Experimental Error Measurement Research Articles

Postural spinal balance defined by net intersegmental moments: Results of a biomechanical approach and experimental errors measurement.

To describe initial results and experimental error measurement of a protocol analyzing Human posture through sagittal intersegmental moments. Postural analysis has been recently improved by development of three-dimensional radiographic imaging systems. However, in various situations such as global sagittal anterior malalignment interpretation of radiographs may not represent the real alignment of the subject. The aim of this study was to present initial results of a 3D biomechanical protocol. This protocol is obtained in a free standing position and characterizes postural balance by measurement of sagittal intersegmental net moments. After elaboration of a specific marker-set, 4 successive recordings were done on two volunteers by three different operators during three sessions in order to evaluate the experimental error measurement. A supplementary acquisition in a "radiographic" posture was also obtained. Once the data acquired, joint center, length, anatomical frame and the center of mass of each body segment was calculated and a mass affected. Sagittal net intersegmental moments were computed in an ascending manner from ground reaction forces at the ankles, knees, hips and the lumbo-sacral and thoraco-lumbar spinal junctions. Cervico-thoracic net intersegmental moment was calculated in a descending manner. Based on average recordings, clinical interpretation of net intersegmental moments (in N.m) showed a dorsal flexion on the ankles (8.6 N.m), a flexion on the knees (7.5 N.m) and an extension on the hips (8.5 N.m). On the spinal junctions, it was flexion moments: 0.34 N.m on the cervico-thoracic; 6.7 N.m on the thoraco-lumbar and 0.65 N.m on the lumbo-sacral. Evaluation of experimental error measurement showed a small inter-trial error (intrinsic variability), with higher inter-session and inter-therapist errors but without important variation between them. For one volunteer the "radiographic" posture was associated to significant changes compared to the free standing position. These initial results confirm the technical feasibility of the protocol. The low intrinsic error and the small differences between inter-session and inter-therapist errors seem to traduce postural variability over time, more than a failure of the protocol. Characterization of sagittal intersegmental net moments can have clinical applications such as evaluation of an unfused segment after a spinal arthrodesis.

Rethinking the Optimal Response Surface Design for a First-Order Model with Two-Factor Interactions, When Protecting against Curvature

There are common choices for best response surface designs for the three-, four-, and five-factor first-order model with all two-factor interactions when the goal is to precisely estimate the model and a measure of experimental error, while protecting against possible curvature from quadratic effects. When the design size is to be kept small, the statistics literature has long recommended the 23 and 25−1 factorial designs with added center runs for this purpose for the three- and five- factor cases, and a Plackett–Burman design with center runs is common for the four- factor case. In this article we evaluate these designs against all other competitors using formal criteria for three objectives. In addition to D-optimality, two new criteria are proposed to measure the precision of the pure error estimate and the ability to detect lack-of-fit from missing model terms. A Pareto frontier approach is used to conduct a formal search for optimal designs based on simultaneously considering the three criteria of interest. Candidate designs with their robustness to weight specifications and sensitivity to different scalings and forms of desirability functions are explored. For different numbers of factors, the standard designs have mixed performance. The Pareto front approach offers insights into how this problem might be more thoroughly examined. A new graphical summary, the synthesized efficiency plot, shows relative performance of designs over user-specified weightings of the different criteria.

Optic-Electronic Systems for Control the Angle and Line Positions of the Elements Unblocked Aperture Radio-Telescope

The construction of new radio telescope RT-70 Suffa requires controlling the angular and linear deformation of the mirror elements. Following issues dealing with this problem are described in this article: 1) the possibility of the design of deformation measurement system based on triangular method 2) the new scheme of optic-electronic measurement system. The great attention during the research was paid to the experimental approval of the theoretical results. The computer simulation error and the experimental error measurement was 0.08 mm at the range 30 mm on a working distance of 25 m, which allows measuring the deformation of radiotelescope construction with the mirror diameter 70 m.

Optic-electronic systems for measuring angle deformations of a fully rotateable radiotelescope

The construction of new large radio telescope RT-70 Suffa requires controlling the element angular deformation. Following issues dealing with this problem are described in this article: 1) the possibility of the design of deformation measurement system based on autoreflection scheme, 2) the new vignetting error compensation method. The great attention during the research was paid to the experimental approval of the theoretical results. The model of the described system had the following characteristics: infrared emission diode AL107B by power 15 mWt as sources of radiation; the focal length of receiver objective by the focal length 500 mm as aperture of receiver videocamera, the CMOS matrix receiver by type OV05610 Color CMOS QSXGA with 2592 * 1944 pixels and one pixel size (2.8 * 2.8) μm2 produced OmniVision as image analyzer. The experimental error measurement was 1.5 arc seconds at the angular range 20 arc. minutes, that allows measure the angle deformation of radiotelescope with the mirror diameter 70 m.

The use of statistical experimental design for PCB process optimisation

Statistical experimental design (SED) can be used as an analytical tool to investigate the effect of a range of PCB processing parameters (variables) on certain final properties (responses). Compared to the “typical” method of carrying out experimental trials, the use of SED can identify “interactions” between variables that may not become apparent without extensive testing otherwise. The SED route also offers a measure of experimental error within the process and can suggest ways to optimise the process, with a reduced number of experimental runs. An application of the SED process is also discussed regarding the evaluation and optimisation of a horizontal liquid photoimageable solder mask (LPISM) spraying process in accordance with certain key factors.

Stochastic modeling of apoptosis tolerance distributions measured by multivariate flow analysis of human leukemia cells

Background Cytofluorometric analysis allows single-cell resolution of all-or-none programmed cell death (apoptosis) responses and permits direct measurement of cumulative frequency distributions (CFDs) of apoptosis sensitivity from which the median apoptosis tolerance can be estimated. Robust estimation of susceptibility to apoptosis within neoplastic cell populations provides a means of either accurately determining pharmacologically induced changes in apoptosis sensitivity or comparing cell population responses to different apoptosis inducers. Methods Experimentally determined CFDs for VP-16 (etoposide)-induced apoptosis were measured by phosphotidylserine surface expression and mitochondrial membrane potential dissipation (ΔΨm) in BV173 leukemia cells. CFDs were modelled by a modified Hill equation using a four-parameter nonlinear regression from which median apoptosis tolerance (K) was estimated. Results Median apoptosis tolerance (K) was estimated from nonlinear regression analysis of CFDs for ΔΨm collapse and loss of membrane asymmetry. The error distribution of K determined from nonlinear regression analysis of 100 simulated CFDs was shown to exhibit an asymmetrical distribution. The asymmetrical likelihood intervals for K were computed iteratively, thereby providing a measure of experimental error. Conclusions A distribution-based approach to apoptosis assay using multivariate flow analysis offers a powerful, quantitative technique for investigating the phenotypical basis of neoplastic cell responsiveness to apoptosis therapy, permitting separation of cell populations on the basis of apoptosis susceptibility. Cytometry 39:266–274, 2000 © 2000 Wiley-Liss, Inc.

Organometallic chemometrics

An interactive minicomputer program in BASIC is presented for implementing abstract factor analysis (AFA) on small core systems. The program converts an original data matrix P = EC into a dispersion (covariance) matrix A = PPT (or PTP), performs a complete eigenanalysis, and determines the correct number of factors spanning the original data space. The criteria for choosing the significant components are based on a combination of (i) size of eigenvalues; (ii) Exner and Malinowski indicator functions; and (iii) minimum number of eigenvectors needed to reproduce the original data matrix within some measure of experimental error. Provision is made for plotting graphical features of the algorithm along with printing options for intermediate results. It is shown that although no unequivocal indicators of the number of factors to be retained can be conceived of, a sound use of the program compounded with chemical expertise and judgment may lead to a satisfactory compression of the original data space.

Blockinq in simular experimental designs

The repetitive use of generated and/or recorded sequences in the model encounters comprising simular experimental designs has been a suggested technique of simulation methodology. The application of the technique has been deemed compatible with the experimental statistician's concept of blocking. The present paper verifies this compatibility, though notes that the resulting block effect must properly be interpreted as a variance component, or random block effect. A corollary to this result is a delineated procedure for selecting the random number seeds for successive encounters with a dynamic, stochastic simulation model, the procedure providing a proper measure of experimental error. The applicability of the established methodology of the design and analysis of experiments to systemic science via simulation modelling is thereby assured.

Treatment comparisons in grazing trials using the animal as experimental unit

SummaryAlthough it is not always valid to regard ‘within herd variation’ as a true measure of experimental error there are occasions when this may be the only feasible measurement. The effect is considered of regarding the animal as the experimental unit on the estimation of the ratio of production of two treatments and an approximate variance for the ratio is obtained. The conditions under which the approximation is valid are considered.