碩士
國防管理學院
資源管理研究所
84
Inventory management has received considerable attention from business in recent years. One of the important task of inventory management is to control the inventory quantity ...and determine the optimal order interval. Many researchers were devoted to the development of various inventory models. K.S.Park, however, developed the first production inventory model for deteriorationg raw materials and a single finished product. Equations for obtaining the exact average total cost function were then derived. K.S.Park couldn't prove that there is an unique optimal solution (ie. convex) for the exact average total cost function of his model. A modified special total cost function was obtained under the assumption of the raw materials with very small decaying rate. This sqecial total cost function was then proved to be convex.
In this paper, we have developed a mathematical method for proving that the Park's exact average total cost functionos is convex. A numerical example is used to illustrate
The multiple transmembrane protein Niemann-Pick C1 like1 (NPC1L1) is essential for intestinal cholesterol absorption. Ezetimibe binds to NPC1L1 and is a clinically used cholesterol absorption ...inhibitor. Recent studies in cultured cells have shown that NPC1L1 mediates cholesterol uptake through vesicular endocytosis that can be blocked by ezetimibe. However, how NPC1L1 and ezetimibe work in the small intestine is unknown. In this study, we found that NPC1L1 distributed in enterocytes of villi and transit-amplifying cells of crypts. Acyl-CoA cholesterol acyltransferase 2 (ACAT2), another important protein for cholesterol absorption by providing cholesteryl esters to chylomicrons, was mainly presented in the apical cytoplasm of enterocytes. NPC1L1 and ACAT2 were highly expressed in jejunum and ileum. ACAT1 presented in the Paneth cells of crypts and mesenchymal cells of villi. In the absence of cholesterol, NPC1L1 was localized on the brush border of enterocytes. Dietary cholesterol induced the internalization of NPC1L1 to the subapical layer beneath the brush border and became partially colocalized with the endosome marker Rab11. Ezetimibe blocked the internalization of NPC1L1 and cholesterol and caused their retention in the plasma membrane. This study demonstrates that NPC1L1 mediates cholesterol entering enterocytes through vesicular endocytosis and that ezetimibe blocks this step in vivo.
PDF
