bluuebunny/crossref_metadata_2025_split huggingface dataset:
Internal planar monopole antenna for GSM/DCS/PCS folder‐type mobile phones
Authors: Teng Pey‐Ling , Chiu Ching‐Yuan , Wong Kin‐Lu 
Published: August 2003

AbstractThis paper presents a novel planar monopole, printed on both sides of a dielectric substrate, which can be concealed within the housing of a folder‐type mobile phone as an internal antenna. The proposed internal planar monopole antenna occupies a small area of 10 × 40 mm2, and is capable of operating in the GSM/DCS/PCS bands. Good radiation characteristics for frequencies across the operating bands are also obtained. Details of the proposed antenna design and the obtained experimental results are presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 106–108, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11140
Dielectric properties of strontium sodium niobate ceramics using the microwave cavity perturbation technique
Authors: Yohannan Jaimon , Jacob Joe , Lonappan Anil , Mathew K. T. 
Published: August 2003

AbstractDielectric properties of strontium sodium niobate ceramics at the S band of microwave frequencies are studied using a network analyzer. The microwave cavity perturbation technique is employed for this study. Dielectric parameters such as complex permittivity and conductivity of strontium sodium niobate ceramics are determined by measuring the changes in the resonant frequencies and Q values of the cavity, due to the introduction of the sample. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 112–115, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11142
Radiating features of capacitive and inductive impedance surfaces
Authors: Bilotti Filiberto , Vegni Lucio 
Published: August 2003

AbstractThe radiating features of capacitive and inductive impedance surfaces are investigated in this paper. The analysis is particularly devoted to integrated structures with reactive ground planes and is performed through a full‐wave Green's function approach in the spectral domain. Some numerical examples, obtained by exploiting such a rigorous formulation, are also presented to illustrate the radiating behaviour of infinitesimal horizontal printed dipoles mounted on reactively loaded integrated structures. It is shown in detail that capacitive surfaces are more suitable than inductive ones for integrated antenna applications, due to both their effectiveness in enhancing the radiation intensity in presence of very thin substrates and their capability of maintaining good radiating performances over a wide frequency range. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 117–121, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11144
A design method for improvement of λg/4 coupled‐line narrow bandpass filter response
Authors: Prigent G. , Rius E. , Le Pennec F. , Le Maguer S. 
Published: August 2003

AbstractThis paper discusses various changes made in classical coupled‐line narrow bandpass filters to somehow improve frequency response. First, the resonator's strip width was broadened to improve the lines' unloadedQfactor. Second, the in/out coupled‐line sections were replaced by tapped‐line feeding. Finally, a transmission zero was added via a geometrical modification that favors nonadjacent resonator coupling. The theoretical and experimental results obtained with these microstrip filters are compared. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 121–125, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11145
Design of stacked offset antenna arrays for ISM‐band applications
Authors: See T. S. P. , Chen Zhi Ning 
Published: August 2003

AbstractIn this paper, a linear dual‐polarized stacked antenna array that operates well within the ISM‐band for W‐LAN base station applications is presented. The array comprises a bottom patch diagonally fed by a microstrip line and a superstrate layer with four parasitic patches stacked above the bottom layer. The design parameters are simulated and the impedance and radiation characteristics of an optimized antenna configuration are presented and compared against the measured results. The antenna is shown to satisfy the requirements for a base‐station antenna and capable of having a broad bandwidth for VSWR ≤ 1.5. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 125–129, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11146
Electrical and optical properties of CaCu3Ti4O12 (CCTO) substrates for microwave devices and antennas
Authors: Kretly L. C. , Almeida A. F. L. , de Oliveira R. S. , Sasaki J. M. , Sombra A. S. B. 
Published: August 2003

AbstractThe solid‐state procedure is used to produce bulk ceramics of CCTO (CaCu3Ti4O12). The samples of the CCTO ceramic are studied by X‐ray powder diffraction and infrared and Raman scattering spectroscopy. The infrared and Raman scattering spectroscopy confirm the formation of the CCTO phase, as seen by X‐ray diffraction (XRD) analysis. One experimental procedure uses an organic binder in the process of shaping the samples. In the second procedure, the samples were prepared without the presence of the organic phase, and we obtained a higher dielectric constant (K = 7370) with higher loss (D = 0.2) at 1 KHz. For the first procedure, a lower dielectric constant (K = 1530) and lower loss (D = 0.11) at 1 KHz were obtained. Simple rectangular antenna prototypes were also designed on substrate samples (C1, C2, P1, and P2). For the antennas with P2, C1, and C2 as substrates, the bandwidth (BW) is 90 MHz (around 3%). The antenna with P1 substrate presents a surprisingly high BW of 270 MHz, which corresponds to a 10% bandwidth. Such a value is in accordance with the requirements for planar antennas in a variety of wireless communication systems such as WLAN, PCS, Wi‐Fi, and other protocols. Therefore, these measurements confirm the potential use of such materials for small high‐dielectric planar antennas (HDAs). These materials are also attractive for capacitor applications as well as for microelectronics and microwave devices (cellular mobile phones, for example), where miniaturization of the devices is crucial. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 145–150, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11152
A new compact 1D PBG microstrip structure with wider stopband based on semiconductor substrate
Authors: Zhang Wenmei , Sun Xiaowei , Mao Junfa , Qian Rong , Zhang Dan 
Published: August 2003

AbstractA new type of compact one dimensional (1D) microstrip photonic bandgap (PBG) used for filters is presented. A semiconductor‐based structure of a miniature band‐stop filter with three cells is simulated, realized, and measured. Basic agreement between the experimental and simulated results have been achieved. The filter with the proposed PBG structure exhibits wide, deep, and steep stop‐band characteristics, and also has less loss and ripples in the pass‐band. Thus, the new PBG structure can be used for low‐pass as well as high‐pass filters. The period of the PBG lattice is about (1/5 ∼ 1/4) λe(λeis the guiding wavelength at the center frequency of the stop‐band), or 0.08 λ0(λ0is the wavelength in air). The filter with the new PBG structure is much easier to fabricate and integrate with other circuits and is more compact than conventional filters. The results in our paper are based on semiconductor substrate and can be applied directly in MIC and MMIC. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 150–152, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11153
Bound solitons with 103‐fs pulse width and 585.5‐fs separation from DI‐NOLM figure‐8 fiber laser
Authors: Gong Y. D. , Shum P. , Tang D. Y. , Lu C. , Cheng T. H. , Qi Z. W. , Guan Y. L. , Lai W. J. , Man W. S. , Tam H. Y. 
Published: August 2003

AbstractUltra‐short bound‐soliton pulses with pulse 103‐fs width and 585.5‐fs separation are observed experimentally from a figure‐8 passive mode‐locked fiber laser incorporated with a dispersion‐imbalanced nonlinear optical loop mirror (DI‐NOLM). To our knowledge, these are the most closely bound solitons produced from fiber laser to date, and the bound‐soliton separation and pulsewidth remains unchanged even after 1.2‐Km single‐mode fiber (SMF) transmission. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 163–164, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11157
Steady‐state sequence synthesis and its application to efficient fat‐suppressed imaging
Authors: Overall William R. , Nishimura Dwight G. , Hu Bob S. 
Published: August 2003

AbstractA new synthesis algorithm, based on the Shinnar‐Le Roux (SLR) transform, can be used to generate fully refocused steady‐state pulse sequences with arbitrary magnetization profiles as a function of off‐resonant precession. This is accomplished by appropriate periodic oscillation of the RF excitation magnitude and phase from echo to echo. The technique is applied to the design of refocused steady‐state free precession (SSFP) sequences with flat profiles, providing the opportunity for banding‐artifact‐free imaging with steady‐state contrast. The algorithm is also used to generate refocused‐SSFP sequences with an arbitrarily broad region of attenuated signal. These sequences are implemented and applied to the problem of steady‐state fat suppression. Preliminary results show signal levels that agree well with theory, and a broad region of suppressed signal at each echo. Total imaging time is kept identical to that of a standard refocused‐SSFP experiment through echo equalization and interleaving. 3D images from the leg of a normal volunteer acquired in 44 s demonstrate the applicability of the technique to fat‐suppressed imaging. Magn Reson Med 50:550–559, 2003. © 2003 Wiley‐Liss, Inc.
Assessment of regional systolic and diastolic dysfunction in familial hypertrophic cardiomyopathy using MR tagging
Authors: Ennis Daniel B. , Epstein Frederick H. , Kellman Peter , Fananapazir Lameh , McVeigh Elliot R. , Arai Andrew E. 
Published: August 2003

AbstractDiastolic and systolic left ventricular (LV) dysfunction often significantly contribute to disabling symptoms in familial hypertrophic cardiomyopathy (FHC). This study compares regional LV function (midwall circumferential strain) during systole and diastole in eight FHC patients and six normal volunteers (NVs) using MR tagging. A prospectively‐gated fast gradient‐echo sequence with an echo‐train readout was modified to support complementary spatial modulation of magnetization (CSPAMM) tagging and full cardiac cycle data acquisition using the cardiac phase to order reconstruction (CAPTOR), thus providing tag persistence and data acquisition during the entire cardiac cycle. Total systolic strains in FHC patients were significantly reduced in septal and inferior regions (both P < 0.01). Early‐diastolic strain rates were reduced in all regions of the FHC group (all P < 0.03). The combination of CSPAMM and CAPTOR allows regional indices of myocardial function to be quantified throughout the cardiac cycle. This technique reveals regional differences in systolic and diastolic impairment in FHC patients. Magn Reson Med 50:638–642, 2003. Published 2003 Wiley‐Liss, Inc.
Lactate doublet quantification and lipid signal suppression using a new biexponential decay filter: Application to simulated and 1H MRS brain tumor time‐domain data
Authors: Serrai Hacene , Senhadji Lotfi , Wang Guoyu , Akoka Serge , Stroman Patrick 
Published: August 2003

AbstractA new postprocessing filter based on the continuous wavelet transform (CWT) method modeled as a biexponential decay function to isolate the lactate doublet from overlapping lipid resonance(s) and estimate its magnetic resonance spectroscopy (MRS) parameters (signal amplitude, resonance frequencies, and apparent relaxation time (T)) is proposed. The new filter employs the same iterative process used in the previously single exponential decay filter. A comparison of the results obtained from application of both filters to simulated data and real 1H MRS data collected from human blood plasma and brain tumors demonstrates that the new filter provides a better estimate of MRS parameters of lactate, with less computation time. Furthermore, the results show that the new filter is less sensitive to noise and provides a direct estimate of J‐coupling value of the lactate doublet. Magn Reson Med 50:623–626, 2003. © 2003 Wiley‐Liss, Inc.
Analysis and generalized correction of the effect of spatial gradient field distortions in diffusion‐weighted imaging
Authors: Bammer R. , Markl M. , Barnett A. , Acar B. , Alley M.T. , Pelc N.J. , Glover G.H. , Moseley M.E. 
Published: August 2003

AbstractNonuniformities of magnetic field gradients can cause serious artifacts in diffusion imaging. While it is well known that nonlinearities of the imaging gradients lead to image warping, those imperfections can also cause spatially dependent errors in the direction and magnitude of the diffusion encoding. This study shows that the potential errors in diffusion imaging are considerable. Further, we show that retrospective corrections can be applied to reduce these errors. A general mathematical framework was formulated to characterize the contribution of gradient nonuniformities to diffusion experiments. The gradient field was approximated using spherical harmonic expansion, and this approximation was employed (after geometric distortions were eliminated) to predict and correct the errors in diffusion encoding. Before the corrections were made, the experiments clearly revealed marked deviations of the calculated diffusivity for fields of view (FOVs) generally used in diffusion experiments. These deviations were most significant farther away from the magnet's isocenter. For an FOV of 25 cm, the resultant errors in absolute diffusivity ranged from approximately –10% to +20%. Within the same FOV, the diffusion‐encoding direction and the orientation of the calculated eigenvectors can be significantly altered if the perturbations by the gradient nonuniformities are not considered. With the proposed correction scheme, most of the errors introduced by gradient nonuniformities can be removed. Magn Reson Med 50:560–569, 2003. © 2003 Wiley‐Liss, Inc.
Measuring the change in CBV upon cortical activation with high temporal resolution using look‐locker EPI and Gd‐DTPA
Authors: Francis S.T. , Pears J.A. , Butterworth S. , Bowtell R.W. , Gowland P.A. 
Published: August 2003

AbstractA method of simultaneously measuring the changes in cerebral blood volume (CBV) and T that occur on brain activation with high temporal resolution was developed. The method involves measuring the change in the longitudinal relaxation time (T1) that occurs following a bolus injection of Gd‐DTPA and converting this measurement to a change in blood volume assuming fast exchange. The sequence was optimized for the measurement of changes in CBV with high temporal resolution. A change in CBV of 27 ± 4% on activation of the primary visual cortex (V1) was measured across four subjects. The time course of changes in T showed a poststimulus undershoot (P = 0.008) corresponding approximately to a period over which CBV was still elevated above baseline, but falling (P = 0.01). The effects of perfusion, nonfulfillment of the assumption of fast exchange and of intrinsic T1 changes on activation on the model used to calculate the change in CBV are discussed. Magn Reson Med 50:483–492, 2003. © 2003 Wiley‐Liss, Inc.
Fast proton spectroscopic imaging using steady‐state free precession methods
Authors: Dreher Wolfgang , Geppert Christian , Althaus Matthias , Leibfritz Dieter 
Published: August 2003

AbstractVarious pulse sequences for fast proton spectroscopic imaging (SI) using the steady‐state free precession (SSFP) condition are proposed. The sequences use either only the FID‐like signal S1, only the echo‐like signal S2, or both signals in separate but adjacent acquisition windows. As in SSFP imaging, S1 and S2 are separated by spoiler gradients. RF excitation is performed by slice‐selective or chemical shift‐selective pulses. The signals are detected in absence of a B0 gradient. Spatial localization is achieved by phase‐encoding gradients which are applied prior to and rewound after each signal acquisition. Measurements with 2D or 3D spatial resolution were performed at 4.7 T on phantoms and healthy rat brain in vivo allowing the detection of uncoupled and J‐coupled spins. The main advantages of SSFP based SI are the short minimum total measurement time (Tmin) and the high signal‐to‐noise ratio per unit measurement time (SNRt). The methods are of particular interest at higher magnetic field strength B0, as TR can be reduced with increasing B0 leading to a reduced Tmin and an increased SNRt. Drawbacks consist of the limited spectral resolution, particularly at lower B0, and the dependence of the signal intensities on T1 and T2. Further improvements are discussed including optimized data processing and signal detection under oscillating B0 gradients leading to a further reduction in Tmin. Magn Reson Med 50:453–460, 2003. © 2003 Wiley‐Liss, Inc.
Comparison of polarization transfer sequences for enhancement of signals in clinical 31P MRS studies
Authors: Mancini Laura , Payne Geoffrey S. , Leach Martin O. 
Published: August 2003

AbstractSeveral 31P MRS studies in tumors in vivo have shown that levels of phosphocholine (PC) and other phosphomonoesters (PME) and phosphodiesters (PDE) are useful prognostic or early‐response indicators. To improve sensitivity for such measurements, four polarization transfer (PT) sequences (insensitive nuclei enhanced by PT (INEPT), distortionless enhancement by PT (DEPT), reverse‐INEPT, and heteronuclear single‐quantum coherence (HSQC)) were assessed theoretically and experimentally. The presence of homonuclear (1H‐1H) and heteronuclear (31P‐1H) couplings of similar magnitude makes theoretical analysis very sensitive to precise model parameters, especially for the 1H‐detected sequences. The 1H‐1H coupling causes the splitting of 1H peaks, and hence reduces the proton spectral resolution. This effect and a 50% signal loss from gradient‐enhanced water suppression negate the usual advantages of 1H‐detection. Among the PT methods, INEPT gave the higher signal enhancement. However, T2 losses during the long echo times (TEs) required by the weak coupling limited the resulting signals from PC. Magn Reson Med 50:578–588, 2003. © 2003 Wiley‐Liss, Inc.
Computation of the fractional anisotropy and mean diffusivity maps without tensor decoding and diagonalization: Theoretical analysis and validation
Authors: Hasan Khader M. , Narayana Ponnada A. 
Published: August 2003

AbstractDiffusion tensor MRI (DT‐MRI) is a promising modality for in vivo mapping of the organization of deep tissues. The most commonly used DT‐MRI invariant maps are the mean diffusivity, μ(D), relative anisotropy (RA), and fractional anisotropy (FA). Because of the computational burden, anisotropy maps are generally computed offline. The availability of a simple procedure to compute RA, FA, and μ(D) online would make DT‐MRI more useful in clinical applications that require immediate feedback. In this study, analytical expressions that relate the commonly used tensor anisotropy measures obtained from the decoded and diagonalized DT with those obtained from the first and second moments of the measured diffusion‐weighted (DW) data are derived. Specifically, it is shown that for the principal icosahedron encoding scheme, RA is related to the mean and standard deviation (SD) of the DW measurements that can be computed online. Since FA is commonly used as an anisotropy measure, an analytical expression relating RA and FA was derived from the tensor invariants. These results were validated using both Monte Carlo simulations and high‐resolution, normal whole‐brain DT‐MRI measurements acquired with different b‐factors, encoding schemes, and signal‐to‐noise ratio (SNR) levels. The bias introduced by the rotationally variant encoding schemes into the diffusion measures is also investigated. Magn Reson Med 50:589–598, 2003. © 2003 Wiley‐Liss, Inc.
Contrast‐enhanced coronary artery imaging using 3D trueFISP
Authors: Deshpande Vibhas S. , Li Debiao 
Published: August 2003

AbstractAn ECG‐triggered, segmented, magnetization‐prepared, 3D, trueFISP sequence was recently developed for coronary artery imaging. Fat saturation was achieved by a chemically selective fat saturation pulse, which is susceptible to field inhomogeneities. In addition, the blood–myocardial contrast was compromised because data were acquired during signal transience to steady state. The goals of this work were to investigate the potential benefits of T1‐shortening agents in improving blood–myocardial contrast, and to develop a technique to make fat suppression robust to resonance offsets for coronary artery imaging using trueFISP. A magnetization‐preparation scheme using saturation and inversion pulses was developed for simultaneous suppression of tissues over a wide range of T1's, including myocardium and fat. An additional advantage of this method is that it is insensitive to heart rate variations. Computer simulations were used to design the magnetization preparation, and volunteer studies were performed to compare precontrast imaging to contrast‐enhanced (CE) imaging. Results showed consistent fat suppression and a 78% increase in the blood–myocardial contrast‐to‐noise ratio (CNR) for postcontrast imaging over precontrast imaging. In conclusion, contrast agents are useful for trueFISP coronary artery imaging. Magn Reson Med 50:570–577, 2003. © 2003 Wiley‐Liss, Inc.
Morphological and carbogen‐based functional MRI of a chemically induced liver tumor model in mice
Authors: Thomas Carole D. , Chenu Evelyne , Walczak Christine , Plessis Marie‐José , Perin François , Volk Andreas 
Published: August 2003

AbstractA multifocal mouse liver tumor model chemically induced with 5,9‐dimethyl‐7H‐dibenzo[c,g]carbazole was investigated by respiratory‐triggered morphological and functional MRI (fMRI) at 4.7 Tesla. The model is characterized by the presence of two tumor types: hypovascular cholangioma and vascularized hepatocellular carcinoma (HCC). Growth curves measured by 3D‐MRI showed limited growth of cholangiomas and rapid growth of HCCs after a latency of about 25 weeks. Functional imaging based on T‐weighted fast gradient‐echo MRI and carbogen breathing was optimized for liver imaging in mice. A response to carbogen was observed in HCCs but not in cholangiomas. Transversal analysis (50 HCCs) of signal change upon carbogen revealed four different types of response patterns: 1) signal increase upon carbogen administration (74%); 2) small or insignificant signal change (10%), 3) transient signal decrease and delayed increase (8%), and 4) signal decrease (8%). Longitudinal follow‐up of a subgroup (N = 17) showed that an initially observed type 1 response, attesting to the presence of a functional vasculature, remained stable for at least 3 weeks in 14 HCCs. A switch from a type 1 response to another response type may be useful for demonstrating, in a noninvasive manner, a disturbance of tumor vasculature induced by anti‐vascular or anti‐angiogenic therapy. Magn Reson Med 50:522–530, 2003. © 2003 Wiley‐Liss, Inc.