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At least 631 records · Page 35Linked to original sources
PubMed1985

Comparison of crosspoint and least-squares regression methods in computation of membrane protein flux parameters from lymph flux analysis.

To compute two parameters of capillary protein transport of reflection coefficient (sigma) and permeability--surface area product (PS), two major methods have been employed. The first, or crosspoint method, uses two sets of lymph flow (Jv) and lymph/plasma protein concentration ratios (R) and solves the irreversible thermodynamic relationship between sigma and PS by simultaneous solution. The second, or least squares method, analyzes the total R versus Jv curve by finding a best fit of all points to the irreversible thermodynamic relationship of R versus Jv. Three theoretical membranes were analyzed with both methods by imposing random errors of 10 or 20% in R and Jv. It was found that such errors, especially in R, were associated with substantial decreases in the percent of successful computations by the crosspoint method. In tight membranes (sigma = 0.9) both methods gave comparable values. For intermediate (sigma = 0.5) and loose membranes (sigma = 0.2) the least-squares method was less specific than the crosspoint method, since up to 9% of random values of R and Jv would be included within the 95% limits for the method. Moreover, attributing homogeneous variance to input data and sampling Jv at geometric intervals exaggerated the variability of the least-squares method output parameters over those obtained by the crosspoint method. Because of nonspecificity, and the fact that the least squares method does not allow for the possibility that sigma and PS are direct functions of hydrostatic capillary pressure or Jv, the crosspoint method appears superior to the least-squares method for computation of sigma and PS from R and Jv.

Capillary Permeability↗
PubMedDate not supplied

Slipped capital femoral epiphysis: comparison of a roentgenographic method and computed tomography in determining slip severity.

Various conventional roentgenographic methods have been proposed to determine the severity of chronic slipped capital femoral epiphysis (SCFE) on the sagittal plane, with some maintaining that computed tomography (CT) is more accurate and reproduces better than roentgenography. We used a modified Dunlap's technique and angular measurement to determine slip severity. Three orthopaedists obtained data from roentgenograms and CT of 20 hips with chronic SCFE. Statistical analysis showed concordance between our method and the measurements and reproducibility produced with CT. The results suggest that our method is as effective as and less expensive than CT.

Adolescent↗
PubMed1990

[Bone mineral contents of lumbar vertebrae in postmenopausal women--using a quantitative computed-tomography method].

We measured bone mineral contents of lumbar vertebrae (L1, L2, L3, L4) in 58 post-menopausal female volunteers (49-76 years old), using a quantitative computed-tomography method. We investigated age-related changes of bone mineral content, and analyzed the relation of bone mineral content to vertebral deformity and to physical characteristics. The following results were obtained: (1) There were highly significant correlations and some significant differences among bone mineral contents of L1, L2, L3 and L4. (2) Bone mineral content showed an apparently linear decline with age. (3) A significant negative correlation was observed between bone mineral content and the central deformity index of the vertebral body, but not for the anterio-posterior deformity index. (4) It was difficult to verify an association of bone mineral content with physical characteristics, such as height, weight, and body mass index.

Aged↗
PubMed1996

[Comparison between two diagnostic methods of computer's mathematic model and clinical diagnosis on TCM syndromes of rheumatoid arthritis].

Based on the test result of 14 trace elements in hair of 163 cases of rheumatoid arthritis, we used one of the methods of the computer's mathematic model, DYNAMIC to assign the patients to five groups among multidimensional space. Then, another method, M-DEC was used to diagnose it back on one plane. The result was compared with that by the usual clinical diagnosis, also five groups were obtained, the group of Deficiency of both Liver and Kidney, syndrome of intermingled Cold with Heat, Deficiency of Qi and Yin, syndrome of Dampness-Heat stagnating in collaterals and syndrome of Phlegm-Dampness stagnating in collaterals. And Kappa was 0.77, greater than 0.6. It displayed the consistency in observation of these two methods, which was shown reliable. After that, we have detected the sensitivity of the syndrome diagnosis by computer's mathematic model method, the result was 96.67% and the specificity of that was 95.15%. So we consider this method could give us an objective judgment on TCM syndromes of rheumatoid arthritis.

Adult↗
PubMed2003

Review of methods and computer codes for interpretation of bioassay data.

Internal dose determination is an essential component of individual monitoring programmes for workers or members of the public exposed to radionuclides, and methods and computer programs are required for dose assessment. A recent international European Radiation Dosimetry Group (EURADOS) intercomparison has shown unacceptably large ranges in the results assessment. An ICRP working party has been initiated to consider what guidance ICRP can give on the use of models and interpret bioassay data in terms of intake/dose. In this field, six codes for bioassay data interpretation, which implement the current ICRP publication 78 biokinetic models, have been reviewed against several criteria with different levels of importance: minor criteria such as the practical use of the code and the graphical capabilities, and major criteria such as the choice of available parameters, peculiarities of data fitting and interpretation, the choice of biokinetic models and the use of uncertainties. All these criteria were assessed using one artificial set of data and two examples extracted from the previous international EURADOS intercomparison.

Administration, Oral↗
PubMed1984

A computer-aided method to evaluate the function of implanted Björk-Shiley prosthetic heart valves.

Evaluation of the function of implanted prosthetic valves is important in early diagnosis of valve dysfunction. Björk-Shiley valves contain two radiopaque rings, which are projected as ellipses in cineradiography. From these ellipses the actual valve opening angle can be calculated. A computer-aided method was developed that enables measurement of ellipse characteristics reliably, independent of projection angle and valve opening. It is demonstrated that calculated and real opening angles differ less than 2 degrees with this method. Using the same technique the tilting angle of the valve ring during the cardiac cycle is computed for evaluation of progression of valve dehiscense in case of a paravalvular leak. Application of the method to patient data is illustrated by three cases. The method is suitable for use by technicians. It can be implemented on a small microprocessor system. The method proved to be a powerful tool in the evaluation of patients with implanted Björk-Shiley valves.

Aortic Valve↗
PubMed1999

Hybrid finite elements and spectral method for computation of the electric potential generated by a nerve cuff electrode.

An original numerical method is developed to compute the 3D electric potential generated by a dot-contact cuff electrode implanted around an axisymmetrical, inhomogeneous, anisotropic nerve. The technique is based on a 2D finite-element approach coupled with a semi-analytical Fourier spectral decomposition to approximate the solution behaviour in the azymuthal direction. The method only requires a 2D FEM mesh and allows an accurate electrode description, with any number of contacts at different angular positions. Results show that the convergence of the Fourier series is very fast: typically, the relative error due to series truncation (estimated by the norm of the difference between the solution computed with M modes and the one computed with M-1 modes, normalised by the norm of the solution computed with M modes) reaches the order of 10(-3) with six spectral modes (M = 6). As a consequence, the whole algorithm has the complexity of a 2D approach.

Computer Simulation↗
PubMed1999

The determination of the collagen and elastin amount in the human varicose vein by the computer morphometric method.

The results of the works dealing with alterations of the connective tissue in varicose vein wall are not ambiguous, so the exact cause of the vein dilatation has still not been established. We were determining the collagen and elastin amounts in human varicose vein wall in comparison with non-dilated long saphenous vein by the light microscopy and computer morphometric method. We have found the lesser amount of collagen in varicose veins than in non-dilated veins, the amounts of the elastin in both the varicose and non-varicose veins were without the statistical significance.

Case-Control Studies↗
PubMed2004

MEGA3: Integrated software for Molecular Evolutionary Genetics Analysis and sequence alignment.

With its theoretical basis firmly established in molecular evolutionary and population genetics, the comparative DNA and protein sequence analysis plays a central role in reconstructing the evolutionary histories of species and multigene families, estimating rates of molecular evolution, and inferring the nature and extent of selective forces shaping the evolution of genes and genomes. The scope of these investigations has now expanded greatly owing to the development of high-throughput sequencing techniques and novel statistical and computational methods. These methods require easy-to-use computer programs. One such effort has been to produce Molecular Evolutionary Genetics Analysis (MEGA) software, with its focus on facilitating the exploration and analysis of the DNA and protein sequence variation from an evolutionary perspective. Currently in its third major release, MEGA3 contains facilities for automatic and manual sequence alignment, web-based mining of databases, inference of the phylogenetic trees, estimation of evolutionary distances and testing evolutionary hypotheses. This paper provides an overview of the statistical methods, computational tools, and visual exploration modules for data input and the results obtainable in MEGA.

Databases, Genetic↗
PubMed1996

A comparison of computer-based methods for the determination of onset of muscle contraction using electromyography.

Little consensus exists in the literature regarding methods for determination of the onset of electromyographic (EMG) activity. The aim of this study was to compare the relative accuracy of a range of computer-based techniques with respect to EMG onset determined visually by an experienced examiner. Twenty-seven methods were compared which varied in terms of EMG processing (low pass filtering at 10, 50 and 500 Hz), threshold value (1, 2 and 3 SD beyond mean of baseline activity) and the number of samples for which the mean must exceed the defined threshold (20, 50 and 100 ms). Three hundred randomly selected trials of a postural task were evaluated using each technique. The visual determination of EMG onset was found to be highly repeatable between days. Linear regression equations were calculated for the values selected by each computer method which indicated that the onset values selected by the majority of the parameter combinations deviated significantly from the visually derived onset values. Several methods accurately selected the time of onset of EMG activity and are recommended for future use.

Adolescent↗
PubMed1995

A computationally efficient method for solving the redundant problem in biomechanics.

Determining the optimal set of musculotendon forces with which to produce a forward dynamic simulation of movement typically involves a huge investment of time and computational resources. A new, computationally efficient method is proposed that simultaneously achieves the desired trajectory and the dynamically optimized set of muscle stresses, and hence forces, according to the maximal endurance criterion function of Crowninshield and Brand (1981). Muscle-induced accelerations of the system resulting from unit stress contractions of individual muscles are superposed via the new pseudoinverse method to yield the desired motion trajectory. The method is tested on a control problem involving a five degree-of-freedom (DOF), 30 muscle, upper extremity model, which incorporates a dual rigid-body forearm to represent pronation and supination more adequately. The pseudoinverse method delivered the desired motion to within 0.25 degrees for each DOF during a three-second simulation. It is anticipated that the methodology can be easily and accurately applied to other highly redundant optimal control problems in biomechanics.

Acceleration↗
PubMed1993

Excision of a trabecular ROI from resin-embedded vertebrae: report on a computer-assisted method.

A major problem when evaluating the accuracy of quantitative computed tomography (QCT) against chemical analysis of bone mineral is to ensure that the same region of interest (ROI) is measured with two techniques. The method described here attempts to reach this objective. Forty-nine lumbar vertebrae were scanned. The mid-vertebral portion was sawed and embedded in a polyester resin. The ROI defined with an automated contour detection was transmitted, using a Hewlett-Packard scanjet, to a computer-assisted milling machine which excised a trabecular ROI sample. The volume of each trabecular sample was determined using an Archimedian method. ROI volumes assessed on QCT were highly correlated with those obtained with the Archimedian method (r = 0.98). The standard error of the estimate was 170 mm3 (4.5%). These results suggest that trabecular samples obtained with this method optimally agree with the ROIs selected on QCT examination.

Bone and Bones↗
PubMedDate not supplied

A comparison of methods to compute the point of force application in handrim wheelchair propulsion: a technical note.

Several methods are available for computing the location of the point of force application (PFA) in manual wheelchair propulsion using kinetic data. We compared five different techniques for computing the PFA location in analysis of data from five wheelchair users propelling their own wheelchairs using their normal propulsion style. The effects of the assumptions used in the calculations on the resulting location of the PFA, handrim force and moment components, and mechanical efficiency (e) were quantified. When kinetic data were used to locate the PFA, the most consistent and stable results were obtained using the assumptions that components of the handrim moment about the anteriorly directed and vertically directed axes were negligible. Some assumptions led to unsolvable equations at points during the propulsion cycle, demonstrating that they were inappropriate. All PFA values calculated with kinetic data were unstable at the beginning and end of the propulsion phase. While differences exist due to individual technique, assuming handrim moment components about the anterior-posterior, vertical, and/or both axes resulted in the most representative results.

Adult↗
PubMed1999

Detecting selective expression of genes and proteins.

Selective expression of a gene product (mRNA or protein) is a pattern in which the expression is markedly high, or markedly low, in one particular tissue compared with its level in other tissues or sources. We present a computational method for the identification of such patterns. The method combines assessments of the reliability of expression quantitation with a statistical test of expression distribution patterns. The method is applicable to small studies or to data mining of abundance data from expression databases, whether mRNA or protein. Though the method was developed originally for gene-expression analyses, the computational method is, in fact, rather general. It is well suited for the identification of exceptional values in many sorts of intensity data, even noisy data, for which assessments of confidences in the sources of the intensities are available. Moreover, the method is indifferent as to whether the intensities are experimentally or computationally derived. We show details of the general method and examples of computational results on gene abundance data.

Algorithms↗
PubMed1993

A new method using computed tomographic scan to measure the rectus femoris-patellar tendon Q-angle comparison with conventional method.

The Q-angle should be the angle generated by a line connecting the anteroinferior iliac spine (AIIS), the bottom of the groove of the femoral condyle, and the tibial tubercle. The Q-angle was measured by computed tomography (CT) in 43 lower limbs with recurrent patellar dislocation and 26 normal controls. The mean Q-angle was 20 degrees in the dislocated group and 13 degrees in controls, a significant difference. No significant difference was found in the Q-angle between the dislocated and control groups using the conventional method. Lower limb rotation had little effect on accuracy of the method.

Adolescent↗
PubMed2004

Comparison of the accuracy of methods of computational haplotype inference using a large empirical dataset.

BACKGROUND: Analyses of genetic data at the level of haplotypes provide increased accuracy and power to infer genotype-phenotype correlations and evolutionary history of a locus. However, empirical determination of haplotypes is expensive and laborious. Therefore, several methods of inferring haplotypes from unphased genotypic data have been proposed, but it is unclear how accurate each of the methods is or which methods are superior. The accuracy of some of the leading methods of computational haplotype inference (PL-EM, Phase, SNPHAP, Haplotyper) are compared using a large set of 308 empirically determined haplotypes based on 15 SNPs, among which 36 haplotypes were observed to occur. This study presents several advantages over many previous comparisons of haplotype inference methods: a large number of subjects are included, the number of known haplotypes is much smaller than the number of chromosomes surveyed, a range in values of linkage disequilibrium, presence of rare SNP alleles, and considerable dispersion in the frequencies of haplotypes. RESULTS: In contrast to some previous comparisons of haplotype inference methods, there was very little difference in the accuracy of the various methods in terms of either assignment of haplotypes to individuals or estimation of haplotype frequencies. Although none of the methods inferred all of the known haplotypes, the assignment of haplotypes to subjects was about 90% correct for individuals heterozygous for up to three SNPs and was about 80% correct for up to five heterozygous sites. All of the methods identified every haplotype with a frequency above 1%, and none assigned a frequency above 1% to an incorrect haplotype. CONCLUSIONS: All of the methods of haplotype inference have high accuracy and one can have confidence in inferences made by any one of the methods. The ability to identify even rare (>/= 1%) haplotypes is reassuring for efforts to identify haplotypes that contribute to disease in a significant proportion of a population. Assignment of haplotypes is relatively accurate among subjects heterozygous for up to 5 sites, and this might be the largest number of SNPs for which one should define haplotype blocks or have confidence in haplotype assignments.

Algorithms↗