A Top-Down Methodology

The power of SWIFT rests with its ability to keep the analysis at a high level where this is needed. This abstraction might be criticised for lacking rigour and attention to detail but this does not necessarily follow. We need to ensure that the degree of analysis is commensurate with the level of risk to focus our efforts in the right place. 

Thus the more quickly we can differentiate areas of greater risk, the sooner we can plan and prioritise our approach. 

The high level approach offered by SWIFT quickly weeds out those aspects of the system for which an in-depth analysis is frankly unwarranted. More to the point, it focuses the mind on those areas which would benefit from further analysis and, ultimately, the implementation of additional risk reduction measures. 

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Auditors should select the audit method most appropriate for their intended audit purpose. Initial quality system audits or regularly scheduled audits are likely candidates for the top-down approach, while audits conducted as part of a root cause analysis, for example, may best employ a bottom-up approach. The FDA employs a similar approach to inspections. Regular scheduled biennial inspections are more likely to employ a top-down methodology. For cause inspections conducted in response to a specific product issue such as a recall are more likely to employ a bottom-up approach. FDA investigators may employ a combination approach during biennial inspections if investigators are aware of specific quality problems that they wish to include in the inspection. 

Unfortunately, fluorination and other sidewall functionalization methods can perturb the electronic nature of the SWNT. An approach by Smalley,and Stoddart and Heath, to increasing the solubility without disturbing the electronic nature of the SWNTs was to wrap polymers around the SWNTs but leave individual tubes electronic properties unaffected. Stoddart and Heath found that the SWNT ropes were not separated into individually wrapped tubes the entire rope was wrapped. Smalley found that individual tubes were wrapped with polymer the wrapped tubes did not exhibit the roping behavior. While Smalley was able to demonstrate removal of the polymer from the tubes, it is not clear, however, how easily the SWNTs can be manipulated and subsequently used in electronic circuits. In any case, the placement of SWNTs into controlled configurations has been by a top-down methodology, for the most part. Significant advances will be needed to take advantage of controlled placement at dimensions that exploit a molecule s small size. 

The foundation for any safety system application is a thorough imderstanding of the problem to be solved. The proems industry seems to have reached consensus on the use of a top down methodology that was developed about 30 years ago and is generally known as the hazard study method. 

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