bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic susceptibility quantification for arbitrarily shaped objects in inhomogeneous fields
Authors: Li Lin 
Published: October 2004

AbstractMagnetic susceptibility measurement has wide‐ranging applications in MR technical development and medical applications. A general susceptibility quantitation method for objects of arbitrary shapes in inhomogeneous magnetic fields is presented in this study. Based on the mean value properties of magnetic fields, the polarizing magnetic field at the location of interest inside an object can be exactly obtained in situ from the field values on a spherical surface enclosing the object. With numerical computation of the self‐demagnetizing field and correction of contact shifts, magnetic susceptibilities were quantitatively measured for CuSO4 phantoms based on their MR gradient echo phase maps. Magn Reson Med 46:907–916, 2001. © 2001 Wiley‐Liss, Inc.
Molecular factors that determine Curie spin relaxation in dysprosium complexes†
Authors: Caravan P. , Greenfield M.T. , Bulte J.W.M. 
Published: October 2004

AbstractDysprosium complexes can serve as transverse relaxation (T2) agents for water protons through chemical exchange and the Curie spin relaxation mechanism. Using a pair of matched dysprosium(III) complexes, Dy‐L1 (contains one inner‐sphere water) and Dy‐L2 (no inner‐sphere water), it is shown that the transverse relaxation of bulk water is predominantly an inner‐sphere effect. The kinetics of water exchange at Dy‐L1 were determined by 17O NMR. Proton transverse relaxation by Dy‐L1 at high fields is governed primarily through a large chemical shift difference between free and bound water. Dy‐L1 forms a noncovalent adduct with human serum albumin which dramatically lengthens the rotational correlation time, τR, causing the dipole–dipole component of the Curie spin mechanism to become significant and transverse relaxivity to increase by 3–8 times that of the unbound chelate. These findings aid in the design of new molecular species as efficient r2 agents. Magn Reson Med 46:917–922, 2001. Published 2001 Wiley‐Liss, Inc.
Ex vivo MR microimaging of neuronal damage after kainate‐induced status epilepticus in rat: Correlation with quantitative histology
Authors: Pirttilä Tiina‐Riikka M. , Pitkänen Asla , Tuunanen Jarkko , Kauppinen Risto A. 
Published: October 2004

AbstractThe present study was designed to investigate whether T2‐weighted signal changes obtained by microimaging of paraformaldehyde‐fixed brain correlate with the histologically quantified damage in a model of status epilepticus (SE) induced by kainic acid in the rat. Animals were killed at several time points up to 8 weeks after a single intraperitoneal kainate (KA) injection (9 mg/kg). Perfusion‐fixed brains were embedded in gelatin for MR microimaging at 9.4T. After the MRI analysis, the gelatin was removed and the brains were cryoprotected and processed for quantitative histology. Severity of neuronal damage and gliosis were assessed from thionin‐stained serial sections. Correlative analysis of microimaging and histology data was done in the hippocampus, amygdala, parietal rhinal cortex (PaRH), piriform cortex (Pir), and entorhinal cortex. The relative signal intensities in T2‐weighted images correlate with the severity of neuronal damage in the matched histological sections (correlation coefficients of 0.752–0.826). Our data show that MR microimaging ex vivo detects the degree of neuronal damage and its anatomical distribution after KA‐induced SE, thus providing a useful tool for detecting the dynamics of progressive neuronal damage after prolonged seizures. Magn Reson Med 46:946–954, 2001. © 2001 Wiley‐Liss, Inc.
High‐resolution intracranial and cervical MRA at 3.0T: Technical considerations and initial experience
Authors: Bernstein Matt A. , Huston John , Lin Chen , Gibbs Gordon F. , Felmlee Joel P. 
Published: October 2004

AbstractInitial experience with intracranial and cervical MRA at 3.0T is reported. Phantom measurements (corrected for relaxation effects) show S/N (3.0T) = 2.14 ± 0.08 × S/N (1.5T) in identical‐geometry head coils. A 3.0T 3DTOF intracranial imaging protocol with higher‐order autoshimming was developed and compared to 1.5T 3DTOF in 12 patients with aneurysms. A comparison by two radiologists showed the 3.0T to be significantly better (P < 0.001) for visualization of the aneurysms. The feasibility of cervical and intracranial contrast enhanced MR angiography (CEMRA) at 3.0T is also examined. The relaxivity of the gadolinium contrast agent decreases by only about 4–7% when the field strength is increased from 1.5 to 3.0T. Cervical 3.0T CEMRA was obtained in eight patients, two of whom had 1.5T studies available for direct comparison. Image comparison suggests 3.0T to be a favorable field strength for cervical CEMRA. Voxel volumes of 0.62–0.73 mm3 (not including zero‐filling) were readily achieved at 3.0T with the use of a single‐channel transmit‐receive head or cervical coil, a 25 mL bolus of gadoteridol, and a 3D pulse sequence with a 66% sampling efficiency. This spatial resolution allowed visualization of intracranial aneurysms, carotid dissections, and atherosclerotic disease including ulcerations. Potential drawbacks of 3.0T MRA are increased SAR and T dephasing compared to 1.5T. Image comparison suggests signal loss due to T dephasing will not be substantially more problematic than at 1.5T. The dependence of RF power deposition on TR for CEMRA is calculated and discussed. Magn Reson Med 46:955–962, 2001. © 2001 Wiley‐Liss, Inc.
Arterial spin labeling in combination with a look‐locker sampling strategy: Inflow turbo‐sampling EPI‐FAIR (ITS‐FAIR)
Authors: Günther Matthias , Bock Michael , Schad Lothar R. 
Published: October 2004

AbstractArterial spin labeling (ASL) permits quantification of tissue perfusion without the use of MR contrast agents. With standard ASL techniques such as flow‐sensitive alternating inversion recovery (FAIR) the signal from arterial blood is measured at a fixed inversion delay after magnetic labeling. As no image information is sampled during this delay, FAIR measurements are inefficient and time‐consuming. In this work the FAIR preparation was combined with a Look‐Locker acquisition to sample not one but a series of images after each labeling pulse. This new method allows monitoring of the temporal dynamics of blood inflow. To quantify perfusion, a theoretical model for the signal dynamics during the Look‐Locker readout was developed and applied. Also, the imaging parameters of the new ITS‐FAIR technique were optimized using an expression for the variance of the calculated perfusion. For the given scanner hardware the parameters were: temporal resolution 100 ms, 23 images, flip‐angle 25.4°. In a normal volunteer experiment with these parameters an average perfusion value of 48.2 ± 12.1 ml/100 g/min was measured in the brain. With the ability to obtain ITS‐FAIR time series with high temporal resolution arterial transit times in the range of −138 − 1054 ms were measured, where nonphysical negative values were found in voxels containing large vessels. Magn Reson Med 46:974–984, 2001. © 2001 Wiley‐Liss, Inc.
Temperature mapping of frozen tissue using eddy current compensated half excitation RF pulses
Authors: Wansapura Janaka P. , Daniel Bruce L. , Pauly John , Butts Kim 
Published: October 2004

AbstractCryosurgery has been shown to be an effective therapy for prostate cancer. Temperature monitoring throughout the cryosurgical iceball could dramatically improve efficacy, since end temperatures of at least –40°C are required. The results of this study indicate that MR thermometry based on tissue R has the potential to provide this information. Frozen tissue appears as a complete signal void on conventional MRI. Ultrashort echo times (TEs), achievable with half pulse excitation and a short spiral readout, allow frozen tissue to be imaged and MR characteristics to be measured. However, half pulse excitation is highly sensitive to eddy current distortions of the slice‐select gradient. In this work, the effects of eddy currents on the half pulse technique are characterized and methods to overcome these effects are developed. The methods include: 1) eddy current compensated slice‐select gradients, and 2) a correction for the phase shift between the first and second half excitations at the center of the slice. The effectiveness of these methods is demonstrated in R maps calculated within the frozen region during cryoablation. Magn Reson Med 46:985–992, 2001. © 2001 Wiley‐Liss, Inc.
Pulmonary MR angiography with contrast agent at 4 Tesla: A preliminary result
Authors: Uematsu Hidemasa , Dougherty Lawrence , Takahashi Masaya , Ohno Yoshiharu , Nakatsu Masashi , Song Hee Kwon , Ferrari Victor A. , Gefter Warren B. , Schnall Mitchell D. , Hatabu Hiroto 
Published: October 2004

AbstractIn this study, pulmonary MR angiography (MRA) using a tailored coil at 4 Tesla in conjunction with an intravenous injection of contrast agent is described. Three‐dimensional gradient‐echo images were obtained during the intravenous injection of 0.05, 0.1, and 0.2 mmol/kg body weight of gadodiamide to investigate the signal enhancement effect of the contrast agent in pulmonary arteries qualitatively and quantitatively. In the qualitative analysis, the subsegmental branches were visualized on every dose. In the quantitative analysis, the average contrast‐to‐noise ratios (CNRs) of the main pulmonary arteries increased in a dose‐dependent manner. However, the CNRs of segmental arteries did not increase as the dose of contrast agent increased, as observed at 1.5 Tesla MRI. These observations demonstrate the feasibility of delineating the pulmonary vasculature using a contrast agent; however, our results also suggest possible high‐field‐related disabilities that need to be overcome before high‐field (≥4 Tesla) MRI can be used to full advantage. Magn Reson Med 46:1028–1030, 2001. © 2001 Wiley‐Liss, Inc.
Tracking local volume 3D‐echo‐planar coronary artery imaging
Authors: Gatehouse P.D. , Keegan J. , Yang G.Z. , Mohiaddin R.H. , Firmin D.N. 
Published: October 2004

AbstractAiming for robust high‐resolution free respiration coronary artery imaging, localized tracking volume selective 3D‐EPI at spatial resolution 1.25 × 1.25 × 3 mm and temporal resolution 65 ms was evaluated in 14 normal subjects. Subject‐specific motion tracking factors were measured between diaphragm navigator and coronary artery in S‐I and A‐P directions. Imaging was repeated with and without tracking, accepting 128 cardiac cycles over a 20‐mm range from free breathing. Reference images with minimal respiratory motion (5‐mm range) used LED‐guided multiple breathholds. Depending on accurate motion measurement, coronary arteries were imaged with tracking, in a 20‐mm range of free breathing, with increased scan efficiency but without significant loss of image quality compared to multiple breathhold imaging. Magn Reson Med 46:1031–1036, 2001. © 2001 Wiley‐Liss, Inc.
MR angiography using spin‐lock flow tagging
Authors: Azhari Haim , McKenzie Charles A. , Edelman Robert R. 
Published: October 2004

AbstractA method for MR angiography using an RF labeling technique is suggested. The method utilizes a slice‐selective spin‐lock pulse sequence for tagging the spins of inflowing blood. The pulse sequence begins with a spatially selective 90°x RF pulse, followed by a nonselective composite locking pulse of 135°y − n[360°y]‐135°y and by a 90°‐x pulse. A spoiler gradient is then applied. A rapid imaging stage, which yields a T1ρ‐weighted signal from the tagged spins, completes the sequence. Untagged spins are thoroughly dephased and consequently suppressed in the image. Thus, contrast is obtained without an injection of a contrast material or image subtraction. Furthermore, the flow of the tagged bolus can be visualized. The sequence was implemented on phantoms and on human volunteers using a 1.5T scanner. The results indicate the feasibility of the suggested sequence. Magn Reson Med 46:1041–1044, 2001. © 2001 Wiley‐Liss, Inc.
Patterns in spatial point locations: Local indicators of spatial association in a minefield with clutter
Authors: Cressie Noel , Collins Linda Brant 
Published: October 2004

AbstractThe problem of detecting a minefield in the presence of clutter can be abstracted to that of detecting a spatial pattern within a set of point locations. The point locations are superpositions of several patterns, one of which corresponds to mines. In contrast to previous articles that take a formal, model‐based approach, this article proposes a statistical methodology that is distinctly exploratory. Each point location is considered separately, and its contributions to a global measure of spatial distances between locations are featured. Different patterns and unusual points can be more easily identified on the new scale. Both minefield data and simulated point patterns demonstrate the power of the method. © 2001 John Wiley & Sons, Inc., Naval Research Logistics 48:333–347, 2001
An application of yield management for Internet Service Providers
Authors: Nair Suresh K. , Bapna Ravi 
Published: October 2004

AbstractIn this paper we study strategies for better utilizing the network capacity of Internet Service Providers (ISPs) when they are faced with stochastic and dynamic arrivals and departures of customers attempting to log‐on or log‐off, respectively. We propose a method in which, depending on the number of modems available, and the arrival and departure rates of different classes of customers, a decision is made whether to accept or reject a log‐on request. The problem is formulated as a continuous time Markov Decision Process for which optimal policies can be readily derived using techniques such as value iteration. This decision maximizes the discounted value to ISPs while improving service levels for higher class customers. The methodology is similar to yield management techniques successfully used in airlines, hotels, etc. However, there are sufficient differences, such as no predefined time horizon or reservations, that make this model interesting to pursue and challenging. This work was completed in collaboration with one of the largest ISPs in Connecticut. The problem is topical, and approaches such as those proposed here are sought by users. © 2001 John Wiley & Sons, Inc., Naval Research Logistics 48:348–362, 2001
The NBUL class of life distribution and replacement policy comparisons
Authors: Yue Dequan , Cao Jinhua 
Published: October 2004

AbstractLet X and Xτ denote the lifetime and the residual life at age τ of a system, respectively. X is said to be a NBUL random variable if Xτ is smaller than X in Laplace order, i.e., Xτ ≤L X. We obtain some characterizations for this class of life distribution by means of the lifetime of a series system and the residual life at random time. We also discuss preservation properties for this class of life distribution under shock models. Finally, under the assumption that the lifetimes have the NBUL property, we make stochastic comparisons between some basic replacement policies. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48: 578–591, 2001.
An integer programming model for the weekly tour scheduling problem
Authors: Çezik Tolga , Günlük Oktay , Luss Hanan 
Published: October 2004

AbstractWe study a workforce planning and scheduling problem in which weekly tours of agents must be designed. Our motivation for this study comes from a call center application where agents serve customers in response to incoming phone calls. Similar to many other applications in the services industry, the demand for service in call centers varies significantly within a day and among days of the week. In our model, a weekly tour of an agent consists of five daily shifts and two days off, where daily shifts within a tour may be different from each other. The starting times of any two consecutive shifts, however, may not differ by more than a specified bound. Furthermore, a tour must also satisfy constraints regarding the days off, for example, it may be required that one of the days off is on a weekend day. The objective is to determine a collection of weekly tours that satisfy the demand for agents' services, while minimizing the total labor cost of the workforce. We describe an integer programming model where a weekly tour is obtained by combining seven daily shift scheduling models and days‐off constraints in a network flow framework. The model is flexible and can accommodate different daily models with varying levels of detail. It readily handles different days‐off rules and constraints regarding start time differentials in consecutive days. Computational results are also presented. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48: 607–624, 2001.
On‐line algorithms for minimizing makespan on batch processing machines
Authors: Zhang Gouchuan , Cai Xiaoqiang , Wong C.K. 
Published: October 2004

AbstractWe consider problem of scheduling jobs on‐line on batch processing machines with dynamic job arrivals to minimize makespan. A batch machine can handle up to B jobs simultaneously. The jobs that are processed together from a batch, and all jobs in a batch start and complete at the same time. The processing time of a batch is given by the longest processing time of any job in the batch. Each job becomes available at its arrival time, which is unknown in advance, and its processing time becomes known upon its arrival. In the first part of this paper, we address the single batch processing machine scheduling problem. First we deal with two variants: the unbounded model where B is sufficiently large and the bounded model where jobs have two distinct arrival times. For both variants, we provide on‐line algorithms with worst‐case ratio
$(\sqrt{5}+1)/2$
(the inverse of the Golden ratio) and prove that these results are the best possible. Furthermore, we generalize our algorithms to the general case and show a worst‐case ratio of 2. We then consider the unbounded case for parallel batch processing machine scheduling. Lower bound are given, and two on‐line algorithms are presented. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48: 241–258, 2001
Convergence of the Galerkin approximation of a degenerate evolution problem in electrocardiology
Authors: Sanfelici Simona 
Published: October 2004

AbstractIn this work we consider the reaction‐diffusion system of FitzHugh‐Nagumo type describing the behavior of the electrical conduction in an anisotropic cardiac muscle. The analysis of the Galerkin semidiscrete space approximation to this system is approached by means of a suitable variational formulation in the framework of abstract degenerate evolution equations.The main results concern convergence analysis and a priori stability estimates for the semidiscrete solution. These abstract results are then applied to the cardiac problem and for the finite element Galerkin approximation we achieve optimal order convergence. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 218–240, 2002; DOI 10.1002/num.1000
Decision Aiding, Not Dispute Resolution: Creating Insights through Structured Environmental Decisions
Authors: Gregory Robin , McDaniels Tim , Fields Daryl 
Published: October 2004

AbstractPublic participation in environmental decisions has become commonplace. A favored model for public input is to use the tools of dispute resolution to seek consensus among members of a multi‐party stakeholder group. The authors believe that a focus on dispute resolution and consensus building can pose impediments to the creation of insights for decisionmakers and lead to the adoption of inferior policy choices. Instead, they advocate an alternative approach to stakeholder participation characterized as “decision aiding” through a structured process based on constructive, multi‐attribute techniques and value‐focused thinking. In this paper some of the major difficulties posed by a dispute‐resolution approach are articulated, the principles of a decision‐aiding process reviewed, and this alternative approach illustrated by describing a stakeholder consultation involving water‐use planning for a hydroelectric facility on the Alouette River in British Columbia, Canada. © 2001 by the Association for Public Policy Analysis and Management.
Testing a Financial Incentive to Promote Re‐employment among Displaced Workers: The Canadian Earnings Supplement Project (ESP)
Authors: Bloom Howard S. , Schwartz Saul , Lui‐Gurr Susanna , Lee Suk‐Won , Peng Jason , Bancroft Wendy 
Published: October 2004

AbstractThis article presents findings from a randomized experiment conducted in four Canadian provinces to measure the effects of a generous financial incentive that was designed to promote rapid re‐employment among workers who were displaced from their jobs by changing economic conditions. The incentive tested was an earnings supplement which, for as long as 2 years and as much as $250 weekly, would replace 75 percent of the earnings loss incurred by displaced workers who took a new lower‐paying full‐time job within six months of receiving a supplement offer. Findings from the experiment indicate that although persons offered the supplement understood its terms and conditions, only 2 out of 10 actually received supplement payments. Furthermore, the supplement offer had little effect on job‐search behavior, employment prospects, or receipt of unemployment insurance. Nevertheless, persons who received supplement payments benefited from them substantially. On average, they received payments for 64 weeks, totaling $8,705. © 2001 by the Association for Public Policy Analysis and Management.
What Research Can Tell Policymakers about School Choice
Authors: Teske Paul , Schneider Mark 
Published: October 2004

AbstractAmerican school systems have implemented several different kinds of school choice policies, and most of them
are controversial. The research literature on various forms of school choice reveals some areas of consensus,
but other areas where the results of studies diverge. Consensus results show that parents are more satisfied
with choice, that they report using academic preferences to make choices, and that they tend to be more involved
with their child's education as a consequence of choice. There is some, though mixed, evidence of improved
test scores for children involved with various forms of choice. Actual parental use of choice and gathering of
information, however, show some evidence of stratification, not always by race or income, but often by the level
of parental involvement and motivation. These results provide considerable evidence about the effects on
students whose parents have made an active choice, but more policy research is needed on the effects of
competition on students in schools that have not been chosen. © 2001 by the Association for Public Policy
Analysis and Management.
Poverty across the Life Cycle: Evidence from the PSID
Authors: Rank Mark R. , Hirschl Thomas A. 
Published: October 2004

AbstractThe likelihood of experiencing poverty at some point during the adult life cycle is estimated. These
probabilities are derived through a set of life tables built upon 25 waves of data from the Panel Study of
Income Dynamics, and represent an alternative approach to studying poverty than prior empirical studies. Life
table analyses are divided into early adulthood (ages 20–40), middle adulthood (ages
40–60),and later adulthood (ages 60–80). The findings indicate that individuals
within the sample face a significant risk of poverty at some point during their adult lives, particularly during
the early and later stages of adulthood. Duration tends to be relatively short (1 or 2 years), but
once poverty occurs, it is likely to occur again. Results also reveal the profound life‐course effect
that race, education, and gender have upon the likelihood of encountering poverty during the adult years.
Several policy and research implications are discussed. © 2001 by the Association for Public Policy
Analysis and Management.