengguo , Zhang Zhiyi , Lu Zhenguo , Liu Jiaren , Wu Fang , Mrad Nezih , Albert Jacques
Published: January 2007

An Optical fiber Bragg grating sensor interrogation device based on monolithically integrated echelle diffractive grating and detector arrays on an InP chip is designed and prototyped. The device weighs less than 60 g and measures smaller than 45 mm × 30 mm × 15 mm, and it is specifically designed for potential integration into aerospace applications. This study discusses this device's operation principle and presents some initial experimental results reflecting its performance. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 668–671, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22236
The high isolation dual‐band inverted F antenna diversity system with the small N‐section resonators on the ground plane
Authors: Kim Ki‐Jin , Ahn Kwang‐Ho
Published: January 2007

The high isolated dual‐band inverted‐F diversity systems for portable devices, operating in 2.4 GHz band (2400–2484 MHz) and 5.2 GHz band (5150–5350 MHz), are presented. To reduce the mutual coupling and get high isolation between two internal dual‐band antennas, we proposed the small N‐section resonators in the form of slots on the ground plane. The optimized small size resonators for high isolation, antenna radiation efficiency, and high effective diversity are analyzed. Because of their small size, N‐section resonators can be widely used in small diversity systems that require high isolation between antennas. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 731–734, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22238
Novel ROF network architecture for providing both wireless and wired broadband services
Authors: Yu Jianjun , Jia Zhensheng , Yu Jianguo , Wang Ting , Chang Gee Kung
Published: January 2007

We propose and experimentally demonstrate that a novel and low‐cost radio over fiber network architecture for providing wireless and wired dual services at 2.5 Gb/s. The base‐band signals are directly detected by a low‐cost receiver with a 2 GHz bandwidth low‐pass filter, while the RF signals are down‐converted by a mixer and an electrical local oscillator signal. Our experimental results show the millimeter wave in this network architecture exhibits less than 1 dB power penalty over 20 km fiber after providing the dual services. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 659–662, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22243
Novel bandpass filter with wide stopband using double‐sided parallel‐strip line
Authors: Zhang Xiu‐Yin , Li Jia‐Lin , Xue Quan
Published: January 2007

A novel bandpass filter using double‐sided parallel‐strip line (DSPSL) is proposed in this paper. Based on the differential characteristics of DSPSL, the proposed filter has a wide stopband up to the third spurious resonance frequency. Also, this filter can achieve high power‐handling capability because the linewidth of DSPSL is wider than that of microstrip with the same characteristic impedance. A demonstration filter was designed, fabricated, and measured. Theoretical and experimental results are presented and show good agreement. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 722–724, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22244
Investigations of the circulation effects in the structure using ferrite coupled slot‐line section
Authors: Kusiek A. , Marynowski M. , Mazur J.
Published: January 2007

This paper describes investigations of the longitudinally ferrite circulator realized in slot‐line technology. The proposed planar structure of circulator allowed to achieve small dimensions of the device. Also, the insertion losses comparable to ones actually published for microstrip structures were obtained. The basic steps of design procedure using scattering matrix of the circulator arrangement were presented. The S‐parameters of circulator were simulated and next verified via experiment. The operation bandwidth from 12 to 19 GHz with reflection loss and isolation better than 10 dB and average insertion loss 2.5 dB were measured for fabricated model of circulator. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 692–696, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22246
Application of algebraic domain decomposition combined with Krylov subspace iterative methods to solve 3D vector finite element equations
Authors: Ping X. W. , Chen R. S.
Published: January 2007

In this paper, a parallel algorithm based on MPI (Message Passing Interface) parallel computing library for the finite element method is presented to analyze three‐dimensional electromagnetic devices. The algebraic domain decomposition method is used in the algorithm. The original problem is decomposed into several subproblems according to its features. Each of them is allocated to one process in one computation node and solved independently with a direct method. The data are exchanged by communication between adjacent subdomains with overlapped data based on the MPI network. The example of its application is given. Numerical shows that the proposed algorithm can get excellent performance vs. price ratio and can save much memory and CPU time than sequential computing. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 686–692, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22247
Design of microwave devices by segmentation, finite elements, reduced‐order models, and neural networks
Authors: Cid Juan M. , García Jesús , Monge Javier , Zapata Juan
Published: January 2007

An accurate and fast neural model for complex microwave circuits is efficiently obtained by using segmentation and exploiting the knowledge of frequency response obtained from reduced order models. Information arriving from the excited modes in the connection ports of the regions to be modeled is included analytically. The frequency response modeling is similar to that of reduced order Padé models, which are used to compute the necessary training data easily. Overall optimization can then be used efficiently. Several examples that illustrate the capacities of the method are also presented. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 655–659, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22448
Real‐time adaptive methods for treatment of mobile organs by MRI‐controlled high‐intensity focused ultrasound
Authors: de Senneville Baudouin Denis , Mougenot Charles , Moonen Chrit T.W.
Published: January 2007

Focused ultrasound (US) is a unique and noninvasive technique for local deposition of thermal energy deep inside the body. MRI guidance offers the additional benefits of excellent target visualization and continuous temperature mapping. However, treating a moving target poses severe problems because 1) motion‐related thermometry artifacts must be corrected, 2) the US focal point must be relocated according to the target displacement. In this paper a complete MRI‐compatible, high‐intensity focused US (HIFU) system is described together with adaptive methods that allow continuous MR thermometry and therapeutic US with real‐time tracking of a moving target, online motion correction of the thermometry maps, and regional temperature control based on the proportional, integral, and derivative method. The hardware is based on a 256‐element phased‐array transducer with rapid electronic displacement of the focal point. The exact location of the target during US firing is anticipated using automatic analysis of periodic motions. The methods were tested with moving phantoms undergoing either rigid body or elastic periodical motions. The results show accurate tracking of the focal point. Focal and regional temperature control is demonstrated with a performance similar to that obtained with stationary phantoms. Magn Reson Med 57:319–330, 2007. © 2007 Wiley‐Liss, Inc.
Basis function cross‐correlations for Robust k‐space sample density compensation, with application to the design of radiofrequency excitations
Authors: Mitsouras Dimitris , Mulkern Robert V. , Afacan Onur , Brooks Dana H. , Rybicki Frank J.
Published: January 2007

The problem of k‐space sample density compensation is restated as the normalization of the independent information that can be expressed by the ensemble of Fourier basis functions corresponding to the trajectory. Specifically, multiple samples (complex exponential functions) may be contributing to each independent information element (independent basis function). Normalization can be accomplished by solving a linear system based on the cross‐correlation matrix of the underlying Fourier basis functions. The solution to this system is straightforward and can be obtained without resorting to discretization since the cross‐correlations of Fourier basis functions are analytically known. Furthermore, no restrictions are placed on the k‐space trajectory and its point‐spread function. Additionally, the linear system can be used to elucidate key trade‐offs involved in k‐space trajectory design. The approach can be used to compensate samples acquired for image reconstruction or designed for low flip angle radiofrequency (RF) excitation. Here it is demonstrated for the latter application, using reversed spiral trajectories. In this case the linear system approach enables one to easily incorporate additional constraints such as smoothness to the solution. For typical RF excitation durations (<20 ms) it is shown that density compensation can even be achieved without numerical iteration. Magn Reson Med 57:338–352, 2007. © 2007 Wiley‐Liss, Inc.
Diffusion imaging of the in vivo heart using spin echoes–considerations on bulk motion sensitivity
Authors: Gamper Urs , Boesiger Peter , Kozerke Sebastian
Published: January 2007

Cardiac diffusion MRI based on stimulated‐echo acquisition mode (STEAM) techniques is hampered by its inherent low signal‐to‐noise ratio (SNR) efficiency. Diffusion imaging using standard spin‐echo (SE) techniques, on the other hand, offers higher SNRs but has been considered impractical for the beating heart due to excessive signal attenuation from cardiac bulk motion. In this work the effect of systolic cardiac motion on different diffusion‐encoding schemes was studied in detail. Numerical simulations based on in vivo motion data (acquired by MRI tagging techniques) demonstrate an up to 10‐fold decrease in bulk motion sensitivity of the diffusion encoding if the first‐order moment of the diffusion‐encoding gradients is nullified. It is shown that the remaining systolic phase pattern on the myocardium does not influence the magnitude images if the spatial resolution is chosen to be higher than 4 mm. Given these relatively low resolution requirements, we obtained in vivo diffusion‐weighted (DW) short‐axis images from four healthy volunteers using an SE‐based diffusion‐encoding sequence with excitation and refocusing in orthogonal planes for field of view (FOV) reduction. The results showed no significant signal loss due to cardiac motion, and the direction of the principal eigenvalues was found to be in good agreement with known myocardial fiber orientation. Magn Reson Med 57:331–337, 2007. © 2007 Wiley‐Liss, Inc.
Development of a compact MRI system for measuring the trabecular bone microstructure of the finger
Authors: Iita Nachiko , Handa Shinya , Tomiha Sadanori , Kose Katsumi
Published: January 2007

A compact MRI system for measuring the trabecular bone (TB) microstructure of the finger using a high‐field‐strength (1.0T) permanent magnet was developed. The entire system was installed in a 0.6 m × 1.2 m space. One male and 36 female subjects participated in the imaging experiments. The TB of the distal phalanx of the middle finger was imaged at a voxel resolution of (160 μm)3 using a three‐dimensional (3D) driven equilibrium spin‐echo (SE) imaging sequence (imaging time = ∼14 min). The image data sets obtained yielded two distinct peaks for the bone and marrow in image intensity histograms when no motion was present. The structural parameters obtained through 3D image analysis show that this compact system is potentially useful for evaluating bone quality. Magn Reson Med 57:272–277, 2007. © 2007 Wiley‐Liss, Inc.
In vivo 13C saturation transfer effect of the lactate dehydrogenase reaction
Authors: Xu Su , Yang Jehoon , Shen Jun
Published: January 2007

Lactate dehydrogenase (LDH, EC 1.1.1.27) catalyzes an exchange reaction between pyruvate and lactate. It is demonstrated here that this reaction is sufficiently fast to cause a significant magnetization (saturation) transfer effect when the 13C resonance of pyruvate is saturated by a continuous‐wave (CW) RF pulse. Infusion of [2‐13C]glucose was used to allow labeling of pyruvate C2 at 207.9 ppm to determine the pseudo first‐order rate constant of the unidirectional lactate → pyruvate flux in vivo. During systemic administration of GABAA receptor antagonist bicuculline, this pseudo first‐order rate constant was determined to be 0.08 ± 0.01 s−1 (mean ± SD, N = 4) in halothane‐anesthetized adult rat brains. In 9L and C6 rat glioma models, the 13C saturation transfer effect of the LDH reaction was also detected in vivo. Our results demonstrate that the 13C magnetization transfer effect of the LDH reaction may be useful as a novel marker for utilizing noninvasive in vivo MRS to study many physiological and pathological conditions, such as cancer. Magn Reson Med 57:258–264, 2007. © 2007 Wiley‐Liss, Inc.
Frequency stabilization using infinite impulse response filtering for SSFP fMRI at 3T
Authors: Wu Ming‐Long , Wu Pei‐Hsin , Huang Teng‐Yi , Shih Yi‐Yu , Chou Ming‐Chung , Liu Hua‐Shan , Chung Hsiao‐Wen , Chen Cheng‐Yu
Published: January 2007

The steady‐state free precession (SSFP) method has been shown to exhibit strong potential for distortion‐free functional magnetic resonance imaging (fMRI). One major challenge of SSFP fMRI is that the frequency band corresponding to the highest functional sensitivity is extremely narrow, leading to substantial loss of functional contrast in the presence of magnetic field drifts. In this study we propose a frequency stabilization scheme whereby an RF pulse with small flip angle is applied before each image scan, and the initial phase of the free induction decay (FID) signals is extracted to reflect temporal field drifts. A simple infinite impulse response (IIR) filter is further employed to obtain a low‐pass‐filtered estimate of the central reference frequency for the upcoming scan. Experimental results suggest that the proposed scheme can stabilize the frequency settings in accordance with field drifts, with oscillation amplitudes of <0.5 Hz. Phantom studies showed that both slow drifts and fast fluctuations were prominently reduced, resulting in less than 5% signal variations. Visual fMRI at submillimeter in‐plane resolution further demonstrated 15% activation signals that were nicely registered in the microvessels within the sulci. It is concluded that the IIR‐filtered frequency stabilization is an effective technique for achieving reliable SSFP fMR images at high field strengths. Magn Reson Med 57:369–379, 2007. © 2007 Wiley‐Liss, Inc.
Optimizing the precision‐per‐unit‐time of quantitative MR metrics: Examples forT1,T2, and DTI
Authors: Fleysher Lazar , Fleysher Roman , Liu Songtao , Zaaraoui Wafaa , Gonen Oded
Published: January 2007

Quantitative MR metrics (e.g.,T1,T2, diffusion coefficients, and magnetization transfer ratios (MTRs etc)) are often derived from two images collected with one acquisition parameter changed between them (the “two‐point” method). Since a low signal‐to‐noise‐ratio (SNR) adversely affects the precision of these metrics, averaging is frequently used, although improvement accrues slowly—in proportion to the square root of imaging time. Fortunately, the relationship between the images' SNRs and the metric's precision can be exploited to our advantage. Using error propagation rules, we show that for a given sequence, specifying the total imaging time uniquely determines the optimal acquisition protocol. Specifically, instead of changing only one acquisition parameter and repeating the imaging pair until all available time is spent, we propose to adjustallof the parameters and the number of averages at each point according to their contribution to the sought metric's precision. The tactic is shown to increase the precision of the well‐known two‐pointT1,T2, and diffusion coefficients estimation by 13–90% for the same sample, sequence, hardware, and duration. It is also shown that under this general framework, precision accrues faster than the square root of time. Tables of optimal parameters are provided for various experimental scenarios. Magn Reson Med 57:380–387, 2007. © 2007 Wiley‐Liss, Inc.
Theoretical MRI contrast model for exogenous T2 agents
Authors: Mills Parker H. , Ahrens Eric T.
Published: January 2007

The rational development of new generations of MRI contrast agents (CAs) requires a scheme for predicting contrast enhancement. Previous contrast predictions have been based largely on empirical results in specific systems. Here we present a general theoretical model for evaluating the minimum concentration of T2 CA required for satisfactory image contrast. This analytic contrast model is applicable to a wide range of T2‐type agents and delivery scenarios, and requires only a few readily evaluated parameters. We demonstrated the model by predicting contrast produced by superparamagnetic ferumoxide and the iron storage protein, ferritin. We then experimentally verified the predictions using suspensions of Feridex® and ferritin in phantoms. The model was also used to compare the contrast efficacy of the metal ions in two clinically approved T1‐ and T2‐type CAs. In the Appendix we present a numerical formalism that is useful for relating image contrast and agent concentration when gradient‐echo (GRE) T‐weighted (TW) pulse sequences are used. Magn Reson Med 57:442–447, 2007. © 2007 Wiley‐Liss, Inc.
Fractional encoding of harmonic motions in MR elastography
Authors: Rump Jens , Klatt Dieter , Braun Jürgen , Warmuth Carsten , Sack Ingolf
Published: January 2007

In MR elastography (MRE) shear waves are magnetically encoded by bipolar gradients that usually oscillate with the same frequency fv as the mechanical vibration. As a result, both the repetition time (TR) and echo time (TE) of such an MRE sequence are greater than the vibration period 1/fv. This causes long acquisition times and considerable signal dephasing in tissue with short transverse relaxation times. Here we propose a reverse concept with TR ≤ 1/fv which we call “fractional” MRE, i.e., only a fraction of one vibration cycle per TR, can be used for motion sensitization. The benefit of fractional MRE is twofold: 1) acquisition times in seconds can be achieved for a single‐phase difference wave image, and 2) materials that combine low elasticity, high viscosity, and short T relaxation times show an increased phase‐to‐noise ratio (PNR). A twofold increase of the phase signal is predicted for liver‐like materials. Volunteer studies performed in liver and biceps show the benefit of fractional MRE. Furthermore, we demonstrate the feasibility of the technique for in vivo myocardial MRE by visualizing transverse wave propagation in the interventricular septum (IVS). Magn Reson Med 57:388–395, 2007. © 2007 Wiley‐Liss, Inc.
Short‐term efficacy of group pelvic floor training under intensive supervision versus unsupervised home training for female stress urinary incontinence: A randomized pilot study
Authors: Konstantinidou Eleni , Apostolidis Apostolos , Kondelidis Nikolaos , Tsimtsiou Zoi , Hatzichristou Dimitrios , Ioannides Evangelos
Published: January 2007

Aims

Current management guidelines propose pelvic floor muscle training (PFMT) as first line treatment for female stress urinary incontinence (SUI). The aim of this study is to compare the efficacy of group PFMT under intensive supervision to that of individual home therapy in women with SUI.

Material and Methods

Thirty women with clinical and urodynamic diagnosis of SUI were randomized in two equal‐number groups. Following a common demonstration course, Group A women received a detailed schedule for home training, while Group B in addition attended a weekly hospital group visit. At 12 weeks both groups were assessed for changes in subjective and objective outcomes.

Results

Twenty‐two women, (10 Group A, 12 Group B) with a mean age of 47.3 years completed the study. Although significant (P < 0.05) improvements were noted in both groups in quality of life scores, number of incontinence episodes/week, 24‐hr frequency, and endurance, repetitions and fast contractions upon vaginal assessment of the PFMs, comparative analysis at the end of the study demonstrated significantly better results for women in Group B, who also improved in daily pad usage, underwear wetting, modified Oxford grading of the PFMs and hold with cough. Consequently, significantly more women in Group B reported improvement in their continence (100% vs. 20% in Group A).

Conclusions

Group PFMT under intensive supervision produced significantly better improvements in primary and secondary outcomes in the short‐term compared to individual, unsupervised home application of PFMT. Neurourol. Urodynam. 26:486–491, 2007. © 2007 Wiley‐Liss, Inc.
Just keep it simple: a field experiment on fundraising letters
Authors: Bekkers René , Crutzen Olaf
Published: January 2007

This paper studies how the use of a colour picture in fundraising letters affect response rates and the amount donated in a fundraising campaign. Envelopes, with a full colour picture were tested against envelopes, without a picture in a controlled field experiment at a national religious charity in the Netherlands. Letters (89 937) were sent out to planned as well as incidental donors in four experimental groups. Results show that packages with more graphics yield lower donations, because both response rates are lower and the amount donated per letter is lower. We interpret this finding from donor aversion against high fundraising costs.

Copyright © 2007 John Wiley & Sons, Ltd.
Influence of hyperbranched against linear architecture on crystallization behavior of poly(ε‐caprolactone)s in binary blends with poly(vinyl chloride)
Authors: Choi Jeongsoo , Chun Sang‐Wook , Kwak Seung‐Yeop
Published: January 2007

Nonisothermal and isothermal crystallization behaviors of the hyperbranched poly(ε‐caprolactone) (HPCL)/poly(vinyl chloride) (PVC) and linear poly(ε‐caprolactone) (LPCL)/(PVC) blends were characterized with various blend composition such as 100/0, 95/5, 90/10, and 80/20, respectively. HPCL was synthesized through polycondensation of AB2 macromonomer while LPCL and PVC were commercially purchased. The architectural characterization performed on 1H NMR spectra revealed that HPCL consisted of about 3 AB2 units and the linear segments consisted of 25 ε‐CL units. Through the nonisothermal crystallization analyses by modified Avrami approach with DSC crystallization exotherms, it was found that the crystallization rate was retarded by the increase in the noncrystallizable component (PVC) in the blends. This is in good agreement with the results of the isothermal crystallization analyses where time resolved small angle light scattering (SALS) and polarized optical microscopy (POM) were used. The effect of molecular architectural difference between HPCL and LPCL on the crystallization of their binary blends with PVC was elucidated by comparing the crystallization kinetic parameters. Both the nonisothermal and isothermal crystallization analyses showed that the crystallization rates of HPCL/PVC blends was faster than LPCL/PVC blends at given blend compositions. The faster crystallization of the HPCL/PVC blends is ascribed to the two specific architectural characteristics of HPCL; the branched structure and the incorporated long linear segments. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 577–589, 2007
Tests of walking ability at different speeds in patients with knee osteoarthritis
Authors: Börjesson Margareta , Weidenhielm Lars , Elfving Britt , Olsson Elisabeth
Published: January 2007

Background and Purpose. Measurements of walking speeds are commonly used as an objective measure of functional performance in patients with knee osteoarthritis (OA) and are easily performed in a clinical setting. However, the choice in which the walking speed evaluation should be performed is controversial. The aim of this study was to identify the most discriminating walking speed after surgical interventions in patients with knee osteoarthritis, and to compare the responsiveness of the different gait speeds. Method. A prospective clinical one‐year follow‐up study involving 54 patients with knee osteoarthritis (63 (±5) years of age) who were operated with either a unicompartmental knee arthroplasty or a high tibial osteotomy was undertaken. Thirty‐nine patients had unilateral knee OA and 15 patients had bilateral knee OA or other symptoms from the lower extremities that could influence walking. The patients were examined at a gait laboratory before surgery, and one year after surgery. The patients were instructed to walk at slow, normal and fast walking speed. Results. All patients (n =54) walked faster one year after the surgical intervention compared to before surgery (p =0.001) at slow (+15%), normal (+8%) and fast (+7%) walking speed. This increase was similar for the three walking speeds (p =0.171). Patients with unilateral knee OA (n =39) reached an average change of+0.12 m/s, which was considered clinically important, while patients with bilateral knee OA (n =15) did not increase their walking speed>0.12 m/s. Effect size was moderate for slow walking speed and small for normal and fast walking speeds, respectively. Conclusions. The different walking speeds were equally good in detecting changes one year after surgical interventions. In this study, responsiveness favoured slow walking speed, however, the advantages of normal walking speed are discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Interaction of spatially separated oxygen–vacancy centers in CaF2 crystals due to an excitation‐induced short‐time molecular bond
Authors: Pologrudov V. V. , Penzina E. E. , Kheder K. K.
Published: January 2007

Electro‐physical and optical methods have been used to investigate oxygen–vacancy centers in CaF2:O2– crystals. The study revealed a new luminescence excitation band peaking at 4.27 eV. The excitation with the light from the region of this band is accompanied by electron transfer. It is found that the decay of luminescence is not exponential and is described by Becquerel's empirical law. New evidence has been obtained for thermostimulated depolarization associated with both ionic and electronic phenomena within the crystal. Activation energies for thermostimulated processes have been estimated. The results can be interpreted as providing evidence for the excitation‐induced short‐time molecular bond between spatially separated oxygen–vacancy defects. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impedance characteristics of Pb(Fe2/3W1/3)O3–BiFeO3 composites
Authors: Choudhary R. N. P. , Pradhan Dillip K. , Tirado C. M. , Bonilla G. E. , Katiyar R. S.
Published: January 2007

A single phase formation of PFW (Pb(Fe2/3W1/3)O3)–BFO (BiFeO3) composites prepared by mechanical activation, followed by mixed oxide method was checked by an X‐ray diffraction technique. Detailed studies of the impedance parameters suggest that addition of small amount of multiferroic BFO (10%) in PFW matrix produces a low frequency dielectric dispersion (i.e., relaxor characteristics) in the composite phase. Non‐Debye type of relaxation phenomena has been observed in the PFW‐BFO composites. The higher value of ε ′ at the lower frequency is explained on the basis of the Maxwell–Wagner (MW) polarization model. Complex impedance analysis enable us to separate grain and grain boundary contributions of materials, and it is found that grain boundary resistance is greater than grain resistance irrespective of composition at higher temperatures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The emergence of a community of practice in engineering education
Authors: Kolikant Yifat Ben‐David , McKenna Ann , Yalvac Bugrahan
Published: January 2007

This chapter describes how engineering faculty and learning scientists developed a collective wisdom—shared language, capabilities, and world view—in order to work together to achieve a common goal of developing course materials in the domain of biomedical engineering.
Establishing experiences to develop a wisdom of professional practice
Authors: Walker Joan M. T. , Brophy Sean P. , Hodge Lynn Liao , Bransford John D.
Published: January 2007

This study evaluated students' perceptions of two types of instructional materials focused on engineering professionalism: a passage of advice about professionalism and the same passage with a video enacting the advice. The role of experience in learning about professionalism is discussed, with particular emphasis on how educational materials might be tailored to meet the needs of first‐year and advanced undergraduates.
Learning content using complex data in project‐based science: An example from high school biology in urban classrooms
Authors: Kanter David E. , Schreck Melissa
Published: January 2007

This chapter explores the extent to which project‐based science (PBS) curricula designed with supports for students' inquiry into complex scientific data can help urban students make sense of such data and promote their deep understanding of standards‐based content. We review qualitative and quantitative data from classroom enactments of a PBS high school biology curriculum called Disease Detectives.
The effect of a bioengineering unit across high school contexts: An initial investigation in urban, suburban, and rural domains
Authors: Klein Stacy S. , Geist Melissa J.
Published: January 2007

This chapter describes the implementation and assessment of a high school‐level bioengineering curriculum unit in urban, suburban, and rural settings.
Implementing learning‐science research in university settings: New research opportunities
Authors: McKenna Ann
Published: January 2007

This chapter highlights some specific differences encountered between K–12 and higher education settings as a way to provide context for several research studies under way in engineering education. Specifically, this chapter highlights differences in three aspects of an academic learning environment: faculty, students, and subject matter.
Transient bilateral ovarian enlargement associated with large retroperitoneal lymphoma
Authors: Dalloul M. , Sherer D. M. , Gorelick C. , Serur E. , Zinn H. , Sanmugarajah J. , Zigalo A. , Abulafia O.
Published: January 2007

Bilateral ovarian enlargement may reflect benign or malignant processes of the ovary. Benign causes of ovarian enlargement include luteomas, tumors such as mature cystic teratomas, fibrothecomas, cystadenomas and rare conditions including capillary hemangioma and massive edema of the ovaries. Ovarian malignancies include epithelial, stromal and germ‐cell tumors. Primary malignancies that may exhibit metastases to the ovaries include gastrointestinal, breast and soft tissue tumors such as lymphoma. We present an unusual case in which a patient presenting with weakness and mild lower abdominal and pelvic pain was noted at sonography to have bilaterally enlarged ovaries with features similar to those of massive ovarian edema as described previously, which has been associated with venous and lymphatic obstruction. Subsequent computerized tomography (CT) imaging depicted a large retroperitoneal tumor, CT‐guided biopsy of which revealed diffuse large B cell lymphoma. The patient responded well to chemotherapy with significant shrinkage of the tumor, and reappearance of normal findings on ovarian sonography. This case demonstrates that bilaterally enlarged ovaries may be the first clinical evidence of a large retroperitoneal tumor and that in such cases CT imaging may be warranted. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.
What's up? What young teens and parents want from youth programs
Authors: Marczak Mary S. , Dworkin Jodi , Skuza Jennifer , Beyer Janet
Published: January 2007

Youth and parents provide critical voices regarding what young teens do, want, and need from out‐of‐school opportunities.
Beyond access and supply: Youth‐led strategies to captivate young people's interest in and demand for youth programs and opportunities
Authors: Saito Rebecca N.
Published: January 2007

Working on supply and access are necessary but not sufficient for the task of increasing young people's engagement in positive youth programs, activities, and informal opportunities. Youth become the marketing experts in this endeavor to increase participation in youth programs, particularly by those who typically do not participate.
Intentional youth programs: Taking theory to practice
Authors: Walker Joyce A.
Published: January 2007

Intentionality, including a lived ethos of positive youth development, is the key to success in engaging young people in out‐of‐school learning experiences that meet their developmental needs and everyday interests.
Improving quality at the point of service
Authors: Smith Charles , Akiva Tom , Arrieux Dominique , Jones Monica M.
Published: January 2007

Quality in youth programs happens at the point of service and is driven by staff intentionality, supportive professional communities, and aligned system priorities.
The Diagnostic Utility of Midcarpal Anesthetic Injection in the Evaluation of Chronic Wrist Pain
Authors: Bell S. Josh , Hofmeister Eric P. , Moran Steven L. , Shin Alexander Y.
Published: January 2007

The evaluation of chronic wrist pain can be a diagnostic dilemma. Lidocaine injections combined with corticosteroids are often used for both diagnosis and therapy. The purpose of this study was to determine if a midcarpal injection of lidocaine could serve as a diagnostic tool in patients with chronic wrist pain. Specifically, the relationship of pain relief from the injection and improvement of grip strength were compared to the presence of intracarpal pathology as confirmed by wrist arthroscopy. Forty-five patients with chronic wrist pain underwent a midcarpal injection of lidocaine with or without corticosteroids. Forty of the 45 underwent comcomitant steroid injections; a majority of the 40 patients reported relief of pain for two or more weeks. Improvement of pain and improvement of grip strength were determined. Each of these patients subsequently underwent a radiocarpal and midcarpal arthroscopy, and the pathologic findings of arthroscopy were compared to the improvement of pain and grip strength. These data were compared to a cohort of six volunteers without history of wrist pain or trauma that underwent midcarpal injection of lidocaine. Statistical analysis was performed using Reciever-Operator-Characteristic analysis. The average age of patients with chronic pain was 30.3 years, with an average of 9.8 months of wrist pain. The ultimate diagnoses included 35 patients with carpal instability dissociative, two with nondissociative instability, seven with complex instability of the carpus, three with extensor carpi ulnaris tendonitis and one with deQuervain's tenosynovitis. After lidocaine injection, the normal cohort had a mean loss of 2 kg (-5.3%) ( p=0.02) in grip strength, whereas the experimental cohort had a mean improvement in grip strength of 5.73 kg (34.4%). Improvement of pain after injection did not correlate with pathologic arthroscopic findings ( p=0.92). Improvement in grip strength after midcarpal lidocaine injection of 6 kg or 28% had a 73% sensitivity and a 70% specificity ( p=0.02) of having intracarpal pathology at the time of arthroscopy. Of the chronic wrist pain patients, only four had a normal arthroscopy, and the remainder had at least one area of significant pathology attributing to their pain. We conclude that a midcarpal injection of lidocaine can serve as an effective diagnostic tool in the evaluation of the patient with chronic wrist pain. Improvement of grip of 28% with or without relief of pain is highly correlated with intracarpal pathology.