Sensitivity analysis of longitudinal binary quality of life data with drop-out: an example using the EORTC QLQ-C30

in Statistics in Medicine (2001), 20(24), 3901-20

Analysing quality of life data (QOL) may be complicated for several reasons. Quality of life data not only involves repeated measures but is also usually collected on ordered categorical responses. In ... [more ▼]

Analysing quality of life data (QOL) may be complicated for several reasons. Quality of life data not only involves repeated measures but is also usually collected on ordered categorical responses. In addition, it is evident that not all patients provide the same number of assessments, due to attrition caused by death or other medical reasons. In the recent statistical literature, increasing attention is given to methods which can handle non-continuous outcomes in the presence of missing data. The aim of this paper is to investigate the effect on statistical conclusions of applying different modelling techniques to QOL data generated from an EORTC phase III trial. Treatment effects and treatment differences are of major concern. First, a random-effects model is fitted, relating a binary longitudinal response (derived from the physical functioning scale of the QLQ-C30) to several covariates. In a second approach, marginal models are fitted, retaining the response variable and the mean structure used before. The fitted marginal models only differ with respect to the considered estimation procedure: generalized estimating equations (GEE); weighted generalized estimating equations (WGEE), and maximum likelihood (ML). [less ▲]

Sensitivity analysis of phase response curves

Conference (2011, March 16)

Sensitivity analysis of programmed cell death and implications for crosstalk phenomena during tumor necrosis factor stimulation

in Proc. of the 2006 IEEE Conference on Control Applications (2006)

Different methods for analyzing the sensitivity of the direct signal transduction pathway of receptor-induced apoptosis to parameter changes are presented. Apoptosis is a form of programmed cell death ... [more ▼]

Different methods for analyzing the sensitivity of the direct signal transduction pathway of receptor-induced apoptosis to parameter changes are presented. Apoptosis is a form of programmed cell death, removing unwanted cells within multicellular organisms to maintain a proper balance between cell reproduction and death. The results indicate the importance of controlling activated caspases by direct inhibition to prevent apoptosis. A misregulation of IAP molecules, one of the main inhibitors, appears to be especially critical. The results indicate how an increased production of this molecule promotes survival and might promote cancer progression, while a reduced degradation might not, thereby providing insight of potential pharmaceutical relevance and also stimulating experimental verification. The different engineering methods applied, nicely complement each other to provide valuable insight into this important process. Because IAPs, among others, are also an important connection to other signaling pathways, the results will enable a more efficient extension of the current model. This is outlined at the example of tumor necrosis factor induced signaling pathways [less ▲]

Sensitivity analysis on the elastic buckling and ultimate strength of continuous stiffened aluminium plates under combined in-plane compression and lateral pressure

in Thin-Walled Structures (2009), 47

Sensitivity Analysis on Ultimate Hull Bending Moment and Multi-Criteria Comparative Analysis of Existing Method

in Conf ASRANet, Integrating Structural Reliability Analysis with Advanced Structural Analysis, Session 8 (2002, July)

Sensitivity Analysis With Unstructured Free Mesh Generators in 2-D Shape Optimization

in Herskowitz, José (Ed.) Proceedings of Structural Optimization 93, The World Congress on Optimal Design of Structural Systems (1993, August)

Shape optimization has to consider new progress in mesh generators to take full benefits from the use of free unstructured meshes in realistic industrial optimization. The main difficulty relies in the ... [more ▼]

Shape optimization has to consider new progress in mesh generators to take full benefits from the use of free unstructured meshes in realistic industrial optimization. The main difficulty relies in the mesh flow determination during sensitivity analysis. The authors present their experience in applying smoothing techniques to transmit boundary perturbations to the inner mesh. It is explained how smoothing can be used to evaluate velocity fields in a simple and inexpensive way while guarantying reliability, efficiency and precision. A wide range of smoothing procedures are compared and confronted with other velocity field approaches to investigate their advantages and drawback. Finally, applications of smoothing procedures in the commercial optimization package OPTI-SAMCEF are described. [less ▲]

Sensitivity and precision of a heterologous PAG (Pregnancy-Associated Glycoprotein) radioimmunoassay.

in Arquivos - Faculdade de Veterinária, UFRGS (1998), 26(1 (Suppl)), 372-373

Sensitivity and resolution of ERT for soil moisture monitoring in contour hedgerow intercropping systems: a methodological analysis

Scientific conference (2011)

Sensitivity in shape optimization of complex 3D geometries using level sets and non-conforming finite elements

Conference (2009, September)

For the last 20 years shape optimization has been stocking to penetrate industrial and real-life applications, whereas topology optimization was experiencing a fast growing soar and extensions to various ... [more ▼]

For the last 20 years shape optimization has been stocking to penetrate industrial and real-life applications, whereas topology optimization was experiencing a fast growing soar and extensions to various applications. By the way there is still a great interest in shape optimization because of the intrinsic capability of shape description to facilitate considering complex problems involving local stress and manufacturing constraints for instance. The level set description proposed by Osher and Sethian (1988) opened new perspectives to handle variable boundaries as in shape optimization. The implicit description of the geometrical entities allows for a more friendly and flexible manipulation of the geometry and overcome some restrictions related to the explicit approach of the geometry used in CAD systems: for example it is possible to reduce the topological complexity by removing or merging geometric entities (i.e. holes can merge or disappear) without degenerating the model, which was major restriction of shape optimization. A few years ago, the level set method was nicely complemented by the XFEM (eXtended Finite Element Method) proposed by Moes et al (1999). This approach greatly reduces the difficulty of considering time-variable boundaries and complex geometries by using non-conforming meshes. This is definitively an advantage to circumvent the so-called velocity field to carry out shape sensitivity and mesh relocation difficulties, especially with thin walled structures or 3D designs. The present research is continuing along and extending works by Duysinx et al (2006) and Van Miegroet and Duysinx (2007) to consider shape optimization based on a parametric level set description and XFEM. The work that is carried out in a common research project EFCONICO sponsored by the Walloon Region of Belgium aims at extending preliminary results 3 D structure and complex geometries, increasing the reliability of the method, enhancing the performances using advanced mesh generators as Gmsh, etc. In particular the paper presents new theoretical developments and their numerical implementation in sensitivity analysis with respect to parametric design variable of level sets. The developments are illustrated with numerical applications dealing with complex shape applications involving 3D geometries and the boundary conditions along design variable boundaries. [less ▲]

Sensitivity of a global oceanic carbon cycle model to the circulation and to the fate of organic matter: preliminary results

in Physics & Chemistry of the Earth - Parts A/B/C (1996), 21