Calibration: Determination, by measurement or comparison with a standard, of the correct value of each scale reading on a meter or other measuring instrument; or determination of the settings of a control device that correspond to particular values of voltage, current, frequency or other output.Reproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Reference Standards: A basis of value established for the measure of quantity, weight, extent or quality, e.g. weight standards, standard solutions, methods, techniques, and procedures used in diagnosis and therapy.Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Quality Control: A system for verifying and maintaining a desired level of quality in a product or process by careful planning, use of proper equipment, continued inspection, and corrective action as required. (Random House Unabridged Dictionary, 2d ed)Equipment Design: Methods of creating machines and devices.Algorithms: A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.Equipment Failure Analysis: The evaluation of incidents involving the loss of function of a device. These evaluations are used for a variety of purposes such as to determine the failure rates, the causes of failures, costs of failures, and the reliability and maintainability of devices.Fossils: Remains, impressions, or traces of animals or plants of past geological times which have been preserved in the earth's crust.Phantoms, Imaging: Devices or objects in various imaging techniques used to visualize or enhance visualization by simulating conditions encountered in the procedure. Phantoms are used very often in procedures employing or measuring x-irradiation or radioactive material to evaluate performance. Phantoms often have properties similar to human tissue. Water demonstrates absorbing properties similar to normal tissue, hence water-filled phantoms are used to map radiation levels. Phantoms are used also as teaching aids to simulate real conditions with x-ray or ultrasonic machines. (From Iturralde, Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990)Limit of Detection: Concentration or quantity that is derived from the smallest measure that can be detected with reasonable certainty for a given analytical procedure.Flow Injection Analysis: The analysis of a chemical substance by inserting a sample into a carrier stream of reagent using a sample injection valve that propels the sample downstream where mixing occurs in a coiled tube, then passes into a flow-through detector and a recorder or other data handling device.Chromatography, High Pressure Liquid: Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed.Models, Statistical: Statistical formulations or analyses which, when applied to data and found to fit the data, are then used to verify the assumptions and parameters used in the analysis. Examples of statistical models are the linear model, binomial model, polynomial model, two-parameter model, etc.Autoanalysis: Method of analyzing chemicals using automation.Chemistry Techniques, Analytical: Methodologies used for the isolation, identification, detection, and quantitation of chemical substances.Transducers: Any device or element which converts an input signal into an output signal of a different form. Examples include the microphone, phonographic pickup, loudspeaker, barometer, photoelectric cell, automobile horn, doorbell, and underwater sound transducer. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)Indicators and Reagents: Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents. (From Grant & Hackh's Chemical Dictionary, 5th ed, p301, p499)Spectroscopy, Near-Infrared: A noninvasive technique that uses the differential absorption properties of hemoglobin and myoglobin to evaluate tissue oxygenation and indirectly can measure regional hemodynamics and blood flow. Near-infrared light (NIR) can propagate through tissues and at particular wavelengths is differentially absorbed by oxygenated vs. deoxygenated forms of hemoglobin and myoglobin. Illumination of intact tissue with NIR allows qualitative assessment of changes in the tissue concentration of these molecules. The analysis is also used to determine body composition.Perceptual Distortion: Lack of correspondence between the way a stimulus is commonly perceived and the way an individual perceives it under given conditions.Weights and Measures: Measuring and weighing systems and processes.Least-Squares Analysis: A principle of estimation in which the estimates of a set of parameters in a statistical model are those quantities minimizing the sum of squared differences between the observed values of a dependent variable and the values predicted by the model.Models, Theoretical: Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.Nomograms: Graphical representation of a statistical model containing scales for calculating the prognostic weight of a value for each individual variable. Nomograms are instruments that can be used to predict outcomes using specific clinical parameters. They use ALGORITHMS that incorporate several variables to calculate the predicted probability that a patient will achieve a particular clinical endpoint.Biosensing Techniques: Any of a variety of procedures which use biomolecular probes to measure the presence or concentration of biological molecules, biological structures, microorganisms, etc., by translating a biochemical interaction at the probe surface into a quantifiable physical signal.Radiometry: The measurement of radiation by photography, as in x-ray film and film badge, by Geiger-Mueller tube, and by SCINTILLATION COUNTING.Gas Chromatography-Mass Spectrometry: A microanalytical technique combining mass spectrometry and gas chromatography for the qualitative as well as quantitative determinations of compounds.Chromatography, Liquid: Chromatographic techniques in which the mobile phase is a liquid.Electrodes: Electric conductors through which electric currents enter or leave a medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum.Monitoring, Ambulatory: The use of electronic equipment to observe or record physiologic processes while the patient undergoes normal daily activities.Tandem Mass Spectrometry: A mass spectrometry technique using two (MS/MS) or more mass analyzers. With two in tandem, the precursor ions are mass-selected by a first mass analyzer, and focused into a collision region where they are then fragmented into product ions which are then characterized by a second mass analyzer. A variety of techniques are used to separate the compounds, ionize them, and introduce them to the first mass analyzer. For example, for in GC-MS/MS, GAS CHROMATOGRAPHY-MASS SPECTROMETRY is involved in separating relatively small compounds by GAS CHROMATOGRAPHY prior to injecting them into an ionization chamber for the mass selection.Immunoassay: A technique using antibodies for identifying or quantifying a substance. Usually the substance being studied serves as antigen both in antibody production and in measurement of antibody by the test substance.Optical Processes: Behavior of LIGHT and its interactions with itself and materials.Spectrometry, Mass, Electrospray Ionization: A mass spectrometry technique used for analysis of nonvolatile compounds such as proteins and macromolecules. The technique involves preparing electrically charged droplets from analyte molecules dissolved in solvent. The electrically charged droplets enter a vacuum chamber where the solvent is evaporated. Evaporation of solvent reduces the droplet size, thereby increasing the coulombic repulsion within the droplet. As the charged droplets get smaller, the excess charge within them causes them to disintegrate and release analyte molecules. The volatilized analyte molecules are then analyzed by mass spectrometry.Artifacts: Any visible result of a procedure which is caused by the procedure itself and not by the entity being analyzed. Common examples include histological structures introduced by tissue processing, radiographic images of structures that are not naturally present in living tissue, and products of chemical reactions that occur during analysis.ROC Curve: A graphic means for assessing the ability of a screening test to discriminate between healthy and diseased persons; may also be used in other studies, e.g., distinguishing stimuli responses as to a faint stimuli or nonstimuli.Freeze Drying: Method of tissue preparation in which the tissue specimen is frozen and then dehydrated at low temperature in a high vacuum. This method is also used for dehydrating pharmaceutical and food products.Prothrombin Time: Clotting time of PLASMA recalcified in the presence of excess TISSUE THROMBOPLASTIN. Factors measured are FIBRINOGEN; PROTHROMBIN; FACTOR V; FACTOR VII; and FACTOR X. It is used for monitoring anticoagulant therapy with COUMARINS.Spectrophotometry, Ultraviolet: Determination of the spectra of ultraviolet absorption by specific molecules in gases or liquids, for example Cl2, SO2, NO2, CS2, ozone, mercury vapor, and various unsaturated compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Secobarbital: A barbiturate that is used as a sedative. Secobarbital is reported to have no anti-anxiety activity.Linear Models: Statistical models in which the value of a parameter for a given value of a factor is assumed to be equal to a + bx, where a and b are constants. The models predict a linear regression.Radiographic Image Enhancement: Improvement in the quality of an x-ray image by use of an intensifying screen, tube, or filter and by optimum exposure techniques. Digital processing methods are often employed.Bayes Theorem: A theorem in probability theory named for Thomas Bayes (1702-1761). In epidemiology, it is used to obtain the probability of disease in a group of people with some characteristic on the basis of the overall rate of that disease and of the likelihood of that characteristic in healthy and diseased individuals. The most familiar application is in clinical decision analysis where it is used for estimating the probability of a particular diagnosis given the appearance of some symptoms or test result.Solid Phase Extraction: An extraction method that separates analytes using a solid phase and a liquid phase. It is used for preparative sample cleanup before analysis by CHROMATOGRAPHY and other analytical methods.Optical Fibers: Thin strands of transparent material, usually glass, that are used for transmitting light waves over long distances.Germanium: A rare metal element with a blue-gray appearance and atomic symbol Ge, atomic number 32, and atomic weight 72.63.Computer Simulation: Computer-based representation of physical systems and phenomena such as chemical processes.Ear Canal: The narrow passage way that conducts the sound collected by the EAR AURICLE to the TYMPANIC MEMBRANE.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Film Dosimetry: Use of a device (film badge) for measuring exposure of individuals to radiation. It is usually made of metal, plastic, or paper and loaded with one or more pieces of x-ray film.Nephelometry and Turbidimetry: Chemical analysis based on the phenomenon whereby light, passing through a medium with dispersed particles of a different refractive index from that of the medium, is attenuated in intensity by scattering. In turbidimetry, the intensity of light transmitted through the medium, the unscattered light, is measured. In nephelometry, the intensity of the scattered light is measured, usually, but not necessarily, at right angles to the incident light beam.Radioactivity: The spontaneous transformation of a nuclide into one or more different nuclides, accompanied by either the emission of particles from the nucleus, nuclear capture or ejection of orbital electrons, or fission. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Pharmaceutical Preparations: Drugs intended for human or veterinary use, presented in their finished dosage form. Included here are materials used in the preparation and/or formulation of the finished dosage form.Mass Spectrometry: An analytical method used in determining the identity of a chemical based on its mass using mass analyzers/mass spectrometers.Drug Stability: The chemical and physical integrity of a pharmaceutical product.Acceleration: An increase in the rate of speed.Uncertainty: The condition in which reasonable knowledge regarding risks, benefits, or the future is not available.Microchemistry: The development and use of techniques and equipment to study or perform chemical reactions, with small quantities of materials, frequently less than a milligram or a milliliter.Data Display: The visual display of data in a man-machine system. An example is when data is called from the computer and transmitted to a CATHODE RAY TUBE DISPLAY or LIQUID CRYSTAL display.Thermometers: Measuring instruments for determining the temperature of matter. Most thermometers used in the field of medicine are designed for measuring body temperature or for use in the clinical laboratory. (From UMDNS, 1999)Regression Analysis: Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see LINEAR MODELS) the relationship is constrained to be a straight line and LEAST-SQUARES ANALYSIS is used to determine the best fit. In logistic regression (see LOGISTIC MODELS) the dependent variable is qualitative rather than continuously variable and LIKELIHOOD FUNCTIONS are used to find the best relationship. In multiple regression, the dependent variable is considered to depend on more than a single independent variable.Image Processing, Computer-Assisted: A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.Data Interpretation, Statistical: Application of statistical procedures to analyze specific observed or assumed facts from a particular study.Fluorescent Dyes: Agents that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags.Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Clinical Chemistry Tests: Laboratory tests demonstrating the presence of physiologically significant substances in the blood, urine, tissue, and body fluids with application to the diagnosis or therapy of disease.Blood Chemical Analysis: An examination of chemicals in the blood.Fiducial Markers: Materials used as reference points for imaging studies.Chemistry, Clinical: The specialty of ANALYTIC CHEMISTRY applied to assays of physiologically important substances found in blood, urine, tissues, and other biological fluids for the purpose of aiding the physician in making a diagnosis or following therapy.Tomography Scanners, X-Ray Computed: X-ray image-detecting devices that make a focused image of body structures lying in a predetermined plane from which more complex images are computed.Optics and Photonics: A specialized field of physics and engineering involved in studying the behavior and properties of light and the technology of analyzing, generating, transmitting, and manipulating ELECTROMAGNETIC RADIATION in the visible, infrared, and ultraviolet range.Photogrammetry: Making measurements by the use of stereoscopic photographs.Electrochemistry: The study of chemical changes resulting from electrical action and electrical activity resulting from chemical changes.Risk Assessment: The qualitative or quantitative estimation of the likelihood of adverse effects that may result from exposure to specified health hazards or from the absence of beneficial influences. (Last, Dictionary of Epidemiology, 1988)Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Infrared Rays: That portion of the electromagnetic spectrum usually sensed as heat. Infrared wavelengths are longer than those of visible light, extending into the microwave frequencies. They are used therapeutically as heat, and also to warm food in restaurants.Acoustics: The branch of physics that deals with sound and sound waves. In medicine it is often applied in procedures in speech and hearing studies. With regard to the environment, it refers to the characteristics of a room, auditorium, theatre, building, etc. that determines the audibility or fidelity of sounds in it. (From Random House Unabridged Dictionary, 2d ed)Tablets: Solid dosage forms, of varying weight, size, and shape, which may be molded or compressed, and which contain a medicinal substance in pure or diluted form. (Dorland, 28th ed)Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Indicator Dilution Techniques: Methods for assessing flow through a system by injection of a known quantity of an indicator, such as a dye, radionuclide, or chilled liquid, into the system and monitoring its concentration over time at a specific point in the system. (From Dorland, 28th ed)

Validation of the Rockall risk scoring system in upper gastrointestinal bleeding. (1/3865)

BACKGROUND: Several scoring systems have been developed to predict the risk of rebleeding or death in patients with upper gastrointestinal bleeding (UGIB). These risk scoring systems have not been validated in a new patient population outside the clinical context of the original study. AIMS: To assess internal and external validity of a simple risk scoring system recently developed by Rockall and coworkers. METHODS: Calibration and discrimination were assessed as measures of validity of the scoring system. Internal validity was assessed using an independent, but similar patient sample studied by Rockall and coworkers, after developing the scoring system (Rockall's validation sample). External validity was assessed using patients admitted to several hospitals in Amsterdam (Vreeburg's validation sample). Calibration was evaluated by a chi2 goodness of fit test, and discrimination was evaluated by calculating the area under the receiver operating characteristic (ROC) curve. RESULTS: Calibration indicated a poor fit in both validation samples for the prediction of rebleeding (p<0.0001, Vreeburg; p=0.007, Rockall), but a better fit for the prediction of mortality in both validation samples (p=0.2, Vreeburg; p=0.3, Rockall). The areas under the ROC curves were rather low in both validation samples for the prediction of rebleeding (0.61, Vreeburg; 0.70, Rockall), but higher for the prediction of mortality (0.73, Vreeburg; 0.81, Rockall). CONCLUSIONS: The risk scoring system developed by Rockall and coworkers is a clinically useful scoring system for stratifying patients with acute UGIB into high and low risk categories for mortality. For the prediction of rebleeding, however, the performance of this scoring system was unsatisfactory.  (+info)

Performance and specificity of monoclonal immunoassays for cyclosporine monitoring: how specific is specific? (2/3865)

BACKGROUND: Immunoassays designed for the selective measurement of cyclosporin A (CsA) inadvertently show cross-reactivity for CsA metabolites. The extent and clinical significance of the resulting overestimation is controversial. A comprehensive assessment of old and new methods in clinical specimens is needed. METHODS: In a comprehensive evaluation, CsA was analyzed in 145 samples with the new CEDIA assay and compared with the Emit assay with the old and new pretreatments, the TDx monoclonal and polyclonal assays, the AxSYM, and HPLC. All samples were from patients with liver and/or kidney transplants. RESULTS: The CEDIA offered the easiest handling, followed by the AxSYM, which showed the longest calibration stability. The TDx monoclonal assay provided the lowest detection limit and the lowest CVs. The mean differences compared with HPLC were as follows: Emit, 9-12%; CEDIA, 18%; AxSYM, 29%; and TDx monoclonal, 57%. The CycloTrac RIA paralleled the Emit results. In contrast to the mean differences, substantial (>200%) and variable overestimations of the CsA concentration were observed in individual patient samples. Metabolic ratios, estimates of the overall concentrations of several cross-reacting metabolites (nonspecific TDx polyclonal/specific reference method), correlated with the apparent biases of the various monoclonal assays. Metabolic ratios varied up to 10-fold, which translated into biases for individual samples between -7% and +174%. The higher the cross-reactivity of an assay was, the higher was the range of biases observed. The interindividual differences markedly exceeded other factors of influence (organ transplanted, hepatic function). CONCLUSION: Because assay bias cannot be predicted in individual samples, substantially erratic CsA dosing can result. The specificity of CsA assays for parent CsA remains a major concern.  (+info)

TE671 cell-based ELISA for anti-acetylcholine receptor antibody determination in myasthenia gravis. (3/3865)

BACKGROUND: Acetylcholine receptor (AChR) from human muscles is the antigen used currently in radioimmunoprecipitation assays (RIPAs) for the determination of anti-AChR antibodies in the diagnosis of myasthenia gravis (MG). Our aim was to develop and validate an ELISA using TE671 cells as the source of AChR. METHODS: After TE671 cell homogenization, the crude AChR extract was used for plate coating. Anti-AChR antibodies were determined in 207 MG patients and in 77 controls. RESULTS: The mean intra- and interassay CVs (for two samples with different anti-AChR antibody concentrations) were 9.7% and 15.7%, respectively. Test sensitivity and specificity, for generalized MG, were 79.5% (95% confidence interval, 72.8-85.0%) and 96.1% (89.0-99.1%). The detection limit was 2 nmol/L. Anti-AChR antibody concentrations from 53 MG patients, as tested with our ELISA, showed good agreement with an RIPA with a mean difference (SD) of 1.0 (5.6) nmol/L. CONCLUSION: Our ELISA is a simple screening test for the diagnosis of MG and enables rapid and inexpensive patient follow-up.  (+info)

LocaLisa: new technique for real-time 3-dimensional localization of regular intracardiac electrodes. (4/3865)

BACKGROUND: Estimation of the 3-dimensional (3D) position of ablation electrodes from fluoroscopic images is inadequate if a systematic lesion pattern is required in the treatment of complex arrhythmogenic substrates. METHODS AND RESULTS: We developed a new technique for online 3D localization of intracardiac electrodes. Regular catheter electrodes are used as sensors for a high-frequency transthoracic electrical field, which is applied via standard skin electrodes. We investigated localization accuracy within the right atrium, right ventricle, and left ventricle by comparing measured and true interelectrode distances of a decapolar catheter. Long-term stability was analyzed by localization of the most proximal His bundle before and after slow pathway ablation. Electrogram recordings were unaffected by the applied electrical field. Localization data from 3 catheter positions, widely distributed within the right atrium, right ventricle, or left ventricle, were analyzed in 10 patients per group. The relationship between measured and true electrode positions was highly linear, with an average correlation coefficient of 0.996, 0.997, and 0.999 for the right atrium, right ventricle, and left ventricle, respectively. Localization accuracy was better than 2 mm, with an additional scaling error of 8% to 14%. After 2 hours, localization of the proximal His bundle was reproducible within 1.4+/-1.1 mm. CONCLUSIONS: This new technique enables accurate and reproducible real-time localization of electrode positions in cardiac mapping and ablation procedures. Its application does not distort the quality of electrograms and can be applied to any electrode catheter.  (+info)

European interlaboratory comparison of breath 13CO2 analysis. (5/3865)

The BIOMED I programme Stable Isotopes in Gastroenterology and Nutrition (SIGN) has focused upon evaluation and standardisation of stable isotope breath tests using 13C labelled substrates. The programme dealt with comparison of 13C substrates, test meals, test conditions, analysis techniques, and calculation procedures. Analytical techniques applied for 13CO2 analysis were evaluated by taking an inventory of instrumentation, calibration protocols, and analysis procedures. Two ring tests were initiated measuring 13C abundances of carbonate materials. Evaluating the data it was found that seven different models of isotope ratio mass spectrometers (IRMS) were used by the participants applying both the dual inlet system and the continuous flow configuration. Eight different brands of certified 13C reference materials were used with a 13C abundance varying from delta 13CPDB -37.2 to +2.0/1000. CO2 was liberated from certified material by three techniques and different working standards were used varying from -47.4 to +0.4/1000 in their delta 13CPDB value. The standard deviations (SDs) found for all measurements by all participants were 0.25/1000 and 0.50/1000 for two carbonates used in the ring tests. The individual variation for the single participants varied from 0.02 /1000 (dual inlet system) to 0.14/1000 (continuous flow system). The measurement of the difference between two carbonates showed a SD of 0.33/1000 calculated for all participants. Internal precision of IRMS as indicated by the specifications of the different instrument suppliers is < 0.3/1000 for continuous flow systems. In this respect it can be concluded that all participants are working well within the instrument specifications even including sample preparation. Increased overall interlaboratory variation is therefore likely to be due to non-instrumental conditions. It is possible that consistent differences in sample handling leading to isotope fractionation are the causes for interlaboratory variation. Breath analysis does not require sample preparation. As such, interlaboratory variation will be less than observed for the carbonate samples and within the range indicated as internal precision for continuous flow instruments. From this it is concluded that pure analytical interlaboratory variation is acceptable despite the many differences in instrumentation and analytical protocols. Coordinated metabolic studies appear possible, in which different European laboratories perform 13CO2 analysis. Evaluation of compatibility of the analytical systems remains advisable, however.  (+info)

The length and eruption rates of incisor teeth in rats after one or more of them had been unimpeded. (6/3865)

The eruption rate and length of all four incisor teeth in rats were measured under ether anaesthesia by recording the position of marks on their labial surfaces at 2-day intervals, using calibrated graticules in microscope eyepieces. The rats were divided into four groups and either a lower, an upper, both a lower and an upper, or no incisors were unimpeded. This paper describes the changes when the unimpeded incisors returned to the occlusion. Neither the unimpeded nor the impeded incisors simply returned to control values immediately the period of unimpeded eruption ended, but showed transient changes in their lengths and eruption rates. The results confirm that eruption rates are determined by the sum of the lengths of the lower and upper incisors, rather than by their own lengths, with longer teeth erupting more slowly. Specifically, restoring the bevel to the incisors did not slow their eruption below normal impeded rates. The slowing of the eruption of the longer of two adjacent incisors was related to the length differences of the incisors in the same jaw, not to the sum of the differences in both jaws. Contact with the contralateral incisor in the opposite jaw slowed the eruption of an incisor more than contact with the ipsilateral incisor.  (+info)

Fluorimetric determination of aluminum traces in hemodialysis solutions using Mordant Red 19. (7/3865)

A sensitive and accurate method for the spectrofluorimetric determination of trace levels of aluminum in hemodialysis solutions using Mordant Red 19 as the complexation reagent has been developed. The optimal experimental conditions for the concentration of fluorimetric reagent, pH, temperature, and the specific type of matrix are reported. The emission of the fluorescent metal chelate was measured at 555 nm, excitation at 478 nm. Linearity between emission intensity and aluminum concentration was found in the 2-20 ppb range in standard aluminum solutions. Limit of detection was 0.4 ppb. The aluminum amounts in some commercial hemodialysis solutions were determined by means of the extrapolation method. The proposed method proved to be suitable in terms of sensitivity and accuracy for the determination of aluminum in dialysis fluids.  (+info)

Determination of tin, vanadium, iron, and molybdenum in various matrices by atomic absorption spectrometry using a simultaneous liquid-liquid extraction procedure. (8/3865)

An atomic-absorption spectrometric method is described for the determination of tin, vanadium, iron, and molybdenum in two certified reference materials, food samples, and petroleum crude. After treatment with acids, these elements are separated from matrix elements by simultaneous solvent extraction of 5,5'-methylenedisalicylohydroxamic acid complexes from HCl/NaClO4 solution into an isobutyl methyl ketone/tributyl phosphate solution. The detection limits range from 0.018 to 0.19 microg/mL (n = 3), and the relative standard deviations do not exceed 2.0% at levels of 0.5, 0.6, 2.0, and 7.0 microg/mL of Fe, Mo, V, and Sn, respectively. The method is selective and suffers only from interference by Zr(IV), Ti(IV), Th(IV), W(VI), PO4(3-), and F-.  (+info)

  • First the calibration is described from a theoretical point of view, deriving the calculation of Fourier coefficients out of a measurement set. (
  • They had a very nice very accurate Fluke calibration tool for people to use at the event (owned by another HAM club) that could generate very accurate test signals to check all the different multimeter measurement ranges (DC voltage and current, AC current and voltage at different frequencies, resistance, etc. (
  • The basis for the new calibration procedure is to construct a statistical error model that captures the characteristics of the measurement errors. (
  • This ensures that sensitivity is constant at all times, allowing the operator to concentrate on measurement tasks without having to worry about sensitivity calibration. (
  • Consistent measurement is possible without worrying about sensitivity calibration. (
  • This is why the balance captures changes in room temperature that affect sensitivity and automatically starts calibration using built-in weights. (
  • The balance starts calibration using built-in weights at preset times of the day. (
  • The balance incorporates motor-driven calibration weights. (
  • Sensor Calibration using Nonparametric Statistical Characterization of Error Models," 3rd IEEE Conference on Sensors (Sensors'2004), pp. 1456-1459, October 2004. (
  • Traditionally, calibration has usually been conducted by considering a set of measurements in a single time frame and restricted to linear systems with the assumption of equal-quality sensors and single modality. (
  • The package supports eight IRT models and four calibration methods. (
  • Dichotomous Models: 1PL, 2PL, 3PL Polytomous Models: -Graded response model -Partial credit model -Generalized partial credit model -Nominal response model -Multiple-choice model Calibration Methods: -Mean/Mean -Mean/Sigma -Haebara -Stocking-Lord Any combination of dichotomous and polytomous items can be supplied with intermingled unique and common items for as many items and groups as system memory allows. (
  • Linking constants are computed and returned for all the calibration methods, and (if desired) ability and/or item parameters can be rescaled and returned using any of the estimated linking constants. (
  • Many of the examples (and the associated output) can be found in published articles or books, and the output from the various calibration methods has been checked against other available linking software. (
  • Includes a primary indium reference material, ASTM E967 and E968 test methods describing the calibration protocol, and the associated ISO 9000 documentation providing both temperature and enthalpy calibration traceability. (
  • Includes primary indium and secondary aluminum reference materials, ASTM E-1363, E-2113 or E-831 test methods describing the calibration protocols, and the associated ISO 9000 documentation. (
  • In addition, statistical validation and evaluation methods such as resubstitution, is used in order to establish the interval of confidence for both the error model and the calibration model. (
  • A qualified Field Service Representative with an average of 15 years' experience, will provide calibration using reference materials traceable to a National Reference Laboratory and appropriate ASTM International Standard Procedures. (
  • Kits containing the traceable reference material and appropriate test protocol are available for customers who wish to perform their own calibration. (
  • Subsequently these BUFR files are used in a simulation run of the ocean calibration in order to assess the influence of the errors in the calibration process. (
  • The software needed for the calibration process is embedded directly into the TV for calibration. (
  • The software walks the user through a step-by-step calibration process that maximizes the colors for the specific environment the TV is in. (
  • Getting Started: Running the separate calibration is typically a two-step process. (
  • Hi,I want to share my experience of implementing calibration process in SAP.we have use SAP MM,SAP QM and SAP PM module for mapping required scenario. (
  • Calibration is the process of identifying and correcting for the systematic bias component of the error in sensor measurements. (
  • The detected 2D image points are reconstructed into 3D data points based on the mathematical model developed by the calibration process. (
  • 1.Calibration order get generated in system automatically base of calibration(IW39). (
  • 3.On release of order, In case of Inhouse Calibration, Inspection lot will get generated,Quality Inspector can perform calibration and update result in system against Inspection lot ( QA32 ).after completion of operation,operation confirmation was done.Calibration order status updated as completed. (
  • The calibration method is based on Fourier analysis of the data and has also been used by [STOFFELEN and [HERSCHBACH (
  • The calibration software is used with existing ERS data and with simulated ASCAT data. (
  • Then examples of a typical ocean calibration are shown using a standard input data set from ERS, July 1999. (
  • Calibration results for different weighting method, different input data period, and different GMF are presented. (
  • The ocean calibration differences between real and simulated data need to be further investigated. (
  • Here's how you can reset your Apple Watch fitness calibration data and make sure your wearable tracks your workouts and walks far more accurately. (
  • Tap on the Reset Fitness Calibration Data. (
  • I will not recommend resetting the fitness calibration data on your Apple Watch on a regular basis. (
  • In this report the ocean calibration method is described and the results from ERS runs and error simulation are presented. (
  • Then the calibration software itself and the way this method is implemented is described in more detail. (
  • Includes secondary alumel and nickel Curie temperature reference materials, a suitable magnet, ASTM E-1582 test method describing the calibration protocol, and associated ISO 9000 documentation. (
  • The overall errors of each method and their significance on the calibration are modeled to determine the characteristic offsets inherent to the accelerometer. (
  • An ocean calibration tool is developed for the calibration of the forthcoming ASCAT scatterometer on board of the METOP satellite. (
  • The aim of ocean calibration is, by comparing the average measured backscatter from the antennae to the simulated backscatter from collocated NWP winds, to assess the absolute values of the measurements and the GMF and to show that there is no interbeam bias. (
  • The output from the ocean calibration over a certain period can be used to correct biases in the ocean calibration over another period. (
  • 3.Automatic reminder for Test Equipment Calibration. (
  • If you set calibration times before important measurements (e.g. before starting work in the morning, or during the lunch or evening break), the balance will automatically start calibration when the preset time is reached. (
  • We propose four alternatives to make the transition from the constructed error model to the calibration model, which is represented by piecewise polynomials. (
  • Each test was compared to the theoretical acceleration model to determine the effectiveness of the calibration technique. (
  • The results show that the impact of the wind component errors on the calibration is the largest, as compared to the impact of the instrument noise and the geophysical noise. (
  • The impact of such a correction is examined, and it is shown that for ERS the calibration results are stable over a longer period of time. (
  • This thesis presents a fast and robust calibration technique for a low-cost 3D laser scanner. (
  • Since switching to Linux earlier this year, my desktop and laptop monitors have been uncalibrated because of my ignorance of how to do monitor calibration on Linux. (
  • The NIST LBIR facility provides radiometric calibrations of these blackbodies so that various government test facilities as well as contractor facilities for MDA have a common NIST traceability. (
  • The calibration report provides the customer with the total radiant power measured at the ACR aperture and the corresponding deduced blackbody radiometric temperature. (
  • The RASCAL algorithm for radiometric self-calibration takes as input a set of images of a static scene taken under different exposures and rough estimates of the exposure values used, and computes the radiometric response function of the imaging system as well as high dynamic range image of the scene. (
  • AFMETCAL ( Air Force METrology and CALibration Program Office ), located in Heath , Ohio is the primary manager of metrology services for the U.S. Air Force . (
  • The Air Force created the Air Force Metrology and Calibration Program Office (AFMETCAL) at Heath, Ohio, to manage metrology services for the Air Force, retain engineering authority for all calibrations performed in the PMEL labs throughout the Air Force, and manage the contractor operated Air Force Primary Standards Lab. (
  • With our calibration services you can feel safe that your instruments always perform as expected. (
  • Our comprehensive certification and calibration services ensure that your products meet all relevant regulations, and compliance is recognised with the ISO 9001 certificate, valid for 12 months. (
  • Our calibration services for onshore and offshore oil and gas environments include support from our accredited laboratories and fully qualified engineers. (
  • Shared oil and gas pipelines instigate the need for independent calibration services. (
  • Engaging reliable calibration services assists oil and gas organisations in preventing drifting and inaccuracies and ensures that equipment continues to meet its manufacturer's specifications. (
  • Our calibration services will benefit your organisation through a full range of solutions and consultancy options, excellent communication channels, quality certification, offsite and onsite support and a global footprint in the oil and gas industry. (
  • Informing you of necessary equipment repair or replacement forms part of our calibration services. (
  • Saving you time, money and resources, working with us as your Total Quality Assurance calibration services partner will allow you to focus on core activities. (
  • Offering Calibration Services for our clients across the globe. (
  • With our vast industry experience we offer satisfactory services to our clients such as Frequency Meter Calibration, Tach Dwell Meter Calibration, Universal Testing Machine Calibration, Pitch Micrometer Calibration, Groove Micrometer Calibration, Flange Micrometer Calibration, Depth Micrometer Calibration, Calibration Of Digital Manometer Instruments. (
  • 1. +91-8079447805 Arrow Instruments Calibration We are engaged in offering Calibration Services for our clients across the globe. (
  • 2. About Us Arrow Instruments Calibration established in 2002 has emerged as a well- established service provider, exporter, importer and trader of Calibration Services. (
  • The calibration is performed in the environmentally conditioned room and our onsite our calibration services will not affect the production unit in any way. (
  • Our team members are technology specialists and strengthened with the industrial know-how that assists us to deliver latest calibration services with the assurance of high performance. (
  • The USNO provides precise and accurate calibration services to remote users around the world. (
  • The changes will impact a small number of high level electrical calibration services, but most customers using our calibration services can expect a negligible impact. (
  • With our torque tool calibration and repair services, we've seen a spike in electronics, automotive, and other industries seeking to maintain existing fastening tools in the face of cost-cutting,' states Eddie Silverberg. (
  • By providing products and services for both in-house calibration and repair, and a full-time torque calibration and repair staff at Flexible, the firm has been able to help with the increasing demand for these types of customer requests. (
  • The calibrations services listed check or characterize particular instruments, devices, and sets of standards. (
  • Tektronix is the nation's leading provider of multi-brand calibration services . (
  • Vaisala provides On-site calibration services for selected data loggers and instruments used in Continuous monitoring systems . (
  • Learn about calibration services that are available through one of our many certified service centers, located throughout the world. (
  • Find out about the wealth of Support Services available for your Calibration products. (
  • Since there are good observations of temperature and salinity available from satellites and buoys, foraminifera from the sediment trap are also being used to improve the calibration of foraminiferal chemistry and oceanographic parameters. (
  • The CIO contributes to ongoing international research to improve the calibration curve. (
  • Stefani Sassos, Ms, Rdn, Cso, Good Housekeeping , "Everything You Need to Know About the New Peloton Bike+, According to Our Fitness Experts," 14 Dec. 2020 To make matters more complicated, the ALMA observatory recently identified an error in its calibration system that produced a spectrum of Venus with a lot of noise for Greaves and her colleagues to work with. (
  • In particular, full radiance and irradiance calibration using Earth and sun observation paths are performed with NIST calibrated light sources for the Polarisation Unit (PU) and the main channels. (
  • A typical blackbody calibration is described in the article listed below under Selected Publications, "Cryogenic blackbody calibrations at the National Institute of Standards and Technology (NIST) Low background infrared (LBIR) facility. (
  • W. Groeneveld, H. Schouwenaars, H. Termeer, A self calibration technique for monolithic high-resolution D/A converters. (
  • The latest calibration files that are used by sisrmg (including sisph2pi_110397.fits, which is also used by sispi ) are distributed with FTOOLS in the refdata area, but they can also be found here . (
  • Check out the latest Calibration Engineer Jobs or see Calibration Engineer Salaries at other companies. (
  • First, optimizing an engine to create a base engine calibration at its various steady-state operating points, typically on a dynamometer test rig. (
  • While the CAN Calibration Protocol or CCP is a reasonably well known standard in Europe that continues to gain acceptance, its exposure in the American automotive electronics arena has to some extent been limited to the engine calibration area. (
  • With a national network of resources, a robust quality program and broad capabilities, we offer standard and custom solutions to deliver fast, accurate calibration when and how it's needed. (
  • These calibrations are performed in a thermal vacuum chamber at the instrument calibration contractor's site (TNO/TPD). (
  • Two instruments at the end of the robotic arm on NASA's Mars rover Curiosity use the calibration targets attached to a shoulder joint of the arm. (
  • The Calibration Group has been developing and operating the Calibration Facility Oberpfaffenhofen (CALIF), comprising various calibration targets like corner reflectors, transponders and ground receivers in L-, C- and X-band, and the required infrastructure for the preparation and execution of calibration campaigns over large test sites. (
  • The Institute is well equipped with three different types of calibration targets and maintains a laboratory for the precise adjustment of electronic devices. (
  • This must be done even if the same calibration star can be used for all the science targets. (
  • However, AATSR is essentially a self-calibrating instrument, deriving calibration coefficients for the thermal and visible channels via its on-board calibration targets . (
  • In Cycle 27 the WFC3 team will carry out an extended calibration program to monitor the behavior of the UVIS and IR channels and to provide the best calibration data for scientific programs. (
  • Motivated by the different properties of each of the WFC3/UVIS e2v CCD detectors, UVIS photometric calibrations are now determined independently for each CCD. (
  • The core for our calibration and verification algorithms is the CALIX software, which is currently being upgraded for TerraSAR-X and ALOS. (
  • Therefore, there are no specific external calibration algorithms involved. (
  • The calibration curve shows large deviations from the theoretical curve, probably because the earth magnetic field used to be weaker, enabling more cosmic rays to penetrate the atmosphere and enhancing the 14 C content. (
  • The in-flight calibration of the ASCA instruments is an on-going effort. (
  • Since the ASCA database is huge, Guest Observers who, during the course of their analysis come across additional problems or anything that may contribute to our current knowledge of the calibration are encouraged to notify the ASCA GOF by using our Feedback form . (
  • Files and information regarding the ASCA calibrations are kept in the HEASARC Calibration Database . (
  • On this page we highlight some calibration files and articles that are most commonly required for ASCA analysis. (
  • The latest Response Matrices are available from the ASCA calibration database . (
  • With DAkkS calibration certificates , we document the calibration of reference workpieces, gauge blocks, spheres, setting rings/mandrels, multi-sphere test standards, one-dimensional ball rails, measuring gauges, high-precision gauges and many other types of testing equipment. (
  • Turn the calibration screw until the gauge reads 0 psi for models TP970 and TP973. (
  • Move the "Day" calibration screw -- with 13 psi as the main air pressure -- until the gauge reads 0 psi for model TP971. (
  • Turn the "Summer" calibration screw -- with 13 psi as the main air pressure -- until the gauge reads 0 psi for model TP972. (
  • The calibration of K-cells on Madge was performed by Chris Burrows using a Beam flux gauge to calculate beam equivalent pressures and a QCM to calculate rates of deposition. (
  • The standard instrument for each test device varies accordingly, e.g., a dead weight tester for pressure gauge calibration and a dry block temperature tester for temperature gauge calibration. (
  • It is processed in accordance with ANSI/NCSL Z540-1 1994*, and returned with a "Report of Calibration" with "as found" and "as left" readings including test uncertainties. (
  • Assists customers with questions/problems regarding tank calibration reports. (
  • The inverse sensitivity values written to the PHOTFLAM image header keyword are the CORRECT values for flux calibration for all except the UV filters observed on UVIS2. (
  • Inverse sensitivity values for UVIS2 are written to the keyword PHTFLAM2 but should not be used for flux calibration with calibrated data products retrieved from MAST, since calwf3 by default will scale the UVIS2 chip by the chip sensitivity ratio to match UVIS1. (
  • To create another calibration certificate return to the request page . (
  • Your device may be sent to a local Welch Allyn Repair Center for calibration, or visit the device product page to access the User Manual for instructions on performing a calibration check. (
  • At the same time the next DAC-element is put into calibration mode. (
  • The average turnaround time for calibrations is 2 weeks. (
  • Ability to learn Saybolt tank calibration software applications through instruction provided by Saybolt within a reasonable time limit. (
  • The authors then describe their and their students' designs (and success) in building a CubeSat designated H2 (Hooponopono) to replace the RADCAL satellite (used for radar calibration) which ceased communication in May 2013, 17 years after its predicted life time of three years. (
  • Unless otherwise stated, each service covers calibration of an item on a one time per request basis. (
  • A calibration and configuration algorithm operates to establish the sensor ranges of all sensors installed and disables certain configurable features if the associated sensors are not present. (
  • These and other objects are achieved by the present invention which includes a microprocessor which executes a hitch control algorithm and a calibration and configuration algorithm. (
  • Purchasing is now managing all calibration service requests. (
  • Calibration Plans for each instrument and mode are described in detail in their corresponding User Manual , and their execution times are not charged to the Service Mode programmes. (
  • Official calibration certificates and service reports proof the system performance for internal and external auditing needs. (
  • Scott Oldham, Car and Driver , "2021 Porsche Panamera Turbo S E-Hybrid Sport Turismo Flexes 690 HP," 7 Dec. 2020 In critical applications and recreational situations alike, headphone EQ calibration can make an astonishing difference in listener experience and overall enjoyment. (
  • Popular Science , "Best headphones: Get good-quality audio equipment at your budget," 17 Dec. 2020 The presidential election required deft calibration to get along peaceably with relatives or friends with differing views. (
  • Phoebe Wall Howard, Detroit Free Press , "Ford recalls 2021 E-series for burn risk, 2020-21 Explorer and Aviators for power loss," 23 Dec. 2020 Steering responses feel a hair crisper, as Toyota revised the steering calibration to make the effort buildup more linear as cornering loads increase. (
  • David Beard, Car and Driver , "Tested: 2021 Toyota Supra 3.0 Gains Horsepower and Refinement," 17 Aug. 2020 With regular vigorous use over the past three months, the bike maintained its great condition and did not require re- calibration , though calibrating the bike is simple if needed. (
  • A fine culmination of facilities as well as sophisticated technology support, we together as a team ensure in successfully meeting calibration related demands of varied industries. (
  • Operates the computer system as necessary, including Microsoft Word, Excel, Windows, E-mail functions or the equivalent, and the Saybolt tank calibration software, in order to successfully complete assigned tasks. (