bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacy of small reconstruction plates in vascularized bone graft mandibular reconstruction
Authors: Farwell D. Gregory , Kezirian Eric J. , Heydt Jennifer L. , Yueh Bevan , Futran Neal D.
Published: June 2006

Background:

Utilization of vascularized bone grafts rigidly fixated with titanium reconstruction plates is the method of choice for reconstruction of segmental mandibular defects. We hypothesized that the use of the newer 2.0‐mm locking reconstruction plate (LRP) is not associated with higher rates of complications when compared with larger, previously used plating systems.

Methods:

A retrospective case series of 184 patients undergoing 185 vascularized bone graft reconstruction procedures of the mandible was conducted.

Results:

There were 37 plate complications. There was no significant difference in complication rates for the 2 most used plate types (14.5% with the 2.0‐mm LRP and 22.2% with the 2.4‐mm LRP).

Conclusions:

Use of the smaller 2.0‐mm LRP was not associated with an increase in the complications of plate fracture, exposure, infection, or nonunion. Because of its lower profile and ease of application, the 2.0‐mm LRP is our plate of choice for mandibular reconstruction. © 2006 Wiley Periodicals, Inc. Head Neck, 2006
Susceptibility‐weighted imaging to visualize blood products and improve tumor contrast in the study of brain masses
Authors: Sehgal Vivek , Delproposto Zachary , Haddar Djamel , Haacke E. Mark , Sloan Andrew E. , Zamorano Lucia J. , Barger Geoffery , Hu Jiani , Xu Yingbiao , Prabhakaran Karthik Praveen , Elangovan Ilaya R. , Neelavalli Jaladhar , Reichenbach Jürgen R.
Published: June 2006

Purpose

To evaluate the diagnostic value of susceptibility‐weighted imaging (SWI) for studying brain masses.

Materials and Methods

SWI is a high‐resolution, three‐dimensional, fully velocity‐compensated gradient‐echo sequence that uses both magnitude and phase data. Custom postprocessing is applied to enhance the contrast in the magnitude images between tissues with different susceptibilities. This sequence was applied to 44 patients (24 males and 20 females, 15–89 years old, mean age = 50.3 years) with brain masses, pre‐ and/or postcontrast, and compared with conventional sequences (T1, T1 postcontrast, T2, proton density (PD), fluid‐attenuated inversion recovery (FLAIR) and diffusion‐weighted imaging (DWI) at 1.5T). Correlation with pathology was obtained in 12 cases. All images were reviewed independently by three radiologists.

Results

In the evaluation of tumor visibility, boundary definition, blood products, venous vasculature, architecture, and edema, SWI gave better information than the standard T1‐weighted postcontrast images in 11%, 14%, 71%, 73%, 63%, and 75% of the data, respectively, in a subgroup of 38 patients. This demonstrates that the information presented by SWI is complementary in nature to that available from conventional methods. On the whole, SWI was much more sensitive for showing blood products and venous vasculature. SWI showed a useful FLAIR‐like contrast and complemented the information obtained by conventional T1 postcontrast sequences regarding the internal architecture of the lesions. Good pathologic correlations were found for blood products as predicted by SWI.

Conclusion

SWI should prove useful for tumor characterization because of its ability to better highlight blood products and venous vasculature and reveal new internal architecture. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Manipulation of image intensity distribution at 7.0 T: Passive RF shimming and focusing with dielectric materials
Authors: Yang Qing X. , Mao Weihua , Wang Jinghua , Smith Michael B. , Lei Hao , Zhang Xiaoliang , Ugurbil Kamil , Chen Wei
Published: June 2006

Purpose

To investigate the effects of high dielectric material padding on RF field distribution in the human head at 7.0 T, and demonstrate the feasibility and effectiveness of RF passive shimming and focusing with such an approach.

Materials and Methods

The intensity distribution changes of gradient‐recalled‐echo (GRE) and spin‐echo (SE) images of a human head acquired with water pads (dielectric constant = 78) placed in specified configurations around the head at 7.0 T were evaluated and compared with computer simulation results using the finite difference time domain (FDTD) method. The contributions to the B1 field distribution change from the displacement current and conductive current of a given configuration of dielectric padding were determined with computer simulations.

Results

MR image intensity distribution in the human head with an RF coil at 7.0 T can be changed drastically by placing water pads around the head. Computer simulations reveal that the high permittivity of water pads results in a strong displacement current that enhances image intensity in the nearby region and alters the intensity distribution of the entire brain.

Conclusion

The image intensity distribution in the human head at ultra‐high field strengths can be effectively manipulated with high permittivity padding. Utilizing this effect, the B1 field inside the human head of a given RF coil can be adjusted to reduce the B1 field inhomogeneity artifact associated with the wave behavior (RF passive shimming) or to locally enhance the signal‐to‐noise ratio (SNR) in targeted regions of interest (ROIs; RF field focusing). J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Importance of perfusion in myocardial viability studies using delayed contrast‐enhanced magnetic resonance imaging
Authors: Hedström Erik , Arheden Håkan , Eriksson Rolf , Johansson Lars , Ahlstrom Håkan , Bjerner Tomas
Published: June 2006

Purpose

To investigate whether an extracellular gadolinium‐(Gd)‐based contrast agent (CA) enters nonperfused myocardium during acute coronary occlusion, and whether nonperfused myocardium presents as hyperintense in delayed contrast‐enhanced (DE) MR images in the absence of CA in that region.

Materials and Methods

The left anterior descending coronary artery (LAD) was occluded for 200 minutes in six pigs. The longitudinal relaxation rate (R1) in blood, perfused myocardium, and nonperfused myocardium was repeatedly measured using a Look‐Locker sequence before and during the first hour after administration of Gd‐DTPA‐BMA.

Results

While blood and perfused myocardium showed a major increase in R1 after CA administration, nonperfused myocardium did not. R1 in nonperfused myocardium was significantly lower than in blood and perfused myocardium during the first hour after CA administration. When the signal from perfused myocardium was nulled, demarcation of the hyperintense nonperfused myocardium was achieved in all of the study animals.

Conclusion

Gd‐DTPA‐BMA does not enter ischemic myocardium within one hour after administration during acute coronary occlusion. The ischemic region with complete absence of CA still appears bright when the signal from perfused myocardium is nulled using inversion‐recovery DE‐MRI. This finding is important for understanding the basic pathophysiology of inversion‐recovery viability imaging, as well as for imaging of acute coronary syndromes. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Phase contrast MR imaging to measure changes in collateral blood flow after stenting of recurrent aortic coarctation: Initial experience
Authors: Pujadas Sandra , Reddy Gautham P. , Weber Oliver , Tan Christopher , Moore Philip , Higgins Charles B.
Published: June 2006

Purpose

To assess the feasibility of using phase contrast magnetic resonance (PC‐MR) imaging to measure the change in collateral blood flow early after stenting of aortic coarctation.

Materials and Methods

A total of 10 consecutive patients with coarctation of the aorta underwent MR imaging, X‐ray angiography, and stent placement. PC‐MR at two sites in the descending aorta was performed before and early after stenting in order to estimate collateral inflow to the descending thoracic aorta. The collateral flow and collateral flow percentage before and after stent placement were compared.

Results

Before stenting, the mean proximal aortic flow = 43.9 ± 14.6 mL/second; mean distal flow = 54.2 ± 10 mL/second; collateral flow = 10.2 ± 6.8 mL/second; and collateral flow percentage = 30.1 ± 27.9%. After stenting, the mean proximal aortic flow = 62.1 ± 17.9 mL/second; mean distal flow = 60 ± 19 mL/second; collateral flow = –1.9 ± 3.7 mL/second; and collateral flow percentage = –3.3 ± 6.8%.

Conclusion

PC‐MR can be used to measure changes in collateral circulation after stent treatment of coarctation of the aorta. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Discrimination between UV radiation‐induced and thermally induced spectral changes in AT‐paired DNA oligomers using UV resonance Raman spectroscopy
Authors: Jirasek Andrew , Schulze H. Georg , Hughesman Curtis H. , Creagh A. Louise , Haynes Charles A. , Blades Michael W. , Turner Robin F. B.
Published: June 2006

Ultraviolet resonance Raman spectroscopy (UVRRS) was used to monitor UV radiation and thermal energy deposition in 12‐ and 18‐mer AT oligomers. Difference spectroscopy and two‐dimensional correlation spectroscopy (2DCOS) were used to characterize the distinct spectral responses manifested by the two processes, and to examine their potential cooperative and/or independent effects on the ensemble spectrum. Experiments utilizing incremental doses of 257‐nm radiation revealed that the most affected bands are those involving double bonds when the sample temperature was held constant. Complementary experiments utilizing sample heating indicated that the most affected bands were those involving hydrogen‐bond disruption. Finally, it is shown that bands associated with Watson–Crick hydrogen‐bond disruption are the most affected in rapidly heat‐cycled samples. The results also suggest that both radiation and thermal effects produce independent structural changes in AT oligomers and, furthermore, that these effects are complementary when the experiments involve single‐strand DNA fragments. When using UVRRS to study one of these perturbations (e.g. thermal stability of DNA), the concurrent perturbation (e.g. UV exposure) must not be neglected, since UV exposure is inherent in the UVRR process. These findings thus have implications for the use of UVRRS in the study of DNA dynamics. Copyright © 2006 John Wiley & Sons, Ltd.
Polyphenol oxidase activity in grass and its effect on plant‐mediated lipolysis and proteolysis of Dactylis glomerata (cocksfoot) in a simulated rumen environment
Authors: Lee Michael RF , Olmos Colmenero Jose de J , Winters Ana L , Scollan Nigel D , Minchin Frank R
Published: June 2006

Little is known about the level or activity of polyphenol oxidase (PPO) in grasses and its potential impact on proteolysis and lipolysis. Six grass species were initially screened for PPO activity (740.6, 291.9, 213.6, 119.0, 16.3 and 6.5 U g−1 fresh weight (FW) for cocksfoot, hybrid ryegrass, Italian ryegrass, perennial ryegrass, timothy and tall fescue respectively). Cocksfoot, which expressed the highest activity, was then used to determine the effect of PPO on plant‐mediated proteolysis and lipolysis in a simulated rumen environment. Sourced cocksfoot was macerated and incubated in an antibiotic‐containing anaerobic medium with or without ascorbate to deactivate PPO in the dark at 39 °C over five time points. At each time point (0, 1, 2, 6 and 24 h), six replicate samples were destructively harvested; three of the replicates were used for lipid analysis and the other three for protein, free amino acid and bound phenol determination. Characterisation of the herbage showed PPO activities of 649.6 and 0 U g−1 FW, which were reflected in the extent of phenol (derived from quinones) binding to protein after 24 h of incubation, namely 65.1 and 29.6 mg bound phenol g−1 protein (P < 0.001) for cocksfoot and cocksfoot + ascorbate respectively. Proteolysis, measured as free amino acids released into the incubation buffer, was significantly reduced (P < 0.001) with increasing PPO activity, with values after the 24 h incubation of 0.03 and 0.07 mmol L−1 g−1 FW for cocksfoot and cocksfoot + ascorbate respectively. Lipolysis, measured as the proportional decline in the membrane lipid polar fraction, was likewise reduced (P < 0.001) with increasing PPO activity, with values after the 24 h incubation of 0.43 and 0.65 for cocksfoot and cocksfoot + ascorbate respectively. Changes that occurred in protein and the lipid fractions (polar fraction, monoacylglycerol + diacylglycerol, triacylglycerol and free fatty acids) during the incubations are also reported and discussed. These results support the selection of forages high in PPO activity to reduce protein and lipid losses in silo and potentially in the rumen. Copyright © 2006 Society of Chemical Industry
Theoretical investigation of transient elastohydrodynamic lubrication with newtonian solid–liquid lubricants
Authors: Mongkolwongrojn M. , Thammakosol K.
Published: June 2006

This paper reports a theoretical investigation of transient elastohydrodynamic lubrication of a line contact. A time‐dependent Reynolds equation and elasticity equations for compressible solid–liquid lubricants were solved using finite volume and multigrid techniques. The lubricants used were mineral oils mixed with very small solid particles, MoS2 and PTFE which can be treated as Newtonian fluids. The two surfaces were initially at rest and in contact. The transient oil film pressure and oil film thickness were calculated numerically. This simulation showed the significant effects of solid particles on the lubrication characteristics. Copyright © 2006 John Wiley & Sons, Ltd.
Epidemiology of primary focal dystonias in the western area of tottori prefecture in Japan: Comparison with prevalence evaluated in 1993
Authors: Fukuda Hiroki , Kusumi Masayoshi , Nakashima Kenji
Published: June 2006

An epidemiological survey of primary focal dystonias in the western area of Tottori Prefecture in Japan was conducted in 2003, and the results were compared with those of a previous survey in 1993. The service‐based prevalence of primary focal dystonia was 13.7 per 100,000 population, representing an increase from that found in the 1993 survey. In 1997, botulinum toxin type A was approved for use in Japan to treat blepharospasm, and the increased number of patients now being evaluated and diagnosed with focal dystonias at medical centers throughout Japan may be responsible for this increased prevalence. Prevalence by subtype per 100,000 population was as follows: facial dystonia, 6.5; spasmodic torticollis, 2.0; writer's cramp, 4.4; and other focal dystonias; 0.8. Facial dystonia showed the most marked increase in service‐based prevalence among these subtypes. © 2006 Movement Disorder Society
T2‐weighted balanced SSFP imaging (T2‐TIDE) using variable flip angles
Authors: Paul Dominik , Markl Michael , Fautz Hans‐Peter , Hennig Jürgen
Published: June 2006

A new technique for acquiring T2‐weighted, balanced steady‐state free precession (b‐SSFP) images is presented. Based on the recently proposed transition into driven equilibrium (TIDE) method, T2‐TIDE uses a special flip angle scheme to achieve T2‐weighted signal decay during the transient phase. In combination with half‐Fourier image acquisition, T2‐weighted images can be obtained using T2‐TIDE. Numerical simulations were performed to analyze the signal behavior of T2‐TIDE in comparison with TSE and b‐SSFP. The results indicate identical signal evolution of T2‐TIDE and TSE during the transient phase. T2‐TIDE was used in phantom experiments, and quantitative ROI analysis shows a linear relationship between TSE and T2‐TIDE SNR values. T2‐TIDE was also applied to abdominal and head imaging on healthy volunteers. The resulting images were analyzed quantitatively and compared with standard T2‐weighted and standard b‐SSFP methods. T2‐TIDE images clearly revealed T2 contrast and less blurring compared to T2‐HASTE images. In combination with a magnetization preparation technique, STIR‐weighted images were obtained. T2‐TIDE is a robust technique for acquiring T2‐weighted images while exploiting the advantages of b‐SSFP imaging, such as high signal‐to‐noise ratio (SNR) and short TRs. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Toward single breath‐hold whole‐heart coverage coronary MRA using highly accelerated parallel imaging with a 32‐channel MR system
Authors: Niendorf Thoralf , Hardy Christopher J. , Giaquinto Randy O. , Gross Patrick , Cline Harvey E. , Zhu Yudong , Kenwood Gontran , Cohen Shmuel , Grant Aaron K. , Joshi Sanjay , Rofsky Neil M. , Sodickson Daniel K.
Published: June 2006

Coronary MR angiography (CMRA) is generally confined to the acquisition of multiple targeted slabs with coverage dictated by the competing constraints of signal‐to‐noise ratio (SNR), physiological motion, and scan time. This work addresses these obstacles by demonstrating the technical feasibility of using a 32‐channel coil array and receiver system for highly accelerated volumetric breath‐hold CMRA. The use of the 32‐element array in unaccelerated CMRA studies provided a baseline SNR increase of as much as 40% over conventional cardiac‐optimized phased array coils, which resulted in substantially enhanced image quality and improved delineation of the coronary arteries. Modest accelerations were used to reduce breath‐hold durations for tailored coverage of the coronary arteries using targeted multi‐oblique slabs to as little as 10 s. Finally, high net accelerations were combined with the SNR advantages of a 3D steady‐state free precession (SSFP) technique to achieve previously unattainable comprehensive volumetric coverage of the coronary arteries in a single breath‐hold. The merits and limitations of this simplified volumetric imaging approach are discussed and its implications for coronary MRA are considered. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Q‐ball reconstruction of multimodal fiber orientations using the spherical harmonic basis
Authors: Hess Christopher P. , Mukherjee Pratik , Han Eric T. , Xu Duan , Vigneron Daniel B.
Published: June 2006

Diffusion tensor imaging (DTI) accurately delineates white matter pathways when the Gaussian model of diffusion is valid. However, DTI yields erroneous results when diffusion takes on a more complex distribution, as is the case in the brain when fiber tracts cross. High angular resolution diffusion imaging (HARDI) overcomes this limitation of DTI by more fully characterizing the angular dependence of intravoxel diffusion. Among the various HARDI methods that have been proposed, QBI offers advantages such as linearity, model independence, and relatively easy implementation. In this work, reconstruction of the q‐ball orientation distribution function (ODF) is reformulated in terms of spherical harmonic basis functions, yielding an analytic solution with useful properties of a frequency domain representation. The harmonic basis is parsimonious for typical b‐values, which enables the ODF to be synthesized from a relatively small number of noisy measurements and thus brings the technique closer to clinical feasibility from the standpoint of total imaging time. The proposed method is assessed using Monte Carlo computer simulations and compared with conventional q‐ball reconstruction using spherical RBFs. In vivo results from 3T whole‐brain HARDI of adult volunteers are also provided to verify the underlying mathematical theory. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
History of the stiffness method
Authors: Samuelsson A. , Zienkiewicz O. C.
Published: June 2006

This paper presents a brief history of the development of the stiffness method. We start by tracing the evolution of the method to solve discrete‐type problems such as trusses and frames composed of two node members. We then describe the method as it is applied to solve continuum problems modelled by finite‐difference and finite‐element methods. Copyright © 2006 John Wiley & Sons, Ltd.
Hybrid and enhanced finite element methods for problems of soil consolidation
Authors: Zhou X. X. , Chow Y. K. , Leung C. F.
Published: June 2006

Hybrid and enhanced finite element methods with bi‐linear interpolations for both the solid displacements and the pore fluid pressures are derived based on mixed variational principles for problems of elastic soil consolidation. Both plane strain and axisymmetric problems are studied. It is found that by choosing appropriate interpolation of enhanced strains in the enhanced method, and by choosing appropriate interpolations of strains, effective stresses and enhanced strains in the hybrid method, the oscillations of nodal pore pressures can be eliminated. Several numerical examples demonstrating the capability and performance of the enhanced and hybrid finite element methods are presented. It is also shown that for some situations, such as problems involving high Poisson's ratio and in other related problems where bending effects are evident, the performance of the enhanced and hybrid methods are superior to that of the conventional displacement‐based method. The results from the hybrid method are better than those from the enhanced method for some situations, such as problems in which soil permeability is variable or discontinuous within elements. Since all the element parameters except the nodal displacements and nodal pore pressures are assumed in the element level and can be eliminated by static condensation, the implementations of the enhanced method and the hybrid method are basically the same as the conventional displacement‐based finite element method. The present enhanced method and hybrid method can be easily extended to non‐linear consolidation problems. Copyright © 2006 John Wiley & Sons, Ltd.
Assessment of the cost and accuracy of the generalized FEM
Authors: Strouboulis Theofanis , Zhang Lin , Babuška Ivo
Published: June 2006

In this paper, we address the cost versus accuracy capabilities for the generalized FEM (GFEM) which was developed in (Comput. Methods Appl. Mech. Eng. 2003; 192:3109–3161, Int. J. Numer. Meth. Engng 2004; 60:1639–1672, Ph.D. Thesis, Texas A&M University, College Station, TX, August 2003 (Advisor: T. Strouboulis)), and also the construction of two‐sided a posteriori error estimates, which can be used to assess the achieved accuracy at all levels of the method. Copyright © 2006 John Wiley & Sons, Ltd.
Inexact FETI‐DP methods
Authors: Klawonn Axel , Rheinbach Oliver
Published: June 2006

Inexact FETI‐DP domain decomposition methods are considered. Preconditioners based on formulations of FETI‐DP as a saddle point problem are used which allow for an inexact solution of the coarse problem. A positive definite reformulation of the preconditioned saddle point problem, which also allows for approximate solvers, is considered as well. In the formulation that iterates on the original FETI‐DP saddle point system, it is also possible to solve the local Neumann subdomain problems inexactly. Given good approximate solvers for the local and coarse problems, convergence bounds of the same quality as for the standard FETI‐DP methods are obtained. Numerical experiments which compare the convergence of the inexact methods with that of standard FETI‐DP are shown for 2D and 3D elasticity using GMRES and CG as Krylov space methods. Based on parallel computations, a comparison of one variant of the inexact FETI‐DP algorithms and the standard FETI‐DP method is carried out and similar parallel performance is achieved. Parallel scalability of the inexact variant is also demonstrated. It is shown that for a very large number of subdomains and a very large coarse problem, the inexact method can be superior. Copyright © 2006 John Wiley & Sons, Ltd.
High‐order DGTD methods for dispersive Maxwell's equations and modelling of silver nanowire coupling
Authors: Ji Xia , Cai Wei , Zhang Pingwen
Published: June 2006

A high‐order discontinuous Galerkin time‐domain (DGTD) method for Maxwell's equations for dispersive media of Drude type is derived and then used to study the coupling of 2D silver nanowires, which have potential applications in optical circuits without the restriction of diffraction limits of traditional dielectric waveguides. We have demonstrated the high accuracy of the DGTD for the electromagnetic wave scattering in dispersive media and its flexibility in modelling the plasmon resonant phenomena of coupled silver nanowires. Specifically, we study the cross sections of coupled nanowires, the dependence of the resonance on the number of nanowires with more resolved resonance information than the traditional FDTD Yee scheme, time‐domain behaviour of waves impinging on coupled silver nanowires of a funnel configuration, and the energy loss of resonant modes in a linear chain of circular and ellipse nanowires. Copyright © 2006 John Wiley & Sons, Ltd.
An interior‐point algorithm for elastoplasticity
Authors: Krabbenhoft K. , Lyamin A. V. , Sloan S. W. , Wriggers P.
Published: June 2006

The problem of small‐deformation, rate‐independent elastoplasticity is treated using convex programming theory and algorithms. A finite‐step variational formulation is first derived after which the relevant potential is discretized in space and subsequently viewed as the Lagrangian associated with a convex mathematical program. Next, an algorithm, based on the classical primal–dual interior point method, is developed. Several key modifications to the conventional implementation of this algorithm are made to fully exploit the nature of the common elastoplastic boundary value problem. The resulting method is compared to state‐of‐the‐art elastoplastic procedures for which both similarities and differences are found. Finally, a number of examples are solved, demonstrating the capabilities of the algorithm when applied to standard perfect plasticity, hardening multisurface plasticity, and problems involving softening. Copyright © 2006 John Wiley & Sons, Ltd.
Optimization of large‐scale truss structures using sparse SAND formulations
Authors: Wang Qian , Arora Jasbir S.
Published: June 2006

Sparsity features of simultaneous analysis and design (SAND) formulations are studied and exploited for optimization of large‐scale truss structures. Three formulations are described and implemented with an existing analysis code. SAND formulations have large number of variables; however, gradients of the functions and Hessian of the Lagrangian are quite sparsely populated. Therefore, this structure of the problem is exploited and an optimization algorithm with sparse matrix capability is used to solve large‐scale problems. An existing analysis software is integrated with an optimizer based on a sparse sequential quadratic programming (SQP) algorithm to solve sample problems. The formulations and algorithms work quite well for the sample problems, and their performances are compared and discussed. For all the cases considered, the SAND formulations out perform the conventional formulation except one case. Further research is suggested to fully study and utilize sparse features of the alternative SAND formulations and to develop more efficient sparse solvers for large‐scale and more complex applications. Copyright © 2006 John Wiley & Sons, Ltd.
Analysis of two‐grid methods for reaction‐diffusion equations by expanded mixed finite element methods
Authors: Chen Yanping , Liu Huan‐Wen , Liu Shang
Published: June 2006

We present two efficient methods of two‐grid scheme for the approximation of two‐dimensional semi‐linear reaction‐diffusion equations using an expanded mixed finite element method. To linearize the discretized equations, we use two Newton iterations on the fine grid in our methods. Firstly, we solve an original non‐linear problem on the coarse grid. Then we use twice Newton iterations on the fine grid in our first method, and while in second method we make a correction on the coarse grid between two Newton iterations on the fine grid. These two‐grid ideas are from Xu's work (SIAM J. Sci. Comput. 1994; 15:231–237; SIAM J. Numer. Anal. 1996; 33:1759–1777) on standard finite element method. We extend the ideas to the mixed finite element method. Moreover, we obtain the error estimates for two algorithms of two‐grid method. It is showed that coarse space can be extremely coarse and we achieve asymptotically optimal approximation as long as the mesh sizes satisfy H =𝒪(h¼) in the first algorithm and H =𝒪(h⅙) in second algorithm. Copyright © 2006 John Wiley & Sons, Ltd.
A fast and robust iterative solver for nonlinear contact problems using a primal‐dual active set strategy and algebraic multigrid
Authors: Brunssen S. , Schmid F. , Schäfer M. , Wohlmuth B.
Published: June 2006

For extending the usability of implicit FE codes for large‐scale forming simulations, the computation time has to be decreased dramatically. In principle this can be achieved by using iterative solvers. In order to facilitate the use of this kind of solvers, one needs a contact algorithm which does not deteriorate the condition number of the system matrix and therefore does not slow down the convergence of iterative solvers like penalty formulations do. Additionally, an algorithm is desirable which does not blow up the size of the system matrix like methods using standard Lagrange multipliers. The work detailed in this paper shows that a contact algorithm based on a primal‐dual active set strategy provides these advantages and therefore is highly efficient with respect to computation time in combination with fast iterative solvers, especially algebraic multigrid methods. Copyright © 2006 John Wiley & Sons, Ltd.
Psychological distress in long‐term survivors of solid tumors diagnosed in childhood: A report from the childhood cancer survivor study
Authors: Zebrack Brad J. , Zevon Michael A. , Turk Norman , Nagarajan Rajaram , Whitton John , Robison Leslie L. , Zeltzer Lonnie K.
Published: June 2006

Purpose

To evaluate and compare psychological distress in long‐term survivors of solid tumors diagnosed in childhood and their siblings, and to identify significant correlates of psychological distress.

Procedure

Adult survivors (2,778) of solid tumors diagnosed in childhood and 2,925 siblings completed a long‐term follow‐up questionnaire assessing symptoms associated with depression, somatization, and anxiety, as well as demographic, health, and medical information.

Results

Overall, a large majority of siblings and survivors reported few, if any, symptoms of psychological distress. In the aggregate, solid tumor cancer survivors reported significantly higher levels of global distress as measured by the Brief Symptom Inventory (BSI‐18), as well as higher levels of somatization and anxiety, when compared to siblings. However, when compared to population norms, both survivors and siblings reported lower levels of global and dimensional distress. Female gender, lower educational and income attainment, perceived poor health status and reports of current health problems all were associated with reporting psychological distress symptoms for both survivors and siblings. Among survivors, having a limb amputation was associated with reporting fewer symptoms of global and dimensional distress.

Conclusion

Poor health status, low levels of income, education, and employment appear to be predictors of distress for survivors of solid tumors. Thus, interventions that promote health and facilitate educational advancement, income attainment and social interaction to minimize isolation and maximize social support may reduce psychological distress and promote quality of life for childhood cancer survivors. Pediatr Blood Cancer 2007;49:47–51. © 2006 Wiley‐Liss, Inc.
Growth impairment after ifosfamide‐induced nephrotoxicity in children
Authors: Stöhr Wolfgang , Patzer Ludwig , Paulides Marios , Kremers Anja , Beck Jörn‐Dirk , Langer Thorsten , Rossi Rainer
Published: June 2006

Background

The goal of this study was to analyze long‐term consequences of ifosfamide‐induced nephrotoxicity on growth and renal function in children treated for cancer.

Procedure

In a retrospective study, departments for pediatric oncology and nephrology in Germany, Austria, and Switzerland were asked to report patients with serious long‐term nephrotoxicity after ifosfamide‐treatment. Data at first appearance of renal dysfunction and at the last renal examination were collected using a standardized questionnaire.

Results

Fifty‐nine patients with tubulopathy (35 severe, 24 moderate) following ifosfamide therapy were eligible for analysis of long‐term outcome (median follow‐up 4 years, range 1.1 to 12.9). Median height standard deviation score was significantly reduced at renal diagnosis, and at last renal examination (−1.7 and −2.1 respectively, P < 0.01 at each point in time). Patients with tubulopathy also had stunted growth in comparison with a control group of cancer patients without renal disease (mean difference at last examination: 7.3 cm (95% confidence interval: 2.5 to 12.1 cm). In patients with severe tubulopathy, glomerular filtration rate deteriorated significantly over time. End‐stage renal disease was reported in one patient only, not solely caused by ifosfamide.

Conclusion

Depending on the extent of tubular dysfunction, patients with ifosfamide‐induced nephrotoxicity experienced significant growth impairment and a slow decline in glomerular filtration rate. Pediatr Blood Cancer 2007;48:571–576. © 2006 Wiley‐Liss, Inc.
First trimester diagnosis of sirenomelia
Authors: Van Keirsbilck J. , Cannie M. , Robrechts C. , de Ravel T. , Dymarkowski S. , Van den Bosch T. , Van Schoubroeck D.
Published: June 2006

We present a case of sirenomelia diagnosed on a first trimester ultrasound at 10 weeks' gestation and confirmed on 3D‐ultrasound and MRI. The pregnancy was terminated at 15 gestational weeks and the post‐mortem examination, including RX and microscopy, is presented. The sirenomelia sequence is a rare and lethal anomaly characterized by fusion, rotation, hypotrophy or atrophy of the lower limbs and severe urogenital abnormalities leading to oligohydramnios in the second half of pregnancy. Our case illustrates that the diagnosis of sirenomelia can be reliably made in the first trimester. Copyright © 2006 John Wiley & Sons, Ltd.
Maternal serum ADAM12 levels in Down and Edwards' syndrome pregnancies at 9–12 weeks' gestation
Authors: Laigaard Jennie , Cuckle Howard , Wewer Ulla M. , Christiansen Michael
Published: June 2006

Background

Maternal serum ADAM12 is reduced, on average, in early first‐trimester Down and Edwards' syndrome pregnancies but the extent of reduction declines with gestation. Here we study levels at 9–12 weeks when the marker might be used concurrently with other established markers.

Methods

Samples from 16 Down and 2 Edwards' syndrome cases were retrieved from storage and tested together with 313 unaffected singleton pregnancies using a semi‐automated time‐resolved immuno‐fluorometric assay. Results were expressed in multiples of the gestation‐specific median (MoM) based on regression.

Results

The median in Down syndrome was 0.94 MoM with a 10th–90th centile range of 0.22–1.63 MoM compared with 1.00 and 0.33–2.24 MoM in unaffected controls (P = 0.21, one‐side Wilcoxon Rank Sum Test). The two Edwards' syndrome cases had values 0.31 and 2.17 MoM.

Conclusions

ADAM12 cannot be used concurrently with other markers in the late first trimester. However, it does have the potential to be used earlier in pregnancy either concurrently with other early markers or in a sequential or contingent protocol. More data will be required to reliably predict the performance of either approach. Copyright © 2006 John Wiley & Sons, Ltd.
Prenatal Marfan syndrome: report of one case and review of the literature
Authors: Lopes K. R. M. , Delezoide A. L. , Baumann C. , Vuillard E. , Luton D. , Chitrit Y. , Azancot A.
Published: June 2006

Objectives

Our objective was to describe the features of prenatal Marfan syndrome.

Methods

Doppler fetal echocardiograms were performed. The morphology and rhythm of the fetal heart were examined sequentially.

Results

The case was referred because of cardiomegaly and dilated great vessels. Sequential Doppler echocardiographic evaluation led to the diagnosis of prenatal Marfan syndrome. The main features are cardiomegaly, dysplastic atrioventricular valves with tricuspid regurgitation and dilated great vessels, which can be aneurysmal at their origin. The fetus died in utero at 39 weeks of gestation because of cardiac failure. Pathological study confirmed the Marfan habitus and complications. Molecular genetic study showed a de novo point mutation in exon 26 of the FBN1 gene.

Conclusion

We report a case of prenatal Marfan syndrome diagnosed by sequential evaluation of the cardiac signs, which are essential for prenatal diagnosis. The prognosis seems as poor as the neonatal one. The prenatal diagnosis is essential for adequate counselling. Copyright © 2006 John Wiley & Sons, Ltd.
Multi‐centre first‐trimester screening for Down syndrome in the Netherlands in routine clinical practice
Authors: Schielen P. C. J. I. , van Leeuwen‐Spruijt M. , Belmouden I. , Elvers L. H. , Jonker M. , Loeber J. G.
Published: June 2006

Objectives

This is the first report on the results of a first‐trimester combined‐test screening programme in the Netherlands in a multi‐centre routine clinical setting.

Methods

Between July 2002 and May 2004, blood samples were taken from subjects in 44 centres in the Netherlands and sent to our laboratory to assay for maternal serum concentrations of fβ‐hCG and PAPP‐A. Fetal nuchal translucency (NT) was measured in the participating centres at a gestational age (GA) of 10–14 weeks. Results of those pregnancies for which a combined biochemical and NT risk was calculated were included in the epidemiological analysis of this study.

Results

A total of 4033 singleton pregnancies were included in the analysis. The median maternal age of the analysed group was 36.5 years. The distribution of GA was biphasic, with median GA of 10.3 and 12.1 weeks, respectively. The detection rate using the combined ultrasound and serum screening at a cut‐off level of 1 in 250 was 71% (15/21), with a screen‐positive rate of 4.7%.

Conclusion

The results of this study show that the first‐trimester combined test is suitable as a prenatal screening test in a multi‐centre routine clinical setting in the Netherlands. Strict performance evaluation should identify weaknesses in the organisation that impair the performance of the test. Here, the performance of NT was especially identified as a candidate for improvement. Copyright © 2006 John Wiley & Sons, Ltd.
Carrier diagnostics and prevention of hemoglobinopathies in early pregnancy in The Netherlands: a pilot study
Authors: Giordano P. C. , Plancke A. , Van Meir C. A. , Janssen C. A. H. , Kok P. J. M. J. , Van Rooijen‐Nijdam I. H. , Tanis B. C. , van Huisseling J. C. M. , Versteegh F. G. A.
Published: June 2006

Background

We have offered, for the first time in The Netherlands, carrier diagnostics for hemoglobinopathies (HbP) to early pregnant women. The aim of this study was to establish whether carrier analysis would be welcome by the public and feasible at the outpatient level.

Method

One hundred and thirty‐nine randomly selected women were informed and offered basic carrier diagnostics at the first pregnancy control.

Results

Carrier diagnostics was accepted by 136 women (97.8%). The population consisted of 31% of recent immigrants and 69% of native Dutch. One carrier of HbS and one of β‐thalassemia were found, both among the group of the recent immigrants. In both cases, partners were tested excluding a couple at risk. In addition, five carriers of α+‐thalassemia were diagnosed at the molecular level, one of them in the native Dutch population. Basic carrier analysis was done both at the Hospital Laboratory and at the Reference Laboratory. No discrepancies were found.

Conclusions

This pilot study shows that (1) as predicted the prevalence of risk‐related HbP and of α+‐thalassemia is high in the immigrant population. (2) The compliance with carrier analysis in both native Dutch and immigrants is virtually total and (3) carrier diagnosis in early pregnancy and partner analysis in Hospital Laboratories is possible and is an effective tool for primary prevention of HbP in The Netherlands. Copyright © 2006 John Wiley & Sons, Ltd.
Synthesis and characterization of polypeptide containing liver‐targeting group
Authors: Cha Rui‐tao , Du Tian , Li Ji‐hong , Yuan Zhi
Published: June 2006

Glycyrrhetinic acid, glycyrrhizic acid and bile acid were reported to be accumulated in liver. A series of novel liver‐specific targeting polypeptides, poly(γ‐benzyl‐L‐glutamate), were synthesized by ring‐opening polymerization (ROP) of N‐carboxyanhydride of γ‐benzyl‐L‐glutamate (BLG‐NCA) with amine‐terminated compounds containing the above‐mentioned liver‐targeting group as an initiator. The molecular weights of the polypeptides were measured by gel permeation chromatography. The structures of these polypeptides and their initiators were confirmed by FTIR and 1H‐NMR spectroscopy. The results demonstrate that it is an efficient strategy to introduce a liver‐targeting group into polymers via amine‐terminated compounds containing glycyrrhetinic acid, glycyrrhizic acid and bile acid. The novel polymers have potential medical applications in targeted drug delivery. Copyright © 2006 Society of Chemical Industry
Kinetics and mechanism of the reactions of S‐4‐nitrophenyl 4‐methylthiobenzoate with secondary alicyclic amines and pyridines
Authors: Castro Enrique A. , Aguayo Raul , Bessolo Jorge , Santos José G.
Published: June 2006

The reactions of the title substrate with a series of six secondary alicyclic amines and a series of eight pyridines are subjected to a kinetic investigation in 44 wt% ethanol‐water, at 25.0°C, and an ionic strength of 0.2 mol · dm−3. Under amine excess pseudo first‐order rate coefficients (kobs) are obtained. Plots of kobs against free amine concentration at constant pH are linear, with the slope (kN) independent of pH. The Brønsted‐type plots (log kN against pKa of the conjugate acids of the amines) are non‐linear, with the curvature center located at pKa (pK) 9.7 and 9.4, for the reactions of secondary alicyclic amines and pyridines, respectively. The plots are consistent with a zwitterionic tetrahedral intermediate (T±) on the reaction path and a change in rate‐determining step. The greater pK value for secondary alicyclic amines than pyridines is explained by the greater nucleofugality from T± of secondary alicyclic amines compared to isobasic pyridines. These pK values are lower than those found for the reactions of S‐4‐nitrophenyl 4‐Y‐substituted thiolbenzoates (Y = H, Cl, NO2) with the corresponding amine series. These results indicate that electron donation from the non‐leaving group in T± favors leaving group expulsion from T± relative to amine expulsion. Copyright © 2006 John Wiley & Sons, Ltd.
A missing data approach to semi‐competing risks problems
Authors: Dignam James J. , Wieand Kelly , Rathouz Paul J.
Published: June 2006

For event time data involving multiple mutually exclusive competing causes of failure, classic competing risks results show that marginal survival distributions are not identifiable. In a related instance, one or more failure modes may be observed provided that the failure events occur in a specific order. In such situations, sometimes referred to as semi‐competing risks problems, the observations may under realistic assumptions lend information about parameters of interest that would be nonidentifiable in the strict competing risks case. Here, we present an approach that makes use of partially observable multiple modes of failures to obtain an estimate of the marginal distribution of one event type that may occur prior to the occurrence of another event type or be precluded by it. We apply the proposed method to the problem of estimating the distribution of time to tumour recurrence at specific sites among breast cancer patients participating in randomized clinical trials. Copyright © 2006 John Wiley & Sons, Ltd.
Application of the promotion time cure model with time‐changing exposure to the study of HIV/AIDS and other infectious diseases
Authors: Tournoud M. , Ecochard R.
Published: June 2006

Infectious diseases are caused by single or successive contacts with pathogens. Nevertheless, contacts with pathogens do not implicate infection. In 1993, Yakovlevet al.proposed a model to study a population of cancer patients with a cured fraction, a well adapted model to describe an infectious disease with a unique infection occasion. Extensions of this model have been proposed in the recent years. We present a mechanistic formulation in the context of infectious diseases with multiple infection occasions. It is a mixture model that enables to study risk factors associated with infection intensity at each infection occasion and factors shortening the delay from exposure to clinical event. Simulations are performed to evaluate the model fitting and two examples are presented for illustration: an analysis of an HIV‐1 mother‐to‐child transmission data set and an analysis of nosocomial urinary tract infections data set. Copyright © 2006 John Wiley & Sons, Ltd.
Repeated measures analyses of dose timing of antiretroviral medication and its relationship to HIV virologic outcomes
Authors: Liu Honghu , Miller Loren G. , Golin Carol E. , Hays Ron D. , Wu Tongtong , Wenger Neil S. , Kaplan Andrew H.
Published: June 2006

Medication adherence is a critical predictor of the effectiveness of antiretroviral medications in the treatment of HIV/AIDS. Studies of adherence, however, have focused primarily on the per cent of prescribed doses taken (per cent adherence). In the Adherence and Efficacy of Protease Inhibitor Therapy study, we collected detailed adherence data including dose timing information as well as data regarding patients' virologic responses. For 48 weeks, adherence data and virologic outcomes were collected every 4 weeks, and demographics and other measures were collected at baseline and at weeks 8, 24, and 48. We constructed eight different dose timing error (DTE) measures and evaluated their associations with virologic outcomes using longitudinal analyses. Repeated measures mixed effect models were fitted to evaluate the predicting power of each of the DTE measures. Among 52 036 electronically measured doses obtained from 122 patients, DTE measures significantly predicted virologic outcomes. Of the eight different DTE measures, the six DTE measures were significantly predictive of virologic outcomes even after controlling for per cent adherence. In conclusion, we identified several measures of DTE that explain HIV virologic outcomes not captured by traditional adherence measures. Investigations of adherence to antiretrovirals would benefit from measuring not only per cent adherence but dose timing adherence. Copyright © 2006 John Wiley & Sons, Ltd.
Incorporating missingness for estimation of marginal regression models with multiple source predictors
Authors: Litman Heather J. , Horton Nicholas J. , Hernández Bernardo , Laird Nan M.
Published: June 2006

Multiple informant data refers to information obtained from different individuals or sources used to measure the same construct; for example, researchers might collect information regarding child psychopathology from the child's teacher and the child's parent. Frequently, studies with multiple informants have incomplete observations; in some cases the missingness of informants is substantial. We introduce aMaximum Likelihood(ML) technique to fit models with multiple informants as predictors that permits missingness in the predictors as well as the response. We provide closed form solutions when possible and analytically compare the ML technique to the existingGeneralized Estimating Equations(GEE) approach. We demonstrate that the ML approach can be used to compare the effect of the informants on response without standardizing the data. Simulations incorporating missingness show that ML is more efficient than the existing GEE method. In the presence of MCAR missing data, we find through a simulation study that the ML approach is robust to a relatively extreme departure from the normality assumption. We implement both methods in a study investigating the association between physical activity and obesity with activity measured using multiple informants (children and their mothers). Copyright © 2006 John Wiley & Sons, Ltd.