Measurement protocols

Samples that contain suspended matter are among the most difficult types from which to obtain accurate pH readings because of the so-called suspension effect, ie, the suspended particles produce abnormal Hquid-junction potentials at the reference electrode (16). This effect is especially noticeable with soil slurries, pastes, and other types of colloidal suspensions. In the case of a slurry that separates into two layers, pH differences of several units may result, depending on the placement of the electrodes in the layers. Internal consistency is achieved by pH measurement using carefully prescribed measurement protocols, as has been used in the determination of soil pH (17). 

Table 8-1 Measurement protocol for a cathodic protection installation (example) 1. General Data...

The chemical compositions of the isolated Au SR clusters were investigated by mass spectrometry [15,16,18, 22,32-35]. TEM was used to confirm that the species detected by the mass spectrometer represents the clusters in the sample. Figure 3a is a schematic representation of the top view of the mass spectrometer, which consists of five stages of differentially pumped vacuum chambers. The apparatus accommodates two t5 pes of ion sources, electrospray ionization (ESI) and laser-desorption ionization (EDI), and a time-of-flight (TOE) mass spectrometer with a reflectron. Details of the apparatus and the measurement protocols are described below. 

Thorium. Multiple-collector measurement protocols by TIMS for thorium isotopic analysis typically involve the simultaneous measurement of Th and °Th (for silicate rocks), or Th and °Th, then Th and Th (for low- Th samples), using an axial ion counter and off-axis Faraday collector (Table 1). Various methods are used to correct for the relative gain between the low-level and Faraday detectors and 2a-uncertainties of l-5%o are typically obtained (Palacz et al. 1992 Cohen et al. 1992 McDermott et al. 1993 Rubin 2001). Charge-collection TIMS protocols enable Th, °Th and Th to be monitored simultaneously on a multiple-Faraday array and can achieve measurement uncertainties at the sub-permil level (Esat et al. 1995 Stirling et al. 1995). 

Numerous radon and radon decay measurements in houses are now being made by a large number of private and governmental organizations. In order to assure valid and consistent measurements, it is important that proven methods be used following standardized procedures. To address this need, EPA issued "Interim Indoor Radon and Radon Decay Product Measurement Protocols" and established a Radon/Radon Progeny Measurement Proficiency program. 

In February 1986, EPA issued a document (Ronca-Battista et al., 1986) titled "Interim Radon and Radon Decay Product Measurement Protocols," describing seven methods for measuring radon and its decay products in houses. The methods addressed are those that have been evaluated by EPA and found to be satisfactory other methods may be added as they are reviewed by EPA. In addition, portions of the document may be revised as new information and data becomes available. 

E., Interim Indoor Radon and Radon Decay Product Measurement Protocols, EPA 520/1-8604, U.S. Environmental Protection Agency, Washington, D.C. (April 1986). 

Lacking international and local cooperation an insufficient cooperation and coordination between different implementation scales. This leads to discrepancies in prioritisation of measures and their effects, depending on the scale considered. This lack of common objectives occurred with harmonisation of measurement protocols and with selection and implementation of measures between countries and institutions during the implementation of first generation RBMPs. 

A variety of measurement methods have been developed for determining the water activity of food materials and are well described in texts such as Rahman (1995), Wiederhold (1997), and Bell and Labuza (2000). In general, water activity is a relatively easy parameter to measure, which can be an advantage, especially for use in the food industry. Depending on the technique selected, the water activity of a food material can be measured in a time frame of minutes (e.g., electronic instrument). In addition, individuals can be trained, with a limited amount of instruction, to make water activity measurements. Consequently, when appropriate, water activity measurements can be made relatively quickly by personnel overseeing a manufacturing line for quality assurance purposes. Measurement protocols, such as calibration procedures and proper temperature control, should be implemented to assure the accuracy of online c/w measurements. 

In addition to possible variations between methods, there may also be variations in Tg within a method, depending on the measurement protocol employed. For example, the DCS Tg midpoint for a quench-cooled ( 100 K/min) maltose sample, heated at a scanning rate of lOK/min, was 43.1 0.21 °C, whereas for a maltose sample prepared using equal heating and cooling rates of lOK/min the Tg was 41.2 0.10°C (Schmidt and Lammert, 1996). For the same samples, DSC Tg Active temperatures were also calculated. Tg Active for the quench-cooled sample was 41.0 0.20 °C, whereas for the equal-rate sample, Tg Active was 38.6 0.06 °C. 

In addition, very few observations are pristine and basic measurements such as angular deviation of a needle on a display, linear expansion of a fluid, voltages on an electronic device, only represent analogs of the observation to be made. These observations are themselves dependent on a model of the measurement process attached to the particular device. For instance, we may assume that the deviation of a needle on a display connected to a resistance is proportional to the number of charged particles received by the resistance. The model of the measurement is usually well constrained and the analyst should be in control of the deterministic part through calibration, working curves, assessment of non-linearity, etc. If the physics of the measurement is correctly understood, the residual deviations from the experimental calibration may be considered as random deviates. Their assessment is an integral part of the measurement protocol and the moments of these random deviations should be known to the analyst and incorporated in the model. 

Slope/bias correction This method, which is really a postprocessing of model outputs, is one of the simplest improvement methods, and can be quite effective in cases where temporal shifts in analyzer response are expected [105]. However, when used, it should be accompanied by a well-defined sampling and measurement protocol, in order to generate a sufficiently large population of time-localized standards that can be used to determine stable estimates of slope and bias correction factors. 

Certified Reference Materials. Certified Reference Materials are materials whose properties have been guaranteed or certified by recognized bodies. The certified analyses of these materials can be used as an estimate of the "true" value for assessment of accuracy. The United States National Bureau of Standards (NBS) provides an inventory of various materials whose compositions (and properties) have been measured using definitive and reference methods. These materials, Standard Reference Materials (SRM s), when used in conjunction with reference methods, i.e., one of demonstrated accuracy, make it possible to transfer accuracy between measurement protocols. 

Francois, Y., Zhang, K., Varenne, A., and Gareil, R, New integrated measurement protocol using capillary electrophoresis instrumentation for the determination of viscosity, conductivity and absorbance of ionic liquid-molecular solvent mixtures. Anal. Chim. Acta, 562,164-170, 2006. 

Data acquisition parameters. Precision and accuracy in the measurement of isotope ratios can be improved if the number of measurements is increased (e.g. if the measurement time is increased). Various measurement protocols can be applied and those whereby the time actually spent on measuring the isotope ratios of interest is maximised are preferable. The data acquisition parameters of an ICP-MS device that can be changed to improve the isotope ratio precision... 

While the measurement protocol is fairly simple, there are a number of important factors that need to be considered when using the drop shape analysis method. First, a sufficient visual contrast between the drop and the surrounding liquid is required to be able to extract the drop profile. If the external phase is slightly turbid, or if the refractive indices of the two phases match each other, it may be difficult or even impossible to extract the drop profile. If possible, the more turbid phase should be chosen as the internal drop-forming... 

This chapter presents, in a natural order, the different steps for obtaining an exploitable parametric map i.e., the modeling of acquired data in terms of noise and signal (Section 2), the optimization of the measurement protocol parameters (Section 3) and the actual methods of reconstruction that lead from the acquisition space to the parametric space (Section 4). The last part looks at certain applications and the current limits of these approaches (Section 5). 

A general measurement protocol consists of collecting n noisy samples by changing the value of the explanatory variables. To a vector x then corresponds a vector of measurements y in each voxel of the image. This section presents several strategies for choosing x in order to optimize the quality of estimation a priori. 

To optimize or compare measurement protocols, an index of quality must be quantified for each estimated parameter. For a parameter taken separately, the performance of estimation is a function of both the variance (or precision) and the bias (or accuracy) of the estimate. The covariance matrix of each unbiased estimator 0 checks the inequality of Frechet-Cramer-Rao 24... 

This example has been chosen to show that it is possible to calculate the optimal performance of a measurement protocol in conditions close to those in the field. For a set value of 6 (actually the unknown parameter) it is then possible to seek the value of x that minimizes CRB for a set number n. This optimization is often impossible to carry out analytically when n>2 and/or when matrix I has a complex... 

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