Stabilität der tatsächlichen Schadenssumme gegen eine Variation des Kollektivumfangs, der Kerbschärfe und des Kollektivhöchstwertes am Beispiel der warmausgehärteten Knetlegierung AlMgSi 1

Using the concept of damage accumulation for the fatigue design of components under operational conditions, the correct damage sum is an important quantity. Assuming the tehoretical quantity D=1, the calculated life time is often higher than the experimental. Therefore the real damage sum combined with the corresponding modified Miner rule should be determined. The investigation is based on fatigue tests with different notched specimens under constant amplitude loading and various gaussian spectra. Damage calculation were carried out by four different modifications of the Miner rule: Miner original, Miner-Haibach, Miner elementar (Corton-Dolan) and Miner-Liu-Zenner. The applied methods showed different behaviour concering a variation of spectrum length, stress concentration and load level. The modification of Miner's rule according to Haibach showed the highest insensitivity with regard to stress concentration and spectrum lenght

A Cross-Talk Between Microbiota-Derived Short-Chain Fatty Acids and the Host Mucosal Immune System Regulates Intestinal Homeostasis and Inflammatory Bowel Disease

International audienceGut microbiota has a fundamental role in the energy homeostasis of the host and is essential for proper "education" of the immune system. Intestinal microbial communities are able to ferment dietary fiber releasing short-chain fatty acids (SCFAs). The SCFAs, particularly butyrate (BT), regulate innate and adaptive immune cell generation, trafficing, and function. For example, BT has an anti-inflammatory effect by inhibiting the recruitment and proinflammatory activity of neutrophils, macrophages, dendritic cells, and effector T cells and by increasing the number and activity of regulatory T cells. Gut microbial dysbiosis, ie, a microbial community imbalance, has been suggested to play a role in the development of inflammatory bowel disease (IBD). The relationship between dysbiosis and IBD has been difficult to prove, especially in humans, and is probably complex and dynamic, rather than one of a simple cause and effect relationship. However, IBD patients have dysbiosis with reduced numbers of SCFAs-producing bacteria and reduced BT concentration that is linked to a marked increase in the number of proinflammatory immune cells in the gut mucosa of these patients. Thus, microbial dysbiosis and reduced BT concentration may be a factor in the emergence and severity of IBD. Understanding the relationship between microbial dysbiosis and reduced BT concentration to IBD may lead to novel therapeutic interventions