Use of a capacitance measurement device for surrogate noncontact conductance measurement

A capacitance to digital converter (AD7746) is used in the same mode as noncontact conductance detectors. The detector output is linearly proportional to specific conductance (sigma) at low sigma values but becomes nonlinear and reaches a plateau value at sigma approximately >0.75 mS/cm, regardless of the nature of the electrolyte. For all applications at sub- to low-mM concentrations, the device, available as an evaluation board, provides a very affordable nothing-else-required means of contactless surrogate conductivity detection from capillary scale to larger bore conduits. For the same measurement cell volume, the detector provides virtually the same limits of detection (LODs) as a standard galvanic contact conductivity detector in conventional scale suppressed conductometric ion chromatography. The detection limits deteriorate as the conduit inner diameter decreases.     

Electrochemical measurement of phenothiazine-interacted DNA

The amount of DNA was measured by using thioridazine, which would be attached to the DNA, as an electrochemical indicator. An indicator (thioridazine) solution, a test solution (DNA solution), and a poly-l-lysine solution were successively placed on a glassy carbon electrode, and the electrode was allowed to dry; DNA was immobilized on an electrode surface by the electrostatic binding between DNA and poly-l-lysine. The electrode was immersed into a buffer solution for 15 min, and then differential pulse voltammetry (DPV) was carried out: the oxidation current peak of thioridazine was observed, and its magnitude depended on the amount of DNA in the solution which was used for preparing the electrode. It could be estimated between 0.2 microg DNA (corresponds to 630 pmol nucleotides) to 20 microg DNA (63 nmol nucleotides) from the oxidation peak current of DPV.     

Matrix infrared measurement of TiN

Gas-phase reaction of active nitrogen with TiCl₄ produces TiN, which has been stabilized in a Kr matrix at 10 K and measured by FTIR. The vibrational frequency of 1037 cm^?1 in the matrix confirms the newest gas-phase analysis giving 1039.6 cm^?1.     

Radon measurement uncertainty: Comparison between passive short-term and active measurement

The measurement of indoor ²²²Rn is not as straightforward as commonly perceived. The most commonly used measurement method is a passive, short-term device using activated charcoal that collects gases, typically for 3–7 days. Short-term measurements are popular because a radon determination is often required by a homebuyer and the buying transaction needs to be completed within 30–60 days. From deployment to obtaining the result from a laboratory reading the passive short-term device can take about 2 weeks. Active measurements, in which a portable alpha-particle counter is placed within a house and air pumped through a scintillation cell have been compared to passive short-term measurements and found to be consistent. For transactions requiring faster or immediate results, active counting methods appear to be a reliable method for measurement.     

Voltammetric measurement of reduced nicotinamide-adenine nucleotides and application to amperometric measurement of enzyme reactions.

The electrochemical oxidations of reduced nicotinamide-adenine dinucleotide and reduced nicotinamide-adenine dinucleotide phosphate on platinum and carbon electrodes are described. Well defined voltammetric anodic waves are observed on carbon electrodes, with a linear relationship between peak height and concentration for 0–0.5mM NADH and NADPH. Amperometric methods for NAD oxidoreductase analyses by direct electrochemical oxidation of the reduced nucleotide have been developed for lactic dehydrogenase and ethanol in serum.     

Uncertainty-based measurement quality control

According to a simple acceptance decision rule for measurement quality control, a measured value will be accepted if the expanded uncertainty of the measurements is not greater than a preset maximum permissible uncertainty. Otherwise, the measured value will be rejected. The expanded uncertainty may be calculated as the z-based uncertainty (the half-width of the z-interval) when the measurement population standard deviation σ is known or the sample size is large (30 or greater), or by a sample-based uncertainty estimator when σ is unknown and the sample size is small. The decision made based on the z-based uncertainty will be deterministic and may be assumed to be correct. However, the decision made based on a sample-based uncertainty estimator will be uncertain. This paper develops the mathematical formulations for computing the probability of acceptance for two sample-based uncertainty estimators: the t-based uncertainty (the half-width of the t-interval) and an unbiased uncertainty estimator. The risk of incorrect decision-making, in terms of the false acceptance probability and false rejection probability, is derived from the probability of acceptance. The theoretical analyses indicate that the t-based uncertainty may result in significantly high false rejection probability when the sample size is very small (especially for samples of size 2). For some applications, the unbiased uncertainty estimator may be superior to the t-based uncertainty for measurement quality control. Several examples from acoustic Doppler current profiler streamflow measurements are presented to demonstrate the performance of the t-based uncertainty and the unbiased uncertainty estimator.     

Temperature measurement and control

Several factors in temperature measurement that can affect the precision of melting points and phase-change phenomena are discussed. In many cases, critical errors may arise in the measurement and control of temperatures due to incorrect placement and/or interpretation of the output of temperature sensors in the various system types that are in current use. Advantages can be obtained by using one temperature sensor only for temperature measurement and temperature control in a low mass infrared gold image fumace for the analytical studies in both the constant rate and stepwise isothermal thermoanalytical heating and cooling modes. Illustrations of the use of this instrumentation for measurements in both modes are given.     

Traceability issues in measurement

This paper reviews the current state of play of the Mutual Recognition Arrangement created by the International Committee for Weights and Measures in 1999. The aim of the MRA is to provide a framework within which National Metrology Institutes can demonstrate the equivalence of their realisations of the units and quantities of the SI system to which accredited laboratories are traceable. The article offers some views on the need for traceable measurements, their relevance to technical barriers to trade, and the use that is being made of the MRA framework by national and international bodies.     

Local redox potential measurement

A local potential measurement method that can be easily used in an anaerobic solution was settled and the potential probe was tested with a simple and fast electrochemical system. From the local potential value, plotted versus the distance to the working electrode, the concentration profile of the electrochemically consumed species can be calculated. The comparison of this experimental concentration profile to the theoretical one, which is based on Nernst hypothesis, enables us to assess the screening effect induced by the potential probe on the potential and current distributions. Thus, it is possible to calculate the potential profile that would be recorded by an ideal probe.     

Rapid measurement of three-dimensional diffusion tensor

In this article, the authors demonstrate a rapid NMR method to measure a full three-dimensional diffusion tensor. This method is based on a multiple modulation multiple echo sequence and utilizes static and pulsed magnetic field gradients to measure diffusion along multiple directions simultaneously. The pulse sequence was optimized using a well-known linear inversion metric (condition number) and successfully tested on both isotropic (water) and anisotropic (asparagus) diffusion systems.     

The meaning of measurement in metrology

The latest version of the International Vocabulary of Metrology gives a meaning of measurement restricted to quantities that can be represented by numerical values and placed in an ordinal sequence. This restrictive definition fits poorly with both the colloquial and the wider scientific understanding of measurement. This paper suggests an extension to the metrological definition of measurement, based on the measurement classification scheme of Stevens, to incorporate non-numerical and nominal measurements. The more inclusive definition and the classification scheme offers insights into the utility, metrological traceability, and limitations of measurements and uncertainty treatments, and enables clarification of other measurement-related definitions.     

Laboratory measurement of human cytokines.

Cytokines mediate and modulate different physiological systems. Accurate and sensitive methods for their measurement are being developed using bioassays, immunoassays, measurement of their mRNA, receptor binding assays, and immunochemical procedures. The most clinically significant cytokines and their assay methods are briefly reviewed. The need for standardization of assays is stressed.