When to validate

It is much easier to detect and correct for overlooked problems with a crystal structure during or immediately at the end of an analysis than during the publication process. Early on structure validation also allows the investigator to go back to the experiment, when appropriate, for the gathering of additional data. Validation software should be available on the platform where the structure is solved and refined or accessible on that platform through the web. 

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How does one determine when to validate cleaning procedures ... 

Knowing When to Validate Cleaning Procedures Can be Tricky... 

Gibson, W. and Evans, K.P., Validation Fundamentals How to, What to, When to Validate, Interpharm Press, Buffalo, Grove, IL, 1998. 

Table 8.13 states why, how, and when to validate and who should take care (cfr. also ref. [63]). Everyone should validate/qualily each process, system and piece of equipment that is used in a laboratory. The validation process is enforced in regulated industries (FDA s and EPA s GLP) and recommended in those interested in European markets (ISO 9000). A validation program builds confidence that products are of high quality and that they can be taken as a sound basis for decision making. It is clear, however, that validation is not absolute proof Also, manufacturers cannot validate users equipment. 

The raw data collected during the experiment are then analyzed. Frequently the data must be reduced or transformed to a more readily analyzable form. A statistical treatment of the data is used to evaluate the accuracy and precision of the analysis and to validate the procedure. These results are compared with the criteria established during the design of the experiment, and then the design is reconsidered, additional experimental trials are run, or a solution to the problem is proposed. When a solution is proposed, the results are subject to an external evaluation that may result in a new problem and the beginning of a new analytical cycle. 

When we compare industrial air technology (lAT) with comfort ventilation, we can see that technologically our task is very challenging. To fulfill all the needs of the end user is often impossible. If the lAQ is fulfilled, the amount of air may be so large that draftiness is too high. We must also have the courage to say what is possible and what is not. We also have to cteate tools to validate this. 

It should be noted that the data collection and conversion effort is not trivial, it is company and plant-specific and requires substantial effort and coordination between intracompany groups. No statistical treatment can make up for inaccurate or incomplete raw data. The keys to valid, high-quality data are thoroughness and quality of personnel training comprehensive procedures for data collection, reduction, handling and protection (from raw records to final failure rates) and the ability to audit and trace the origins of finished data. Finally, the system must be structured and the data must be coded so that they can be located within a well-designed failure rate taxonomy. When done properly, valuable and uniquely applicable failure rate data and equipment reliability information can be obtained. 

Markovian perturbation theory as well as impact theory describe solely the exponential asymptotic behaviour of rotational relaxation. However, it makes no difference to this theory whether the interaction with a medium is a sequence of pair collisions or a weak collective perturbation. Being binary, the impact theory holds when collisions are well separated (tc < to) while the perturbation theory is broader. If it is valid, a new collision may start before the preceding one has been completed when To < Tc TJ = t0/(1 - y). 

When not enough examples are available to make an independent monitoring set, the cross-validation procedure can be applied (see Chapter 10). The data set is split into C different parts and each part is used once as monitoring set. The network is trained and tested C times. The results of the C test sessions give an indication on the performance of the network. It is strongly advised to validate the network that has been trained by the above procedure with a second independent test set (see Section 44.5.10). 

It is essential to realize that reference materials must only be employed for the pur-pose(s) for which they are intended. The use of such materials for analytical methods other then those described in the monographs is unacceptable, except when the user carries out the necessary testing to validate the reference substance for a particular test... 

Startup is the time when the validity of all the approximations made in the design stage is tested in practice. It is also a test of the competency of the contractor and his crews, and of the ability of the equipment to meet its predicted performance levels. It is a time of stress when everyone is racking their brains trying to figure out why something is not responding as expected. It can also be a very expensive operation in terms of both time and money. 

The complete four-component system is necessary when the diagnostic requirement is rapid, low unit-cost analysis for both the strain-level characterization of pathogenic agents and identification of hoax bio-terror materials. Using the complete system, we are proposing to validate MS-based microbial taxonomy and to transfer the technology from an analytical research to a clinical or public health production-diagnosis environment. 

When using fluorophores of known lifetime, it is important to validate the lifetime used. Fluorescence lifetimes can be sensitive to concentration, temperature, pH, and other environmental variables. Fluorophores from different suppliers can have variable purity. As a result, one should not assume that a value reported in the literature will be exactly transferable to other labs and conditions. Users of the method should be particularly careful to use low concentrations of fluorophore (<10 /iM) to avoid a variety of processes which can perturb lifetimes in solution. There are a limited number of well characterized fluorophores. If one is not available for a particular wavelength this will require a change of filters leaving the method with nothing to recommend it over reflection and scatter. 

When the FMS method was first introduced, a series of test calculations were performed using analytical PESs. These calculations tested the numerical convergence with respect to the parameters that define the nuclear basis set (number of basis functions and their width) and the spawning algorithm (e.g., Xo and MULTISPAWN). These studies were used to validate the method, and therefore we refrained from making any approximations beyond the use of a... 

When no validation data are available, then all of the relevant parameters will have to be studied. The degree of rigour with which the study is carried out will depend on issues such as criticality of the measurement and the availability of validation data on similar methods. There will be cases in the laboratory where a method has been used, satisfactorily, for a long period of time but there is no documentation to demonstrate the performance of the method. It seems unreasonable to require full revalidation when a method has been used successfully for some years. However, the need for objective evidence prevents the validity of such a method being taken for granted. A possible approach is to follow the plan below ... 

Unfortunately, MAMBAC tends to be less robust than MAXCOV under unfavorable circumstances, such as low taxon base rates, poor indicator validities, and high nuisance correlations. Specifically, taxonic plots often look flat and sometimes concave when the validity of indicators is less than 1.5 SD or when nuisance correlations are higher than. 35 (Meehl Yonce, 1994). A low taxon base rate can obscure the plots even more. For this reason, MAMBAC findings should be interpreted with special care and should be accompanied by MAXCOV analyses whenever possible. MAXCOV can assess the extent to which ideal conditions have been violated and can provide the investigator with information needed for making sound judgments about the trustworthiness of MAMBAC results. 

Newcomers to a particular area of catalysis may use these volumes to validate their techniques, and, when a choice of methods is available, use the background information better to delineate the optimum strategy to try to accomplish a previously unknown conversion. 

These stories describe some of the roads taken to solve the puzzle of illness caused by exposure to chemicals. For many the journey is long and involves a parade of doctors and misdiagnoses. Often MCS is discounted by health care professionals and others who doubt the validity of the illness. When the validity of an illness is discounted, the ill suffer profound discord within their world, according to Kathy Charmaz in her book Good Days, Bad Days The Self in Chronic Illness and Time. This discord can be heard in the collection of narratives in this volume. 

When designing instrument qualifications for automated dissolution systems, some key considerations are determining the functions to validate, cost, testing using equipment... 

Also the study did not employ performance reference componnds, which are required to validate attainment of equilibrinm. We inclnde this exercise to show that lipid normalization is problematic even when both matrices attain eqnilibrinm and do not recommend the procedure without further proof of concept. 

Figures 57 and 58 shows the estimation results for the intervals of the unmeasured states Cti and Z. Notice how the interval bounds estimated by the interval observer envelop correctly these unmeasured states. For all the other unmeasured states, notice that although the interval observer design did not allow us to tune the convergence rate, the interval observer showed excellent robustness and stability properties and provided satisfactory estimation results in the event of highly corrupted measurements and operational failures. Notice in particular, the robustness of the interval observer around day 25 when the inlet concentrations drastically increased and when a major disturbance occurred at day 31, due to an operational failure, resulting in a rapid fall of both, the dilution rate (which actually fell to zero) and the substrate concentration readings. Off-line readings of Cti and Z (not used in the state estimation calculations) were also added to validate the proposed interval observer design (see Figures 57 and 58). It should be noticed that the compromise between the convergence rate and robustness was not fully achieved until the estimation error dynamics reached the steady state.

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