Accuracy evaluation applications

A commercial instrument by the Swiss company CSEM (now CSM) was tested in the course of a project at the Research Institute for Pigments and Paints (Forschungs-institut fur Pigmente und Lacke e.V. (FPL)). This instrument is based on the method developed at the DuPont Marshall Lab. Objective of the project - where manufacturers of paints, raw materials and automobiles worked together - was the evaluation of the CSEM nano-scratch-tester regarding reproducibility, accuracy and applicability under the aspect of a realistic determination of scratch resistance. 

Once a procedure for an analysis has been selected, we must decide whether it can be applied direetly to the problem at hand, or it must be tested. The answer to this question is not simple and depends on a number of considerations. If the method chosen is the subject of a single literature reference, or at most a few, there may be real value in a preliminary laboratory evaluation. With experience, we become more and more cautious about accepting claims regarding the accuracy and applicability of a new method. All too often, statements found in the literature tend to be overly optimistic a few hours spent in testing the procedure in the laboratory may be enlightening. 

Accuracy is applicable to PK assays while recovery is associated with ADA methods. The majority of ADA assays do not use a standard curve because a well-characterized reference standard is not obtainable. In addition, ADA responses are usually heterogeneous and differ from subject to subject, such that calculating accuracy is not relevant. Thus, recovery is employed to demonstrate that the matrix does not interfere with the detection of the ADA. In practice, the response for the maximum dilution (titer) of matrix that has been spiked with ADA versus matrix without ADA is evaluated and should remain within an acceptable range. The acceptance ranges for recovery are usually expressed in response values rather than concentration units (accuracy). The ADA used in recovery experiments maybe obtained from one subject, a pool of subjects, or even from a different species than the test subjects and thus does not necessarily reflect the ADAs in the study samples. 

Run Acceptance Criteria. Run acceptance criteria are used to accept or reject a run because of its performance. As a consequence, no dehned run acceptance criteria are applicable during method development. Prestudy validation runs are accepted based on the standard curve acceptance criteria. No run can be rejected because of poor performance of a sample during precision and accuracy evaluation all data from prestudy validation runs are reported unless there has been a clearly recognizable error during sample preparation or measurement. Despite the fact that the standard curve must satisfy the criteria described for standard curves above, in-study runs are accepted based primarily on the performance of the QC samples. As stated above in the paragraph on precision and accuracy, the 4-6-30 rule is recommended (i.e., at least four of six QC samples must be within 30% of their theoretical values and at least 50% of the values for each level must satisfy the 30% limit. 

Recognizing that most failure criteria are limited in their accuracy [8,9], researchers worldwide have undertaken collaborative efforts to evaluate different failure criteria to determine their accuracy and applicability in order to find the best one [10]. These efforts, in particular the worldwide failure exercise in [10], have underlined the fact that despite the large number (over 20) of failure criteria, there is no single one that seems to capture failure of composites accurately for a wide range of loading situations and materials. However, they have pointed out that certain criteria are more accurate and/or have a wider range of applicability than others. Most notable among these are the Puck criterion and the LaRC 03 failure criterion. 

The second line of inquiry alluded to was the use of modem computational power, both hardware and software, for the evaluation of pair distribution functions. When the Kirkwood-Buff paper was published, the use of computers for this kind of scientific computation was in its infancy. Indeed, one can say that it was in its prenatal stage. It is difficult to put a date on the time when computers became powerful enough to compute pair correlation functions and, consequently, KB integrals with sufficient accuracy for application to real systems. They have certainly reached that stage at the time of the writing of these words. The computational method of choice in carrying out these calculations is the molecular dynamics method. Since this kind of calculation is discussed in detail in several of the later chapters of this work, we eschew discussion here. 

Doppler reactivity is the other important parameter in FBR cores because it assures the intrinsic safety characteristics of the core. The present cross-section adjustment method cannot treat the Doppler reactivity which is dominated by resonance-peak broadening of cross-sections. We have launched a new study to extend the applicability of the cross-section adjustment and design accuracy evaluation system to the Doppler effect. The basic method to evaluate sensitivity of self-shielding factors has been successfully derived from a generalized perturbation theory, and a prototype system to calculate the Doppler sensitivity is now under verification. 

The hydrogen evolution method is also superior to the estimation of corrosion rate from polarization curve in terms of measurement accuracy. The application of the traditional Tafel extrapolation in estimating the corrosion rates of Mg and its alloys is actually questionable and in many cases can lead to a misleading result, although it has been employed to investigate or evaluate the corrosion performance of Mg and its alloys in some studies (Bonora et al, 2000 Eliezer et al, 2000 Hallopeau et al., 1997 Krishnamurthy et al., 1988 Mathieu et al., 2000). 

In reviewing the permit application, the local, state, or federal permitting authority will normally evaluate the apphcation for completeness, (Hieck the accuracy of calculations, analyze the stated emissions... 

Eortunately, a 3D model does not have to be absolutely perfect to be helpful in biology, as demonstrated by the applications listed above. However, the type of question that can be addressed with a particular model does depend on the model s accuracy. At the low end of the accuracy spectrum, there are models that are based on less than 25% sequence identity and have sometimes less than 50% of their atoms within 3.5 A of their correct positions. However, such models still have the correct fold, and even knowing only the fold of a protein is frequently sufficient to predict its approximate biochemical function. More specifically, only nine out of 80 fold families known in 1994 contained proteins (domains) that were not in the same functional class, although 32% of all protein structures belonged to one of the nine superfolds [229]. Models in this low range of accuracy combined with model evaluation can be used for confirming or rejecting a match between remotely related proteins [9,58]. 

The relative merits of various MO methods have been discussed in die literature. In general, the ab initio type of calculations will be more reliable, but the semiempirical calculations are faster in terms of computer time. The complexity of calculation also increases rapidly as the number of atoms in the molecule increases. The choice of a method is normally made on the basis of evidence that the method is adequate for the problem at hand and the availability of appropriate computer programs and equipment. Results should be subjected to critical evaluation by comparison widi experimental data or checked by representative calculations using higher-level mediods. Table 1.12 lists some reported deviations from experimental AHf for some small hydrocarbons. The extent of deviation gives an indication of the accuracy of the various types of MO calculations in this application. 

When evaluating gas concentrations in practical applications, a reterence spectrum is least squares fitted to the received absorption spectrum. This im proves the system accuracy, since the spectral fingerprint over the whole scanning range contributes to the result.- ... 

A fully automated instrumental procedure has been developed for analyzing residual corrosion inhibitors in production waters in the field. The method uses ultraviolet (UV) and fluorescence spectrophotometric techniques to characterize different types of corrosion inhibitors. Laboratory evaluations showed that fluorescence is more suitable for field application because errors from high salinity, contamination, and matrix effect are minimized in fluorescence analysis. Comparison of the automated fluorescence technique with the classic extraction-dye transfer technique showed definite advantages of the former with respect to ease, speed, accuracy, and precision [1658],... 

---