bluuebunny/crossref_metadata_2025_split huggingface dataset:
Circularly polarized low‐profile square dielectric resonator antenna with a loading patch
Authors: Hsiao Fu‐Ren , Chiou Tzung‐Wern , Wong Kin‐Lu 
Published: September 2002

AbstractWith the loading of a rectangular patch having a suitable aspect ratio, circular polarization (CP) radiation of low‐profile square dielectric resonator (DR) antennas can easily be obtained. The proposed antenna design can easily be excited by using a microstrip‐line feed, and many prototypes with various sizes of the loading rectangular patch have been implemented. Details of the antenna design are described, and experimental results of the obtained CP performance are presented. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 157–159, 2001.
Experimental investigation of the frequency‐selective property of an array of dual‐tuned printed dipoles
Authors: Sarkar P. P. , Sarkar D. , Das S. , Sarkar S. , Chowdhury S. K. 
Published: September 2002

AbstractThe frequency‐selective property of an array of rectangular dipole microstrip patches resonant at dual frequencies (within the same frequency band) has been investigated experimentally. Measured data indicate a 40 dB separation between the transmission and reflection bands of the frequency‐selective surface (FSS) in the normalized transmitted electric field versus frequency plot. Experimental investigation of the FSS of an array of rectangular dipole microstrip patches resonant at a single frequency shows that the bandwidth of the reflection band is very narrow. In our present investigation, resonance at dual frequencies within the same frequency band has been used to broaden the bandwidth of the reflection band. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 189–190, 2001.
Optimization synthesis of broadband circularly polarized microstrip antennas by hybrid genetic algorithm
Authors: Zentner Radovan , Sipus Zvonimir , Bartolic Juraj 
Published: September 2002

AbstractIn this paper, the synthesis of a stacked patch antenna for circular polarization is presented. The antenna is analyzed by the full‐wave approach based on the method of moments in the spectral domain. In order to find the optimal antenna parameters, a hybrid genetic algorithm that combines a global search of the common genetic algorithm and the efficiency of the direct search method is developed. The experimental results show SWR<2, with an axial ratio lower than 4 dB within 14% bandwidth. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 197–201, 2001.
Design of narrowband amplifiers with conditionally stable transistors
Authors: Benvenuti Dario , Cicolani Maurizio , Pisa Stefano , Tommasino Pasquale , Trifiletti Alessandro 
Published: September 2002

AbstractA technique to design narrowband amplifiers by using conditionally stable transistors is presented. The proposed analytical approach allows us to design lossless matching networks, by providing power matching at one port and minimum mismatch at the other port. The use of this technique leads to high gain as well as proper stability margins. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 208–210, 2001.
Small and high‐directivity bow‐tie patch antenna based on the Sierpinski fractal
Authors: Anguera Jaume , Puente Carles , Borja Carmen , Montero Raquel , Soler Jordi 
Published: September 2002

AbstractThe unique geometrical properties of fractals have been proven to be useful to design advanced antennas. Enhanced performance in terms of size, gain, or multifrequency behavior is observed in fractal‐shaped antennas. Here, a small and high‐directivity antenna based on the Sierpinski fractal is presented. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 239–241, 2001.
Allogeneic bone marrow transplantation in first remission rescues children with Philadelphia chromosome‐positive acute lymphoblastic leukemia: Tokyo Children's Cancer Study Group (TCCSG) studies L89‐12 and L92‐13*
Authors: Mori Taijiro , Manabe Atsushi , Tsuchida Masahiro , Hanada Ryoji , Yabe Hiromasa , Ohara Akira , Saito Tomohiro , Nakazawa Shinpei 
Published: September 2002

AbstractBackgroundThe prognosis of Philadelphia chromosome‐positive acute lymphoblastic leukemia (Ph+ ALL) is generally poor and reports from large studies are scarce. We evaluated the efficacy of allogeneic bone marrow transplantation (allo‐BMT) for children with this type of leukemia.ProcedureThe chemotherapy regimens consisted of an induction phase and very intensive consolidation followed by a reinduction phase and late intensification treatment. The selection of treatment modalities such as chemotherapy, allo‐BMT, or autologous transplantation was made by each institute. The principal endpoint was the outcome of children with Ph+ ALL according to the treatment options.ResultsThirty‐two patients (4.3%) were diagnosed as Ph+ ALL out of the 741 cases of ALL consecutively enrolled in two protocols of the Tokyo Children's Cancer Study Group (TCCSG) from 1989 to 1994. Thirty patients (93.8%) were induced into complete remission (CR). Of these 30 patients, eight children electively received allo‐BMT in the first CR. Six of these patients are in continuous remission at a median follow‐up of 58 (range 48–105) months after the diagnosis. One patient died following recurrence and another patient died of graft vs. host disease. Three patients treated with autologous BMT or peripheral blood stem cell transplantation in the first CR experienced a subsequent relapse. In the remaining 19 patients, 13 patients were treated with very high‐risk chemotherapy alone and all relapsed within 28 months. One patient was excluded from the analysis because he was treated with standard‐risk chemotherapy until relapse. The other five patients were also excluded from the analysis because Philadelphia chromosome was not detected until they relapsed. None of the relapsed patients survived in spite of treatment including allo‐BMT. In multivariate analysis, only allo‐BMT remained as an independent factor for good prognosis.ConclusionsThe only way to cure children with Ph+ ALL was allo‐BMT in this study and its outcome seemed promising. Med Pediatr Oncol 2001;37:426–431. © 2001 Wiley‐Liss, Inc.
Extravascular proton‐density changes as a non‐BOLD component of contrast in fMRI of the human spinal cord
Authors: Stroman P.W. , Krause V. , Malisza K.L. , Frankenstein U.N. , Tomanek B. 
Published: September 2002

AbstractThe fractional signal intensity change (ΔS/S) observed during activation in T2‐weighted fMRI of the spinal cord has previously been shown to depend linearly on the echo time (TE) but to have a positive value of roughly 2.5% extrapolated to zero TE. In this study we investigated the origin of this finding by measuring the ΔS/S in spinal fMRI with very short TEs. Our results demonstrate that the ΔS/S does not approach zero, but has a value as high as 3.3% at TE = 11 ms. At TEs > 33 ms we observed the linear relationship between ΔS/S and TE as in previous studies. These data demonstrate that there is a non‐BOLD contribution to signal changes observed in spinal fMRI. We hypothesize that this contribution is a local proton density increase due to increased water exudation from capillaries with increased blood flow during neuronal activation, and term this effect “signal enhancement by extravascular protons” (SEEP). Magn Reson Med 48:122–127, 2002. © 2002 Wiley‐Liss, Inc.
Diffusion tensor imaging using single‐shot SENSE‐EPI
Authors: Bammer Roland , Auer Martin , Keeling Stephen L. , Augustin Michael , Stables Lara A. , Prokesch Rupert W. , Stollberger Rudolf , Moseley Michael E. , Fazekas Franz 
Published: September 2002

AbstractSENSitivity Encoding (SENSE) greatly enhances the quality of diffusion‐weighted echo‐planar imaging (EPI) by reducing blurring and off‐resonance artifacts. Such improvement would also be desirable for diffusion tensor imaging (DTI), but measures derived from the diffusion tensor can be extremely sensitive to any kind of image distortion. Whether DTI is feasible in combination with SENSE has not yet been explored, and is the focus of this study. Using a SENSE‐reduction factor of 2, DTI scans in eight healthy volunteers were carried out with regular‐ and high‐resolution acquisition matrices. To further improve the stability of the SENSE reconstruction, a new coil‐sensitivity estimation technique based on variational calculus and the principles of matrix regularization was applied. With SENSE, maps of the trace of the diffusion tensor and of fractional anisotropy (FA) had improved spatial resolution and less geometric distortion. Overall, the geometric distortions were substantially removed and a significant resolution enhancement was achieved with almost the same scan time as regular EPI. DTI was even possible without the use of quadrature body coil (QBC) reference scans. Geometry‐factor‐related noise enhancement was only discernible in maps generated with higher‐resolution matrices. Error boundaries for residual fluctuations in SENSE reconstructions are discussed. Our results suggest that SENSE can be combined with DTI and may present an important adjunct for future neuroimaging applications of this technique. Magn Reson Med 48:128–136, 2002. © 2002 Wiley‐Liss, Inc.
Test‐retest reliability estimation of functional MRI data
Authors: Maitra Ranjan , Roys Steven R. , Gullapalli Rao P. 
Published: September 2002

AbstractFunctional magnetic resonance imaging (fMRI) data are commonly used to construct activation maps for the human brain. It is important to quantify the reliability of such maps. We have developed statistical models to provide precise estimates for reliability from several runs of the same paradigm over time. Specifically, our method extends the premise of maximum likelihood (ML) developed by Genovese et al. (Magn Reson Med 1997;38:497–507) by incorporating spatial context into the estimation process. Experiments indicate that our methodology provides more conservative estimates of true positives compared to those obtained by Genovese et al. The reliability estimates can be used to obtain voxel‐specific reliability measures for activated as well as inactivated regions in future experiments. We derive statistical methodology to determine optimal thresholds for region‐ and context‐specific activations. Empirical guidelines are also provided on the number of repeat scans to acquire in order to arrive at accurate reliability estimates. We report the results from experiments involving a motor paradigm performed on a single subject several times over a period of 2 months. Magn Reson Med 48:62–70, 2002. © 2002 Wiley‐Liss, Inc.
Application of the static dephasing regime theory to superparamagnetic iron‐oxide loaded cells
Authors: Bowen Chris V. , Zhang Xiaowei , Saab George , Gareau Paula J. , Rutt Brian K. 
Published: September 2002

AbstractThe relaxation rates of iron‐oxide nanoparticles compartmentalized within cells were studied and found to satisfy predictions of the static dephasing (SD) regime theory. THP‐1 cells in cell culture were loaded using two different iron‐oxide nanoparticles (superparamagnetic iron‐oxide (SPIO) and ultrasmall SPIO (USPIO)) with four different iron concentrations (0.05, 0.1, 0.2, and 0.3 mg/ml) and for five different incubation times (6, 12, 24, 36, and 48 hr). Cellular iron‐oxide uptake was assessed using a newly developed imaging version of MR susceptometry, and was found to be linear with both dose and incubation time. R sensitivity to iron‐oxide loaded cells was found to be 70 times greater than for R2, and 3100 times greater than for R1. This differs greatly from uniformly distributed nanoparticles and is consistent with a cellular bulk magnetic susceptibility (BMS) relaxation mechanism. The cellular magnetic moment was large enough that R2′ relaxivity agreed closely with SD regime theory predictions for all cell samples tested

where the local magnetic dose (LMD) is the sample magnetization due to the presence of iron‐oxide particles). Uniform suspensions of SPIO and USPIO produced R2′ relaxivities that were a factor of 3 and 8 less, respectively, than SD regime theory predictions. These results are consistent with theoretical estimates of the required mass of iron per compartment needed to guarantee SD‐regime‐dominant relaxivity. For cellular samples, R2 was shown to be dependent on both the concentration and distribution of iron‐oxide particles, while R2′ was sensitive to iron‐oxide concentration alone. This work is an important first step in quantifying cellular iron content and ultimately mapping the density of a targeted cell population. Magn Reson Med 48:52–61, 2002. © 2002 Wiley‐Liss, Inc.
High‐resolution MRI of cardiac function with projection reconstruction and steady‐state free precession
Authors: Peters Dana C. , Ennis Daniel B. , McVeigh Elliot R. 
Published: September 2002

AbstractThe purpose of this study was to investigate the trabecular structure of the endocardial wall of the living human heart, and the effect of that structure on the measurement of myocardial function using MRI. High‐resolution MR images (0.8 × 0.8 × 8 mm voxels) of cardiac function were obtained in five volunteers using a combination of undersampled projection reconstruction (PR) and steady‐state free precession (SSFP) contrast in ECG‐gated breath‐held scans. These images provide movies of cardiac function with new levels of endocardial detail. The trabecular‐papillary muscle complex, consisting of a mixture of blood and endocardial structures, is measured to constitute as much as 50% of the myocardial wall in some sectors. Myocardial wall strain measurements derived from tagged MR images show correlation between regions of trabeculae and papillary muscles and regions of high strain, leading to an overestimation of function in the lateral wall. Magn Reson Med 48:82–88, 2002. Published 2002 Wiley‐Liss, Inc.
Image distortion correction in EPI: Comparison of field mapping with point spread function mapping
Authors: Zeng Huairen , Constable R. Todd 
Published: September 2002

AbstractEcho‐planar imaging (EPI) can provide rapid imaging by acquiring a complete k‐space data set in a single acquisition. However, this approach suffers from distortion effects in geometry and intensity, resulting in poor image quality. The distortions, caused primarily by field inhomogeneities, lead to intensity loss and voxel shifts, the latter of which are particularly severe in the phase‐encode direction. Two promising approaches to correct the distortion in EPI are field mapping and point spread function (PSF) mapping. The field mapping method measures the field distortions and translates these into voxel shifts, which can be used to assign image intensities to the correct voxel locations. The PSF approach uses acquisitions with additional phase‐encoding gradients applied in the x, y, and/or z directions to map the 1D, 2D, or 3D PSF of each voxel. These PSFs encode the spatial information about the distortion and the overall distribution of intensities from a single voxel. The measured image is the convolution of the undistorted density and the PSF. Measuring the PSF allows the distortion in geometry and intensity to be corrected. This work compares the efficacy of these methods with equal time allowed for field mapping and PSF mapping. Magn Reson Med 48:137–146, 2002. © 2002 Wiley‐Liss, Inc.
Mapping myocardial perfusion with an intravascular MR contrast agent: Robustness of deconvolution methods at various blood flows
Authors: Neyran Bruno , Janier Marc F. , Casali Cendrine , Revel Didier , Canet Soulas Emmanuelle P. 
Published: September 2002

AbstractEvaluation of quantitative parameters such as regional myocardial blood flow (rMBF), blood volume (rMBV), and mean transit time (rMTT) by MRI is gaining acceptance for clinical applications, but still lacks robust postprocessing methods for map generation. Moreover, robustness should be preserved over the full range of myocardial flows and volumes. Using experimental data from an isolated pig heart preparation, synthetic MR kinetics were generated and four deconvolution approaches were evaluated. These methods were then applied to the first‐pass T1 images of the isolated pig heart using an intravascular contrast agent and rMBF, rMBV and rMTT maps were generated. In both synthetic and experimental data, the fit between calculated and original data reached equally good results with the four techniques. rMBV was the only parameter estimated correctly in numerical experiments. Moreover, using the algebraic method ARMA, abnormal regions were well delineated on rMBV maps. At high flows, rMBF was underestimated at the experimental noise level. Finally, rMTT maps appeared noisy and highly unreliable, especially at high flows. In conclusion, over the myocardial flow range, i.e., 0–400 ml/min/100g, rMBF identification was biased in presence of noise, whereas rMBV was correctly identified. Thus, rMBV mapping could be a fast and robust way to detect abnormal myocardial regions. Magn Reson Med 48:166–179, 2002. © 2002 Wiley‐Liss, Inc.
Independent component analysis of fMRI data in the complex domain
Authors: Calhoun V.D. , Adalı T. , Pearlson G.D. , van Zijl P.C.M. , Pekar J.J. 
Published: September 2002

AbstractIn BOLD fMRI a series of MR images is acquired and examined for task‐related amplitude changes. These functional changes are small, so it is important to maximize detection efficiency. Virtually all fMRI processing strategies utilize magnitude information and ignore the phase, resulting in an unnecessary loss of efficiency. As the optimum way to model the phase information is not clear, a flexible modeling technique is useful. To analyze complex data sets, independent component analysis (ICA), a data‐driven approach, is proposed. In ICA, the data are modeled as spatially independent components multiplied by their respective time‐courses. There are thus three possible approaches: 1) the time‐courses can be complex‐valued, 2) the images can be complex‐valued, or 3) both the time‐courses and the images can be complex‐valued. These analytic approaches are applied to data from a visual stimulation paradigm, and results from three complex analysis models are presented and compared with magnitude‐only results. Using the criterion of the number of contiguous activated voxels at a given threshold, an average of 12–23% more voxels are detected by complex‐valued ICA estimation at a threshold of |Z| > 2.5. Additionally, preliminary results from the complex models reveal a phase modulation similar to the magnitude time‐course in some voxels, and oppositely modulated in other voxels. Magn Reson Med 48:180–192, 2002. © 2002 Wiley‐Liss, Inc.
The formation of dunes, antidunes, and rapidly damping waves in alluvial channels
Authors: Huang L.‐H. , Chiang Y.‐L. 
Published: September 2002

AbstractUnder the effect of a constant current for a long time, a water channel of infinitely long and constant depth interacting with a uniform sandbed of infinite thickness is used to simulate the formation of dunes, antidunes and rapidly damping waves in alluvial channels. The theory of potential flow is applied to the channel flow, while Biot's theory of poroelasticity is adopted to deal with erodible bed material. The governing equations, together with free surface, bed surface, and far field boundary conditions, form a complete boundary‐value problem without applying empirical sediment discharge formulas as in conventional researches. The comparison of the present result with Kennedy's (Journal of Fluid Mechanics, 1963; 16: 521–544) instability analysis not only indicates the appropriateness of the present work, but also reveals the advantage of the present study due to its ability to find all kinds of bed forms (including the rapidly damping waves that Kennedy could not find) and of solving for the unclear lagged distance δ introduced in Kennedy's work. Copyright © 2001 John Wiley & Sons, Ltd.
Characterization and reconstruction of a rock fracture surface by geostatistics
Authors: Marache A. , Riss J. , Gentier S. , Chilès J.‐P. 
Published: September 2002

AbstractIt is well understood that, in studying the mechanical and hydromechanical behaviour of rock joints, their morphology must be taken into account. A geostatistical approach has been developed for characterizing the morphology of fracture surfaces at a decimetre scale. This allows the analysis of the spatial variability of elevations, and their first and second derivatives, with the intention of producing a model that gives a numerical three‐dimensional (3D) representation of the lower and upper surfaces of the fracture. Two samples (I and II) located close together were cored across a natural fracture. The experimental data are the elevations recorded along profiles (using recording steps of 0.5 and 0.02 mm, respectively, for the samples I and II). The goal of this study is to model the surface topography of sample I, so getting estimates for elevations at each node of a square grid whose mesh size will be, for mechanical purposes, no larger than the recording step. Since the fracture surface within the sample core is not strictly horizontal, geostatistical methods are applied to residuals of elevations of sample I. Further, since structural information is necessary at very low scale, theoretical models of variograms of elevations, first and second derivatives are fitted using data of both that sample I and sample II. The geostatistical reconstructions are computed using kriging and conditional simulation methods. In order to validate these reconstructions, variograms and distributions of experimental data are compared with variograms and distributions of the fitted data. Copyright © 2002 John Wiley & Sons, Ltd.
A quick check of network performance
Authors: Hicks Jeffrey T. , Walker John Q. 
Published: September 2002

AbstractHave you ever tried to measure the response time across a network? Do you sometimes wonder what throughput rate you're getting over a particular link? Are you concerned about the impact of adding streaming multimedia traffic to a network? Would you like to know the exact route your data is taking? Individual tools are available to measure the throughput and response time of your applications, trace a network route, or test a network's capacity for handling multimedia traffic. But a software tool called Qcheck can perform all of these tasks and more, while providing a quick check of network performance. Copyright © 2001 John Wiley & Sons, Ltd.