Experimental design, flexibility

Frequency as an experimental variable offers additional design flexibility. This approach has several advantages. The most important one is the lack of polarization of the contacts. The second one is the fact that equivalent electrical circuit analysis can be used that aids in elucidation of the transduction mechanisms. Perhaps the most important distinguishing feature of this class of conductometric sensors is the fact that their impedance is measured in the direction normal to their surface. In fact, there may be no requirement on their DC conductivity and their response can be obtained from their capacitive behavior. In the following section, we examine so-called impedance sensors (or impedimetric sensors see Fig. 8.1b). 

While sample documentation and tracking protocols, as well as QA/QC procedures, have been in place and in effect for many years, their application is tailored to the needs and resources of each individual project, with some exploratory or field-feedback studies requiring much less verification than other regulatory or complaint series. Flexibility in experimental design is imperative if a facet of an investigation is to be completed in accordance with its significance and allocated resources. However, since several of our programs are potentially answerable to GLP s, it was deemed important that the laboratories current level of compliance be established so as to accurately measure the full fiscal and scientific impact to be felt if we should attempt to institute a formal GLP structure. 

A shelf or tail suspension apparatus to suspend mice. The apparatuses may be wooden or plastic boxes (e.g., 680 X 365 x 280 mm), painted to contrast with mice. The design of the TST apparatus is usually negotiable, given that the animal is securely attached to a solid suspension apparatus and that this apparatus is at least 35 cm above the nearest surface (18, 19). Several companies provide behavioral tracking software that is flexible with the variations in experimental design and would yield reliable data that would translate between designs (Table 16.1). Additionally, there are also prefabricated apparatuses that can be purchased (see Table 16.2 for details). 

In this section, we exemplify the power of hypothesis-driven screening. Three chemogenomics projects, and the impact of flexible experimental design enabled by HTCP Picking capabilities are discussed. Two of these examples are drawn from the area of infectious diseases the third example describes a neuroscience project. 

Depending on the experimental design, the number of Abs involved in the immunocomplex formation reaction is varying. A t-Ag, like a bacteria toxin, can be directly immobilized on a reaction substrate and can be quantified with a labeled detection antibody (d-Ab) in a direct immunoassay, involving a single t5q)e of Ab. This technique is however limited, since t-Ags for direct surface immobilization have to be available. A more flexible technique, called sandwich immunoassay, consists to flank the t-Ag to be detected between a capture antibody (c-Ab) linked to a reaction substrate and a labeled d-Ab (see Fig. 3b). In this technique, the t-Ag is specific for both c-Ab and d-Ab. Also an enzyme can be used to label the d-Ab, and, in... 

An alternative to revealed preference data is represented by stated-preference data, which are often considered more informative because of the higher flexibility that the experimental design can provide (Louviere et al, 2000). Such an approach is commonly employed for studying preferences for fruit and vegetable products (van dcr Pol and Ryan, 1996). 

---