bluuebunny/crossref_metadata_2025_split huggingface dataset:
23Na MRI accurately measures fixed charge density in articular cartilage
Authors: Shapiro Erik M. , Borthakur Arijitt , Gougoutas Alexander , Reddy Ravinder 
Published: August 2002

AbstractOne of the initiating steps of osteoarthritis is the loss of proteoglycan (PG) molecules from the cartilage matrix. One method for assessing cartilage integrity, therefore, is to measure the PG content or fixed charge density (FCD) of cartilage. This report shows the feasibility of calculating FCD by 23Na MRI and introduces MRI protocols for human studies, in vivo. 23Na MRI was used to measure the sodium concentration inside bovine patellar cartilage. The sodium concentration was then converted to FCD (mM) by considering ideal Donnan equilibrium. These FCD measurements were compared to FCD measurements obtained through standard dimethylmethylene blue PG assays. There was a high correlation (slope = 0.89, r2 = 0.81) between the FCD measurements obtained by 23Na MRI and those obtained by the PG assays. These methods were then employed in quantifying the FCD of articular cartilage of human volunteers in vivo. Two imaging protocols were compared: one using a birdcage coil, the other using a transmit/receive surface coil. Both methodologies gave similar results, with the average sodium concentration of normal human patellar cartilage ranging from ∼240 to 260 mM. This corresponds to FCDs of –158 mM to –182 mM. Magn Reson Med 47:284–291, 2002. © 2002 Wiley‐Liss, Inc.
Direct in vivo measurement of human cerebral GABA concentration using MEGA‐editing at 7 Tesla
Authors: Terpstra Melissa , Ugurbil Kamil , Gruetter Rolf 
Published: August 2002

AbstractSpectral editing of the GABA spin system is hampered by coediting of macromolecule (MM) coherences. To reduce contamination arising from MMs in spectra edited for GABA, the highest field strength currently available for human experimentation (7 Tesla) and MEGA‐based editing were used. Despite judicious choice of experimental parameters, MM contamination was found to arise from field drifts. When the MM contribution was accounted for, [GABA] = 0.75 ± 0.14 μmol/g (mean ± SD, N = 16) relative to 8 μmol/g creatine (Cr), whereas without accounting for the MM signal [GABA*] = 0.88 ± 0.23 μmol/g (mean ± SD, N = 16). Incorporating the direct experimental assessment of MM contamination to the edited GABA signal substantially reduced the variance of the measurement, resulting in concentrations that were in excellent agreement with previous 13C labeling experiments. Magn Reson Med 47:1009–1012, 2002. © 2002 Wiley‐Liss, Inc.
17O relaxation time and NMR sensitivity of cerebral water and their field dependence
Authors: Zhu Xiao‐Hong , Merkle Hellmut , Kwag Jae‐Hwan , Ugurbil Kamil , Chen Wei 
Published: August 2002

Abstract17O spin relaxation times and sensitivity of detection were measured for natural abundance H217O in the rat brain at 4.7 and 9.4 Tesla. The relaxation times were found to be magnetic field independent (T2 = 3.03 ± 0.08 ms, T = 1.79 ± 0.04 ms, and T1 = 4.47 ± 0.14 ms at 4.7T (N = 5); T2 = 3.03 ± 0.09 ms, T = 1.80 ± 0.06 ms, and T1 = 4.84 ± 0.18 ms at 9.4T (N = 5)), consistent with the concept that the dominant relaxation mechanism is the quadrupolar interaction for this nucleus. The 17O NMR sensitivity was more than fourfold higher at 9.4T than at 4.7T, for both the rat brain and a sodium chloride solution. With this sensitivity gain, it was possible to obtain localized 17O spectra with an excellent signal‐to‐noise ratio (SNR) within 15 s of data acquisition despite the relatively low gyromagnetic ratio of this nucleus. Such a 15‐s 2D 17O‐MRS imaging data set obtained for natural abundance H217O in the rat brain yielded an SNR greater than 40:1 for a ∼16μl voxel. This approach was employed to measure cerebral blood flow using a bolus injection of H217O via one internal carotid artery. These results demonstrate the ability of 17O‐MRS imaging to reliably map the H217O dynamics in the brain tissue, and its potential for determining tissue blood flow and oxygen consumption rate changes in vivo. Magn Reson Med 45:543–549, 2001. © 2001 Wiley‐Liss, Inc.
Coupling of neural activity and BOLD fMRI response: New insights by combination of fMRI and VEP experiments in transition from single events to continuous stimulation
Authors: Janz C. , Heinrich S.P. , Kornmayer J. , Bach M. , Hennig J. 
Published: August 2002

AbstractFunctional magnetic resonance imaging (fMRI) measures the correlation between the fMRI response and stimulus properties. A linear relationship between neural activity and fMRI response is commonly assumed. However, the response to repetitive stimulation cannot be explained by a simple superposition of single‐event responses. This might be due to neural adaptation or the hemodynamic changes underlying the fMRI BOLD response. To assess the influence of adaptation, the BOLD responses and visual evoked potentials (VEPs) to identical stimuli were recorded. To achieve different adaptation levels, 2‐s stimulus epochs alternated with different interstimulus intervals (ISI = 0.0, 0.4, 0.8, 2.0, and 12 s) were presented. Neural adaptation during the checkerboard reversal paradigm used for fMRI measurements is demonstrated. Even if the measured VEP amplitude is used as the weighting function for a linear model, the measured BOLD fMRI signal time‐course is not adequately predicted. Magn Reson Med 46:482–486, 2001. © 2001 Wiley‐Liss, Inc.
Creating a library of generalized Fourier sampling patterns for irregular 2D regions of support
Authors: Nagle S.K. , Levin D.N. 
Published: August 2002

AbstractMultiple‐region MRI (mrMRI) represents a generalization of the Shannon sampling theorem to permit sparsek‐space sampling whenever the scanned object or its high‐contrast edges are confined to multiple known regions. Use of an optimal mrMRI sampling pattern produces an image with root‐mean‐squared (RMS) noise over the supporting regions equal to the RMS noise in a conventional Fourier image with the same total area of support. Analytical solutions for such sampling patterns have been described previously for all arrangements of two or three (noncollinear) supporting regions. This work describes a robust numerical method for creating a library of optimal and near‐optimal mrMRI sampling patterns for more complicated geometries. The average noise amplification over all sampling patterns in the demonstration library was only 4%, with 30% of the sampling patterns resulting in no noise amplification whatsoever. Magn Reson Med 46:624–627, 2001. © 2001 Wiley‐Liss, Inc.
Unifying linear prior‐information‐driven methods for accelerated image acquisition
Authors: Tsao Jeffrey , Behnia Babak , Webb Andrew G. 
Published: August 2002

AbstractIn the ongoing quest for faster imaging and higher spatial resolution, several methods have been developed to speed up data acquisition by incorporating prior information about the object being imaged. This study shows that many of these methods can be integrated into a single common equation. The unified framework provides a conceptual link that facilitates comparison among these methods to reveal their strengths and weaknesses. By considering the limitations of existing methods, a new member in this class of methods was developed. The broad‐use linear acquisition speed‐up technique (BLAST) uses the estimated amount of change within the FOV as prior information. BLAST has the flexibility of incorporating a variable amount of prior information to avoid the misleading appearance of “phantom features,” which arise from overconstraining the reconstruction. Examples from dynamic imaging and MR thermometry are shown. Magn Reson Med 46:652–660, 2001. © 2001 Wiley‐Liss, Inc.
Mapping the velocity vector onto the spin vector: Two‐dimensional velocity‐selective spin excitation for MR flow imaging†
Authors: Wen Han 
Published: August 2002

AbstractThis article presents a two‐dimensional velocity‐selective spin excitation (2D‐VSP) method that enables quantitative imaging of motion in two directions in a single scan, without the need for image subtraction or combination. It is based on the idea of mapping a 2D velocity vector directly onto the transverse magnetization vector, such that the signal intensity reflects the speed of motion, while the signal phase represents the direction of motion. Experimental demonstration is presented in conjunction with an analysis of the accuracy of this method. VSP methods are often limited by inconsistent static signal suppression under variable shim and RF conditions. By using adiabatic RF pulses in a 2D‐VSP composite that possesses time‐reversal symmetry, consistent background suppression of 30‐fold or higher was demonstrated over experimental conditions of ±200 Hz off‐resonance and 30% RF field variation. Magn Reson Med 46:767–772, 2001. © 2001 Wiley‐Liss, Inc.
Electromyography of sternocleidomastoid muscle in ALS: A prospective study
Authors: Li Jun , Petajan Jack , Smith Gordon , Bromberg Mark 
Published: August 2002

AbstractNeedle electromyography (EMG) of the tongue is difficult to perform because of frequent uncontrollable movement. We chose the sternocleidomastoid (SCM) muscle as a possible alternative for assessing the involvement of the rostral neuraxis in amyotrophic lateral sclerosis (ALS). We prospectively studied 21 ALS patients during our initial diagnostic evaluation. EMG parameters that we recorded included the presence of abnormal spontaneous activity, pattern of motor unit potential recruitment, and configuration of motor unit action potentials. For the six patients with bulbar‐onset ALS, three had abnormalities in the SCM and three had abnormalities in the tongue. In contrast, for the 15 patients with limb‐onset ALS, 9 had abnormalities in the SCM, and only 3 had abnormalities in the tongue. Our results demonstrate the utility of needle EMG of the SCM in the evaluation of ALS. EMG of the SCM carries a similar sensitivity as the tongue in ALS patients with bulbar symptoms, but is more sensitive than the tongue in patients without bulbar symptoms. SCM innervation includes the rostral cervical cord and brainstem, and EMG abnormalities in this muscle support a diffuse involvement, which is unique to ALS. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002
Partial peripheral motor nerve lesions induce changes in the conduction properties of remaining intact motoneurons
Authors: Havton Leif A. , Hotson John R. , Kellerth Jan‐Olof 
Published: August 2002

AbstractA partial injury or loss of peripheral motor axons is followed by compensatory sprouting of remaining intact motor axons in order to reinnervate muscle. Little is known, however, about the electrophysiologic properties proximally of these intact motoneurons and their axons following injury of neighboring motor axons. We studied the conduction properties of intact cat motor axons and motoneurons proximal to the site of a partial peripheral nerve section. Twelve weeks after the partial transection of the cat medial gastrocnemius motor nerve, there was a significant (7%) reduction in conduction velocity and a 13% prolongation in afterhyperpolarization half–decay time in the remaining intact motoneurons, compared with controls. Partial injury to motor nerves thus induces reactive electrophysiologic changes in the remaining intact motoneurons and their axons, perhaps associated with compensatory sprouting within partially denervated muscle. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 662–666, 2001
Distal sensory nerve conduction of the superficial peroneal nerve: New method and its clinical application
Authors: Oh Shin J. , Demirci Mehmet , Dajani Badr , Melo Aluisio C. , Claussen Gwen C. 
Published: August 2002

AbstractThe superficial peroneal nerve subserves sensation on the entire surface of the dorsum of the foot, except in small areas. All previously reported techniques for evaluating nerve conduction along this nerve tested a proximal portion of the nerve. We report a new method for evaluating sensory nerve conduction of the four branches of the distal superficial peroneal nerve. Two branches to the second and third toes of the medial dorsal cutaneous nerve and two branches to the fourth and fifth toes of the intermediate dorsal cutaneous nerve were studied orthodromically and antidromically in 37 feet of 21 normal volunteers using surface stimulating and recording electrodes and with a distance of 10 cm between the stimulating and recording electrodes. Maximum nerve conduction velocities (NCV) ranged from 41.8 to 46.9 m/s, and mean response amplitude ranged from 6.5 to 7.6 μV with the orthodromic technique. Values for NCV were almost identical when elicited by antidromic and orthodromic techniques, but response amplitudes were higher with the antidromic technique. Mean amplitudes of the distal superficial peroneal nerve were about 50% of the proximal superficial peroneal, and the conduction velocity in the distal superficial peroneal was slower than that in the proximal superficial peroneal nerve, by 8–14 m/s. In seven cases, distal superficial peroneal neuropathy was confirmed with this technique: two with proper digital neuropathy, two with medial dorsal cutaneous neuropathy, and three with intermediate dorsal cutaneous neuropathy. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 689–694, 2001
Quantitative assessment of cutaneous thermal and vibration sensation and thermal pain detection thresholds in healthy children and adolescents
Authors: Meier Petra M. , Berde Charles B. , DiCanzio James , Zurakowski David , Sethna Navil F. 
Published: August 2002

AbstractQuantitative sensory testing (QST) is a noninvasive, computer‐assisted method for assessing function in peripheral small and large sensory fibers. In order to use QST for clinical neurological assessment in children, it is necessary: (1) to determine whether children can reliably perform these tests and (2) to characterize normal ranges in healthy children. Values of cold sensation, warm sensation, cold pain, heat pain, and vibration sensation detection thresholds were determined in the hand and foot with the method of limits (MLI) and method of levels (MLE) in 101 healthy children aged 6–17 years using a commercially available device. Both MLI and MLE were well‐accepted by children, and there was good reproducibility between two sessions. The MLE takes longer to perform but produces lower thermal detection thresholds than the MLI. In the MLI, vibration and warm sensation showed higher thresholds in the foot than hand, whereas cold pain showed lower thresholds in the foot than hand. Based on these results, QST may be used to document and monitor the clinical course of sensory abnormalities in children with neurological disorders or neuropathic pain. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1339–1345, 2001
An accelerated algorithm for parameter identification in a hierarchical plasticity model accounting for material constraints
Authors: Simoni L. , Schrefler B. A. 
Published: August 2002

AbstractThe parameter identification procedure proposed in this paper is based on the solution of an inverse problem, which relies on the minimization of an error function of least‐squares type. The solution of the ensuing optimization problem, which is a constrained one owing to the presence of physical links between the optimization parameters, is performed by means of a particular technique of the feasible direction type, which is modified and improved when the problem turns to an unconstrained one. The algorithm is particularly efficient in the presence of hierarchical material models. The numerical properties of the proposed procedure are discussed and its behaviour is compared with usual optimization methods when applied to constrained and unconstrained problems. Copyright © 2001 John Wiley & Sons, Ltd.
On integration of a cyclic soil plasticity model
Authors: Manzari Majid T. , Prachathananukit Rung 
Published: August 2002

AbstractPerformance of three classes of explicit and implicit time‐stepping integrators is assessed for a cyclic plasticity constitutive model for sands. The model is representative of an important class of cyclic plasticity models for soils and includes both isotropic and nonlinear kinematic hardening. The implicit algorithm is based on the closest point projection method and the explicit algorithm follows a cutting‐plane integration procedure. A sub‐stepping technique was also implemented. The performance of these algorithms is assessed through a series of numerical simulations ranging from simulations of laboratory tests (such as triaxial and bi‐axial compression, direct shear, and cyclic triaxial tests) to the analysis of a typical boundary value problem of geotechnical earthquake engineering. These simulations show that the closest point projection algorithm remains stable and accurate for relatively large strain increments and for cases where the mean effective stress in a soil element reaches very small values leading to a liquefaction state. It is also shown that while the cutting plane (CP) and sub‐stepping (SS) algorithms provide high efficiency and good accuracy for small to medium size strain increments, their accuracy and efficiency deteriorate faster than the closest point projection method for large strain increments. The CP and SS algorithms also face convergence difficulties in the liquefaction analysis when the soil approaches very small mean effective stresses. Copyright © 2001 John Wiley & Sons, Ltd.
Implicit numerical integration for a kinematic hardening soil plasticity model
Authors: Rouainia M. , Muir Wood D. 
Published: August 2002

AbstractSoil models based on kinematic hardening together with elements of bounding surface plasticity, provide a means of introducing some memory of recent history and stiffness variation in the predicted response of soils. Such models provide an improvement on simple elasto‐plastic models in describing soil behaviour under non‐monotonic loading. Routine use of such models requires robust numerical integration schemes. Explicit integration of highly non‐linear models requires extremely small steps in order to guarantee convergence. Here, a fully implicit scheme is presented for a simple kinematic hardening extension of the Cam clay soil model. The algorithm is based on the operator split methodology and the implicit Euler backward integration scheme is proposed to integrate the rate form of the constitutive relations. This algorithm maintains a quadratic rate of asymptotic convergence when used with a Newton–Raphson iterative procedure. Various strain‐driven axisymmetric triaxial paths are simulated in order to demonstrate the efficiency and good performance of the proposed algorithm. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of down times of jib cranes—A stochastic approach
Authors: Dharmadhikari Avinash , Deshmukh S.R. 
Published: August 2002

AbstractIn this paper a case study dealing with the maintenance problem of jib cranes is presented. A jib crane is viewed as a complex system whose performance is observed as a single realization over period of time. After pointing out limitations of existing stochastic models to analyze the observed realization a new family of bivariate stochastic processes is introduced. The data of jib crane is analyzed using new model and cross‐validated using part of the data set. It is noted that the new family of stochastic processes is useful to analyze bivariate data where one of the variables is finitely valued and the other is nonnegative and continuous. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 231–243, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10006
The multiplicative representation for multiple objectives optimization with an application for arms procurement
Authors: Brauers Willem K. 
Published: August 2002

AbstractMultiple Objectives Optimization is much seen in combination with linear functions and even with linear programming, together with an adding of the objectives by using weights. With distance functions, normalization instead of weights is used. It is also possible that together with an additive direct influence of the objectives on the utility function a mutual utility of the objectives exists under the form of a multiplicative representation. A critical comment is brought on some representations of this kind. A full‐multiplicative form may offer other opportunities, which will be discussed at length in an effort to exclude weights and normalization. This theoretical approach is followed by an application for arms procurement. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 327–340, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10014
Sequential and systematic sampling plans for the Markov‐dependent production process
Authors: P. Vellaisamy  , Sankar S. 
Published: August 2002

AbstractAcceptance sampling plans are used to assess the quality of an ongoing production process, in addition to the lot acceptance. In this paper, we consider sampling inspection plans for monitoring the Markov‐dependent production process. We construct sequential plans that satisfy the usual probability requirements at acceptable quality level and rejectable quality level and, in addition, possess the minimum average sample number under semicurtailed inspection. As these plans result in large sample sizes, especially when the serial correlation is high, we suggest new plans called “systematic sampling plans.” The minimum average sample number systematic plans that satisfy the probability requirements are constructed. Our algorithm uses some simple recurrence relations to compute the required acceptance probabilities. The optimal systematic plans require much smaller sample sizes and acceptance numbers, compared to the sequential plans. However, they need larger production runs to make a decision. Tables for choosing appropriate sequential and systematic plans are provided. The problem of selecting the best systematic sampling plan is also addressed. The operating characteristic curves of some of the sequential and the systematic plans are compared, and are observed to be almost identical. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48: 451–467, 2001
A single‐period inventory placement problem for a serial supply chain
Authors: Chung Chia‐Shin , Flynn James , Stalinski Piotr 
Published: August 2002

AbstractThis article addresses the inventory placement problem in a serial supply chain facing a stochastic demand for a single planning period. All customer demand is served from stage 1, where the product is stored in its final form. If the demand exceeds the supply at stage 1, then stage 1 is resupplied from stocks held at the upstream stages 2 through N, where the product may be stored in finished form or as raw materials or subassemblies. All stocking decisions are made before the demand occurs. The demand is nonnegative and continuous with a known probability distribution, and the purchasing, holding, shipping, processing, and shortage costs are proportional. There are no fixed costs. All unsatisfied demand is lost. The objective is to select the stock quantities that should be placed different stages so as to maximize the expected profit. Under reasonable cost assumptions, this leads to a convex constrained optimization problem. We characterize the properties of the optimal solution and propose an effective algorithm for its computation. For the case of normal demands, the calculations can be done on a spreadsheet. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48:506–517, 2001