Investing and packing removable partial denture bases to minimize vertical processing error.
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Dental Casting Technique↗
SEARCH · PubMed Health
Results for “Error minimization”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
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Locating, characterizing and minimizing sources of error for a paper case-based structured oral examination in a multi-campus clerkship.
OBJECTIVE: To determine consistency of assessment in a new paper case-based structured oral examination in a multi-community pediatrics clerkship, and to identify correctable problems in the administration of examination and assessment process. METHOD: Nine paper case-based oral examinations were audio-taped. From audio-tapes five community coordinators scored examiner behaviors and graded student performance. Correlations among examiner behaviors scores were examined. Graphs identified grading patterns of evaluators. The effect of exam-giving on evaluators was assessed by t-test. Reliability of grades was calculated and the effect of reducing assessment problems was modeled. RESULTS: Exam-givers differed most in their "teaching-guiding" behavior, and this negatively correlated with student grades. Exam reliability was lowered mainly by evaluator differences in leniency and grading pattern; less important was absence of standardization in cases. CONCLUSIONS: While grade reliability was low in early use of the paper case-based oral examination, modeling of plausible effects of training and monitoring for greater uniformity in administration of the examination and assigning scores suggests that more adequate reliabilities can be attained.
Clinical Clerkship↗
Planned, complete C.S. orientation minimizes employee fears, errors.
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Education, Continuing↗
Reader error in determining minimal inhibitory concentrations with microdilution susceptibility test panels.
Microdilution susceptibility test panels were independently read by two different technologists. One or more discrepancies between readers occurred with 5% of the 25,022 recorded minimal inhibitory concentrations, but only 0.4% of the tests varied by greater than or equal to 2 dilution intervals.
Anti-Bacterial Agents↗
Wavelet-like receptive fields emerges by non-linear minimization of neuron error.
Redundancy reduction as a form of neural coding has been since the early sixties a topic of large research interest. A number of strategies has been proposed, but the one which is attracting most attention recently assumes that this coding is carried out so that the output signals are mutually independent. In this work we go one step further and suggest an strategy to deal also with non-orthogonal signals (i.e., "dependent" signals). Moreover, instead of working with the usual squared error, we design a neuron where the non-linearity is operating on the error. It is computationally more economic and, importantly, the permutation/scaling problem is avoided. The framework is given with a biological background, as we avocate throughout the manuscript that the algorithm fits well the single neuron and redundancy reduction doctrine. Moreover, we show that wavelet-like receptive fields emerges from natural images processed by this algorithm.
Algorithms↗
Development and application of a micro-capillary rheometer for in-vitro evaluation of parenteral injectability.
A micro-capillary rheometer was developed to determine the rheology and injectability of parenteral formulations. The rheometer consisted of a micro-capillary and a glass syringe attached to an Instron that drove the syringe plunger at predetermined speeds and measured resulting forces on the plunger. The cross-head speed and the measured force were used to calculate the shear rate and the shear stress respectively, according to the Hagen-Poiseuille equation. The resulting rheograms of several Newtonian standards showed excellent linearity over a broad range of about 10 x 10(3) to 160 x 10(3) s(-1) and produced accurate and reproducible viscosity determinations over the viscosity range of about 10 x 10(-3) to 100 x 10(-3) Pa.s. The developed methodology focussed primarily on the minimization of errors associated with the determination of the wall frictional force using both direct measurement and linear regression to determine this parameter from the data. The effect of micro-capillary diameter, syringe cross-sectional area and micro-capillary length was explored in an effort to increase the measured force so that wall frictional force errors could be minimized. The micro-capillary rheometer gave reproducible and accurate rheograms over a range of shear rates consistent with the shear rate range used in clinical practice, and showed that Newtonian and non-Newtonian rheological behaviours could be evaluated quantitatively.
Betamethasone↗
Design of optimal polarimeters: maximization of signal-to-noise ratio and minimization of systematic error.
The relationship between system condition and signal-to-noise ratio (SNR) in reconstructed Stokes parameter images is investigated for rotating compensator, variable retardance, and rotating analyzer Stokes vector (SV) polarimeters. A variety of optimal configurations are presented for each class of systems. The operation of polarimeters is discussed in terms of a four-dimensional conical vector space; and the concept of nonorthogonal bases, frames, and tight frames is introduced to describe the operation of SV polarimeters. Although SNR is an important consideration, performance of a polarimeter in the presence of errors in the calibration and alignment of the optical components is also important. The relationship between system condition and error performance is investigated, and it is shown that an optimum system from the point of view of SNR is not always an optimum system with respect to error performance. A detailed theory of error performance is presented, and the error of a SV polarimeter is shown to be related to the stability and condition number of the polarization processing matrices. The rms error is found to fall off as the inverse of the number of measurements taken. Finally, the concepts used to optimize SV polarimeters are extended to be useful for full Mueller matrix polarimeters.
Journal Article↗
An evaluation of prescribing errors in primary care in Bahrain.
OBJECTIVES: Prescribing errors are preventable and are considered an important target for improving healthcare. The aim of this study was to identify prescribing errors and their determinants in a primary care setting. METHODS: Prescriptions with errors were collected on a daily basis by the pharmacy staff during the first two weeks of September 2003 in 18 out of 20 primary care health centers in Bahrain. Prescribing errors were classified as omission (minor and major), commission and integration errors. RESULTS: Out of 77,511 prescriptions dispensed, 5,959 (7.7%) were identified to contain errors. The frequency of prescribed medication items in 5,959 prescriptions was 16,091. Of these medications, 13,630 (84.7%) were with errors and only 13.2% were written using generic names. Minor errors of omission such as absence of physician's stamp (34.4%), date (9.8%), and information about patients' address (3.8%), age (3.5%) and sex (0.5%) were not specified. Major errors of omission accounted for 93.6% and were as follows: strength/dose (31.0%), length of therapy/ quantity (29.5%), dosage form (19.7%), and frequency of dosing (13.4%). In 6.3% errors of commission (incorrect information) the most common was strength/dose (3.3%), followed by frequency of dosing (2.6%), dosage form (0.3%), and length of therapy/quantity (0.1%). Major errors of omission associated with topical preparations were significantly higher than those with systemic preparations. However, prescriptions with systemic preparations had a higher rate of commission errors. Significant differences in errors were found in prescriptions ordered by family physicians and general practitioners. In 9.2% of prescriptions with errors, potential drug-drug interactions were expected. CONCLUSIONS: This nationwide survey revealed that in primary care, a considerable proportion of prescriptions contained errors. Strategies to minimize medication errors by improving the prescribing skills, adherence to essential drugs list, and use of National Formulary are needed.
Bahrain↗
Articulator-related registration--a simple concept for minimizing eccentric occlusal errors in the articulator.
PURPOSE: The purpose of this study was to develop an easy-to-use procedure for individual registration and to test its accuracy. Unlike common principles, the method should be based on a transfer of the articulator geometry to the patient. MATERIALS AND METHODS: The system consists of an articulator holding a bite plate in a standard position. The bite plate connects to an electronic recording system, which transfers the articulator's condylar points virtually to the patient's mandible by a centric relation record. The trajectories of the transferred points are recorded during mandibular protrusions and laterotrusions. From the trajectories, sagittal condylar and Bennett angles are measured and are adjusted at the articulator after mounting of the casts via the bite plate. Using a mechanical testing device, the accuracy of the measured angles was examined by comparison with preset values varying from 10 to 60 degrees (condylar angle) and from 0 to 40 degrees (Bennett angle) in 10-degree increments. RESULTS: The mean deviations of measured condylar angles from preset values ranged between 1.5 and 0 degrees. The mean deviations of the Bennett angles ranged from -0.5 to -1.3 degrees. CONCLUSION: The transfer of articulator geometry to the patient reduces the number of individual parameters necessary to imitate jaw motion to the condylar and Bennett angles. This leads to a significant simplification in registration and cast transfer. Since the required parameters are recorded with high accuracy, the method could be an alternative to traditional sophisticated instrumental registration.
Centric Relation↗
Avoiding common pitfalls in qualitative data collection and transcription.
The subjective nature of qualitative research necessitates scrupulous scientific methods to ensure valid results. Although qualitative methods such as grounded theory, phenomenology, and ethnography yield rich data, consumers of research need to be able to trust the findings reported in such studies. Researchers are responsible for establishing the trustworthiness of qualitative research through a variety of ways. Specific challenges faced in the field can seriously threaten the dependability of the data. However, by minimizing potential errors that can occur when doing fieldwork, researchers can increase the trustworthiness of the study. The purpose of this article is to present three of the pitfalls that can occur in qualitative research during data collection and transcription: equipment failure, environmental hazards, and transcription errors. Specific strategies to minimize the risk for avoidable errors will be discussed.
Data Collection↗
Interinstrument variability in Hertel-type exophthalmometers.
PURPOSE: To investigate variability in measurements of axial globe position taken with different exophthalmometers of the same style and manufacturer by the same observer. METHODS: In this small clinical study, 10 Hertel-type mirror exophthalmometers were used to measure the degree of exophthalmos of a plastic head. The deepest points on the lateral orbital margins were marked to ensure accurate placement of the instrument. A single observer, masked to previous measurements, recorded multiple measurements with each instrument over several days. RESULTS: Variation was seen between instruments from different manufacturers and more interestingly, between the same design of instruments from the same company. The measurement of axial globe position varied by up to 2.9 mm between instruments of the same make. There was also variation in the measurement of the relative axial globe position of the model. This measurement varied from 0.6 to 2.4 mm. The mean variation of readings taken with the same instrument was 0.5 mm. CONCLUSIONS: It is already considered good practice to minimize interobserver error by recording the make of exophthalmometer used. This small study also suggests that the same instrument should be used for each examination to minimize error caused by variation between instruments of the same make. Variation of 1.5 to 2.0 mm could affect patient treatment when a difference in measurement of 2 mm is regarded as significant during serial or relative exophthalmometry.
Anthropometry↗
Error entropy in classification problems: a univariate data analysis.
Entropy-based cost functions are enjoying a growing attractiveness in unsupervised and supervised classification tasks. Better performances in terms both of error rate and speed of convergence have been reported. In this letter, we study the principle of error entropy minimization (EEM) from a theoretical point of view. We use Shannon's entropy and study univariate data splitting in two-class problems. In this setting, the error variable is a discrete random variable, leading to a not too complicated mathematical analysis of the error entropy. We start by showing that for uniformly distributed data, there is equivalence between the EEM split and the optimal classifier. In a more general setting, we prove the necessary conditions for this equivalence and show the existence of class configurations where the optimal classifier corresponds to maximum error entropy. The presented theoretical results provide practical guidelines that are illustrated with a set of experiments with both real and simulated data sets, where the effectiveness of EEM is compared with the usual mean square error minimization.
Classification↗
Cutting errors in preparation of femoral components in total knee arthroplasty.
Cutting errors that occur during preparation of the femoral component can deter fixation in cementless total knee arthroplasty. This study evaluated the causes of femoral cutting errors and identified methods to minimize these errors. The cutting error caused by toggle of the saw blade in the guide-slot was measured with wood blocks, a cutting guide with 1.5 mm guide slots, and four kinds of saw blades (narrow and wide blades with thicknesses of standard 1.2 mm and thicker 1.4 mm). Another cause of cutting errors, relative motions between the cutting guide and distal femur due to vibration of the saw blade during bone cuts, was measured with preserved cadaver femurs. Various combined fixation methods with intramedullary rod, pins, and clamps were compared. The maximum cutting error caused by toggle of the saw blade in the slot was significantly reduced by using the thicker 1.4 mm saw blade, but the differences between wide and narrow blades in each thickness were not significant. Mean maximum cutting error at the cutting depth of 5 cm with 1.2 mm thick saw blades was 802 microns, and with 1.4 mm thick saw blades it was 488 microns. In the measurement of relative motion, fixation with only pins or clamps did not provide tight fixation and had deflections from 200 microns to more than 1 mm. The best fixation was obtained by combining fixation methods of intramedullary rod and pins or clamps. This resulted in total movement of less than 100 microns. The results of this study indicate that both toggle of the saw blade in the slot and motion of the cutting guide can cause major cutting errors. Cutting error can be minimized by using thicker saw blades and by fixing the cutting guide to the distal femur with combined fixation methods of a central rod and peripheral pins or clamps.
Bone Cements↗
Minimization of target positioning error in accelerator-based radiosurgery.
The stereotactic radiosurgery system used at the Mallinckrodt Institute of Radiology is patterned after that developed at the Joint Center for Radiation Therapy (Brigham & Women's Hospital, Boston, MA) and uses the Brown-Roberts-Wells computed tomography (CT) stereotactic system. The patient's head is attached to a stand that rotates with the treatment couch. The irradiation is conducted using a set of converging arcs of irradiation. Because of mechanical limitations, no accelerator or treatment couch is capable of placing the center of the radiation beam at precisely the same point for all gantry and couch angles and a compromise must be made when locating the nominal isocenter. The stand settings are checked by placing a radiopaque QA sphere at the desired target location. The QA sphere is imaged using a series of eight films exposed at a set of couch and gantry angles that encompass the treatment angles. The distances between the QA sphere image and the center of the radiation field indicate if the correct coordinates were set on the stand and if the radiation beam converges to a sufficiently small region (< 0.1-cm diameter) for treatment. A mathematical procedure has been developed to use the film-measured position errors to determine a stand offset that will minimize the distance between the accelerator isocenter and the target. The technique is capable of reducing the average placement error, as measured by imaging the QA sphere, to 0.035 cm with a maximum deviation of 0.07 cm.
Humans↗
Relationship between dipole parameter estimation errors and measurement conditions in magnetoencephalography.
The relationship between dipole parameter estimation errors and measurement conditions in magnetoencephalography is determined by computer simulation. The model uses a single current dipole in a spherical homogeneous medium. Dipole parameters are estimated using a moving dipole procedure. Signal-to-noise ratio (SNR) is defined as the square-root of the ratio of the average signal power to the average noise power over all measurement points. At SNR > 20, accurate estimation can be carried out independently of dipole depth and coil size. At SNR < 20, dipole depth influences estimation error. When the dipole is located near the center of the sphere, the measurement region should include both extrema of the magnetic field to minimize estimation error. However, when the dipole is not so deep, the position of the measurement region does not influence estimation error. When SNR < 4, estimation error increases as coil size increases. Coil size minimizing estimation error is determined by the ratio of environmental magnetic field noise to electrical noise. For a constant size of measurement region, increasing the number of measurement points decreases estimation error to a certain level. This error level depends on SNR. The number of measurement points required to minimize estimation error also depends on SNR.
Computer Simulation↗
Minimizing false-positive errors in hormonal pulse detection.
To explore the problem of type I (false-positive) statistical errors associated with enumerating endocrine pulses, we used the analysis of immunoactive luteinizing hormone (LH) pulses as a paradigm. In this system, the distribution of measurement error was found to approximate a Gaussian pattern. Moreover, the choice of a fixed threshold criterion to identify a hormone pulse (as generally undertaken to date) was shown to yield significantly different false-positive error rates under different experimental conditions. Therefore, we developed a technique to minimize the detection of false-positive signals and to maintain an essentially uniform error rate among different experimental groups. This simple technique requires that the pulse-detection threshold be adjusted in relation to the degree of intra-assay measurement error present. Our method should facilitate the valid comparison of endocrine pulse frequencies in normal physiological states vs. those associated with hormonal deficiency when measurement error is typically greater. In addition, this approach will aid in a more meaningful assessment of pulse concordance between two or more different hormonal species (i.e., in different assays) and will assist in comparisons of pulse properties quantitated in different laboratories. In summary, rates of false-positive pulse detection using conventional fixed-threshold criteria are materially influenced by even small differences in within-assay variance. We present a technique to minimize this type I statistical error and to maintain an essentially uniform error rate among different experimental groups.
False Positive Reactions↗
The two-dimensional histogram as a constraint for protein phase improvement.
The joint distribution of electron density and its gradient in a protein electron-density map was examined. This joint distribution was represented by a two-dimensional histogram (2D histogram) of electron-density values and the modulus of the gradient. 16 structures representing distinct protein-fold families were selected to study the dependence of the 2D histogram on resolution, overall temperature factor, structural conformation and phase error. The similarity between the histograms for a pair of structures was measured by correlation coefficient, and the residual provided a measure of the difference. The 2D histogram was found to vary with resolution and overall temperature factor, but was found to be insensitive to structure conformation. The average correlation coefficient between pairs of 2D histograms at three different resolutions examined was 0.90 with a standard deviation of 0.04. The average residual for the same condition was 0.13 with a standard deviation of 0.03. The 2D histogram was also found to be sensitive to phase error. The average correlation coefficient and residual between 2D histograms with 10 degrees phase difference are 0.71 and 0.18, respectively. The variation of the 2D histogram resulting from structure-conformation changes was estimated to be equivalent to that of a 4 degrees phase error. This establishes the minimal phase error that a 2D histogram-matching method could achieve. The conservation of the 2D histogram with respect to structure conformation enables the prediction of the ideal 2D histogram for unknown structures. The sensitivity of the 2D histogram to phase error suggests that it could be used as a target for the density-modification method and also could be used as a figure of merit for phase selection in ab initio phasing.
Electrons↗
Regional bone mass measurement from whole-body dual energy X-ray absorptiometry scan.
There are no data on the relative accuracy and precision of regional bone mass measurement from whole-body dual energy X-ray absorptiometry (DXA) scans in small young subjects. Twelve domestic swine piglets (2550-17,660 g) were scanned on a single-beam and on a fan beam densitometer using each humerus and femur as the region of interest to determine the validity of five different scan modes: two infant whole body (IWB), two spine, and one rat whole body (RWB) scan mode in the determination of regional bone mass measurements. DXA bone mineral content (BMC( measurements from RWB and IWB fan beam and IWB single-beam scans were highly predictive of ash weight (adjusted r2 = 0.98, 0.94, 0.94, respectively). Correlation between left and right limbs was highly significant (p < 0.001 for all comparisons) for ash weight (r = 0.99) and for DXA measurements of BMC (r = 0.92-0.99), area (r = 0.92-0.99), and bone mineral density (r = 0.87-0.99) for all modes of DXA scan. Repeatability (as standard deviation of differences of repeated scans) varied with scan mode and DXA parameters and ranged from 1.5 to 7.6%and from 1.8 to 14.7% for intra-and interoperator, respectively. We conclude that regional DXA measurements from IWB and RWB scans can be assessed accurately and with adequate precision for clinical use in subjects with low bone mass comparable with infants and young children. The RWB scan is useful for research studies. However, appropriate training and documentation of precision errors is needed to minimize repeatability errors.
Absorptiometry, Photon↗