Achilles’ heel approach

In spite of the fact that both studies have reported important spectral features associated with the structure-property relationship, an Achilles heel of both approaches results from the necessity of using optically transparent films to allow infrared light to pass through the sample. New materials, such as fibers and composites, cannot be studied by transmission FT-IR techniques because they are often optically opaque. Thus, in order to monitor structural changes induced by external forces, it is necessary to utilize a method permitting the detection of infrared spectra on any material, regardless of its optical properties, shape or thickness. 

Almost all of previously discussed syntheses were based on this principle. The Achilles heel of this approach is the problem of achieving an acceptable overall yield. In consecutive reactions the final yield, of course, will depend upon the yields obtained in the intermediate stages. If the average yield per individual step is designated as Y, then the total yield of the product after the nth stage will be Y = Y". If Y is equal to 80%, a very acceptable yield, then the dependence of the overall yield on the number of steps would be as follows ... 

The Achilles heel of project management is the time and resource estimate. In the majority of cases these are actually wrong. The only question is the level of inaccuracy in the estimate. There is no real scientific approach to better estimates and, similarly with all forecasts, it is more of an art and a feel to estimating than a science. Consequently, due to the uncertainty of projects and estimates, it is best to try to work with two numbers the most likely and the high number (Fig. 6). New, workable (as opposed to PERT) approaches to project management (i.e. critical chain project management) are available to schedule around uncertainty.f ... 

These issues are ones of extrapolation and as noted by Preston (2005) such extrapolations are the Achilles heel of risk assessment (Preston 2005). The U.S. EPA, The International Program on Chemical Safety (IPCS), and The International Life Sciences Institute (ILSI), for example, have proposed a framework based on the mode of action of a chemical, the key events that define a particular mode of action, and a human relevance framework for assessing the plausibility of an animal mode of action to humans. It is this approach that will be described and discussed in this chapter. 

In the first chapter written by Carlsen an important step is the introduction of "noise - deficient" QSARs. The basics of HDT are briefly repeated before the central item how to get information about unknown properties is discussed. In comparison to usual methods, which are well known and widespread in the scientific literature, the approach shown by Carlsen does neither assume linearity in the property-property relationships nor any distribution properties. The method can be considered as parameter free. "Giving the molecules an identity" is the very idea how to rank a chemical whose environmental relevant data are unknown but some structural descriptors. Although the incomparabilities may be considered as "Achilles heel" Carlsen shows in his chapter how to handle such situations by means of linear extensions, probability distributions and the concept of averaged ranks. 

A priori the incomparisons may turn out as an Achilles heel of the partial order ranking method. However, the adoption of the linear extension approach apparently remedies this, at least to a certain extent. 

Several related methods have been developed during the past years. The Achilles heel of this approach is the treatment of the interaction between the link atom and classical part of the system, and the proper simulation of the bonds between the two kinds of subsystems [17]. Other shortcomings come from the nature of the link atom. 

Dialysis vascular access is currently the lifeline for hemodialysis patients. Unfortunately, due to the many complications associated with dialysis vascular access, it is also the Achilles heel of hemodialysis. A relatively ignored aspect of dialysis vascular access pertains to patient safety. The first part of this chapter will describe patient safety issues in the traditional context of arteriovenous fistulas (AVFs), arteriovenous grafts (AVGs) and tunneled central venous catheter (tCVC). In the second half of this chapter, however, we will make the case that a nontraditional approach which emphasizes (a) individualization of care, and (b) patient preferences and patient involvement maybe our best opportunity to improve patient safety in hemodialysis patients. 

Despite the obvious advantages of the formal equivalence checking approach, there are limitations. Formal tools appear to provide the ultimate assurance of design correctness. At the end of a run, the program provides counter-examples for each specified property specified by developer which were found not valid. Every property is 100% covered. But the Achilles heel of the process is determining how completely the set of properties covers the design intent. This requires human-in-the-loop - the skill of experienced designers. 

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