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50 pagesInternational audienceProduct development processes comprise highly creative and knowledge-intensive tasks that involve extensive information exchange and communication among geographically distributed teams. Due to the geographical and institutional separation between the different systems involved in the product lifecycle, retrieving, sharing and exchanging product knowledge is becoming a key issue in information systems of extended enterprise. This paper addresses the issue and challenges of product knowledge traceability during the product development. The aim of this research effort is to enhance the exchange and use of product knowledge acquired during the development process. In order to satisfy the needs for acquisition and reuse of product knowledge, a product knowledge representation framework is proposed. Key elements to support traceability during product development process are identified. The key idea behind this research effort is based on the premises that an important step towards achieving product knowledge sharing is providing traceability across various product knowledge elements that are used in product development phases, i.e. design and manufacturing. Two complementary case studies illustrating the benefit of traceability are presented. The potential role of traceability is described, first to support the decision making process during engineering change management, and second to support product oriented modelling for knowledge sharing and exchanging to meet quality requirements

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Adrenal function and aging have been the object of intense interest recently, especially as regards dehydroepiandrosterone sulfate (DHEA-S), which is of major importance, since it is distinct from cortisol and aldosterone in declining with age. In a group of healthy old Tunisians, we investigated the association between cortisol and DHEA-S, on the one hand, and age, sex, lifestyle, physical health, including the body mass index (BMI), physical activity, and smoking indicators, on the other hand. We observed that cortisol concentrations did not change with aging, while DHEA-S concentrations decrease with age in both sexes. Cortisol/ DHEA-S ratio, however, increases with aging. Our results revealed that DHEA-S levels are affected neither by physical activity nor by weight. It appears also that current smoking could not affect the level of DHEA-S. Relationships were found between DHEA-S concentrations and BMI, then between DHEA-S levels and serum cholesterol, triglycerides and calcium. No modification in the morning serum cortisol was found to be associated with aging. Decrease in DHEA-S levels is, however, clearly associated with this phenomenon. High cortisol/DHEA-S ratio accelerates the occurrence of some adult diseases, such as diabetes mellitus, atherosclerosis, dementia, and osteoporosis. Generally, the adrenal insufficiency marked by a cognitive impairment, immune disorders, sexual dysfunction, and scores for depression and anxiety can be corrected by a replacement of deficient DHEA-S.