bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dependence of venous enhancement on the field of view in 3D contrast‐enhanced MRA using the elliptical centric view order
Authors: Fain Sean B. , Riederer Stephen J. 
Published: August 2002

AbstractThe dependence of venous suppression on the acquisition field of view (FOV) in elliptical centric 3D contrast‐enhanced magnetic resonance angiography (CE‐MRA) is studied theoretically and experimentally. It is hypothesized that a reduced FOV in an arterial phase acquisition results in improved venous suppression. An expression is derived linking the k‐space representation of a vein to venous return time and acquisition parameters. For a y × z FOV reduction from 24 cm × 7.2 cm to 18 cm × 3.6 cm, equivalent voxel size, and venous return times ranging from 0–7 s, the mean improvement in venous suppression ranged from 7.0% for the 19‐mm‐diameter vein to 32.1% in the 6‐mm‐diameter vein, assuming a step function‐shaped venous enhancement profile. Decreased venous enhancement with reduced FOV is also observed for scans with equivalent acquisition times, although the degree of suppression is dependent on the shape of the venous enhancement curve. Magn Reson Med 45:1134–1141, 2001. © 2001 Wiley‐Liss, Inc.
Alternative 1‐13C glucose infusion protocols for clinical 13C MRS examinations of the brain
Authors: Moreno Angel , Blüml Stefan , Hwang Jong‐Hee , Ross Brian D. 
Published: August 2002

AbstractClinical utility of 13C MRS is limited by cost and long examination times. Three 1‐13C glucose infusion protocols—a high‐dose i.v., low‐dose i.v., and oral administration of 1‐13C glucose—were compared on a GE 1.5T MR scanner. Resolution and sensitivity were sufficient to identify 13C glucose (1α and 1β), glutamate (C1–C4), glutamine (C1–C4), aspartate (C2 and C3), lactate, alanine, and bicarbonate in brain spectra. The three protocols were efficacious, as measured by cerebral enrichment of 1‐13C glucose (62%, 42%, and 38%) and its principal metabolite, 4‐13C glutamate (13%, 11%, and 16%), respectively. Intravenous infusion of 1‐13C glucose 0.23 g/kg body weight (low dose) provides equivalent information at one third the cost of previous regimes. Magn Reson Med 46:39–48, 2001. © 2001 Wiley‐Liss, Inc.
Radio frequency magnetic field mapping of a 3 Tesla birdcage coil: Experimental and theoretical dependence on sample properties
Authors: Alecci Marcello , Collins Christopher M. , Smith Michael B. , Jezzard Peter 
Published: August 2002

AbstractThe RF B1 distribution was studied, theoretically and experimentally, in phantoms and in the head of volunteers using a 3 T MRI system equipped with a birdcage coil. Agreement between numerical simulation and experiment demonstrates that B1 distortion at high field can be explained with 3D full‐Maxwell calculations. It was found that the B1 distribution in the transverse plane is strongly dependent on the dielectric properties of the sample. We show that this is a consequence of RF penetration effects combined with RF standing wave effects. In contrast, along the birdcage coil z‐axis the B1 distribution is determined mainly by the coil geometry. In the transverse plane, the region of B1 uniformity (within 10% of the maximum) was 15 cm with oil, 6 cm with distilled water, 11 cm with saline, and 10 cm in the head. Along z the B1 uniformity was 9 cm with phantoms and 7 cm in the head. Magn Reson Med 46:379–385, 2001. © 2001 Wiley‐Liss, Inc.
Gd‐DTPA bolus tracking in the myocardium using T1 fast acquisition relaxation mapping (T1 FARM)
Authors: Bellamy Deanna D. , Pereira Raoul S. , McKenzie Charles A. , Prato Frank S. , Drost Dick J. , Sykes Jane , Wisenberg Gerald 
Published: August 2002

AbstractMRI methods currently used for bolus tracking in the myocardium, such as saturation recovery turbo‐fast low‐angle shot (FLASH) (srTFL), are limited by signal intensity (SI) saturation at high contrast agent (CA) concentrations. By using T1 fast acquisition relaxation mapping (T1 FARM), a Gd‐DTPA bolus (0.075 vs. 0.025 mmol/kg) may be injected without causing saturation. This study tested the feasibility of in vivo T1 FARM bolus tracking under rest/stress conditions in seven beagles with multiple permanently occluded branches of the left anterior descending (LAD) coronary artery. Although it underestimated the myocardial perfusion reserve (MPR) measured ex vivo using radioactive microspheres (mean ± SEM; 3.60 ± 0.26), the MPR determined upon application of the modified Kety model (1.86 ± 0.10) enabled distinction between normal and infarcted tissue. The partition coefficient (λ) estimated at rest and stress using the modified Kety model underestimated ex vivo radioactive measurements in infarcted tissue (0.25 ± 0.01 vs. 0.26 ± 0.01 vs. 0.79 ± 0.08 ml/g, P < 0.0001) yet was accurate in normal tissue (0.28 ± 0.01 vs. 0.30 ± 0.01 vs. 0.33 ± 0.01 ml/g, P = NS). Thus, although unsuitable for myocardial viability assessment, T1 FARM bolus tracking shows potential for assessment of myocardial perfusion. Magn Reson Med 46:555–564, 2001. © 2001 Wiley‐Liss, Inc.
Comparison of aerosolized gadoteridol and gadopentetate dimeglumine for magnetic resonance ventilation imaging of the lung
Authors: Haage Patrick , Karaagac Suleyman , Adam Gerhard , Glowinski Arndt , Günther Rolf W. 
Published: August 2002

AbstractThe purpose of this study was to compare aerosolized gadoteridol and gadopentetate dimeglumine in regard to homogeneity of aerosol distribution and relative pulmonary signal intensity (SI) changes after a 10‐min mechanical ventilation period. Twenty experimental procedures were performed in 10 intubated domestic pigs that were mechanically aerosolized with the nebulized contrast medium. Images were obtained by using a respiratory‐gated T1‐weighted TSE sequence. Pulmonary SI increase for the right and left lung was 26% ± 25% and 25% ± 12%, respectively, for gadopentetate dimeglumine, and 45% ± 12% and 43% ± 10%, respectively, for gadoteridol. Aerosol distribution was rated homogeneous in all cases by two readers. It is concluded that both contrast agents in aerosolized form are capable of depicting pulmonary ventilation in healthy animals with lung capacities comparable to those of humans. SI differences between gadoteridol and gadopentetate dimeglumine are explained by their considerable difference in viscosity. Magn Reson Med 46:803–806, 2001. © 2001 Wiley‐Liss, Inc.
NKT‐associated markers and perforin in hyperplastic thymuses from patients with Myasthenia gravis
Authors: Nagane Yuriko , Utsugisawa Kimiaki , Obara Daiji , Tohgi Hideo 
Published: August 2002

AbstractImmunohistochemical expression of natural killer T (NKT) cell–associated markers (Vα24 and CD56) and perforin in relation to CD44–highly positive (CD44high) cells was studied in hyperplastic thymuses from patients with myasthenia gravis (MG) whose symptoms dramatically improved after thymectomy and compared with non‐MG control thymuses. In the control thymuses, Vα24‐positive (Vα24+) and CD56‐positive (CD56+) cells were sparsely distributed in the medullary area only. In contrast, in hyperplastic MG thymus, Vα24+ and CD56+ cells were more frequent in connective tissue, appeared to have penetrated the thymic parenchyma, and most coexpressed CD44high. Perforin‐positive cells were not present in the control thymus, but were in the connective tissue and perilobular cortical areas in the hyperplastic MG thymus. Most of these perforin‐positive cells were CD44high and were located near blood vessels. They appeared to have migrated directly from the vascular system and penetrated the thymic parenchyma. Some perforin‐positive cells coexpressed Vα24, CD56, or both. These findings suggest that in this particular type of MG thymus, NKT‐like cells may have increased via a CD44‐ and perforin‐mediated mechanism, leading to an imbalance in the immune system that favored an antibody‐mediated autoimmunity against the acetylcholine receptor. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1359–1364, 2001
Differences in responses of cutaneous afferents in the human median and sural nerves to ischemia
Authors: Lin Cindy S.‐Y. , Mogyoros Ilona , Kuwabara Satoshi , Cappelen‐Smith Cecilia , Burke David 
Published: August 2002

AbstractRecent evidence suggests that two conductances responsible for accommodation to changes in membrane potential (a slow K+ conductance and inward rectification [IH]) are less active on cutaneous afferents in the sural nerve than on those in the median nerve, and it has been suggested that these axons would therefore respond differently to stress, whether natural or due to disease. The present study was undertaken in eight healthy volunteers to determine whether these afferents respond differently to the depolarizing and hyperpolarizing stresses that accompany ischemia for 13 min and subsequent recovery. During ischemia, the decrease in threshold was quantitatively less for the sural afferents, as were the changes in the other indices of axonal excitability, presumably because the ischemic depolarization was less for sural afferents. Following release of ischemia, there was, as predicted, a divergence in the pattern of threshold change. With median afferents there was evidence of a transient depolarization, believed to be due to inward rectification, superimposed on a long‐lasting hyperpolarization. The response of sural afferents lacked this transient depolarizing threshold change. Cutaneous afferents in the median and sural nerves behave differently in response to ischemic and postischemic stresses, and it is likely that they will also respond differently to disease processes. In a number of respects the differences between sural and median afferents are analogous to differences between diabetic and normal nerves. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1503–1509, 2001
Frictional contact of laminated elastic half‐spaces allowing interface cavities. Part 2: Numerical results
Authors: Kryshtafovych A. A. , Matysiak S. J. 
Published: August 2002

AbstractThe paper presents some numerical results of the problem on contact of stratified elastic half‐spaces possessing unevenness of their surface layers. The approach of the Jacobi polynomials is used to reduce the singular integral equation of the problem to a system of linear algebraic equations. On the basis of the system's solution the dependence of gaps' geometric characteristics on external load and friction is investigated for two types of initial boundary disturbances, namely a local symmetric recess and a periodic set of recesses at a flat boundary. Numerical results are presented in figures for a few elastic and geometric parameters of joint components. The analysis shows that elastic properties and geometric structure of a laminated half‐space have a significant influence on the shape of interface gaps and their location. Copyright © 2001 John Wiley & Sons, Ltd.
Efficient conditional modeling for geotechnical uncertainty evaluation
Authors: Graettinger A. J. , Lee J. , Reeves H. W. 
Published: August 2002

AbstractA first‐order Taylor series method including direct derivative coding (DDC) is presented as a computationally efficient method for producing the probability distribution associated with calculated geotechnical performance. The probability distribution is employed in reliability analyses to calculate the probability of failure, valuable information that is not typically associated with deterministic analyses. The probability distribution also is used to identify important input parameters and to direct sampling efforts. Another approach to generate the probability distribution is the Monte Carlo (MC) method, however, Taylor series results generally are calculated in less time than the MC approach. One key to the implementation of the Taylor series approach is efficient approximation of the sensitivities required by the Taylor series calculation. DDC provides the technique to produce an efficient Taylor series algorithm. Directly coding the sensitivity analysis into the engineering model is accomplished by automatic and hand programming of derivatives. ADIFOR 2.0 was employed to automatically add derivatives to an existing engineering analysis model. For this paper a meshing program and 3D FEM for soil deformation is used to demonstrate the DDC approach. Although DDC requires a large up‐front programming effort, it is not site or data specific. Therefore, once the derivative programming has been performed, the numerical model can be applied to a wide variety of problems without additional user intervention. Copyright © 2001 John Wiley & Sons, Ltd.
Instability of wave propagation in saturated poroelastoplastic media
Authors: Li Xikui , Zhang Junbo , Zhang Hongwu 
Published: August 2002

AbstractIn the present work, stationary discontinuities and fluttery instabilities of wave propagation in saturated poro‐elastoplastic media are analysed in the frame of Biot theory. The generalized Biot formulations are particularly employed for simulating non‐linear coupled hydro‐mechanical behaviour of the media. Inertial coupling effect between the solid and the fluid phases of the media is also taken into account. The non‐associated Drucker–Prager criterion to describe non‐linear constitutive behaviour of pressure dependent elasto‐plasticity for the solid skeleton of the media is particularly considered. With omission of compressibility of solid grains and the pore fluid, the critical conditions of stationary discontinuities and flutter instabilities occurring in wave propagation are given in explicit forms. It is shown that when the stationary discontinuity is triggered at the surface of discontinuity there still may exist real wave speeds. The wave speeds across the stationary discontinuity surface entirely cease to be real only in non‐associated plasticity, certain ranges of value of Poisson's ratio and when compression stress normal to the surface of discontinuity dominates the stress state at the surface. It is also indicated that the fluttery instabilities, under which some wave speeds cease to be real even in strain hardening stage, may occur prior to stationary discontinuities only for non‐associated plasticity under certain conditions. These conditions are: (1) both the porosity and the Poisson's ratio possess relatively low values and (2) the deviatoric part of the effective stress normal to the surface of discontinuity is compressive. A region in the porosity–Poisson's ratio plot, in which fluttery instabilities are possible to occur, is given. Copyright © 2002 John Wiley & Sons, Ltd.
Duality in constrained multi‐facility location models
Authors: Üster Halit , Love Robert F. 
Published: August 2002

AbstractWe consider the 𝓁p‐norm multi‐facility minisum location problem with linear and distance constraints, and develop the Lagrangian dual formulation for this problem. The model that we consider represents the most general location model in which the dual formulation is not found in the literature. We find that, because of its linear objective function and less number of variables, the Lagrangian dual is more useful. Additionally, the dual formulation eliminates the differentiability problem in the primal formulation. We also provide the Lagrangian dual formulation of the multi‐facility minisum location problem with the 𝓁pb‐norm. Finally, we provide a numerical example for solving the Lagrangian dual formulation and obtaining the optimum facility locations from the solution of the dual formulation. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 410–421, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10010
Magnetic coupling between water and creatine protons in human brain and skeletal muscle, as measured using inversion transfer 1H‐MRS
Authors: Kruiskamp M. J. , de Graaf R. A. , van der Grond J. , Lamerichs R. , Nicolay K. 
Published: August 2002

AbstractUsing the inversion transfer technique, the possible magnetic coupling between water protons and the protons of low‐molecular weight metabolites was investigated in human brain and skeletal muscle at 1.5 T. The localized 1H‐MR spectra were recorded at different times after selective inversion of the water resonance. Water inversion led to a significant transient reduction in the signal intensity of the methyl protons of creatine/phosphocreatine, in both tissues. This is indicative of magnetic coupling between the protons of water and those of creatine/phosphocreatine. Neither the choline and N‐acetylaspartate protons in brain nor the protons of the trimethylammonium pool in skeletal muscle showed a significant magnetic coupling to mobile water. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:

tCr

total creatine

NAA

N‐acetylaspartate

Cho

choline‐containing compounds

TMA

trimethylammonium‐containing compounds.
Comparison of the experimental BOLD signal change in event‐related fMRI with the balloon model
Authors: Feng Ching‐Mei , Liu Ho‐Ling , Fox Peter T. , Gao Jia‐Hong 
Published: August 2002

AbstractEvent‐related functional MRI (ER‐fMRI) based on both blood oxygenation level‐dependent (BOLD) contrast and cerebral blood flow (CBF) contrast has been developed to study the human brain response to transient stimulation. A balloon model has been developed and used in understanding the relationship between changes in CBF and in the BOLD signal in block‐designed fMRI. In this report, the balloon model was used to interpret experimental event‐related fMRI. Using experimental data acquired from CBF‐based ER‐fMRI as an input function in the balloon model, simulated BOLD signal changes were obtained. The simulated time course of the BOLD signal changes was directly compared with the experimentally acquired data. A chi‐square (χ2) test showed excellent correlation between the simulated and experimental data (α ≤ 0.05). Our results have demonstrated that the balloon model is useful in interpreting the transient features of the experimental data from the ER‐fMRI studies. Copyright © 2001 John Wiley & Sons, Ltd.
Monitoring acute inflammatory processes in mouse muscle by MR imaging and spectroscopy: a comparison with pathological results
Authors: Ruiz‐Cabello Jesús , Regadera Javier , Santisteban Carmen , Graña Manuel , Alejo Rigoberto Pérez de , Echave Imanol , Avilés Pablo , Rodriguez Ignacio , Santos Inmaculada , Gargallo Domingo , Cortijo Manuel 
Published: August 2002

AbstractWe have studied an animal model of acute local inflammation in muscle induced by Aspergillus fumigatus by using magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). We have compared our data to those found using histopathology and segmentation maps obtained by the mathematical processing of three‐dimensional T2‐weighted MRI data via a neural network. The MRI patterns agreed satisfactorily with the clinical and biological evidence of the phases of acute local infection and its evolution towards chronicity. The MRS results show a statistically significant increase in inorganic phosphate and a significant decrease in phosphocreatine levels in the inflamed region. Image segmentation made with a self‐organizing, neural‐network map yielded a set of ordered representatives that remained constant for all animals during the inflammatory process, allowing a non‐invasive, three‐dimensional identification and quantification of the inflamed infected regions by MRI. Copyright © 2002 John Wiley & Sons, Ltd.
A new—old algorithm for minimum‐cut and maximum‐flow in closure graphs
Authors: Hochbaum Dorit S. 
Published: August 2002

AbstractWe present an algorithm for solving the minimum‐cut problem on closure graphs without maintaining flow values. The algorithm is based on an optimization algorithm for the open‐pit mining problem that was presented in 1964 (and published in 1965) by Lerchs and Grossmann. The Lerchs—Grossmann algorithm (LG algorithm) solves the maximum closure which is equivalent to the minimum‐cut problem. Yet, it appears substantially different from other algorithms known for solving the minimum‐cut problem and does not employ any concept of flow. Instead, it works with sets of nodes that have a natural interpretation in the context of maximum closure in that they have positive total weight and are closed with respect to some subgraph. We describe the LG algorithm and study its features and the new insights it reveals for the maximum‐closure problem and the maximum‐ flow problem. Specifically, we devise a linear time procedure that evaluates a feasible flow corresponding to any iteration of the algorithm. We show that while the LG algorithm is pseudopolynomial, our variant algorithms have complexity of O(mn log n), where n is the number of nodes and m is the number of arcs in the graph. Modifications of the algorithm allow for efficient sensitivity and parametric analysis also running in time O(mn log n). © 2001 John Wiley & Sons, Inc.
Characterization results of all shortest paths interval routing schemes
Authors: Flammini M. , Gambosi G. , Nanni U. , Tan R.B. 
Published: August 2002

AbstractWe give complete characterizations for the classes of graphs with uniform cost links that admit optimum all shortest paths 1‐SLIRS (strict linear interval routing schemes) and 1‐LIRS (linear interval routing schemes). The characterization of all the interval routing schemes with uniform cost links that represent only a single shortest path is known to be NP‐complete. For any integer k > 0, we also show that the class of graphs with dynamic cost links that admit optimum all shortest paths k‐IRS (SIRS, LIRS, SLIRS) is equivalent to the class of graphs with dynamic cost links that admit an optimum single shortest path k‐IRS (SIRS, LIRS, SLIRS) and also equivalent to the class of graphs with dynamic cost links that admit single paths up to any constant stretch factor k‐IRS (SIRS, LIRS, SLIRS). © 2001 John Wiley & Sons, Inc.
Effects of excess thyroid hormone on cell death, cell proliferation, and new neuron incorporation in the adult zebra finch telencephalon
Authors: Tekumalla P. K. , Tontonoz M. , Hesla M. A. , Kirn J. R. 
Published: August 2002

AbstractWidespread telencephalic neuronal replacement occurs throughout life in birds. We explored the potential relationship between thyroxine (T4) and cell turnover in the adult male zebra finch. We found that many cells in the zebra finch brain, including long‐projection neurons in the high vocal center (HVC), stained positively with an antibody to thyroid hormone receptors (TR). Labeling was generally weak in the ventricular zone (VZ) that gives rise to new neurons but some proliferative VZ cells and/or their progeny, identified by [3H]‐thymidine labeling, co‐labeled with anti‐TR antibody. Acute T4 treatment dramatically increased the number of pyknotic and TUNEL‐positive cells in HVC and other telencephalic regions. In contrast, degenerating cells were never observed in the archistriatum or sub‐telencephalic regions, suggesting that excess T4 augments cell death selectively in regions that show naturally occurring neuronal turnover. VZ mitotic activity was not altered shortly after acute T4 treatment at a dosage that stimulated cell death, although [3H]‐labeling intensity per cell was slightly reduced. Moreover, the incorporation rates for neurons formed shortly before or after acute hormone treatment were no different from control values. Chronic T4 treatment resulted in a reduction in the total number of HVC neurons. Thus, hyperthyroidism augmented neuronal death, which was not compensated for by neuronal replacement. Collectively, these results indicate that excess T4 affects adult neuronal turnover in birds, and raises the possibility that thyroxine plays an important role in the postnatal development of the avian brain and vocal behavior. © 2002 Wiley Periodicals, Inc. J Neurobiol 51: 323–341, 2002