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At least 415 records · Page 23Linked to original sources
PubMed1978

Fiber counting: a source of error corrected.

Optical counting of fibers (from a filter sample of industrial air, for example) involves determining how many fibers are within counting fields which are squares of side lengths. It is correct to count all those fibers which are completely within the field and half of those which intersect only one side. It is shown here to be incorrect to count half those fibers which intersect two sides; the magnitude of this error is calculated, the calculations being verified through a Monte Carlo simulation. The fractional overcount for fibers of length L less than or equal to s is (L/s)2/2pi.

Air Pollutants↗
PubMed1993

Motor response variations: peripheral and central sources of error.

The purpose of this research was to test the hypothesis that the relative involvement of peripheral versus central nervous system activity during response variations determines the locus of error production in a subsequent criterion response. The hypothesis was tested by comparing ipsilateral and contralateral transfer of a criterion response following response variations that emphasized proportionately different involvement of the peripheral and central systems. When subjects were provided with knowledge of results (KR) to maintain a 30% maximum voluntary contraction (MVC), ipsilateral but not contralateral bias errors occurred on a subsequent dynamic response. When subjects maintained a 30% MVC without KR, however, subsequent ipsilateral bias errors were greater than contralateral bias errors. Finally,when subjects imaged a 30% MVC, subsequent bias errors were equivalent across limbs. These results are interpreted as support for the hypothesis.

Journal Article↗
PubMed1986

A source of error in the chromatographic study of 35S-sulfate labeled mucous glycoproteins secreted by the gill epithelium of Mytilus edulis.

HPLC combined with [35S]-sulfate/[3H]-glucosamine radiolabeling were employed to study the synthesis and secretion of mucous glycoproteins. The secreted radiolabeled glycoproteins were separated from the medium by precipitation with a mixture of trichloroacetic-phosphotungstic acids (TCA/PTA). The redissolved glycoproteins were chromatographed on an anion exchange protein column at varying pH of the mobile phase and fractions were collected for liquid scintillation counting. Varying the pH of the mobile phase from pH 3 to 7 resulted in a decrease of glycoprotein bound [35S] from 69.5 to 0.5% of the total recovered [35S]-sulfate with the remainder recovered as free [35S]-sulfate. The [3H]-labeled glycoprotein recovered under the uV peaks at this pH range was 99.5%. When high performance size exclusion chromatography was performed the change in mobile phase pH did not affect the 100% recovery of either [35S]-or [3H]-labels under the uV peaks. No free [35S]-sulfate was obtained when [35S]-labeled glycoproteins were separated from the medium using dialysis. These data suggest that the standard method of TCA/PTA precipitation of [35S]-labeled glycoproteins may cleave the [35S]-sulfate ester linkages to the oligosaccharide chains. The [35S]-sulfate may then rebind to the macromolecule by a relatively strong noncovalent bond. This may prove critical in anion exchange protein HPLC studies.

Animals↗
PubMed1998

Sources of error in bioimpedance spectroscopy.

Two different makes of bioimpedance spectrometer (UniQuest-SEAC SFB-3 and Xitron 4000B) were used for a series of measurements on volunteers and patients in intensive care. Although each machine was accurate over the frequency range 5 to 500 kHz when bench tested on model resistor-capacitor circuits, significant differences in their recorded impedance parameters appeared when used in vivo, especially on intensive care patients. A series of laboratory tests was performed on each machine simulating the situation in vivo to identify possible reasons for these differences. Whilst stray capacitance in the environment was identified as the major contributor to variability in high-frequency performance, interaction between electrode impedance and lead positioning was also a factor. The observed phase shift with frequency or time delay (Td) used in the Xitron modeling software appears to be the result of a time constant caused by stray capacitance and so is unlikely to have any biological meaning. Significant differences in the in vivo numerical values produced by bioimpedance spectrometers may be attributed to instrument design, data processing and, in particular, the clinical environment.

Adult↗
PubMed2005

The patient: a novel source of error in clinical temperature measurement using infrared aural thermometry.

INTRODUCTION: The vital signs are an important component of patient assessment. With respect to body temperature; there has been a move away from mercury-in-glass thermometers toward the relatively inexpensive, safer to use infrared tympanic, auricular, or ear thermometer. Although already in widespread use, the reliability of these devices has increasingly been called into question. Few studies, however, have considered that the problem might reside outside the device itself. OBJECTIVE: To investigate the correlation between left ear temperature and right ear temperature using an infrared tympanic thermometer (ITT). DESIGN: A prospective, single-blind trail with randomized assignment of the first ear to be assessed. SETTING/LOCATION: Welsh Institute of Chiropractic (WIOC), University of Glamorgan. SUBJECTS: One hundred and thirty two (132) asymptomatic subjects who were opportunistically sampled on entry into the WIOC. None of the subjects had any neurologic deficit, or any known underlying pathologic problems. All were students at the University of Glamorgan (age range, 18-48 years). A smaller sample of the same cohort was used on a separate occasion to compare ITTs from 2 different manufacturers using the same protocol. INTERVENTION: Measurement of ear (ear canal/tympanic) temperature bilaterally using an ITT. OUTCOME MEASURES: Bilateral asymmetry in ear canal temperature. Analysis consisted of nonparametric statistical tests, using Spearman's correlation for comparison and the Wilcoxon matched pairs test for differences. RESULTS: In 132 subjects who completed the main study, although a degree of correlation was found, the relationship did not extrapolate through zero. At temperatures more than 0.4 degrees C above or below 36.7 degrees C, there was a significant difference in temperature in the left compared with the right ear. Additionally, the left ear tended to register a lower temperature than the right ear at temperatures below 36.7 degrees C, whereas the left ear tended to read a higher temperature than the right ear above 36.7 degrees C. CONCLUSIONS: The authors suggest that clinicians consider measuring both ears, and take the greater of the readings to be a more accurate reflection of the patient's core temperature. The difference may perhaps even be related to the person's health. This change in methodology should increase the reliability of the measurement and go some way toward restoring confidence in the use of ITT devices.

Adult↗
PubMed1980

Nonimmunologic binding of horseradish peroxidase to hepatitis B surface antigen. A possible source of error in immunohistochemistry.

In the process of establishing the specificity of direct immunoperoxidase staining of liver tissue for hepatitis B surface antigen (HBsAg), an affinity of free horseradish peroxidase (HRP) for HBsAg in hepatocytes (ground-glass cells) was found. Of 95 patients, the horseradish peroxidase reaction was only positive in the livers of the 35 who were chronically HBsAg seropositive and not in the livers from 60 control patients with alcoholic cirrhosis who were HBsAg seronegative. Comparison studies using the orcein technic and immunoperoxidase methods confirmed the observation that both free horseradish peroxidase (not conjugated to an antibody) and HRP conjugated to an antibody unrelated to HBsAg had an affinity to the cytoplasm of hepatocytes containing HBsAg. The precise nature of this affinity is not known, but it is probably due to a reaction between an activated carbohydrate moiety of horseradish peroxidase and the free amino group of HBsAG.

Hepatitis B Surface Antigens↗