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At least 109 records · Page 6Linked to original sources
PubMed2005

Coronary calcium measurements: effect of CT scanner type and calcium measure on rescan reproducibility--MESA study.

PURPOSE: To evaluate the effect of scanner type and calcium measure on the reproducibility of calcium measurements. MATERIALS AND METHODS: This investigation was approved by the institutional review boards of each study site and by the Institutional Review Board of the Los Angeles Biomedical Research Institute. Informed consent for scanning and participation was obtained from all participants. The study was Health Insurance Portability and Accountability Act compliant. The Multi-Ethnic Study of Atherosclerosis (MESA) is a multicenter observational study of 6814 participants undergoing demographic, risk factor, and subclinical disease evaluations. Coronary artery calcium was measured by using duplicate CT scans. Three study centers used electron-beam computed tomography (CT), and three used multi-detector row CT. Coronary artery calcium was detected in 3355 participants. Three calcium measurement methods-Agatston score, calcium volume, and interpolated volume score-were evaluated. Mean absolute differences between calcium measures on scans 1 and 2, excluding cases for which both scans had a measure of zero, was modeled by using linear regression to compare reproducibility between scanner types. A repeated measures analysis of variance test was used to compare reproducibility across calcium measures, with mean percentage absolute difference as the outcome measure. Rescan reproducibility in relation to misregistrations, noise, and motion artifacts was also examined. Variables were log transformed to create a more normal distribution. RESULTS: Concordance for presence of calcium between duplicate scans was high and similar for both electron-beam and multi-detector row CT (96%, kappa = 0.92). Mean absolute difference between calcium scores for the two scans was 15.8 for electron-beam and 16.9 for multi-detector row CT scanners (P = .06). Mean relative differences were 20.1 for Agatston score, 18.3 for calcium volume, and 18.3 for interpolated volume score (P < .01). Reproducibility was lower for scans with versus those without image misregistrations or motion artifacts (P < .01 for both). CONCLUSION: Electron-beam and multi-detector row CT scanners have equivalent reproducibility for measuring coronary artery calcium. Calcium volumes and interpolated volume scores are slightly more reproducible than Agatston scores. Reproducibility is lower for scans with misregistrations or motion artifacts.

Calcinosis↗
PubMed2005

[Measuring blood pressure in the forearm of obese patients: concordance with arm measurement].

BACKGROUND AND OBJECTIVE: The occasional forearm blood pressure (BP) measurement has been accepted for some obese patients. However, few studies have compared the concordance between arm and forearm BP measurements. Our aim was to know whether the forearm BP measurement displays a good concordance with the arm BP measurement in obese patients. SUBJECTS AND METHOD: Cross-sectional descriptive study in an ambulatory setting. By means of convenience sampling, a sample of 54 patients with a body mass index > 26 kg/m2 was selected. The study unit was the upper limb (n = 108). BP was measured 3 times in each arm and forearm (12 measurements in each patient using an automated validated device OMRON 705CP) in a randomized order. RESULTS: Women: 77.8%; mean (SD) aged: 60.2 (12.7) years; body mass index: 38.6 (5.5) kg/m2; 79.6% were hypertensive. BP was higher in forearm than in arm: mean (SD) 137.7 (16.9) mmHg versus 132.1 (18) mmHg, for systolic (S) BP (p < 0.001) and 79.8 (11.2) mmHg versus 78.3 (9.9) mmHg for diastolic (D) BP (p = 0.04), respectively. Intraclass correlation coefficients for arm/forearm measurements were 0.83 (95% confidence interval [CI], 0.77-0.88) and 0.74 (95% CI, 0.65-0.82) for SBP and DBP, respectively. Mean differences between arm and forearm measurements were 5.5 mmHg (95% CI, -14.5 to 25.5) mmHg for SBP and 1.53 mmHg [95% CI, -13.5 to 16.5] for DBP. CONCLUSIONS: BP differences between arm/forearm measurements are clinically outstanding. Therefore, forearm BP measurement does not seem advisable in obese patients.

Aged↗
PubMed1995

Measuring hallux valgus: a comparison of conventional radiography and clinical parameters with regard to measurement accuracy.

To assess the repeatability and error of conventional x-ray measurements, intra- and interobserver evaluations of measurement accuracy were done on 20 preoperative and 40 postoperative (20 chevron and 20 proximal osteotomy) x-rays of hallux valgus patients. Standard x-rays showed an average interobserver error of measurement of 6.4 degrees for the hallux valgus angle, 5.4 degrees for the intermetatarsal angle, and 2.0 mm for the intermetatarsal distance. The intraobserver error did not differ greatly. The repeatability and error of two clinical measurements, ball circumference, and dorsal to plantar range of motion of the first metatarsophalangeal joint were evaluated for 20 healthy volunteers. The ball circumference had an average measurement error of 1.1 cm, whereas the dorsal and plantar range of motion of the great toe had an average measurement error of 12 degrees in dorsiflexion and 16 degrees in plantarflexion. In both clinical and radiographic parameters, linear measurements were more accurate than angular measurements. Although x-rays are of value in hallux valgus surgery, standard x-rays are less accurate than previously assumed. Small changes produced by osteotomies may be hidden by the postoperative measurement error. The results of hallux valgus surgery should primarily be evaluated clinically. When clinical and radiological evaluations are made, linear measurements may be preferable.

Female↗
PubMed2005

Determining sexual dimorphism in frog measurement data: integration of statistical significance, measurement error, effect size and biological significance.

Several analytic techniques have been used to determine sexual dimorphism in vertebrate morphological measurement data with no emergent consensus on which technique is superior. A further confounding problem for frog data is the existence of considerable measurement error. To determine dimorphism, we examine a single hypothesis (Ho = equal means) for two groups (females and males). We demonstrate that frog measurement data meet assumptions for clearly defined statistical hypothesis testing with statistical linear models rather than those of exploratory multivariate techniques such as principal components, correlation or correspondence analysis. In order to distinguish biological from statistical significance of hypotheses, we propose a new protocol that incorporates measurement error and effect size. Measurement error is evaluated with a novel measurement error index. Effect size, widely used in the behavioral sciences and in meta-analysis studies in biology, proves to be the most useful single metric to evaluate whether statistically significant results are biologically meaningful. Definitions for a range of small, medium, and large effect sizes specifically for frog measurement data are provided. Examples with measurement data for species of the frog genus Leptodactylus are presented. The new protocol is recommended not only to evaluate sexual dimorphism for frog data but for any animal measurement data for which the measurement error index and observed or a priori effect sizes can be calculated.

Analysis of Variance↗
PubMed1994

MR measurements of the hippocampus for lateralization of temporal lobe epilepsy: value of measurements of the body vs the whole structure.

OBJECTIVE: Measurements of the volume of the hippocampus have been used preoperatively to determine the side of the hippocampus involved in patients with intractable temporal lobe epilepsy. However, the method used is time consuming and requires special training. The purpose of this study was to determine the validity of using measurements of the volume of the hippocampal body as a substitute for measurements of the volume of the whole hippocampus in patients with temporal lobe epilepsy. SUBJECTS AND METHODS: The study group consisted of 33 patients with intractable temporal lobe epilepsy due to presumed hippocampal sclerosis and 30 control subjects. Of the 33 patients with intractable temporal lobe epilepsy, 30 had hippocampal sclerosis and three had normal findings on pathologic examination of the hippocampus. T2-weighted fast spin-echo images were used to determine hippocampal volumes. Volumes were calculated by summing the sectional areas of the entire hippocampus and of the hippocampal body. Correlation between the volume of the hippocampal body and the volume of the whole hippocampus was determined. The sensitivity and specificity of measurement of the volume of the hippocampal body for lateralizing the foci responsible for seizures in patients with presumed hippocampal sclerosis were compared with those of measurement of the volume of the whole hippocampus. RESULTS: Significant linear relationships were noted between volumes of the hippocampal body and volumes of the whole hippocampus (p < .001). The sensitivity and specificity of measurements of volumes of the hippocampal body were identical to those of measurements of volumes of the whole hippocampus (87% and 100%, respectively). CONCLUSIONS: Our results show that segmental MR measurements of the body of the hippocampus are as accurate as measurements of the whole hippocampus for lateralizing temporal lobe epilepsy before surgery. Because segmental measurements are less time consuming and require less experience to perform, they are considered the procedure of choice.

Adolescent↗
PubMed2001

Genetic correlation estimates between ultrasound measurements on yearling bulls and carcass measurements on finished steers.

Carcass and growth measurements of finished crossbred steers (n = 843) and yearling ultrasound and growth measurements of purebred bulls (n = 5,654) of 11 breeds were analyzed to estimate genetic parameters. Multiple-trait restricted maximum likelihood (REML) was used to estimate heritabilities and genetic correlations between finished steer carcass measurements and yearling bull ultrasound measurements. Separate analyses were conducted to examine the effect of adjustment to three different end points: age, backfat thickness, and weight at measurement. Age-constant heritability estimates from finished steer measurements of hot carcass weight, carcass longissimus muscle area, carcass marbling score, carcass backfat, and average daily feedlot gain were 0.47, 0.45, 0.35, 0.41, and 0.30, respectively. Age-constant heritability estimates from yearling bull measurements of ultrasound longissimus muscle area, ultrasound percentage of intramuscular fat, ultrasound backfat, and average daily postweaning gain were 0.48, 0.23, 0.52, and 0.46, respectively. Similar estimates were found for backfat and weight-constant traits. Age-constant genetic correlation estimates between steer carcass longissimus muscle area and bull ultrasound longissimus muscle area, steer carcass backfat and bull ultrasound backfat, steer carcass marbling and bull ultrasound intramuscular fat, and steer average daily gain and bull average daily gain were 0.66, 0.88, 0.80, and 0.72, respectively. The strong, positive genetic correlation estimates between bull ultrasound measurements and corresponding steer carcass measurements suggest that genetic improvement for steer carcass traits can be achieved by using yearling bull ultrasound measurements as selection criteria.

Adipose Tissue↗
PubMed1993

A comparison of two methods of measuring aqueous flow in humans: fluorophotometry and flare measurement.

The technique of Anjou and Krakau for measuring flare and Krakau's method for estimating aqueous humor flow in humans was compared to the fluorophotometric procedure of Jones and Maurice. The precision of flare was measured in 20 normal human volunteers, and the precision of flow was measured with fluorophotometry in 24 volunteers. In addition, the circadian rhythms of both flow and flare were measured simultaneously in a separate group of 20 subjects. This simultaneous measurement allowed us to calculate the entry rate of scattering substances into the aqueous humor as a function of time of day. This entry rate is critical for measuring flow by the method of Krakau. The mean coefficient of variation (+/- SD) of repeated measurements of flare at the same time of day was 23.2% +/- 10.3%. The mean coefficient of variation of the measurement of aqueous flow by fluorophotometry was 15.9% +/- 8.2%, significantly better than the measurement of flare (p = 0.01). The daytime entry rate of scattering substances into the aqueous humor varied from 1.39 +/- 0.86 microgram/min (calculated as albumin) to 1.05 +/- 0.58 microgram/min. The rates in daytime hours were not significantly different from each other. At night during sleep, the entry rate was 0.67 +/- 0.48 microgram/min, significantly slower (p between 0.002 and < 0.001). These data indicate that the flare technique cannot be used alone to calculate the circadian rhythm of flow and that direct measurement of flow by fluorescein clearance is likely to be the most repeatable and accurate of the two.

Aqueous Humor↗
PubMed2005

[Efficacy and problems of bladder volume measurement using portable three dimensional ultrasound scanning device--in particular, on measuring bladder volume lower than 100ml].

OBJECTIVES: Using a portable three dimensional ultrasound scanning device (The Bladder Scan BVI6100, Diagnostic Ultrasound Corporation), we examined measured values of bladder volume, especially focusing on volume lower than 100 ml. MATERIALS AND METHODS: A total of 100 patients (male: 66, female: 34) were enrolled in the study. We made a comparison study between the measured value (the average of three measurements of bladder urine volume after a trial in male and female modes) using BVI6100, and the actual measured value of the sample obtained by urethral catheterization in each patient. We examined the factors which could increase the error rate. We also introduced the effective techniques to reduce measurement errors. RESULTS: The actual measured values in all patients correlated well with the average value of three measurements after a trial in a male mode of the BVI6100. The correlation coefficient was 0.887, the error rate was--4.6 +/- 24.5%, and the average coefficient of variation was 15.2. It was observed that the measurement result using the BVI6100 is influenced by patient side factors (extracted edges between bladder wall and urine, thickened bladder wall, irregular bladder wall, flattened rate of bladder, mistaking prostate for bladder in male, mistaking bladder for uterus in a female mode, etc.) or examiner side factors (angle between BVI and abdominal wall, compatibility between abdominal wall and ultrasound probe, controlling deflection while using probe, etc). CONCLUSIONS: When appropriate patients are chosen and proper measurement is performed, BVI6100 provides significantly higher accuracy in determining bladder volume, compared with existing abdominal ultrasound methods. BVI6100 is a convenient and extremely effective device also for the measurement of bladder urine over 100 ml.

Aged↗
PubMed1990

Three dimensional shape measurement of teeth. (3) The measurement by the newly developed laser displacement meter with double sensors.

A laser displacement meter which equips two sensors was developed in order to measure the shape of teeth with higher efficiency and accuracy. By this displacement meter the rotational measurement to compensate the data at the shaded points became needless. The measurement of the 6 molar was carried out, and the regions such as cusps and fissures of the occlusal plane were measured precisely without errors. The time required for the measurement was about 10 min. and reduced to one third that of the previous system. While, by the measurement from one direction, the undercut portion such as toothneck is less accurate. Then, 7 molar model was tilted on the gonio stage with +/- 20 degrees and measured divisionally, and two groups of data were connected. By this method, the whole shape of tooth including the undercut portion became to be measurable. In the case of a crown abutment tooth with steeply inclined axial wall and margin, tilting method was also applied to measure more accurately. 7 abutment was tilted with +/- 30 degrees and measured and connected. The gingival and marginal line which are the characteristic spots for designing the crown were recognized. These data thus obtained will be able to give the inner and outer shape of crown for processing the prostheses by CAD/CAM technique.

Crowns↗
PubMed1997

Comparison between continuous brain tissue measurement and cerebrovenous measurement of pO2, pCO2 and pH in a porcine intracranial pressure model.

Simultaneous oxygen measurements in brain tissue (p(ti)O2) and hemoglobin saturation measurement in cerebrovenous blood in patients after severe head injury have shown different results regarding the comparability of the findings in respect to CPP and ICP. This is contrast to theoretical expectations. The aim of this study was to compare continuous ptiO2 measurement with oxygen partial pressure measurement in sagittal sinus (pO2cv) during simultaneously performance in an animal intracranial pressure model. For continuous measurement we used a newly available multisensor probe. We placed a Paratrend 7 probe (BSL, High Wycombe, UK) in the left frontoparietal white matter and measured ptiO2, pCO2 (ptiCO2) pH (pHti) and temperature (t(ti)) while simultaneously measuring these parameters (pcvO2, pcvCO2, pHcv, tcv) in the sagittal sinus in 9 pigs under general anaesthesia. A fogarty balloon catheter was placed supracerebellar infratentorial and inflated stepwise in order to increase ICP. The baseline levels of pO2ti, pCO2ti und pHti in the non-injured brain tissue showed a more extended heterogeneity compared to the findings in cerebrovenous blood. Both, pO2ti and pO2cv were significant correlated to the CPP decrease. In both measurement compartments pCO2 was inverse correlated to the course of CPP and seems the course of pH mainly to determine. p(ti)O2 as well as p(cv)O2 showed a close correlation to the CPP course and have proven to be qualified to indicate metabolic information about the relation of cerebral blood flow and metabolic cerebral demands. The measurement of CO2 tension in both measurement compartments shows a distinct heterogeneity of the absolute values and the results are only weak correlated to CPP. Metabolic influence on this parameter could not be revealed in the used experimental approach.

Animals↗
PubMed2003

What do tender points measure? Influence of distress on 4 measures of tenderness.

OBJECTIVE: To examine the relationship between current pain, distress, and ascending and random measures of tenderness. METHODS: Manual tender point counts and dolorimeter measures of the pressure pain threshold were determined in a sample of 47 women representative of the general population with respect to tenderness. In addition, discrete pressure stimuli of varying intensities to the left thumb were applied in random fashion. Distress was measured with the Brief Symptom Inventory and the Beck Depression Inventory, and pain was evaluated with the Short Form McGill Pain Questionnaire. RESULTS: Only the random measure of tenderness was relatively independent of an individual's current psychological state. The respective correlation coefficients between measures of tenderness and psychological state were generally greatest for the manual tender point count and also significant for the dolorimeter measures. In contrast, all measures were highly correlated with ratings of spontaneous pain, again with the manual tender point count showing the strongest, and the random method the weakest, correlations. Linear regression analysis replicated the results of the correlational analysis. CONCLUSION: As a measure of tenderness, the number of positive tender points is clearly influenced by an individual's distress. Other more sophisticated measures of tenderness that randomly present stimuli in an unpredictable fashion appear to be relatively immune to these biasing effects, although our results obtained in a research setting have yet to be replicated in clinical practice.

Adult↗
PubMed2004

Pitfalls of converting practice guidelines into quality measures: lessons learned from a VA performance measure.

The Department of Veterans Affairs (VA) manages the largest health care system in the United States, and the Institute of Medicine has recommended that many practices of VA quality measurement be applied to the US health care system as a whole. The VA measures quality of care at all of its sites by assessing adherence rates to performance measures, which generally are derived from evidence-based practice guidelines. Higher adherence rates are used as evidence of better quality of care. However, there are problems with converting practice guidelines, intended to offer guidance to clinicians, into performance measures that are meant to identify poor-quality care. We suggest a more balanced perspective on the use of performance measures to define quality by delineating conceptual problems with the conversion of practice guidelines into quality measures. Focusing on colorectal cancer screening, we use a case study at 1 VA facility to illustrate pitfalls that can cause adherence rates to guideline-based performance measures to be poor indicators of the quality of cancer screening. Pitfalls identified included (1) not properly considering illness severity of the sample population audited for adherence to screening, (2) not distinguishing screening from diagnostic procedures when setting achievable target screening rates, and (3) not accounting for patient preferences or clinician judgment when scoring performance measures. For many patients with severe comorbid illnesses or strong preferences against screening, the risks of colorectal cancer screening outweigh the benefits, and the decision to not screen may reflect good quality of care. Performance measures require more thoughtful specification and interpretation to avoid defining high testing rates as good quality of care regardless of who received the test, why it was performed, or whether the patient wanted it.

Colorectal Neoplasms↗
PubMedDate not supplied

A study of the fluorescence measurement using a 96-well microplate by a remodelled parallel luminescent measuring system.

To develop an index to measure alveolar macrophage activity, the fluorescent technique for detection of calcium flux was paid special attention. In this study, a parallel luminescence measuring system was remodelled for fluorescence measurement using a 96-well microplate. The fluorescence indicators widely used to measure cytosolic free calcium ion concentration require excitation at ultraviolet (UV) wavelengths. Instruments to produce UV wavelengths are expensive compared to those used to produce visible wavelengths, and UV wavelengths are potentially injurious to cells. To avoid these problems, Fluo 3 (excitation wavelength in the visible range) was used as the fluorescent dye for detecting calcium ions. The parallel luminometer was remodelled successfully for fluorescent measurement as assessed by the results obtained from the measurements of a common fluorescent dye, fluorescein. Concentrations of free calcium ions were measured using Fluo 3 at 37 degrees C to consider the measurement of calcium flux in living cells. Although a linear relationship between concentrations of free calcium ions and fluorescence were observed, a diminution of fluorescence over time was also observed. To measure calcium flux in living cells, further instrumental and experimental improvements are thus needed.

Calcium↗
PubMed2004

Bone mineral density measurement in the calcaneus with DXL: comparison with hip and spine measurements in a cross-sectional study of an elderly female population.

We investigated the relationship between calcaneal and axial bone mineral density in an elderly female population. We also investigated the influence of changing the reference populations on T-score values. Bone mineral density (BMD) was determined in 388 women (mean age 73 years) participating in a cross-sectional study. BMD values were determined at the left hip and the lumbar spine, L1-L4, using Hologic QDR 4500 equipment for dual X-ray absorptiometry (DXA). The calcaneal measurements were made with DEXA-T, a device using a dual X-ray and laser (DXL) technique that combines DXA measurement with measurement of the heel thickness using a laser reflection technique. DEXA-T is an older version of the Calscan DXL device now commercially available. T-score values were calculated for hip measurements with both the original reference population of the Hologic device and the NHANES III reference population. T scores for heel measurements were calculated with the original reference population of the peripheral device and the Calscan database, a new calcaneal reference population. Changing the reference populations had a great influence on both the heel and the hip T scores, especially those of the femoral neck where the percentage of subjects identified as osteoporotic decreased from 53% to 23%. We conclude that, with the NHANES III and the larger Calscan database, using the cut-off point of -2.5 SD, the heel measurements had optimal accuracy for detecting osteoporosis at either the combination of the lumbar spine and the femoral neck or the combination of the lumbar spine, the femoral neck, the total hip and the trochanter. BMD measurements of the calcaneus with DXL correlated fairly well with measurements at axial sites at the group level, while in individual subjects large deviations were observed between all the measured sites. We also conclude that the influence of the reference populations on the T scores is substantial when different DXA methods are being compared; the total number of subjects classified as osteoporotic varied from 7% to 53% between the sites and with different reference populations.

Absorptiometry, Photon↗
PubMed2003

A new skin-surface device for measuring the curvature and global and segmental ranges of motion of the spine: reliability of measurements and comparison with data reviewed from the literature.

There is an increasing awareness of the risks and dangers of exposure to radiation associated with repeated radiographic assessment of spinal curvature and spinal movements. As such, attempts are continuously being made to develop skin-surface devices for use in examining the progression and response to treatment of various spinal disorders. However, the reliability and validity of measurements recorded with such devices must be established before they can be recommended for use in the research or clinical environment. The aim of this study was to examine the reliability of measurements using a newly developed skin-surface device, the Spinal Mouse. Twenty healthy volunteers (mean age 41 +/- 12 years, nine males, 11 females) took part. On 2 separate days, spinal curvature was measured with the Spinal Mouse during standing, full flexion, and full extension (each three times by each of two examiners). Paired t-tests, intraclass correlation coefficients (ICC), and standard errors of measurement (SEM) with 95% confidence intervals were used to characterise between-day and interexaminer reliability for: standing sacral angle, lumbar lordosis, thoracic kyphosis, and ranges of motion (flexion, extension) of the thoracic spine, lumbar spine, hips, and trunk. The between-day reliability for segmental ranges of flexion was also determined for each motion segment from T1-2 to L5-S1. The majority of parameters measured for the 'global regions' (thoracic, lumbar, or hips) showed good between-day reliability. Depending on the parameter of interest, between-day ICCs ranged from 0.67 to 0.92 for examiner 1 (average 0.82) and 0.57 to 0.95 for examiner 2 (average 0.83); for 70% of the parameters measured, the ICCs were greater than 0.8 and generally highest for the lumbar spine and whole trunk measures. For lumbar spine range of flexion, the SEM was approximately 3 degrees. The ICCs were also good for the interexaminer comparisons, ranging from 0.62 to 0.93 on day 1 (average 0.81) and 0.70 to 0.94 on day 2 (average 0.86), although small systematic differences were sometimes observed in their mean values. The latter were still evident even if both examiners used the same skin markings. For segmental ranges of flexion, the ICCs varied between vertebral levels but overall were lower than for the global measures (average for all levels in all analyses, ICC 0.6). For each examiner, the average between-day SEM over all vertebral levels was approximately 2 degrees. For 'global' regions of the spine, the Spinal Mouse delivered consistently reliable values for standing curvatures and ranges of motion which compared well with those reported in the literature. This suggests that the device can be reliably implemented for in vivo studies of the sagittal profile and range of motion of the spine. As might be expected for the smaller angles being measured, the segmental ranges of flexion showed lower reliability. Their usefulness with regard to the interpretation of individual results and the detection of 'real change' on an individual basis thus remains questionable. Nonetheless, the group mean values showed few between-day differences, suggesting that the device may still be of use in providing clinically interesting data on segmental motion when examining groups of individuals with a given spinal pathology or undergoing some type of intervention.

Adult↗
PubMed1994

Measuring the safety effect of road measures at junctions.

The effects of road measures implemented at main road junctions in 1984-1986 were studied on the basis of police-reported accidents that had occurred at the junctions in 1983-1987. The data were obtained from an extensive junction inventory performed by the District Offices of the Finnish National Road Administration in 1988. A total of 325 three-arm and 298 four-arm junctions were included in the study. The number and type of accidents were studied at each junction both before and after the implementation of the measure. The effects of the measure were determined by comparing the observed number of accidents after the measure with the number that would have been expected to occur at the junction if the measure had not been implemented. The expected number of accidents was calculated on the basis of the observed number of accidents in the before period and the expected number of accidents as predicted by an accident model, utilizing at the same time the information on the variation of the number of accidents at similar junctions revealed by the model. Likelihood functions determined for the effects of the measures were used for studying the accuracy of the estimates of the effects. The likelihood functions can also be utilized later when new before-and-after studies are performed. Road lighting, stop signs, signal control, and lowering of the speed limit value were found to decrease the number of accidents. Through-flow junction widenings, additional lanes for turning vehicles, and road widenings, however, did not seem to affect the safety at junctions to any marked extent. If we had not accounted for the regression-to-the-mean effect, these measures would have seemed to have a positive effect on safety. The study method also enabled us to quantify the regression-to-the-mean effect. The magnitude of the regression effect was on average 20%, i.e. the number of accidents would have decreased by 20% at the junctions studied even if the measures had not been implemented. The magnitude of the regression-to-the-mean varied greatly between the different measures.

Accidents, Traffic↗
PubMed1994

JPCalc, a software package for calculating liquid junction potential corrections in patch-clamp, intracellular, epithelial and bilayer measurements and for correcting junction potential measurements.

The JPCalc program has been designed to graphically illustrate how junction potential contributions arise in various electrophysiological situations, to enable the magnitude and direction of those values to be readily calculated and to show clearly how the resultant appropriate corrections need to be applied to experimental measurements. In particular, the program covers the analysis of junction potential contributions and corrections in all the various different patch-clamp configurations (intact patches, inside-out patches, outside-out patches, whole-cell recording and perforated patches), intracellular recording, epithelial and bilayer measurements. It can also be used to correct experimental measurements designed to try to directly measure junction potentials and to compare both the magnitude and direction of such corrected measurements with their theoretical values. Although it is recommended that all of the above measurements be done with salt-filled electrodes or salt bridges, the program will allow the use of Ag/AgCl reference electrodes in direct contact with bathing solution in most situations. JPCalc also makes use of a library file of mobility and valency data for about 30 ions which can be extended by the user. In addition to its value in correcting electrical measurements, the program with its graphical displays may also be of value in focusing discussion about the contribution of junction potentials to such measurements and in helping to design experiments to either minimize their contribution or to measure their values. The JPCalc program, designed for IBM-compatible computers with color or monochrome monitors, can also be run on Macintosh computers with SoftPC emulation software.

Animals↗