bluuebunny/crossref_metadata_2025_split huggingface dataset:
Apparent diffusion of water, ions, and small molecules in the Xenopus oocyte is consistent with Brownian displacement
Authors: Sehy Jonathan V. , Ackerman Joseph J.H. , Neil Jeffrey J. 
Published: September 2002

AbstractThe incoherent displacement of water in living tissues is of considerable interest because of the widespread use of diffusion‐weighted MRI, for which image contrast is based on the water apparent diffusion coefficient (ADC). It has been hypothesized that the decrease in water ADC associated with brain injury is primarily due to a reduction in the ADC of water in the intracellular space. Xenopus oocytes permit direct measurement of ADC values for intracellular molecules, thereby providing insight into the nature of intracellular motion. In this study, the measured ADC values of small molecules and ions are shown to be primarily size‐dependent, indicating that intracellular water motion in the oocyte is mainly Brownian displacement with little or no role for cytoplasmic streaming. Further, intracellular water ADC values show no dependence on diffusion time over a broad range (3.4–100 ms), suggesting that barriers to displacement are finely spaced (≤ 2–3 μm). The water diffusion shows some small anisotropy, suggesting that the cell has structure, giving water displacement a directional preference. The calculated intracellular apparent viscosity, which reflects the combined effects of barriers to motion, intermolecular binding, and fluid phase viscosity was 2.07 ± 0.09 cP. Magn Reson Med 48:42–51, 2002. © 2002 Wiley‐Liss, Inc.
Effect of adrenergic stimulation on Rb+ uptake in normal and ischemic areas of isolated pig hearts: 87Rb MRI study
Authors: Kupriyanov V.V. , Xiang B. , Sun J. , Jilkina O. 
Published: September 2002

AbstractThe role of adrenergic stimulation in Rb+ uptake in normal and ischemic areas of pig hearts was investigated using an agonist (dobutamine) and an antagonist (S‐propranolol). The left anterior descending artery (LAD) in isolated pig hearts was cannulated to maintain adequate perfusion of the LAD bed (2.2–2.8 ml/min/g). Rb+ loading was initiated by switching perfusion to Rb+‐containing Krebs‐Henseleit (KH) buffer in the presence of 0.1 μM dobutamine, 0.5 μM propranolol, or no drug (control), and the LAD flow was reduced to 10% of the baseline for 120 min. The flow through the LAD was then restored to normal and the drugs were removed. In all groups the rate of Rb+ uptake obtained from serial 87Rb images was severely depressed in the ischemic anterior wall relative to that in the normal posterior wall. Dobutamine increased the rate of Rb+ uptake in the posterior wall (6.3% ± 1.4% vs. 2.5% ± 0.25% per minute in control) and did not affect the rate in the anterior wall (0.86% ± 0.40% vs. 1.14% ± 0.19% per minute in control). Propranolol did not affect Rb+ uptake in either of these areas. We conclude that the stimulation of Rb+ uptake by dobutamine is related to activation of Na+/K+ ATPase and passive Na+ influx in normal tissue. The lack of any effect of propranolol implies a low level of endogenous norepinephrine during low‐flow (LF) ischemia. Magn Reson Med 48:15–20, 2002. © 2002 Wiley‐Liss, Inc.
Multishot 3D slice‐select tailored RF pulses for MRI
Authors: Stenger V. Andrew , Boada Fernando E. , Noll Douglas C. 
Published: September 2002

AbstractA multishot 3D slice‐select tailored RF pulse method is presented for the excitation of slice profiles with arbitrary resolution. This method is derived from the linearity of the small tip angle approximation, allowing for the decomposition of small tip angle tailored RF pulses into separate excitations. The final image is created by complex summation of the images acquired from the individual excitations. This technique overcomes the limitation of requiring a long pulse to excite thin slices with adequate resolution. This has implications in applications including T‐weighted functional MRI in brain regions corrupted by intravoxel dephasing artifacts due to susceptibility variations. Simulations, phantom experiments, and human brain images are presented. It is demonstrated that at most four shots of 40 ms pulse length are needed to excite a 5 mm‐thick slice in the brain with reduced susceptibility artifacts at 3T. Magn Reson Med 48:157–165, 2002. © 2002 Wiley‐Liss, Inc.
On the application of a non‐CPMG single‐shot fast spin‐echo sequence to diffusion tensor MRI of the human brain
Authors: Bastin Mark E. , Le Roux Patrick 
Published: September 2002

AbstractThe strong sensitivity of Carr‐Purcell‐Meiboom‐Gill (CPMG) fast spin‐echo (FSE) sequences, such as rapid acquisition with relaxation enhancement (RARE), to the phase of the prepared transverse magnetization means that artifact‐free single‐shot diffusion‐weighted images can currently only be obtained with a 30–50% reduction in the signal‐to‐noise ratio (SNR). However, this phase sensitivity and signal loss can be addressed in FSE sequences that use quadratic phase modulation of the radiofrequency (RF) refocusing pulses to generate a sustained train of stable echoes. Here the first application of such a non‐CPMG single‐shot FSE (ssFSE) sequence to diffusion tensor MR imaging (DT‐MRI) of the human brain is described. This approach provides high SNR diffusion‐weighted images that have little or no susceptibility to poor B0 magnetic field homogeneity and the strong eddy currents typically present in DT‐MRI experiments. Magn Reson Med 48:6–14, 2002. © 2002 Wiley‐Liss, Inc.
Simultaneous echo refocusing in EPI
Authors: Feinberg David A. , Reese Timothy G. , Wedeen Van J. 
Published: September 2002

AbstractA method to encode multiple two‐dimensional Fourier transform (2D FT) images within a single echo train is presented. This new method, simultaneous echo refocusing (SER), is a departure from prior echo planar image (EPI) sequences which use repeated single‐shot echo trains for multislice imaging. SER simultaneously acquires multiple slices in a single‐shot echo train utilizing a shared refocusing process. The SER technique acquires data faster than conventional multislice EPI since it uses fewer gradient switchings and fewer preparation pulses such as diffusion gradients. SER introduces a new capability to simultaneously record multiple spatially separated sources of physiologic information in subsecond image acquisitions, which enables several applications that are dependent on temporal coherence in MRI data including velocity vector field mapping and brain activation mapping. Magn Reson Med 48:1–5, 2002. © 2002 Wiley‐Liss, Inc.
Numerical study of boundary conditions for solute transport through a porous medium
Authors: Peters Glen P. , Smith David W. 
Published: September 2002

AbstractA transition region may be defined as a region of rapid change in medium properties about the interface between two porous media or at the interface between a porous medium and a reservoir. Modelling the transition region between different porous media can assist in the selection of the most appropriate boundary conditions for the standard advection–dispersion equation (ADE). An advantage of modelling the transition region is that it removes the need for explicitly defining boundary conditions, though boundary conditions may be recovered as limiting cases. As the width of a transition region is reduced, the solution of the transition region model (TR model) becomes equivalent to the solution of the standard ADE model with correct boundary conditions. In this paper numerical simulations using the TR model are employed to select the most appropriate boundary conditions for the standard ADE under a variety of configurations and conditions. It is shown that at the inlet boundary between a reservoir and porous medium, continuity of solute mass flux should be used as the boundary condition. At the boundary interface between two porous media both continuity of solute concentration and solute mass flux should be used. Finally, in a finite porous medium where the solute is allowed to advect freely from the exit point, both continuity of solute concentration and solute mass flux should be used as the outlet boundary condition. The findings made here are discussed with reference to a detailed review of previous relevant theoretical and experimental observations. Copyright © 2001 John Wiley & Sons, Ltd.
Dynamic response of soft poroelastic bed to linear water waves—a boundary layer correction approach
Authors: Hsieh Ping‐Cheng , Huang Liang‐Hsiung , Wang Tsan‐Wen 
Published: September 2002

AbstractAccording to Chen et al. (Journal of Engineering Mechanics, ASCE 1997; 123(10):1041–1049.) a boundary layer exists within the porous bed and near the homogeneous‐water/porous‐bed interface when oscillatory water waves propagate over a soft poroelastic bed. This boundary layer makes the evaluation of the second kind of longitudinal wave inside the soft poroelastic bed very inaccurate. In this study, the boundary layer correction approach for the poroelastic bed is applied to the boundary value problem of linear oscillatory water waves propagating over a soft poroelastic bed. After the analyses of length scale and order of magnitude of physical variables are done, a perturbation expansion for the boundary layer correction approach based on two small parameters is proposed and solved. The solutions are carried out for the first and third kind of waves throughout the entire domain. The second kind of wave which disappears outside the boundary layer is solved systematically inside the boundary layer. The results are compared with the linear wave solutions of Huang and Song (Journal of Engineering Mechanics, ASCE 1993; 119:1003–1020.) to confirm the validity. Moreover, a simplified boundary layer correction formulation which is expected to be very useful in numerical computation is also proposed. Copyright © 2001 John Wiley & Sons, Ltd.
Generating Pareto‐optimal boundary points in multiparty negotiations using constraint proposal method
Authors: Heiskanen Pirja 
Published: September 2002

AbstractIn this paper a constraint proposal method is developed for computing Pareto‐optimal solutions in multiparty negotiations over continuous issues. Constraint proposal methods have been previously studied in a case where the decision set is unconstrained. Here we extend the method to situations with a constrained decision set. In the method the computation of the Pareto‐optimal solutions is decentralized so that the DMs do not have to know each others' value functions. During the procedure they have to indicate their optimal solutions on different sets of linear constraints. When the optimal solutions coincide, the common optimum is a candidate for a Pareto‐optimal point. The constraint proposal method can be used to generate either one Pareto‐optimal solution dominating the status quo solution or several Pareto‐optimal solutions. In latter case a distributive negotiation among the efficient points can be carried out afterwards. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48: 210–225, 2001
Mobility prediction and routing inad hocwireless networks
Authors: Su William , Lee Sung‐Ju , Gerla Mario 
Published: September 2002

AbstractBy exploiting non‐random behaviors for the mobility patterns that mobile users exhibit, we can predict the future state of network topology and perform route reconstruction proactively in a timely manner. Moreover, by using the predicted information on the network topology, we can eliminate transmissions of control packets otherwise needed to reconstruct the route and thus reduce overhead. In this paper, we propose various schemes to improve routing protocol performances by using mobility prediction. We then evaluate the effectiveness of using mobility prediction via simulation. Copyright © 2001 John Wiley & Sons, Ltd.
Enhancing TCP performance with a load‐adaptive RED mechanism
Authors: Aweya James , Ouellette Michel , Montuno Delfin Y. , Chapman Alan 
Published: September 2002

AbstractThis paper describes a technique for enhancing the effectiveness of RED by dynamically changing the threshold settings as the number of connections (and system load) changes. Using this technique, routers and switches can effectively control packet losses and TCP timeouts while maintaining high link utilization. Copyright © 2001 John Wiley & Sons, Ltd.
Network optimization with stochastic traffic flows
Authors: Liu Xian 
Published: September 2002

AbstractConventional management optimization models are being challenged by the evolution of electronic and optical networks and it is necessary to incorporate the stochastic effect of traffic flows into network models. This paper introduces the stochastic programming (SP) methodology to characterize the stochastic traffic. Two network models, capacity assignment and flow assignment, are proposed. One of the SP approaches, the Wait‐and‐See method, is integrated into the presented models. Simulation results are reported. Copyright © 2002 John Wiley & Sons, Ltd.
Postembryonic proliferation in the spiny lobster antennular epithelium: Rate of genesis of olfactory receptor neurons is dependent on molt stage
Authors: Harrison Paul J.H. , Cate Holly S. , Swanson Eric S. , Derby Charles D. 
Published: September 2002

AbstractOlfactory systems undergo continuous growth and turnover in many animals. Many decapod crustaceans, such as lobsters and crayfish, have indeterminate growth, and in these animals, turnover of both peripheral and central components of the olfactory system occurs continuously throughout life. In this study, we examine the dynamics of olfactory receptor neuron (ORN) proliferation in the antennule of the Caribbean spiny lobster, Panulirus argus, using in vivo incorporation of the cell proliferation marker BrdU. We show that addition of ORNs occurs in a “proximal proliferation zone” (PPZ), which exists on the proximo‐lateral margin of the existing ORN population. The PPZ is spatially and temporally dynamic in that it travels as a wave in the proximal and lateral directions in the antennule. This wave results in continuous addition of ORNs throughout the molt cycle. The rate of proliferation, as measured by the size and shape of the PPZ, changes depending on the animal's molt stage. The rate is highest during premolt and lowest during intermolt. ORNs are the most prominent cell‐type produced in the PPZ, but other cell types, including glia, are also produced. Patches of proliferating epithelial cells occur immediately proximal to the PPZ, suggesting that neuronal and glial precursors reside in this region. Possible mechanisms for peripheral and central modulation of ORN development are discussed. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 51–66, 2001
RISK‐1: A novel MAPK homologue in axoplasm that is activated and retrogradely transported after nerve injury
Authors: Sung Ying Ju , Povelones Michael , Ambron Richard T. 
Published: September 2002

AbstractSensory neurons (SNs) of Aplysia are widely used to study the molecular correlates of learning. Among these is the activation of an Aplysia (ap) MAPK that phosphorylates the transcription factor apC/EBPβ. Because crushing the axons of the SNs induces changes similar to learning, we tested the hypothesis that apMAPK is a point of convergence on the pathways for learning and injury. One event in common is long‐term hyperexcitability (LTH), and LTH was induced in the SNs after intrasomatic injection of active vertebrate extracellular signal‐regulated kinase 1 (ERK1; as an apMAPK surrogate). Nerve crush activated an axoplasmic kinase at the site of injury that phosphorylated apC/EBPβ. Surprisingly, this was not apMAPK, but a kinase that was recognized by antibodies to vertebrate ERKs and to doubly phosphorylated, activated ERKs. The activated kinase was transported to the cell body and nucleus and its arrival was concurrent with an injury‐induced increase in apC/EBPβ mRNA and protein. We call this retrogradely transported kinase RISK‐1. RISK‐1 initiated the binding of apC/EBPβ to the ERE enhancer site in vitro and an increase in ERE‐binding was detected in injured neurons containing active RISK‐1. Thus, Aplysia neurons contain two MAPK homologues, one of which is a late acting retrogradely transported injury signal. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 67–79, 2001
Some observations on the l2 convergence of the additive Schwarz preconditioned GMRES method
Authors: Cai Xiao‐Chuan , Zou Jun 
Published: September 2002

AbstractAdditive Schwarz preconditioned GMRES is a powerful method for solving large sparse linear systems of equations on parallel computers. The algorithm is often implemented in the Euclidean norm, or the discrete l2 norm, however, the optimal convergence result is available only in the energy norm (or the equivalent Sobolev H1 norm). Very little progress has been made in the theoretical understanding of the l2 behaviour of this very successful algorithm. To add to the difficulty in developing a full l2 theory, in this note, we construct explicit examples and show that the optimal convergence of additive Schwarz preconditioned GMRES in l2 cannot be obtained using the existing GMRES theory. More precisely speaking, we show that the symmetric part of the preconditioned matrix, which plays a role in the Eisenstat–Elman–Schultz theory, has at least one negative eigenvalue, and we show that the condition number of the best possible eigenmatrix that diagonalizes the preconditioned matrix, key to the Saad–Schultz theory, is bounded from both above and below by constants multiplied by h−1/2. Here h is the finite element mesh size. The results presented in this paper are mostly negative, but we believe that the techniques used in our proofs may have wide applications in the further development of the l2 convergence theory and in other areas of domain decomposition methods. Copyright © 2002 John Wiley & Sons, Ltd.
Some recent issues in computational failure mechanics
Authors: Borst René de 
Published: September 2002

AbstractAn overview is given of some recent developments in computational modelling of localization and failure phenomena in solids. Cohesive‐zone models are considered as well as enrichment of continua using gradients in space and in time. The latter models are applied to static instabilities as well as to propagative instabilities. The determination of the additional parameters that emerge in gradient continua is treated and attention is paid to the spatial resolution that is necessary to properly capture bands of localized deformation. Finally, the impact is considered which imperfection patterns may have on the failure mode. Copyright © 2001 John Wiley & Sons, Ltd.
A micro–macro and parallel computational strategy for highly heterogeneous structures
Authors: Ladevèze P. , Loiseau O. , Dureisseix D. 
Published: September 2002

AbstractA new micro–macro computational strategy is proposed for the analysis of structures which are described up to the micro level, such as composite structures. The description of micro and macro quantities is performed on the interface arising from the decomposition of the structure into an assembly of substructures and interfaces. A traction‐based version of the micro–macro strategy is described and the influence of the numerical parameters as well as the performance of the approach are discussed. Copyright © 2001 John Wiley & Sons, Ltd.
A calcium channel blocker nicardipine protects neurons from zinc‐induced toxicity in rat hippocampus
Authors: Demir Şerif , Bağirici Faruk , Marangoz Cafer 
Published: September 2002

AbstractThe neurotoxicity is an important problem in medicine. The present study was designed to investigate the changes in pyramidal cell density of rat hippocampus after intracortical zinc sulphate (ZnSO4) and calcium channel blocker nicardipine administration. Animals were divided into three groups as control, zinc and zinc+nicardipine groups. Zinc sulphate (500 µg/kg) was injected intracortically into 2 mm lateral of Bregma. The same volume of saline (2µl) was given to the rats belonging to control group. Rats in the third group, zinc + nicardipine were injected in to same injection point.Animal groups were observed for one week. The zinc + nicardipine group received daily nicardipine (10mg/kg/day) for seven days. After a week, the rats were perfused intracardially with neutral formaline. The hippocampal sections were stained with hematoxylen‐eosine. Pyramidal cells per unit length (mm) were counted under light microscope (with 400x magnification). The density of pyramidal cell was found as follows (values presented for each group are belong to right CA1, right CA2, right CA3, left CA1, left CA2, left CA3 respectively): control groups; 126.2 ± 4.5 neuron/mm, 117.3 ± 6.2 neuron/mm, 113.6 ± 4.0 neuron/mm, 129.9 ± 4.0 neuron/mm, 129.8 ± 5.0, 127.7 ± 3.3, zinc groups; 38.3 ± 1.3 neuron/mm, 36.5 ± 1.6 neuron/mm, 34.1 ± 1.2, 35.0 ± 1.4 neuron/mm, 33.9 ± 1.5 neuron/mm, 32.9 ± 1.2 neuron/mm, zinc + nic groups; 87.9 ± 1.4 neuron/mm, 89.9 ± 3.7 neuron/mm, 82.2 ± 2.8 neuron/mm, 91.2 ± 3.8 neuron/mm, 91.9 ± 4.6 neuron/mm, 84.3 ± 4.0 neuron/mm. The differences between groups were found to be statistically significant (p < 0.001).These results suggest that nicardipine considerably reverses the decrease in pyramidal cell density probably caused by zinc administration into the hippocampus of rat. This effect may be due to the prevention of excessive calcium influx and hence the prevention of cell loss. The results also suggest a possible therapeutic role for calcium channel blocker nicardipine in neurodegenerative diseases.
Phosphorylation and inactivation of Bad by GDNF‐activated protein kinase B/Akt in human neuroblastoma cells
Authors: Neff Frauke , Eggert Karla , Schlegel Jürgen 
Published: September 2002

AbstractHere we show, that GDNF activates the endogenous phosphatidylinositol‐3′ kinase (PI3K)/proteinkinase B/Akt (PKB/Akt) signalling pathway and the mitogen activated protein kinase (MAPK) cascade in human neuroblastoma cell line SH‐SY5Y. Consistent with this finding we found a PI3K‐dependent but not MAPK‐dependent binding of phosphorylated Bad proteins to 14‐3‐3 proteins. Our data support the hypothesis that GDNF exerts its neuroprotective effects by activation of the anti‐apoptotic PI3K/Akt signalling pathway and subsequent inactivation of Bad.
Dopamine neurons heterozygous for the Nurr1‐null allele have reduced survival in vitro
Authors: Eells J.B. , Yeung S.K. , Nikodem V.M. 
Published: September 2002

AbstractAlthough Nurr1 is essential for the differentiation of midbrain dopamine neurons, its function in mature dopamine neurons has not been determined. In order to investigate the role of Nurr1 in the survival of dopamine neurons, neurons from the mesencephalon of newborn pups heterozygous for the Nurr1‐null mutation (+/–) or wild‐type (+/+) littermates were grown in culture. Postnatal cultures revealed a significant reduction in the survival and growth of tyrosine hydroxylase immunoreactive (TH‐IR) neurons from Nurr1 +/– pups as early as 1 day in culture despite having normal TH‐IR neuron numbers in vivo. The Nurr1 +/+ and +/– TH‐IR neurons responded to treatment with forskolin, glia cell‐line derived neurotrophic factor and brain‐derived neurotrophic factor, although significantly fewer Nurr +/– TH/IR neurons survived. These data suggest that the loss of a single allele of Nurr1 significantly reduces the survival capacity of postnatal dopamine neurons in vitro without affecting normal development or differentiation.