bluuebunny/crossref_metadata_2025 huggingface dataset:
MR coil design for simultaneous tip tracking and curvature delineation of a catheter
Authors: Zuehlsdorff Sven , Umathum Reiner , Volz Steffen , Hallscheidt Peter , Fink Christian , Semmler Wolfhard , Bock Michael
Published: June 2004

In active catheter tracking, small RF coils are attached to the catheter for localization. For interactive catheter steering at vessel branchings, it is necessary to visualize not only a single point near the catheter tip but also the entire shape and orientation of the catheter's distal end. Therefore, a 35‐mm‐long twisted‐pair RF coil was added to a 5 French intravascular catheter with a single tip‐tracking coil. With the use of small nonmagnetic electronic components at the catheter tip, and a special switching circuitry outside the catheter, the coil assembly could be operated in two different modes. During MRI, the tip‐tracking coil was detuned so that the MR signal was received by the visualization coil only. During tracking, detuning was switched off and the MR signal was predominantly received by the more sensitive tracking coil. The catheter was used in combination with a MR pulse sequence with automatic slice positioning so that the current imaging slice was always placed at the position of the catheter tip. Phantom and animal experiments showed that the catheter tip is better visualized with the combined approach than with a tracking coil alone. Magn Reson Med 52:214–218, 2004. © 2004 Wiley‐Liss, Inc.
Increasing the signal‐to‐noise ratio in DENSE MRI by combining displacement‐encoded echoes
Authors: Kim Daniel , Epstein Frederick H. , Gilson Wesley D. , Axel Leon
Published: June 2004

A new technique was developed to increase the signal‐to‐noise ratio (SNR) in displacement encoding with stimulated echoes (DENSE) MRI. This signal‐averaged DENSE (sav‐DENSE) technique is based on the SNR advantage of extracting a pair of DENSE images with uncorrelated noise from the complex complementary spatial modulation of the magnetization image, and combining them during image reconstruction. Eleven healthy volunteers were imaged at three short‐axis locations with the use of sav‐DENSE, cine DENSE, and myocardial tagging pulse sequences. In this study, sav‐DENSE increased the SNR by 15–34% as compared to cine DENSE. Circumferential strain values measured by sav‐DENSE and myocardial tagging were strongly correlated (slope = 0.95, intercept = –0.02, R = 0.92) and within the 95% limits of agreement. The breath‐hold sav‐DENSE technique yielded relatively accurate and precise quantification of 2D intramyocardial function, with a 40.2‐ms temporal resolution and a 3.5 × 3.5 mm2 spatial resolution. Magn Reson Med 52:188–192, 2004. © 2004 Wiley‐Liss, Inc.
Modified Look‐Locker inversion recovery (MOLLI) for high‐resolution T1 mapping of the heart
Authors: Messroghli Daniel R. , Radjenovic Aleksandra , Kozerke Sebastian , Higgins David M. , Sivananthan Mohan U. , Ridgway John P.
Published: June 2004

A novel pulse sequence scheme is presented that allows the measurement and mapping of myocardial T1 in vivo on a 1.5 Tesla MR system within a single breath‐hold. Two major modifications of conventional Look‐Locker (LL) imaging are introduced: 1) selective data acquisition, and 2) merging of data from multiple LL experiments into one data set. Each modified LL inversion recovery (MOLLI) study consisted of three successive LL inversion recovery (IR) experiments with different inversion times. We acquired images in late diastole using a single‐shot steady‐state free‐precession (SSFP) technique, combined with sensitivity encoding to achieve a data acquisition window of <200 ms duration. We calculated T1 using signal intensities from regions of interest and pixel by pixel. T1 accuracy at different heart rates derived from simulated ECG signals was tested in phantoms. T1 estimates showed small systematic error for T1 values from 191 to 1196 ms. In vivo T1 mapping was performed in two healthy volunteers and in one patient with acute myocardial infarction before and after administration of Gd‐DTPA. T1 values for myocardium and noncardiac structures were in good agreement with values available from the literature. The region of infarction was clearly visualized. MOLLI provides high‐resolution T1 maps of human myocardium in native and post‐contrast situations within a single breath‐hold. Magn Reson Med 52:141–146, 2004. © 2004 Wiley‐Liss, Inc.
BOLD response to direct thalamic stimulation reveals a functional connection between the medial thalamus and the anterior cingulate cortex in the rat
Authors: Shyu Bai‐Chung , Lin Chun‐Yu , Sun Jyh‐Jang , Chen Shin‐Lang , Chang Chen
Published: June 2004

Recent functional neuroimaging studies in humans and rodents have shown that the anterior cingulate cortex (ACC) is activated by painful stimuli, and plays an important role in the affective aspect of pain sensation. The aim of the present study was to develop a suitable stimulation method for direct activation of the brain in fMRI studies and to investigate the functional connectivity in the thalamo‐cingulate pathway. In the first part of the study, tungsten, stainless steel, or glass‐coated carbon fiber microelectrodes were implanted in the left medial thalamus (MT) of anesthetized rats, and T2*‐weighted gradient‐echo (GE) images were obtained in the sagittal plane on a 4.7 T system (Biospec BMT 47/40). Only the images obtained with the carbon fiber electrode were acceptable without a reduction of the signal‐to‐noise ratio (SNR) and image distortion. In the second part of the study, a series of two‐slice GE images were acquired during electrical stimulation of the MT with the use of a carbon fiber electrode. A cross‐correlation analysis showed that the signal intensities of activated areas in the ipsilateral ACC were significantly increased by about 4.5% during MT stimulation. Functional activation, as assessed by the distribution of c‐Fos immunoreactivity, showed strong c‐Fos expression in neurons in the ipsilateral ACC. The present study shows that glass‐coated carbon fiber electrodes are suitable for fMRI studies and can be used to investigate functional thalamocortical activation. Magn Reson Med 52:47–55, 2004. © 2004 Wiley‐Liss, Inc.
Localized 7Li MR spectroscopy and spin relaxation in rat brain in vivo
Authors: Komoroski Richard A. , Pearce John M.
Published: June 2004

Localized 7Li MR point‐resolved spectroscopy (PRESS) was developed as a technique to measure lithium (Li) concentration in rat brain in vivo. Localized 7Li spectra could be obtained at 4.7 T in a 0.7‐ml voxel in rat brain over the entire therapeutic range of serum Li for humans. Localized 7Li spin‐lattice (T1) and spin–spin (T2) relaxation times were measured. Measured intensities were corrected for spin relaxation effects and 7Li MR visibility in vivo. The average T1 was 3.3 ± 0.9 sec, and the average T2 was 82 ± 20 ms. Neither T1 nor T2 correlated with brain concentration. No statistically significant change was found in either T1 or T2 from ∼7–17 days of Li dosing. Magn Reson Med 52:164–168, 2004. © 2004 Wiley‐Liss, Inc.
Functional MRI of the rodent somatosensory pathway using multislice echo planar imaging
Authors: Keilholz Shella D. , Silva Afonso C. , Raman Mira , Merkle Hellmut , Koretsky Alan P.
Published: June 2004

A multislice EPI sequence was used to obtain functional MR images of the entire rat brain with BOLD contrast at 11.7 T. Ten to 11 slices covering the rat brain, with an in‐plane resolution of 300 μm, provided enough sensitivity to detect activation in brain regions known to be involved in the somatosensory pathway during stimulation of the forelimbs. These regions were identified by warping a digitized rat brain atlas to each set of images. Data analysis was constrained to four major areas of the somatosensory pathway: primary and secondary somatosensory cortices, thalamus, and cerebellum. Incidence maps were generated. Electrical stimulation at 3 Hz led to significant activation in the primary sensory cortex in all rats. Activation in the secondary sensory cortex and cerebellum was observed in 70% of the studies, while thalamic activation was observed in 40%. The amplitude of activation was measured for each area, and average response time courses were calculated. Finally, the frequency dependence of the response to forepaw stimulation was measured in each of the activated areas. Optimal activation occurred in all areas at 3 Hz. These results demonstrate that whole‐brain fMRI can be performed on rodents at 11.7 T to probe a well‐defined neural network. Magn Reson Med 52:89–99, 2004. Published 2004 Wiley‐Liss, Inc.
Fourier components of inhomogeneously broadened water resonances in breast: A new source of MRI contrast
Authors: Medved Milica , Newstead Gillian M. , Fan Xiaobing , Du Weiliang , Du Yiping P. , MacEneaney Peter M. , Culp Rita M. , Kelcz Frederick , Olopade Olufunmilayo I. , Zamora Marta A. , Karczmar Gregory S.
Published: June 2004

High spectral and spatial resolution (HiSS) MR data were acquired at 1.5 T using echo‐planar spectroscopic imaging from patients with suspicious breast lesions. The water resonances in small voxels are inhomogenously broadened and often have distinct components. Images were calculated with intensity proportional to the Fourier components of the water resonance in each voxel at different offsets from the peak frequency. The results demonstrate that in breast the off‐peak Fourier component images of water are qualitatively different from those derived from the peak height of the water resonance. These differences most likely reflect underlying anatomy or physiology. In conventional images, the superposition of the various Fourier components of the water signal may cause loss of detail. The synthesis of water Fourier component images from high spectral and spatial resolution data may provide a new form of contrast, and increase sensitivity to subvoxel physiology and anatomy. Magn Reson Med 52:193–196, 2004. © 2004 Wiley‐Liss, Inc.
500‐element ultrasound phased array system for noninvasive focal surgery of the brain: A preliminary rabbit study with ex vivo human skulls
Authors: Hynynen Kullervo , Clement Gregory T. , McDannold Nathan , Vykhodtseva Natalia , King Randy , White P. Jason , Vitek Shuki , Jolesz Ferenc A.
Published: June 2004

The aim of this study was to test a prototype MRI‐compatible focused ultrasound phased array system for trans‐skull brain tissue ablation. Rabbit thigh muscle and brain were sonicated with a prototype, hemispherical 500‐element ultrasound phased array operating at frequencies of 700–800 kHz. An ex vivo human skull sample was placed between the array and the animal tissue. The temperature elevation during 20–30‐sec sonications was monitored using MRI thermometry. The induced focal lesions were observed in T2 and contrast‐enhanced T1‐weighted fast spin echo images. Whole brain histology evaluation was performed after the sonications. The results showed that sharp temperature elevations can be produced both in the thigh muscle and in the brain. High‐power sonications (600–1080 W) produced peak temperatures up to 55°C and focal lesions that were consistent with thermal tissue damage. The lesion size was found to increase with increasing peak temperature. The device was then modified to operate in the orientation that will be used in the clinic and successfully tested in phantom experiments. As a conclusion, this study demonstrates that it is possible to create ultrasound‐induced lesions in vivo through a human skull under MRI guidance with this large‐scale phased array. Magn Reson Med 52:100–107, 2004. © 2004 Wiley‐Liss, Inc.
In vivo cellular imaging of magnetically labeled hybridomas in the spleen with a 1.5‐T clinical MRI system
Authors: Smirnov Pierre , Gazeau Florence , Lewin Maïté , Bacri Jean Claude , Siauve Nathalie , Vayssettes Catherine , Cuénod Charles André , Clément Olivier
Published: June 2004

The feasibility of in vivo cellular imaging using a 1.5 T clinical magnet was studied in the mouse. Hybridoma cells were labeled with anionic γ‐Fe2O3 superparamagnetic iron oxide nanoparticles. These were internalized by the endocytose pathway. Both electron spin resonance and magnetophoresis as a measure of the labeled cells migration velocity under a magnetic field were used to quantify particle uptake. A fast (<2 hr) and substantial (up to 5 pg of iron per cell) internalization of nanoparticles by hybridomas was found, with good agreement between the two methods used. Hybridomas labeled with 2.5 pg iron per cell were injected intraperitoneally to male Swiss nude mice. A decrease in the spleen signal, suggesting a “homing” of labeled hybridomas to this organ, was found 24 hr later by MRI performed at 1.5 T. Furthermore, in labeled cells recovered from the spleen by ex vivo magnetic sorting, a mean of 0.5 pg iron per cell was found, i.e., a value five times lower than that of the injected hybridomas. This finding is consistent with in vivo proliferation of these cells. In addition, the amount of labeled hybridomas present in the spleen was found to correlate with MRI signal intensity. Magn Reson Med 52:73–79, 2004. © 2004 Wiley‐Liss, Inc.
Whole‐brain 3D perfusion MRI at 3.0 T using CASL with a separate labeling coil
Authors: Talagala S. Lalith , Ye Frank Q. , Ledden Patrick J. , Chesnick Scott
Published: June 2004

A variety of continuous and pulsed arterial spin labeling (ASL) perfusion MRI techniques have been demonstrated in recent years. One of the reasons these methods are still not routinely used is the limited extent of the imaging region. Of the ASL methods proposed to date, continuous ASL (CASL) with a separate labeling coil is particularly attractive for whole‐brain studies at high fields. This approach can provide an increased signal‐to‐noise ratio (SNR) in perfusion images because there are no magnetization transfer (MT) effects, and lessen concerns regarding RF power deposition at high field because it uses a local labeling coil. In this work, we demonstrate CASL whole‐brain quantitative perfusion imaging at 3.0 T using a combination of strategies: 3D volume acquisition, background tissue signal suppression, and a separate labeling coil. The results show that this approach can be used to acquire perfusion images in all brain regions with good sensitivity. Further, it is shown that the method can be performed safely on humans without exceeding the current RF power deposition limits. The current method can be extended to higher fields, and further improved by the use of multiple receiver coils and parallel imaging techniques to reduce scan time or provide increased resolution. Magn Reson Med 52:131–140, 2004. Published 2004 Wiley‐Liss, Inc.
Contrast‐enhanced dental MRI for visualization of the teeth and jaw
Authors: Olt Silvia , Jakob Peter M.
Published: June 2004

A technique for contrast‐enhanced dental MRI is described that enables 3D visualization of the oral cavity, including the jaw and teeth. Since teeth are MR‐invisible, the basic principle of this technique is that the teeth and jaw can be observed indirectly through contrast with a surrounding MR‐visible medium. For this purpose, the oral cavity is filled with a nontoxic substance, such as water or MR contrast media, that gives a high MR signal. A 3D data set covering the entire buccal space is acquired, and the image intensities are inverted. Since isosurface reconstructions of the teeth and jaw, as well as panoramic views analogous to orthopantomography, can be extracted from these data, contrast‐enhanced dental MRI may be useful as a flexible tool for dentistry and orthodontics. Moreover, contrast‐enhanced dental MRI works without radiation exposure, and therefore it is an interesting alternative to X‐ray‐based imaging modalities such as conventional radiography and dental CT. In this article, some preliminary results obtained with contrast‐enhanced dental MRI are shown in order to demonstrate the feasibility and performance of this new approach. Magn Reson Med 52:174–176, 2004. © 2004 Wiley‐Liss, Inc.
Fast isotropic volumetric coronary MR angiography using free‐breathing 3D radial balanced FFE acquisition
Authors: Stehning C. , Börnert P. , Nehrke K. , Eggers H. , Dössel O.
Published: June 2004

A shortcoming of current coronary MRA methods with thin‐slab 3D acquisitions is the time‐consuming examination necessitated by extensive scout scanning and precise slice planning. To improve ease of use and cover larger parts of the anatomy, it appears desirable to image the entire heart with high spatial resolution instead. For this purpose, an isotropic 3D‐radial acquisition was employed in this study. This method allows undersampling of k‐space in all three spatial dimensions, and its insensitivity to motion enables extended acquisitions per cardiac cycle. We present initial phantom and in vivo results obtained in volunteers that demonstrate large volume coverage with high isotropic spatial resolution. We were able to visualize all major parts of the coronary arteries retrospectively from the volume data set without compromising the image quality. The scan time ranged from 10 to 14 min during free breathing at a heart rate of 60 bpm, which is comparable to that of a thin‐slab protocol comprising multiple scans for each coronary artery. Magn Reson Med 52:197–203, 2004. © 2004 Wiley‐Liss, Inc.
In vivo 5‐fluorouracil and fluoronucleotide T1 relaxation time measurements using the variable nutation angle method
Authors: Gade Terence P.F. , Spees William M. , Le H. Carl , Zakian Kristen L. , Ponomarev Vladimir , Doubrovin Michael , Gelovani Juri G. , Koutcher Jason A.
Published: June 2004

19Fluorine NMRS has the potential to enable noninvasive predictions of tumor response to 5‐fluorouracil (5FU) therapy based on tumor pharmacokinetics. Knowledge of the T1's of 5FU and its fluoronucleotide anabolites (FNuc) is required for quantitative spectral analysis and selection of optimal pulse parameters. We used the variable nutation angle (VNA) method to determine T1's of 5FU and FNuc in subcutaneous Walker 256 rat mammary carcinosarcoma tumors transfected with a cytosine deaminase/uracil phosphoribosyltransferase fusion gene. We calibrated in vivo NAs using methoxydifluoroacetate to ensure the accuracy of these measurements. The T1's were calculated based on signal intensities acquired with NAs of 20°, 35°, 45°, 60°, and 75°. The acquisition order of these NAs was shuffled to reduce the effect of signal variations. The determined T1's for 5FU and FNuc (2.3 ± 0.1 s and 1.3 ± 0.1 s, respectively) represent the first reported in vivo measurements for these metabolites in tumor. Magn Reson Med 52:169–173, 2004. © 2004 Wiley‐Liss, Inc.
Determination of regional VA/Q by hyperpolarized 3He MRI
Authors: Rizi Rahim R. , Baumgardner James E. , Ishii Masaru , Spector Zebulon Z. , Edvinsson Johan M. , Jalali Aman , Yu Jiangsheng , Itkin Maxim , Lipson David A. , Gefter Warren
Published: June 2004

Alveolar ventilation/perfusion ratio (VA/Q) is a key parameter in functional imaging of the lung. Herein, regional VA/Q was calculated from regional values of alveolar partial pressure of oxygen (PAO2) measured by hyperpolarized 3He gas MRI (HP 3He MRI). Yorkshire pigs (n = 7, mean weight = 25 kg) were paralyzed and maintained under isoflurane anesthesia. Animals were placed into a birdcage coil, then transferred to the bore of a 1.5 T MRI unit. Prior to imaging, animals were manually ventilated with room air for 5 min, then a 3He gas mixture was administered during breathhold and imaging performed. PAO2 was measured based on the decay rate of 3He signal. Subjects' blood gas concentrations were measured and these values and PAO2 values entered into a system of four equations with four unknowns. Calculated VA/Q values were analyzed by preparing frequency distributions for the entire lung and compared to VA/Q frequency distributions previously established in the literature as normal using other diagnostic techniques. Distributions were consistent with those in the literature, indicating that HP 3He MRI may be an accurate, quantitative, noninvasive, and nonradioactive method for acquiring VA/Q for small regions of the lung. Magn Reson Med 52:65–72, 2004. © 2004 Wiley‐Liss, Inc.
Accelerating cardiac cine 3D imaging using k‐t BLAST
Authors: Kozerke Sebastian , Tsao Jeffrey , Razavi Reza , Boesiger Peter
Published: June 2004

By exploiting spatiotemporal correlations in cardiac acquisitions using k‐t BLAST, gated cine 3D acquisitions of the heart were accelerated by a net factor of 4.3, making single breathhold acquisitions possible. Sparse sampling of k‐t space along a sheared grid pattern was implemented into a cine 3D SSFP sequence. The acquisition of low‐resolution training data, which was required to resolve aliasing in the k‐t BLAST method, was either interleaved into the sampling process or obtained in a separate prescan to allow for shorter breathhold durations in patients with heart disease. Volumetric datasets covering the heart with 20 slices at a spatial resolution of 2 × 2 × 5 mm3 were recorded with 20 cardiac phases in a total breathhold duration of 25–27 sec, or 18 sec if partial Fourier sampling was additionally employed. The feasibility of the method was demonstrated on healthy volunteers and on patients. The comparison of endocardial area derived from single slices of the 3D dataset with values extracted from separate single‐slice acquisitions showed no significant differences. By shortening the acquisition substantially, k‐t BLAST may greatly facilitate volumetric imaging of the heart for evaluation of regional wall motion and the assessment of ventricular volume and ejection fraction. Magn Reson Med 52:19–26, 2004. © 2004 Wiley‐Liss, Inc.
Feasibility and performance of breath‐hold 3D true‐FISP coronary MRA using self‐calibrating parallel acquisition
Authors: Park Jaeseok , McCarthy Richard , Li Debiao
Published: June 2004

Spatial resolution in 3D breath‐hold coronary MR angiography (MRA) is limited by imaging time. The purpose of this work was to investigate the feasibility of improving the spatial resolution of coronary MRA using generalized autocalibrating partially parallel acquisition (GRAPPA) and fast imaging with steady state precession (True‐FISP) data acquisition. Coronary data were acquired in 10 healthy volunteers. In five volunteers, the data were fully acquired in k‐space and decimated for GRAPPA with an outer reduction factor (ORF) of 2. The coil calibration in GRAPPA was improved by segmented least‐squares fitting along the frequency‐encoding direction. More than 5% of the total k‐space lines were required for the calibration to achieve acceptable artifact suppression despite slightly lower signal‐to‐noise ratio (SNR). In another five volunteers, coronary data were obtained with both conventional and accelerated data acquisitions in the same imaging time. GRAPPA allowed a submillimeter in‐plane resolution, and improved coronary artery definition with an acceptable loss of SNR. In conclusion, 3D breath‐hold coronary MRA by GRAPPA and True‐FISP is highly feasible. Magn Reson Med 52:7–13, 2004. © 2004 Wiley‐Liss, Inc.
High temporal and spatial resolution 4D MRA using spiral data sampling and sliding window reconstruction
Authors: Zhu He , Buck David G. , Zhang Zhenghui , Zhang Honglei , Wang Paul , Stenger V. Andrew , Prince Martin R. , Wang Yi
Published: June 2004

Contrast‐enhanced magnetic resonance angiography (CE‐MRA) requires high spatial resolution to demonstrate detailed vasculature and high temporal resolution to capture the contrast bolus. Sparse bright voxels in MRA permit substantial undersampling in MRI data acquisition, allowing simultaneous high temporal and spatial resolution. We developed a time‐resolved 3D MRA technique using the efficient spiral sampling trajectory, and performed off‐resonance corrections using inhomogeneity field maps. View sharing and sliding window reconstruction were utilized to generate high temporal resolution. High‐resolution 3D angiograms were generated at 1–2 s per frame, with a 5–8 ml gadolinium dose, in patients with vascular disease. Magn Reson Med 52:14–18, 2004. © 2004 Wiley‐Liss, Inc.
Discriminating between the Weibull and log‐normal distributions
Authors: Kundu Debasis , Manglick Anubhav
Published: June 2004

Log‐normal and Weibull distributions are the most popular distributions for modeling skewed data. In this paper, we consider the ratio of the maximized likelihood in choosing between the two distributions. The asymptotic distribution of the logarithm of the maximized likelihood ratio has been obtained. It is observed that the asymptotic distribution is independent of the unknown parameters. The asymptotic distribution has been used to determine the minimum sample size required to discriminate between two families of distributions for a user specified probability of correct selection. We perform some numerical experiments to observe how the asymptotic methods work for different sample sizes. It is observed that the asymptotic results work quite well even for small samples also. Two real data sets have been analyzed. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
The gradual covering problem
Authors: Drezner Zvi , Wesolowsky George O. , Drezner Tammy
Published: June 2004

In this paper we investigate the gradual covering problem. Within a certain distance from the facility the demand point is fully covered, and beyond another specified distance the demand point is not covered. Between these two given distances the coverage is linear in the distance from the facility. This formulation can be converted to the Weber problem by imposing a special structure on its cost function. The cost is zero (negligible) up to a certain minimum distance, and it is a constant beyond a certain maximum distance. Between these two extreme distances the cost is linear in the distance. The problem is analyzed and a branch and bound procedure is proposed for its solution. Computational results are presented. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
Index policies for the routing of background jobs
Authors: Glazebrook K.D. , Kirkbride C.
Published: June 2004

Arriving (generic) jobs may be processed at one of several service stations, but only when no other (dedicated) jobs are waiting there. We consider the problem of how to route these incoming background jobs to make best use of the spare service capacity available at the stations. We develop an approximative approach to Whittle's proposal for restless bandits to obtain an index policy for routing. The indices concerned are increasing and nonlinear in the station workload. A numerical study testifies to the strong performance of the index policies developed. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
High‐performance liquid chromatography methods for the analysis of adrenergic amines and flavanones in Citrus aurantium L. var. amara
Authors: Pellati Federica , Benvenuti Stefania , Melegari Michele
Published: June 2004

Reverse‐phase HPLC coupled with photodiode array detection was used for the simultaneous separation and determination of naturally occurring adrenergic amines (octopamine, synephrine and tyramine) in fruits and dry extracts of Citrus aurantium L. var. amara and in herbal medicines derived therefrom. Synephrine was the main component in fruits (0.10–0.35%) and in dry extracts (3.00–3.08%) and was present in the range 0.25–0.99% in herbal medicines. Flavanones were analysed in the same samples using a reverse‐phase HPLC technique which allowed the identiﬁcation and quantiﬁcation of neoeriocitrin, narirutin, naringin, hesperidin, neohesperidin, naringenin and hesperetin. C. aurantium fruits and derivatives contained mainly glycosylated ﬂavanones: in particular, naringin and neohesperidin were found to be the major ﬂavonoids and their concentrations ranged from 1.80 to 26.30 and from 3.90 to 14.71 mg/g, respectively. The levels of aglycones were very low in all samples tested. Copyright © 2004 John Wiley & Sons, Ltd.
Modification of Tefzel film through graft copolymerization
Authors: Kaur Inderjeet , Misra BN , Singh Baljit , Gupta Nirupma , Sharma Neelam
Published: June 2004

The graft copolymerization of styrene (st) and methacrylonitrile (MAN) onto Tefzel film in aqueous media by the preirradiation method has been studied. In order to follow the effect of preswelling of the backbone polymer, grafting was attempted onto preirradiated Tefzel film and monomer preswollen, preirradiated Tefzel film. Optimum conditions pertaining to maximum percentage of grafting of st and MAN have been evaluated. Grafting onto preswollen, preirradiated Tefzel film displayed better results. The effect of different alcohols of increasing chain length on the percentage of grafting of st and MAN was also studied. Graft copolymerization of st showed an increase, while grafting with MAN exhibited a decrease, in the percentage of grafting in the presence of alcohols as compared to that obtained in the aqueous medium. Characterization of the graft copolymers was made by IR and thermogravimetric studies. Tefzel‐graft‐polystyrene showed improved thermal stability while the MAN grafted onto preswollen, preirradiated Tefzel film produced graft copolymer with poor thermal stability. Copyright © 2004 Society of Chemical Industry
An ESR and electrochemical approach to the unusual reactivity of ferrocenoylsilanes with organometallic compounds
Authors: Alberti A. , Benaglia M. , Bonini B. F. , Fochi M. , Macciantelli D. , Marcaccio M. , Paolucci F. , Roffia S.
Published: June 2004

ESR studies carried out during the reaction of ferrocenoylsilanes with Grignard reagents at low temperature led to the detection of the radical anions of the former compounds. Cyclic voltammetric experiments indicate that the observed radical anions are likely to originate through an inner‐sphere electron transfer process. Different radical species were observed upon annealing, originating from destruction of the ferrocenyl moiety. Paramagnetic species were also detected on reacting ferrocenoylsilanes with LiAlH4. Copyright © 2004 John Wiley & Sons, Ltd.
Mechanistic studies of intramolecular CH insertion reaction of arylnitrenes: isotope effect, configurational purity and radical clock studies
Authors: Murata Shigeru , Tsubone Yasuhiro , Kawai Reina , Eguchi Daisuke , Tomioka Hideo
Published: June 2004

In order to reveal the mechanism of the intramolecular CH insertion of arylnitrenes, three experiments were carried out: measurement of isotope effects, determination of the extent of configurational retention and radical clock studies. Irradiation of the deuterium‐substituted azide 4‐d in an inert solvent exclusively afforded the indolines 5‐h and 5‐d, in which the kinetic isotope effect kH/kD on the intramolecular CH insertion of the nitrene was evaluated as 12.6–14.7 at room temperature. A chiral chromatographic analysis of the indoline 11 obtained from the optically active azide (S)‐6 revealed that the enantiomeric purity of the starting azide was almost completely lost during the intramolecular CH insertion of the photolytically generated nitrene (enantiomeric excess <10%). The thermolysis of the azide 7 at 180°C mainly gave a mixture of the cyclopropyl ring‐opened products 20–22, together with the intramolecular CH insertion product with an intact cyclopropyl ring 19. On the basis of these observations, we concluded that the intramolecular CH insertion of the nitrene proceeds primarily by the hydrogen abstraction–recombination mechanism. We propose, however, a small contribution of the concerted mechanism to the intramolecular CH insertion, based on the solvent dependence of the isotope effect and the extent of the configurational retention. Copyright © 2004 John Wiley & Sons, Ltd.
Partially prestressed concrete
Authors: Au F T K , Du J S
Published: June 2004

Partial prestressing, which fills the gap between fully prestressed concrete and reinforced concrete, has now been accepted and become normal practice in many regions. The research and development of partially prestressed concrete members with bonded and unbonded tendons made of steel as well as fibre‐reinforced polymer (FRP) are reviewed. The behaviour of bonded partially prestressed concrete members has been extensively studied, and this review mainly focuses on fatigue behaviour, serviceability analysis and time‐dependent effects. The research on unbonded partially prestressed concrete members has mainly focused on prediction of flexural resistance, which is closely related to the ultimate tendon stress at flexural failure. Investigations of the service and ductility behaviour of unbonded partially prestressed concrete members are comparatively limited. Although external prestressing is effective in strengthening flexural concrete members, the strength acquired is accompanied by a reduction in ductility of flexural failure. The amount of prestressing tendons should therefore be carefully chosen to maintain the necessary ductility of the strengthened members. When FRP tendons are used in partially prestressed concrete members, deformability is a key indicator of safety.
Dynamic monitoring applied to the detection of structural modifications: a high‐speed railway bridge study
Authors: Cremona Christian
Published: June 2004

Measurements of vibration on bridges is not a recent practice and many studies have been carried out in the past. What is different nowadays is the increase in the number of dynamic tests carried out on bridges for a better assessment or monitoring of their structural behaviour. The prime objective in a dynamic assessment is the determination, or identification, of the modal characteristics. This includes the natural frequencies, the damping ratios and the mode shapes. For this purpose, dynamic testing is based on three levels: data acquisition (metrology), data treatment (signal processing) and data analysis (modal analysis, assessment). The choice of an appropriate excitation is equally essential. Among its various uses, dynamic assessment as a monitoring and diagnosis technique deserves detailed attention. For many years, the detection of damage has been only by the monitoring of the natural frequencies. The inefficiency of such an approach has led to the development of further techniques. Very recently, various methods have been introduced: the damage index method, the flexibility method and updating methods. Within these methods, the damage index method presents an easy and interesting implementation. However, as to any non‐destructive technique (NDT), these methods are driven by many factors that can influence whether or not the inspection will result in the correct decision as to the absence or presence of structural modifications. Their reliability is therefore an essential point. After pointing out the objectives of dynamic bridge testing, this paper highlights metrology, methodology, computational and practical aspects. All these concepts are highlighted on the monitoring of structural modifications performed on a high‐speed railway bridge under ambient excitation.
Precision calculations of atoms with few valence electrons
Authors: Kozlov M. G.
Published: June 2004

We discuss the possibility of using pair equations for the construction of the effective Hamiltonian Heff for valence electrons of an atom. The low‐energy part of atomic spectrum is found by solving the eigenvalue problem for Heff. In this way it is possible to account efficiently for the valence–valence and core–valence correlations. We tested this method on a toy model of a four‐electron atom with the core 1s2. The spectrum obtained with Heff for two valence electrons is in perfect agreement with the full configuration interaction for all four electrons. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Possible molecular structure of promoted Lewis acidity sites in ZnZSM‐5
Authors: Zhidomirov G. M. , Shubin A. A. , Kazansky V. B. , Van Santen R. A.
Published: June 2004

It is suggested that the abnormal methane IR frequency shift observed in ZnZSM‐5 zeolites is caused by adsorptive interaction of CH4 with particularly strong Zn2+ Lewis sites. Various molecular structures of zinc ion species in high‐silica zeolites are discussed, and it is concluded that increased Lewis acidity of a site is associated with decreased structural stability. It is shown that Zn2+ in zeolite cationic position with distantly placed A1 ions can produce observed shift of vibrational frequencies for adsorbed methane molecule. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Local equilibrium approach for fermi systems and quantum hydrodynamics
Authors: Maximov S. G. , Kuzmenkov L. S. , Guardado Zavala J. L.
Published: June 2004

The quantum distribution function is derived to reach an accordance with quantum hydrodynamics and to conserve quantum properties of the system. This distribution function, when calculating statistical averages, leads to correct local values of the fundamental physical quantities; and the local conservation laws of the microscopic quantum hydrodynamics can be obtained from such statistics by passing to mathematical expectatives. The equation for the one‐particle distribution function generates the many‐particle distribution functions. Then, the BBGKY hierarchy equations are obtained. The one‐particle statistical operator of a system of fermions in the local equilibrium at arbitrary temperatures is calculated. The dynamics of local hydrodynamic functions (chemical potential, hydrodynamic velocity, and temperature) completely determine the dynamics of the one‐particle statistical operator. The quantum hydrodynamic equations for the proton‐neutron system at low temperatures are obtained from the equation for one‐particle distribution function. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
On the importance of dimeric forms of Al and Ga trichlorides in the electrophilic aromatic substitution reactions: An ab initio study
Authors: Volkov Alexey N. , Timoshkin Alexey Y. , Suvorov Andrew V.
Published: June 2004

An ab initio study of the monomeric and dimeric forms of group 13 metal halides in model electrophilic aromatic substitution reaction has been performed. Several computational approaches have been tested. It is found that MP2/LANL2DZ(d)+ results are in good agreement with experiment, in contrast to data obtained at MP2/DZP and MP4/DZP++//MP2/DZP levels of theory. Formation of C6H · M2Cl ion pairs is more favorable compared to C6H · MCl, for both Al and Ga, which suggests that dimeric forms of the metal halides should play a significant role in the electrophilic aromatic substitution reactions. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
HF and DFT calculations of MgO surface energy and electrostatic potential using two‐ and three‐periodic models
Authors: Evarestov R. A. , Bandura A. V.
Published: June 2004

Hartree–Fock (HF) and density functional (DFT) LCAO calculations of single (2D) and periodical (3D) slab models of MgO crystal are presented. HF and DFT methods produce very close results for the surface energy and electrostatic potential and exhibit the same convergence properties, with the slab thickness increasing both for 2D and 3D models. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Robust trajectory tracking for a scale model autonomous helicopter
Authors: Mahony Robert , Hamel Tarek
Published: June 2004

This paper considers the question of obtaining ana prioribound on the tracking performance, for an arbitrary trajectory, of closed‐loop control of an idealized model of a scale model autonomous helicopter. The problem is difficult due to the presence of small body forces that cannot be directly incorporated into the control design. A control Lyapunov function is derived for an approximate model (in which the small body forces are neglected) using backstepping techniques. The Lyapunov function derived is used to analyse the closed‐loop performance of the full system. A theorem is proved that providesa prioribounds on initial error and the trajectory parameters (linear acceleration and its derivatives) that guarantees acceptable tracking performance of the system. The analysis is expected to be of use in verification of trajectory planning procedures. Copyright © 2004 John Wiley & Sons, Ltd.
On the clustering of independent uniform random variables
Authors: Csörgő Sándor , Wu Wei Biao
Published: June 2004

We consider the number Kn of clusters at a distance level dn ∈ (0, 1) of n independent random variables uniformly distributed in [0, 1], or the number Kn of connected components in the random interval graph generated by these variables and dn, and, depending upon how fast dn → 0 as n → ∞, determine the asymptotic distribution of Kn, with rates of convergence, and of related random variables that describe the cluster sizes. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
On the probability of rendezvous in graphs
Authors: Dietzfelbinger Martin , Tamaki Hisao
Published: June 2004

In a simple graph G without isolated nodes the following random experiment is carried out: each node chooses one of its neighbors uniformly at random. We say a rendezvous occurs if there are adjacent nodes u and v such that u chooses v and v chooses u; the probability that this happens is denoted by s(G). Métivier, Saheb, and Zemmari [“Randomized rendezvous,” Algorithms, trees, combinatorics, and probabilities, Eds. G. Gardy and A. Mokkadem, Trends in Mathematics, 183–194. Birkhäuser, Boston, 2000.] asked whether it is true that s(G) ≥ s(Kn) for all n‐node graphs G, where Kn is the complete graph on n nodes. We show that this is the case. Moreover, we show that evaluating s(G) for a given graph G is a #P‐complete problem, even if only d‐regular graphs are considered, for any d ≥ 5. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2005
Changing Ethical Frameworks for a Multicultural World
Authors: Fried Jane
Published: June 2004

Principle‐centered ethics, which have been used to guide ethical behavior for the past fifty years, are now too limited to address many campus dilemmas. Virtue‐centered, community‐based ethical systems must be developed by individual campuses.
Ethics in Management
Authors: Talley F. J.
Published: June 2004

Administrators must balance fiscal constraints, cultural diversity, and the competing expectations of students, faculty, administrators, and other external and internal constituencies in building consensus about ethical decision‐making.
Can middle‐school science textbooks help students learn important ideas? Findings from project 2061's curriculum evaluation study: Life science
Authors: Stern Luli , Roseman Jo Ellen
Published: June 2004

The transfer of matter and energy from one organism to another and between organisms and their physical setting is a fundamental concept in life science. Not surprisingly, this concept is common to the Benchmarks for Science Literacy (American Association for the Advancement of Science, 1993), the National Science Education Standards (National Research Council, 1996), and most state frameworks and likely to appear in any middle‐school science curriculum material. Nonetheless, while topics such as photosynthesis and cellular respiration have been taught for many years, research on student learning indicates that students have difficulties learning these ideas. In this study, nine middle‐school curriculum materials—both widely used and newly developed—were examined in detail for their support of student learning ideas concerning matter and energy transformations in ecosystems specified in the national standards documents. The analysis procedure used in this study was previously developed and field tested by Project 2061 of the AAAS on a variety of curriculum materials. According to our findings, currently available curriculum materials provide little support for the attainment of the key ideas chosen for this study. In general, these materials do not take into account students' prior knowledge, lack representations to clarify abstract ideas, and are deficient in phenomena that can be explained by the key ideas and hence can make them plausible. This article concludes with a discussion of the implications of this study to curriculum development, teaching, and science education research based on shortcomings in today's curricula. © 2004 Wiley Periodicals, Inc. J Res Sci Teach 41: 538–568, 2004
Stereochemistry of [4 + 2] Cycloadditions of Perfluorinated Selenocarbonyls to 1, 3‐Dienes
Authors: Blau Hanne , Grobe Joseph , Erker Gerhard , Lauterwein Jürgen
Published: June 2004

In completely stereospecific [4+2] cycloadditions, the perfluorinated selenocarbonyls 1 and 2 react both with trans‐trans‐2, 4‐hexadiene and cis‐trans‐2, 4‐hexadiene to yield 3, 6‐dihydro‐cis‐3, 6‐dimethyl‐2H‐selenapyrans 3, 4a and 4b. The observed stereoselectivity leads to the conclusion, that the [4+2] cycloaddition of perfluorinated selenocarbonyls follows a concerted pathway. An identical mixture of isomers was isolated when using the precursor for 2, trimethylstannyl (pentafluoroethyl)selane, which reacts with both 1, 3‐dienes over several weeks to form a mixture of syn‐2‐fluoro‐3, 6‐dihydro‐cis‐3, 6‐dimethyl‐2‐trifluoromethyl‐2H‐selenapyran (4a) and anti‐2‐fluoro‐3, 6‐dihydro‐cis‐3, 6‐dimethyl‐2‐trifluoromethyl‐2H‐selenapyran (4b) in the same ratio as found for 2, thus proving the intermediate formation of Se=C(F)CF3 (2). Complex 2D NMR experiments were used to distinguish the isomers 4a and 4b and to assign the 1H, 13C and 19F NMR data of the selenaheterocycles.
Synthese und Charakterisierung von [Zn{Si(NMe2)2(NHCMe3)(NCMe3)}‐(μ‐NC5H4)]2, einem molekularen Einkomponentenvorläufer zur Darstellung von ZnSiN2
Authors: Engering Josef , Jansen Martin
Published: June 2004

Für eine Verwendung als Einkomponentenvorläufer für die Darstellung von ZnSiN2 wurde aus dem zweifach lithiierten Aminosilan Si(NMe2)2(NLi t‐Butyl)2 und [ZnCl2(NC5H5)2] das Siladiazazinkacyclobutan [Zn{Si(NMe2)2(NHCMe3)(NCMe3)}(μ‐NC5H4)]2 erstmals dargestellt. Seine Kristallstruktur wurde am Einkristall gelöst (P1, a = 870.5(3) pm, b = 903.8(3) pm, c = 1530.6(4) pm, α = 96.982(5)°, β = 106.501(5)°, γ = 104.729(5)°). Die CP‐MAS‐NMR‐Daten für die Kerne 13C, 15N und 29Si werden mitgeteilt. Der Vorläuferkomplex wurde mit NH3 vernetzt und das so erhaltene Polymer keramisch zu ZnSiN2 abgebaut, das mittels Elementanalyse, EDX, IR und thermischer Analyse charakterisiert wurde. Die Kristallstruktur konnte bestimmt werden (Röntgenpulverdaten, Profilanpassung: P63mc, a = 315.33(1) pm, c = 508.07(2) pm, RB = 4.87). Das thermische Verhalten des Vorläufermoleküls, die Vernetzung mit NH3 zum Polymer und dessen Zersetzung im Gasstrom wurde eingehend untersucht.
Chemischer Transport von Mischkristallen im System CuMoO4/ZnMoO4
Authors: Steiner U. , Reichelt W. , Däbritz S.
Published: June 2004

Im System CuMoO4/ZnMoO4 existieren zwei Mischkristallreihen Cu1‐xZnxMoO4 mit x=0 bis x=0.15 bzw. x=0.20 bis x=1. Einkristalle von Cu1‐xZnxMoO4 mit definierter Zusammensetzung wurden mittels Chemischen Transports mit den Transportmitteln Cl2, Br2 und NH4Cl im Temperaturgefälle 973K→873K dargestellt. Während mit Cl2 und NH4Cl keine Verschiebung des Cu/Zn‐Verhältnisses zwischen Auflösungs‐ und Abscheidungsraum beobachtet wird, kommt es mit Br2 zur Abscheidung zinkreicherer Mischkristalle. Die experimentellen Ergebnisse werden den Resultaten thermodynamischer Modellrechnungen gegenübergestellt.
Cyanidverbrückte Dreikernkomplexe mit zentralen M(Cyclam)‐Einheiten
Authors: Appelt Ralf , Vahrenkamp Heinrich
Published: June 2004

Durch Umsetzung von Metall‐Cyclam‐Komplexen M(Cyclam)Xn mit metallorganischen Cyaniden LnM′‐CN wurden Dreikernkomplexe LnM′‐CN‐M(Cyclam)‐NC‐M′Ln mit M = Mn, Fe, Co, Ni und M′ = Cr, Fe, Ru erhalten. Mit strukturanalytischen, spektroskopischen und elektrochemischen Methoden wurden sie auf elektronische Wechselwirkungen zwischen den beteiligten Metallzentren untersucht.