bluuebunny/crossref_metadata_2025_split huggingface dataset:
Serial MRI evaluation of cardiac structure and function in mice after reperfused myocardial infarction
Authors: Ross Antwone J. , Yang Zequan , Berr Stuart S. , Gilson Wesley D. , Petersen William C. , Oshinski John N. , French Brent A. 
Published: October 2002

AbstractThis study evaluated the utility of cardiac MRI for assessing the impact of myocardial infarction (MI) on cardiac structure and function in mice following reperfused 1‐ or 2‐hr occlusions of the left anterior descending coronary artery (LAD). When assessed 1 day after MI, the left ventricular ejection fraction (LVEF) had declined by more than half, and remained depressed for the duration of the study. Furthermore, MI initiated dramatic increases in both LV end‐systolic volume (LVESV) and end‐diastolic volume (LVEDV), with a greater than threefold increase in LVESV and a twofold increase in LVEDV by 4 weeks post‐MI. Transmural LV wall thickening (WTh) analysis revealed that noninfarcted myocardium in the remote septal region exhibited an early deficit in contractile function after MI that transiently resolved by day 7, only to be followed by a late phase of dysfunction that became fully manifest by day 28 post‐MI. In conclusion, MRI allows the serial assessment of cardiac structure and function after MI in mice, with a resolution adequate to document both regional and temporal changes. The application of these imaging techniques in transgenic and knock‐out mice will greatly expedite research aimed at defining the functional roles of individual genes in the pathophysiology of LV remodeling (LVR) after reperfused MI. Magn Reson Med 47:1158–1168, 2002. © 2002 Wiley‐Liss, Inc.
Cerebral blood volume measurements by rapid contrast infusion and T‐weighted echo planar MRI
Authors: Tudorica Alina , Fang Li Hai , Hospod Frank , Delucia‐Deranja Evan , Huang Wei , Patlak Clifford S. , Newman George C. 
Published: October 2002

AbstractCerebral blood volume (CBV) provides information complementary to that of cerebral blood flow in cerebral ischemia, tumors, and other conditions. We have developed an alternative theory and method for measuring CBV based on dynamic imaging by MRI or CT during a short contrast infusion. This method avoids several limitations of traditional approaches that involve waiting for steady state or measuring the area under the curve (AUC) during bolus contrast injection. Anesthetized dogs were studied by T‐weighted echo planar imaging during gadolinium‐DTPA infusions lasting 30–60 sec. CBV was calculated from the ratio of the signal changes in tissue and artery. Method responsiveness was compared to AUC measurements using the vasodilator acepromazine. The ratio of signal change in tissue to that in artery rapidly approached an asymptotic value even while the amount of contrast in artery continued to increase. Using 30‐sec infusions, the mean (± SD) of CBV for control animals was 3.6 ± 0.9 ml blood/100 g tissue in gray matter and 2.3 ± 0.8 ml blood/100 g tissue in white matter (ratio = 1.6). Acepromazine increased CBV to 5.7 ± 1.5 ml blood/100 g tissue in gray matter and 3.1 ± 0.8 ml blood/100 g tissue in white matter (ratio = 2.0). AUC measurements after bolus injection yielded similar values for control animals but failed to demonstrate any change after acepromazine. It is possible to measure CBV using dynamic MRI or CT during 30–60‐sec contrast infusions. This method may be more sensitive to changes in CBV than traditional AUC methods. Magn Reson Med 47:1145–1157, 2002. © 2002 Wiley‐Liss, Inc.
Polarization of the RF field in a human head at high field: A study with a quadrature surface coil at 7.0 T
Authors: Wang Jinghua , Yang Qing X. , Zhang Xiaoliang , Collins Christopher M. , Smith Michael B. , Zhu Xiao‐Hong , Adriany Gregor , Ugurbil Kamil , Chen Wei 
Published: October 2002

AbstractThe RF field intensity distribution in the human brain becomes inhomogeneous due to wave behavior at high field. This is further complicated by the spatial distribution of RF field polarization that must be considered to predict image intensity distribution. An additional layer of complexity is involved when a quadrature coil is used for transmission and reception. To study such complicated RF field behavior, a computer modeling method was employed to investigate the RF field of a quadrature surface coil at 300 MHz. Theoretical and experimental results for a phantom and the human head at 7.0 T are presented. The results are theoretically important and practically useful for high‐field quadrature coil design and application. Magn Reson Med 48:362–369, 2002. © 2002 Wiley‐Liss, Inc.
Three‐dimensional spiral MR imaging: Application to renal multiphase contrast‐enhanced angiography
Authors: Amann Michael , Bock Michael , Floemer Frank , Schoenberg Stefan O. , Schad Lothar R. 
Published: October 2002

AbstractA fast MR pulse sequence with spiral in‐plane readout and conventional 3D partition encoding was developed for multiphase contrast‐enhanced magnetic resonance angiography (CE‐MRA) of the renal vasculature. Compared to a standard multiphase 3D CE‐MRA with FLASH readout, an isotropic in‐plane spatial resolution of 1.4 × 1.4 mm2 over 2.0 × 1.4 mm2 could be achieved with a temporal resolution of 6 sec. The theoretical gain of spatial resolution by using the spiral pulse sequence and the performance in the presence of turbulent flow was evaluated in phantom measurements. Multiphase 3D CE‐MRA of the renal arteries was performed in five healthy volunteers using both techniques. A deblurring technique was used to correct the spiral raw data. Thereby, the off‐resonance frequencies were determined by minimizing the imaginary part of the data in image space. The chosen correction algorithm was able to reduce image blurring substantially in all MRA phases. The image quality of the spiral CE‐MRA pulse sequence was comparable to that of the FLASH CE‐MRA with increased spatial resolution and a 25% reduced contrast‐to‐noise ratio. Additionally, artifacts specific to spiral MRI could be observed which had no impact on the assessment of the renal arteries. Magn Reson Med 48:290–296, 2002. © 2002 Wiley‐Liss, Inc.
Regional distribution of slow‐twitch muscle fibers after reinnervation in adult rat hindlimb muscles
Authors: Wang Liangchun , Copray Sjef , Brouwer Nieske , Meek Marcel F. , Kernell Daniel 
Published: October 2002

AbstractIn adult rats, the sciatic nerve was unilaterally sectioned and reunited above the knee. Following a survival time of 21 weeks, five muscles were removed from both lower hindlimbs after determining their intra‐limb positions. In each muscle, cryostat sections from seven equidistant proximo‐distal levels were stained for myofibrillar ATPase. Intramuscular positions were determined for all slow‐twitch type I fibers. Within each muscle, type I fibers were heterogeneously distributed, and the direction of type I fiber accumulation was, on average, almost identical in reinnervated muscles and contralateral controls. Furthermore, as in controls, a proximo‐distal decline of type I fiber density was found in reinnervated muscles. Compared to contralateral controls, reinnervated muscles consistently showed a very high number of type I fibers at close interfiber distances, indicating respecification of muscle fiber types by the ingrowing nerve fibers. The results suggest that slow‐twitch motor axons preferentially grew back toward the original slow‐twitch muscle regions. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002
Modality‐related scalp responses after electrical stimulation of cutaneous and muscular upper limb afferents in humans
Authors: Restuccia Domenico , Valeriani Massimiliano , Insola Angelo , Lo Monaco Mauro , Grassi Eugenio , Barba Carmen , Le Pera Domenica , Mauguière François 
Published: October 2002

AbstractTo elucidate whether the selective electrical stimulation of muscle as well as cutaneous afferents evokes modality‐specific responses in somatosensory evoked potentials (SEPs) recorded on the scalp of humans, we compared scalp SEPs to electrical stimuli applied to the median nerve and to the abductor pollicis brevis (APB) motor point. In three subjects, we also recorded SEPs after stimulation of the distal phalanx of the thumb, which selectively involved cutaneous afferents. Motor point and median nerve SEPs showed the same scalp distribution; moreover, very similar dipole models, showing the same dipolar time courses, explained well the SEPs after both types of stimulation. Since the non‐natural stimulation of muscle afferents evokes responses also in areas specifically devoted to cutaneous input processing, it is conceivable that, in physiological conditions, muscle afferents are differentially gated in somatosensory cortex. The frontocentral N30 response was absent after purely cutaneous stimulation; by contrast, it was relatively more represented in motor point rather than in mixed nerve SEPs. These data suggest that the N30 response is specifically evoked by proprioceptive inputs. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 44–55, 2002
High efficiency transfection of primary skeletal muscle cells with lipid‐based reagents
Authors: Neuhuber Birgit , Huang David I. , Daniels Mathew P. , Torgan Carol E. 
Published: October 2002

AbstractLipofection is a convenient method for gene transfer into muscle cells but reportedly is inefficient. We tested the efficacy of commercially available lipid‐based and polyamine transfection reagents. Primary rat skeletal muscle cell cultures were transfected at three stages of development and assayed after fusion. Efficiency reached 30% during the proliferation stage and up to 23% when most myoblasts had fused into myotubes. Optimization of transfection conditions with three different vectors yielded efficiencies exceeding 50%. Thus, lipid‐based transfection into primary skeletal muscle cells can be several times more efficient than previously reported. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 136–140, 2002
Comparison of MRI and electrophysiological studies for detecting brainstem lesions in traumatic brain injury
Authors: Wedekind Christoph , Hesselmann Volker , Klug Norfrid 
Published: October 2002

AbstractThe yield of magnetic resonance imaging (MRI) and electrophysiological studies in detecting brainstem lesions was assessed in 35 patients suffering from traumatic brain injury (Glasgow Coma Scale, 3–10). As an inclusion criterion, all patients had brainstem trauma as revealed by early MRI or electrophysiological studies. Of the 35 cases, 7 (20%) had brainstem lesions detected by MRI only, whereas in 10 patients (29%), electrophysiological examination disclosed impairment of brainstem function with normal MRI. In 18 (51%) subjects, both diagnostic techniques revealed brainstem lesions. The midbrain was the most common location of lesions. Masseter reflex recording had the highest yield (93%) of abnormal findings. No mismatch with respect to site and side of abnormality occurred between MRI and electrophysiological studies. Outcome analysis indicated an unfavorable course for the vast majority (83%) of patients, regardless of the diagnostic means disclosing traumatic brainstem injury. Therefore, both techniques are effective in disclosing traumatic brainstem injury, with diagnostic overlap in about 50% of cases. In contrast to MRI, electrophysiological investigation is easily performed and repeated at low cost in the setting of an intensive care unit, where such patients are typically hospitalized after trauma. In addition to electrophysiological assessment of brainstem function, MRI is recommended in each case having normal electrophysiological findings when brainstem injury is suspected. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 270–273, 2002
Influences of electromechanical events in defining skeletal muscle properties
Authors: Roy Roland R. , Zhong Hui , Hodgson John A. , Grossman Elena J. , Siengthai Boonclaire , Talmadge Robert J. , Edgerton V. Reggie 
Published: October 2002

AbstractInactivity of the cat soleus muscle was induced via spinal cord isolation (SI), and the cats were maintained for 4 months. The soleus was electrically stimulated while lengthening (SI‐L) or shortening (SI‐S) during a simulated step cycle or during isometric (SI‐I) contractions. For the SI, SI‐S, SI‐L, and SI‐I groups, the soleus weights were 33, 55, 55, and 64% of the control, respectively, and the maximum tetanic tensions were 15, 30, 36, and 44% of the control, respectively. The specific tension was lower in all SI groups than in the control. Absolute forces at stimulation frequencies of 5–200 Hz were smaller in all SI groups than in the control. The SI‐I group tended to have higher values for all force‐related parameters than the other SI groups. Fatigue resistance was similar among all groups. The isometric twitch time‐to‐peak tension was shorter, and the frequency of the stimulation–tension response was shifted to the right in all SI groups with respect to the control. Maximum shortening velocities were 70, 59, and 73% faster for the SI, SI‐S, and SI‐L groups and similar to the control for the SI‐I group. Inactivity resulted in an increased percentage of faster myosin heavy chains (MHCs) that was blunted in the SI‐I and SI‐L groups but not in the SI‐S group. Pure type I MHC fibers atrophied by 80, 59, 58, and 47% in the SI, SI‐S, SI‐L, and SI‐I groups. The data from the SI group quantify the contribution of activity‐independent factors in maintaining the mechanical and phenotypic properties of the cat soleus. Relative to a fast‐fatigable muscle, these results suggest that only 25% of the slowness (type I MHC) and none of the resistance to fatigue of the soleus muscle are dependent on activity‐related factors. Short, daily bouts of electromechanical activation ameliorated several of these adaptations, with the isometric contractions being the most effective countermeasure. The clinical implications of these findings for rehabilitation strategies are discussed. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26:238–251, 2002
Modelling of elastoplastic damage in concrete due to desiccation shrinkage
Authors: Bourgeois F. , Burlion N. , Shao J. F. 
Published: October 2002

AbstractWe present a numerical modelling of elastoplastic damage due to drying shrinkage of concrete in the framework of mechanics of partially saturated porous media. An elastoplastic model coupled with isotropic damage is first formulated. Two plastic flow mechanisms are involved, controlled by applied stress and suction, respectively. A general concept of net effective stress is used in take into account effects of capillary pressure and material damage on stress‐controlled plastic deformation. Damage evolution depends both on elastic and plastic strains. The model's parameters are determined or chosen from relevant experimental data. Comparisons between numerical simulations and experimental data are presented to show the capacity of model to reproduce mains features of concrete behaviour under mechanical loading and during drying shrinkage of concrete. An example of application concerning drying of a concrete wall is finally presented. The results obtained allow to show potential capacity of proposed model for numerical modelling of complex coupling processes in concrete structures. Copyright © 2002 John Wiley & Sons, Ltd.
Probabilistic analysis of underground pillar stability
Authors: Griffiths D. V. , Fenton Gordon A. , Lemons Carisa B. 
Published: October 2002

AbstractThe majority of geotechnical analyses are deterministic, in that the inherent variability of the materials is not modelled directly, rather some ‘factor of safety’ is applied to results computed using ‘average’ properties. In the present study, the influence of spatially varying strength is assessed via numerical experiments involving the compressive strength and stability of pillars typically used in underground construction and mining operations. The model combines random field theory with an elasto‐plastic finite element algorithm in a Monte‐Carlo framework. It is found that the average strength of the rock is not a good indicator of the overall strength of the pillar. The results of this study enable traditional approaches involving factors of safety to be re‐interpreted as a ‘probability of failure’ in the context of reliability based design. Copyright © 2002 John Wiley & Sons, Ltd.
Preprocessing Steiner problems from VLSI layout
Authors: Uchoa Eduardo , Poggi de Aragão Marcus , Ribeiro Celso C. 
Published: October 2002

AbstractVLSI layout applications yield instances of the Steiner tree problem over grid graphs with holes, which are considered hard to be solved by current methods. In particular, preprocessing techniques developed for Steiner problems over general graphs are not likely to reduce, significantly, such VLSI instances. We propose a new preprocessing procedure, extending earlier ideas from the literature and improving their application, so as to make them effective for VLSI problems. We report significant reductions within reasonable computational times, obtained with the application of this procedure to 116 instances of the SteinLib. These reductions allowed a branch and cut to solve 28 of 32 open instances of the SteinLib, some with more than 10,000 vertices and 20,000 edges. © 2002 Wiley Periodicals, Inc.
Buckling optimization and antioptimization of composite plates: uncertain loading combinations
Authors: de Faria Alfredo R. 
Published: October 2002

AbstractThe problem of optimal design for elastic buckling loads of composite plates under uncertain loading conditions is considered. It is observed that this is a multicriterion optimization problem whose solution is time consuming. Thus, an alternative minimax formulation is proposed and demonstrated. The buckling load is maximized with respect to the structural parameters and minimized with respect to variations in the load parameters. The mechanical loads applied to the rectangular plates are a combination of normal compression and shear. Moreover, the admissible loading configurations belong to a convex hull which significantly enhances the optimization procedure. The consideration of an uncertainty degree in the mechanical loads leads to optimal designs which are inherently insensitive to perturbations and/or randomness in the applied loads. Copyright © 2001 John Wiley & Sons, Ltd.
Thermo‐elasto‐plastic finite element analysis of quasi‐state processes in Eulerian reference frames
Authors: Shanghvi J. Y. , Michaleris P. 
Published: October 2002

AbstractAn Eulerian finite element formulation for quasi‐state one way coupled thermo‐elasto‐plastic systems is presented. The formulation is suitable for modeling material processes such as welding and laser surfacing. In an Eulerian frame, the solution field of a quasi‐state process becomes steady state for the heat transfer problem and static for the stress problem. A mixed small deformation displacement elasto‐plastic formulation is proposed. The formulation accounts for temperature dependent material properties and exhibits a robust convergence. Streamline upwind Petrov–Galerkin (SUPG) is used to remove spurious oscillations. Smoothing functions are introduced to relax the non‐differentiable evolution equations and allow for the use of gradient (stiffness) solution scheme via the Newton–Raphson method. A 3‐dimensional simulation of a laser surfacing process is presented to exemplify the formulation. Results from the Eulerian formulation are in good agreement with results from the conventional Lagrangian formulation. However, the Eulerian formulation is approximately 15 times faster than the Lagrangian. Copyright © 2001 John Wiley & Sons, Ltd.
Conservation properties of a time FE method—part III: Mechanical systems with holonomic constraints
Authors: Betsch P. , Steinmann P. 
Published: October 2002

AbstractA Galerkin‐based discretization method for index 3 differential algebraic equations pertaining to finite‐dimensional mechanical systems with holonomic constraints is proposed. In particular, the mixed Galerkin (mG) method is introduced which leads in a natural way to time stepping schemes that inherit major conservation properties of the underlying constrained Hamiltonian system, namely total energy and angular momentum. In addition to that, the constraints on the configuration level and on the velocity/momentum level are fulfilled exactly. The application of the mG method to specific mechanical systems such as the pendulum, rigid body dynamics and the coupled motion of rigid and flexible bodies is presented. Related numerical examples are investigated to evaluate the numerical performance of the mG(1) and mG(2) method. Copyright © 2002 John Wiley & Sons, Ltd.
Low‐frequency assessment of the in situ acoustic absorption of materials in rooms: an inverse problem approach using evolutionary optimization
Authors: Dutilleux Guillaume , Sgard Franck C. , Kristiansen Ulf R. 
Published: October 2002

AbstractThe in situ assessment of the acoustic absorption of materials is often a necessity. The need to cover the whole frequency range of interest for the building engineer has led the authors to an approach involving two frequency‐complementary measurement methods. This paper deals with the part dedicated to low frequencies. The measurement is defined here as a boundary inverse interior problem. A numerical model of the room under investigation, allowing for the computation of the pressure field in the volume, given impedance boundary conditions and a point source, is combined to a global optimization algorithm. The algorithm explores the set of possible boundary conditions in order to minimize the difference between the computed pressure values and the one observed at a few measurement points, leading to the determination of all the boundary conditions at a time. In practice, the finite element method (FEM) or the finite difference method (FDM) is used here to model the room and an Evolution Strategy as the optimization tool. After describing the ES operators, a numerical study is carried out on simulated measurements, both on problem‐ and algorithm‐specific parameters, in the case of an academic two‐dimensional room geometry. The method is then applied to a three‐dimensional room with promising results. Copyright © 2002 John Wiley & Sons, Ltd.
Constitutive modeling of cementitious materials in the framework of chemoplasticity
Authors: Lackner R. , Hellmich Ch. , Mang H. A. 
Published: October 2002

AbstractIn this paper, a multi‐surface plasticity model for chemically reactive media such as shotcrete is described. It consists of the Drucker‐Prager criterion for simulation of compressive failure and the Rankine criterion accounting for brittle material response under tensile loading. The material model is formulated in the principal stress space. The robustness of this formulation and, hence, the applicability of the proposed material model is demonstrated by means of the analysis of the Sieberg tunnel in Lower Austria. Insights into the structural response as well as the level of loading of the tunnel lining are given. Copyright © 2002 John Wiley & Sons, Ltd.
Buoyancy forces and the 2D finite element analysis of flexible offshore pipes and risers
Authors: Yazdchi M. , Crisfield M. A. 
Published: October 2002

AbstractMany analysts use simple lower‐order beam elements for the non‐linear analysis of curved beam and arch structures. The aim of the present paper is to indicate how one may add the effects of buoyancy, steady‐state current loading and riser top‐tension to such an idealization so that it may be used for the analysis of offshore pipes and risers. The current work is restricted to static two‐dimensional modelling but it paves the way for further work in three dimensions, which will include dynamics. Copyright © 2002 John Wiley & Sons, Ltd