bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractA 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

Abstract19Fluorine 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

AbstractAlveolar 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

AbstractBy 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

AbstractSpatial 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

AbstractContrast‐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

AbstractLog‐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

AbstractIn 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

AbstractArriving (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

AbstractReverse‐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

AbstractThe 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

AbstractESR 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

AbstractIn 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

AbstractPartial 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

AbstractMeasurements 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

AbstractWe 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

AbstractIt 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

AbstractThe 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

AbstractAn 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

AbstractHartree–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